Pangaea Ultima Futuro e#8F8

A SHORT COMPILATION OF EARTH HISTORY

HISTORISCHE GEOLOGIE - 450075

A. Immenhauser, Vs. 4.0 - February 2005

The next Pangea, "Pangea Ultima" will form as a result of the subduction of the ocean floor of the North and South Atlantic beneath eastern North America and South America. This supercontinent will have a small ocean basin trapped at its center.

Scotese, C.R., 2002, http://www.scotese.com, (PALEOMAP website)

Page 2 – Vs. 4.0 - February 2005

Table of Contents 1. The Genesis of the Universe ......................................................................................... 4 2. The Proterozoic/Precambrian World.......................................................................... 7 Introduction......................................................................................................................... 7 2.1 The Archean................................................................................................................ 7 Introduction............................................................................................................................................................ 7 Part A. Global Scale .............................................................................................................................................. 7 Part B. Evolution of Life .....................................................................................................................................11 2.2 The Proterozoic ......................................................................................................... 14 Introduction....................................................................................................................... 14 Part A. Global Scale ............................................................................................................................................14 Part B. Evolution and Extinction of Life............................................................................................................16 3. The Early Paleozoic World ........................................................................................ 19 3.1 Introduction................................................................................................................. 19 Part A. Global Scale Paleogeographic and Paleoenvironmental Changes.......................................................19 Part B. Evolution and Extinction of Life............................................................................................................22 4. The Middle Paleozoic World...................................................................................... 27 Introduction....................................................................................................................... 27 Part A. Global Scale Paleogeographic and Paleoenvironmental Changes.......................................................27 Part B. Evolution and Extinction of Life............................................................................................................28 5. The Late Paleozoic World.......................................................................................... 33 Introduction....................................................................................................................... 33 Part A. Global Scale Paleogeographic and Paleoenvironmental Changes.......................................................33 Part B. Evolution and Extinction of Life............................................................................................................35 6. The early and middle Mesozoic world ...................................................................... 39 Introduction....................................................................................................................... 39 Part A. Global Scale Paleogeographic and Paleoenvironmental Changes.......................................................39 Part B. Evolution and Extinction of Life............................................................................................................40 7. The Cretaceous World................................................................................................ 45 Introduction....................................................................................................................... 45 Part A. Global Scale Paleogeographic and Paleoenvironmental Changes.......................................................45 Part B. Evolution and Extinction of Life............................................................................................................46 8. The Paleogene World.................................................................................................. 51 Introduction....................................................................................................................... 51 Part A. Global Scale Changes.............................................................................................................................51 Part B. Evolution of Life .....................................................................................................................................52 9. The Neogene World .................................................................................................... 55 Introduction....................................................................................................................... 55


Part A. Global Scale Paleogeographic and Paleoenvironmental Changes.......................................................55 Part B. Evolution of Life .....................................................................................................................................56 Glossary of Important Geological terms used in this compilation............................. 60 10. Appendix - Special Chapters.................................................................................... 75 10.1 Some remarks on the Geologic framework of Western Europe ............................... 75 Introduction....................................................................................................................... 75 10.1.1 Proto-Europe (Baltica) ........................................................................................... 75 10.1.2 Paleo-Europe (Caledonides) .................................................................................. 76 10.1.3 Meso-Europe (Variscides) ..................................................................................... 77 10.1.4 Neo-Europe (Alpides) .......................................................................................... 78 10.1.4.1 Southern Alps and Adriatic indenter................................................................... 80 10.1.4.2. Apulian plate north of the Periadriatic line: Austrolapine nappe system .......... 81 10.1.4.3. Meliata Ocean and its distal passive margin...................................................... 81 10.1.4.4. Tiza unit............................................................................................................. 82 10.1.4.5. Margna-Sesia fragment ...................................................................................... 82 10.1.4.6. Piedmont-Liguria Ocean .................................................................................... 82 10.1.4.7. Briançonnais terrane .......................................................................................... 83 10.1.4.8. Valais Ocean...................................................................................................... 83 10.1.4.9. European margin................................................................................................ 84 10.1.4.10. Major tectonic units of the Alps....................................................................... 85 10.2 Some basics of Plate Tectonics ............................................................................... 91 10.3 Classification of life ................................................................................................. 93 10.4 Stratigraphic stages................................................................................................. 94 Main references used...................................................................................................... 95


1. THE GENESIS OF THE UNIVERSE AND THE PLANET EARTH

Astronomers tell us that the

universe as we know it began about 15 billion years ago with an explo-sion they call the “Big Bang”. This is based on observations, which most scientists accept as compelling evi-dence for the big-bang theory of uni-verse origin. Today, most astrono-mers believe that the universe is rap-idly expanding. The main argument for this is summarized in the so-called ‘Doppler shift’ theory. With-out going into details, the Doppler shift corresponds to a shift towards red in the spectrum of light reaching us from a distant galaxy. This shift is the equivalent to a 10% reduction in frequency. This 10% reduction can be explained when this galaxy moves away from us with the speed of 108’000’000 km/h. This, in turn, supports the concept of an expanding galaxy. In order to determine the time at which the big bang occurred, as-tronomers have measured the di s-tance between the planet Earth and a receding galaxy as well as its red shift. The relationship found is to be expected if the matter of the universe is flying outward due to an explosion that occurred 15 billion yrs. ago.

The age of the universe can also be approached with decay series of radioactive isotopes. Some of the atoms in the galaxy are radioactive. These atoms (instable mother iso-

topes) decay into non-radioactive, or stable, daughter isotopes. By com-paring the present-day abundance ra-tios for certain long-lived radioactive isotopes with the abundance ratios in red giants we receive a rough number when the elements making our plane-tary system were synthesized. This ratio correlation tells us that the gal-axy must have formed about 14 bil-lion yrs. ago. This result is in good agreement with the 15 billion yrs. de-termined from the Doppler shift. Shortly after the Big Bang, the universe turned dark. Light returned only with the birth of the first stars (suns). About 100’000 yrs. after the big bang, when the expanding matter had cooled to the point where free electrons could become entrapped around the positively charged nuclei, helium and hydrogen gas formed. At this point, the universe consisted only of molecules of gas in a rapidly ex-panding cloud. Then, this cloud separated into clusters that later evolved into galaxies. Within galax-ies, the gas further subdivided to form many billions of stars (such as our sun). At this time, there had been no Earth-like planets. Earth-like planets cannot be formed from hy-drogen or helium. So how did the other 90 elements formed? The elements other than hy-drogen or helium formed in the inte-riors of stars called ‘red giants’.


These massive stars “rapidly” burn their nuclear fuel and then explode, casting a mixture of the 90 missing elements into the neighboring re-gions of the galaxy. The frequency of these events is about one per galaxy per century. Through the course of our galaxy’s history, the formation and demise of about 100 million red giants has converted about 1% of the galaxy’s hydrogen and helium into heavier elements. Nevertheless, how did planets formed from these heavier elements? Our sun is thought to have formed from a small cloud of gas and dust, which succumbed to its own gravitational pull and collapsed. Most of the material in this cloud of dust was drawn into a central body. Thus, our sun has a composition nearly identical to that of the mother cloud. The sun contains about 99% hydrogen and helium and about 1% of the remaining 90 elements.

A small amount of the matter in the cloud ended up in a nebular disk around the newly formed sun. This material later aggregated into planets, such as our Earth, moons, asteroids, and comets. The composi-tion of these objects is very different from that of the sun. This is the result of a gigantic chemical separation. Elements in dust grains and snow-flakes was largely retained, elements in gaseous form were largely driven away by particles streaming forth from the sun. In other words, gaseous elements were pushed towards the outer limits of our solar system. Be-cause of this, the comets and planets of the outer solar system have a

chemical composition that is differ-ent from that of asteroids and planets in the inner solar system. Neverthe-less, when did our solar system formed? All rocks formed from molten liquids are “clocks”. By measuring the concentrations of the radioactive mother isotopes and their decay product (the daughter isotopes), it is possible to establish precisely the time when the rock has been formed.

Some of the stony meteorites that fell on Earth are considered to record the time the solar system (in-cluding the planet Earth) formed. Their age is 4.6 billion yrs. (dated with Rb-Sr, K-Ar, U-Th methods). Further more, the oldest rocks gath-ered on the moon’s surface also pro-vides this age of 4.6 billion yrs. An-cient rocks can be found at the moon’s surface because, unlike that of the Earth, it has no fluid water (no erosion) and is characterized by only weak tectonism. The main constituents of the meteorites that fall on the Earth’s sur-face are oxides of silicon, iron, and magnesium and metallic iron. These objects are pieces broken loose during collisions between objects in the asteroid belt. In chondrite-bearing meteorites (chondrites are stony meteorites that contain “chon-drules”. Chondrules are one mm-sized, spheroidal granules containing chiefly olivine and enstatite/bronzite), the metal and silica phases are ran-domly mixed on a millimeter-scale. This is taken as the initial form for the material ultimately built into the planets. By contrast, in meteorites,


that do not contain chondrules, the silica and the metal phases are sepa-rated.

From this, we get the idea that in the asteroids from which these me-teorites formed, dense metallic iron trickled to the core and the silica phase wrapped itself around this me-tallic core as a silica mantle . This theory may explain the buildup of the Earth as geoid with an iron core and a silica mantle. Isotope clocks suggest

that the separation into core and man-tle be accomplished very early in Earth’s history. It is likely that the volatile elements that make up the Earth’s atmosphere and oceans were purged from the Earth’s interior at the time of core formation. By contrast, the Earth’s crust has formed and re-formed over the entire history of our planet.

Important Terms • Big Bang • Chondrites • Cloud-cluster-galaxy • Core

• Doppler shift • Helium • Hydrogen • Mantle

• Oxides • Radiogenic isotopes • Red giants • Silicates

Review Questions 1.1 Explain why astronomers believe that the universe expands. 1.2 How did the different chemical elements of our solar system form? 1.3 Why did the planet Earth separated into a metallic core and a silica mantle? 1.4 Explain why the planets at the outer margins of our solar system have a differ-ent geochemical composition than those that are located closer to the sun? 1.5 How do astronomers believe that the sun in our solar system formed? Note The Genesis of the Earth and the Archean and Precambrian evolution of our world will also be the topic of a later course: Precambrian Earth Systems (450164)


2. THE PROTEROZOIC/PRECAMBRIAN WORLD

Introduction Since the last century, the interval of earth history that proceeded the Phanerozoic Eon has informally been known as the Pre-Cambrian (the time before the Cambrian) or more correctly the ‘Proterozoic’. The Pre-cambrian includes nearly 90% of geologic time (or the equivalent of more than 21 hours of a 24 hour-day), ranging from 4.45 billion yrs. ago, when the Earth formed, to the start of the Precambrian Period about 4 bil-lion yrs. later. Two eons are formally recognized within the Precambrian: the Archean and the Proterozoic. We will subdivide this first chapter according these two eons of the Pre-cambrian. 2.1 The Archean

Introduction The Archean Eon includes about 45% of the geologic history of our Earth, from about 4.6 to 2.5 billion yrs. ago. During this span of time, the Earth formed and underwent enor-mous physical changes and life de-veloped on it. However, much of the early evolution of our planet remains poorly known. This because Pre-cambrian rocks form less than 20% of the total area of exposed rocks at the

Earth’s surface. Erosion has de-stroyed many Precambrian rocks and metamorphism has altered others. Other Precambrian rocks lie buried under younger sedimentary and vol-canic rocks. Index fossils are seldom because primitive organisms without durable skeletons (that might be pre-served as fossils) predominated until the end of the Precambrian time. Therefore, stratigraphic age correla-tion is largely based on radiometric dating. Most information about the Archean is from cratons , large por-tions of continents that have not ex-perienced tectonic deformation since the Precambrian or early Paleozoic time. A Precambrian shield is a largely Precambrian portion of a cra-ton that is exposed at the Earth’s sur-face. The largest of these is the Ca-nadian Shield. Early in Archean time, the Earth’s crust seems to have differen-tiated from what it is today. By the end of the Archean, large cratons be-gan to form and plate tectonic proc-esses had started to modify these cra-tons in the same way they do now.

Part A. Global Scale The Archean atmosphere and cli-mate.? We assume that the primitive Earth produced its own secondary


atmosphere by emitting gases from within the planet after it formed. The primary atmosphe re possibly formed when the Earth actually ac-creted. Such a primary atmosphere should be rich in hydrogen, helium, methane and ammonia and thus be reducing. Nevertheless, there is little evidence that supports the concept of an early primary atmosphere. If the core , mantle, and crust became di f-ferentiated when the Earth first be-came liquefied, extensive degassing would heave accompanied this differ-entiation. Degassing by way of vol-canic emissions has continued to the present, albeit at a much lower rate than early in the earth’s history. Hydrogen and helium are the only elements of low enough density to have escaped from the earth’s gravitational field during the initial period of rapid degassing. In the ab-sence of plants, little oxygen entered or formed within the early Archean atmosphere and these small quantities were quickly removed by oxidation of iron minerals and other materials at the Earth’s surface.

More dense, volatile elements and compounds – such as carbon, nitrogen, water, and noble gases (neon, argon, nitrogen, and their chemical relatives) are relatively rare in the Earth and its atmosphere today in comparison to their abundance elsewhere in the solar system. These more dense volatiles must have es-caped from planetary condensates before the later coalesced to form the Earth.

The temperature of a planet’s surface depends on the luminosity of

the star it orbits and on the planet’s distance from this star. It also de-pends on the reflectivity of the planet’s surface and on the “green-house” power of its atmosphere.

This is exemplified when comparing Earth and Venus. Al-though nearly equal in size and bulk composition, the ground surface on Venus is nearly 400°C warmer than Earth’s ground surface. The reason for this difference is that on Venus most of the carbon is in the atmos-phere as CO2. As we know, CO2 is a so-called greenhouse gas. That means a portion of the heat that radiates from the sun to the Earth’s surface is kept within its atmosphere due to the presence of greenhouse gases. The high content of CO2 in the Venusian atmosphere raised the surface tem-perature to 400°C. By contrast, on Earth most of the carbon is stored in crystalline rocks, sediments such as carbonate minerals and organic residue. The amount of CO2 in the atmosphere of Earth is 350’000 times less than in the atmosphere of Venus.

Based on the observation of neighboring stars, astrophysicists know that a young Sun initially emits only little heat. Therefore, Earth should have been a lifeless rock for billions of years, because the faint young Sun produced not enough heat to melt ice into liquid water until about 1 Byr BP. Four billion years ago, the sun was only 75% as bright as it is today. This means that Earth should have been completely covered with ice for most of its history. But geological evidence shows that there was plenty of liquid water as far back


as about 4 Byr BP. This puzzling ob-servation is termed the faint young Sun paradox. Many workers now be-lieve that the early Earth possessed a greenhouse atmosphere of ammonia gasses protected by an outer rim of hydrocarbon based smog. This greenhouse atmosphere might have kept the Earth in the temperature field that is suitable for liquid water.

The early oceans.? The rapid degassing of the liquid Earth released hot clouds of water vapor. Initially, the great heat of the Earth would have kept the water in a gaseous state. When the planets sur-face cooled sufficiently water started to exist in the narrow field between 0 and 99°C where it is liquid (but this value also depends on pressure). Once this temperature window was reached, water would have fallen as rain and remained on the Earth’s sur-face as lakes, rivers, and oceans. Like modern rain, the rains that formed the earliest oceans are assumed to have contained few salts. Salts accumu-lated in the early seawater by water (and dissolved CO2) reacting with minerals at the early seafloors. Formation of Archean rocks and con-tinental crust.? The oldest piece of continental crust dated so far is the so-called Aca-nasta-Gneiss from the Slave Prov-ince in NW Canada (4.06 Byr. old). Nevertheless, it is now assumed that fragments of older lithosphere and liquid water existed long before the Acanasta-Gneiss. This is evidenced in the δ18O record in zircons. Accord-

ing to recent research, Earth between 4.4 and 4.0 was not a magma-red-glowing hostile planet but a place covered by tranquil oceans with small islands protruding from these waters. Mean temperatures were – from a geologic point of view – cool, i.e. in average about 200oC or somewhat less. Beneath this value, a portion of the water, previously only existing as vapor, condensates under the high pressure conditions and formed oceans. The scarcity of previous con-tinental fragments is probably the re-sult of the so-called late heavy bom-bardment at about 3.9 Ga., one of the main meteoric bombardments of the young Earth. Areas underlain by Archean rocks are typified by two main types of rock bodies: ‘greenstone belts’ and ‘granite-gneiss complexes’. Other cherts and iron-rich sediments, known as banded iron formations, are also found in the Archean sedi-mentary belts. For example, the Rho-desian Province of southern Africa consists of about 83% gneiss and various granitic rocks; the remaining 17% are largely greenstone belts. The oldest large, well-preserved greenstone belts are those of South Africa, which date from 3.6 billion yrs. An idealized greenstone belt consists of three major rock units: the lower and middle units are dominated by volcanic rocks and the upper unit is sedimentary. The vol-canic rocks of greenstone belts are typically greenish due to their low-grade metamorphism (chlorite min-erals). The occurrence of pillow ba-salts indicates that much of the vol-


canism responsible for the igneous rocks of the greenstone belts was subaqueous; shallow water and subaerial eruptions are indicated by pyroclastics. Sedimentary rocks are a minor component in the lower parts of greenstone belts but become in-creasingly abundant towards the top. The most common ones are succes-sions of graywacke (sandstone con-taining clay and rock fragments) and argillite (slightly metamorphosed mudrocks). Small-scale graded bed-ding and cross bedding indicate that the graywacke-argillite successions are deposits of ancient turbidity cur-rents. Others were deposited in del-tas, tidal-flats, barrier islands and shallow marine shelf environments.

In summary, detrital Archean rocks seem to indicate the presence of basins of moderate depth flanked by volcanoes that spewed out lava. The banded iron formations (BIF) are occasionally widespread but they are seldom very thick. BIF’s are finely layered iron-rich sedi-ments. The layers are generally 5-30mm thick and they are in turn laminated on a scale of mm and thin-ner. They consist of alternating silica layers (chert, SiO2) interbedded with layers of iron minerals. The origin of these rocks is debated but they form the largest iron-deposits of the Earth (see also Chapter 2.2; Part A; Pro-terozoic Rocks). Granite-gneiss complexes have formed since Archean time as well as during it. They result from such severe metamorphism that most of them teach us little about en-vironments of the Archean Eon. Con-

tinental lithosphere consist primar-ily of thick felsic crust (‘felsic’ means composed of feldspars, feldspathoids, and silica) and they are surrounded by the thinner mafic (‘mafic’ means a rock composed chiefly of dark, fer-romagnesian minerals) crust of ocean basins . In this context, it is important to understand that the Earth’s interior cooled from its mol-ten state primarily by convection, which carried hot material to the sur-face. The primitive crust probably formed rapidly during this brief in-terval of cooling as magma flowed to the surface. Most of the Earth’s early crust was composed of mafic material that rose from the denser ultramafic mantle to form relatively thin ocean crust. Nevertheless, how and when did the felsic crust of continents formed? It is believed that it formed secondarily, mostly from oceanic crust that descended into the mantle in subduction zones. Whilst de-scending and melting, this mafic crust released felsic components whose low density caused them to rise to-wards the surface as magma. This process is called partial melting be-cause felsic materials are melted away from ultramafic materials, which melt only at higher tempera-tures. Archean plate tectonics.? Some Archean rocks appear to record plate movements as shown by de-formation belts between presumed colliding cratons and island arcs. However, ophiolite complexes (ophiolites are fragments of oceanic


lithosphere that were thrust upon con-tinental lithosphere), which mark younger convergent plate margins, are rare. It is understood that Earth’s radiogenic heat production has de-creased during time. Thus, during the Archean, when more heat was avail-able, sea-floor spreading and plate motions probably occurred faster and magma was generated more rap-idly. Another factor that favors some kind of Archean plate tectonics is an episode of rapid crustal growth that occurred 3.0 to 2.5 billion years ago. Like continents today, Archean continents probably grew by accre-tion at convergent plate margins , although they probably grew more rapidly because plate motions were faster. In summary, plate tectonics was probably active in the Archean although it differentiated from the present style of plate tectonics, which began during the Proterozoic when large, stable cratons were present.

Part B. Evolution of Life Basic conditions for life on the planet Earth.? Of all the planets in our solar system, only the Earth is well suited to life, as we know it. There are several rea-sons why the Earth is a reasonable place for life to develop. One of the reasons is that its size is ‘right’. On a much larger planet, the gravitational pull of the atmosphere would be so great that the resulting atmospheric density would exclude sunlight. A smaller planet, on the other hand,

would lack sufficient gravitational attraction to retain an atmosphere with life-giving oxygen. The distance of the sun to the Earth is in the small window that Earth’s temperatures are such that most of its free water is liquid, the form that is essential to life. Venus, for example, is too close to the sun to allow water to survive in a liquid state. Mars, our nearest neighbor farther from the sun, has an atmosphere so thin that liquid water evaporates from the planet’s surface immediately. The questionable earliest forms of life.? We must distinguish between the presence of life in the Archean and its preservation. We must also distinguish between life at the sur-face of our planet and possible life in the pore space of its crust. Some workers believe, that ‘surficial’ life evolved from heat-loving primitive organisms (Archeobacteria) that ex-isted beneath the Earth’s surface where they were protected against the hostile early Archean atmosphere. Possible analogues to this subsurface life are found today at so called ‘black smokers’ at the floors of oceans.

Evidence of early life on Earth is only given where fossil ‘traces’ of this life are preserved. Another prob-lem is the ‘pollution’ of ancient rocks by younger forms of life. Nev-ertheless, some evidence points out that life is as old as the oldest rocks known. Graphite, for example, per-haps reflecting concentration of car-bon by primitive organism, is known


in the oldest sedimentary rocks, the banded iron formations. More direct evidence for early life provided Archean stromatolites. Until today, stromatolites are found along the margins of warm seas but they are scarce in comparison to their former abundance. The oldest struc-tures that are thought to be stromato-lites occur in the Pilbara Shield of Australia in rocks 3.4 to 3.5 billion years old. Actual fossils of cyanobacte-ria and other bacteria have also been tentatively been identified in Archean rocks from e.g. Western Australia. These filaments are though to be about 3.5 billion years old. Bacteria, including cyanobacteria, seem to be the only life forms represented in Ar-chean rocks. Bacteria are single-

celled organisms characterized by a primitive kind of cell that does not have a nucleus and whose DNA is not clustered into discrete chromo-somes. It is not clear whether the ear-liest cells required food and energy from their environment (heterotro-phic) to maintain themselves and to reproduce. Adenosine triphosphate (ATP) the source of energy is easily produced from simple gases, and may well had formed inorganically in the Archean world. Whatever the details of the early history of life on Earth may have been, one thing seems certain: There were no animals and advanced animal-like cells that fed upon bacte-ria and cyanobacteria.

Important Terms • Archean • Archeobacteria • Banded Iron Forma-

tion (BIF) • Black smokers • CO2 • Cyanobacteria • Degassing • DNA

• Faint young Sun paradox

• Granite-gneiss com-plexes

• Greenhouse power • Greenstone belts • Heterotrophic • Liquid Water • Ophiolite • Oxidation

• Oxygen • Partial melting • Pilbara Shield • Pre-Cambrian • Proterozoic • Sea-floor spreading • Shield • Single-celled organ-

isms • Stromatolites

Review Questions 2.1.1 What is the difference between Pre-Cambrian, Proterozoic, and Archean?


2.1.2 On what is stratigraphic age correlation based prior to the Cambrian? 2.1.3 Name the largest Precambrian shield. 2.1.4 Describe the Archean atmosphere 2.1.5 Name the factors that influence the temperature of a planet’s surface. 2.1.6 What are the two main types of Archean rock bodies? 2.1.7 How did oceanic and how did continental lithosphere formed? 2.1.8 Why might black smokers be so important for our understanding of the early evolution of live? 2.1.9 Describe the known Archean life forms.


2.2 THE PROTEROZOIC

Introduction The Proterozoic Eon, which suc-ceeded the Archean Eon 2.5. billion yrs. ago, was in many ways more like the subsequent Phanerozoic Eon in which we life. The persistence of large cratons, throughout the Pro-terozoic Eon produced an extensive sedimentary record of deposition in broad, shallow seas. In addition, more Proterozoic than Archean sedimen-tary rocks remained un-metamorphosed and thus accessible for study. A number of major events have characterized the Proterozoic that include mountain-building events and major periods of glacia-tion.

Part A. Global Scale Proterozoic rocks.? Several rock types are typical for the Proterozoic. Amongst these are banded iron formations, quartzite-carbonate-shales, and red beds. Banded iron formations are sedimentary rocks consisting of al-ternating thin layers of silica (chert) and iron minerals. The iron of these formations is mostly iron oxide (hematite and magnetite), but also iron silica, iron carbonate, and iron sulfide occur. Archean banded iron formation’s are small lens-shaped

bodies measuring a few kilometers across and are a few meters thick. Most of them appear to have been deposited in greenstone belts. Pro-terozoic banded iron formation’s are much more common; they are typi-cally hundreds of meters thick and can be traced for hundreds of kilome-ters. Most were deposited in shallow water. Banded iron formation’s are found throughout the geologic record, but the period from 2.5 to 2.0 billion yrs. represents a unique time in Earth history, a time during which 92% of the Earth’s banded iron formation’s formed.

Iron is a highly reactive ele-ment. In the presence of oxygen, it combines to form rust-like oxides that are not easily dissolved in water. In the absence of free oxygen, how-ever, iron is easily taken into solution and can accumulate in large quanti-ties in the world’s oceans. Because there had been no or very little free oxygen, equally little oxygen was dissolved in the oceans. The marked increase in the abundance of stroma-tolites about 2.3 billion yrs. ago re-sulted in an increase in free oxygen in the oceans, because oxygen is a metabolic waste product of photo-synthesizing cyanobacteria that form stromatolites. Apparently, the increase of free oxygen in the world oceans helped to cause the precipita-tion of dissolved iron and silica and thus the formation of banded iron formation’s.

Continental red beds, red sandstone and shales, first appeared about 1.8 billion yrs. ago, following


the deposition of Proterozoic banded iron formation’s. The red color of these deposits is caused by the pres-ence of ferric oxide, usually as the mineral hematite, which forms under oxidizing conditions. These deposits become increasingly abundant through the Proterozoic and are quite common in the Phanerozoic. Red beds from the Waterberg Group of South Africa are considered being the oldest deposits of this type. The red color of these rocks is related to de-posits that were deposited in conti-nental environments and particularly in fluviatile systems. Proterozoic plate tectonics.? About 2 billion years ago, the so-called Slave Terrane behaved like rigid continental crust when it was rifted and deformed. This is indica-tive for a markedly cooler crust than it had been 3 billion years ago, when magmas were pushing up from the mantle to the surface.

Archean cratons assembled through a series of island arc and microcontinent collisions. These provided the nuclei around which Proterozoic continental crust accreted and formed the much larger cratons. The Proterozoic supercontinent con-sisted of three larger units termed Laurentia, Gondwana, and Baltica. Laurentia, the great northern conti-nent, consisted mostly of North America and Greenland, parts of northwestern Scotland, and perhaps parts of the Baltic Shield of Scandi-navia.

Gondwana, der great southern continent, consisted of Australia,

Antarctica, India, Afro-Arabia, and South America.

Baltica consisted of large por-tions of the present-day Baltic re-gions (East Sea). The first major episode in the Proterozoic evolution of Laurentia occurred between 2.0 and 1.8 billion yrs., during the Early Proterozoic. During this interval, several major orogens developed. Orogens are zones of deformed rocks, many of which have been metamorphosed and intruded by plutons. These cratons commonly delineate the sutures be-tween the smaller cratons that formed e.g., Laurentia. No major episode in the growth of Laurentia occurred be-tween 1.6 and 1.3 billion yrs. Never-theless, during this period extensive igneous activity took place. These volcanic rocks did not increase the area of Laurentia because they were intruded into or erupted onto already existing crust. These igneous rocks are buried beneath Phanerozoic strata in many areas, but they are exposed in eastern Canada, extend across southern Greenland, and occur in the Baltic Shield of Scandinavia. The origin of this volcanism is debated, some workers believe that the huge craton acted as an isolating shield that caused temperature beneath it to rise to the point where non-orogenic igneous activity started. Another major episode in the evolution of Laurentia is the Gren-ville orogeny in the eastern United States and Canada that occurred be-tween 1.3 and 1.0 billion years ago. The Grenville deformation represents


the final episode of continental accre-tion of Laurentia. Proterozoic glacial phases.? Laurentian climates were quite cool, 2 billion years ago. This is shown by glaciers that spread over the land. Deposits of these Early Proterozoic glaciations are spectacularly pre-served in southern Canada but also present in Wyoming, Finland, south-ern Africa, and India showing the large extent of this Early Proterozoic glaciation. Well-laminated mudstones in these sections most likely represent varves that formed in standing water in front of glaciers. Some of these contain dropstones, larger pebbles that were dropped to the bottom of the sea or lake from ice that melted. A second glacial phase oc-curred in the Late Proterozoic, about 850 and 600 million years ago. Til-lites and other glacial deposits of Late Proterozoic age can be found on all major continents of the world. It is possible that most of the Earth was in a cold-house stage then. This is in-dicated by glacial deposits found even in regions that were located close to the equator. Some workers have used the term “snowball earth” and believe that the entire planet - in-cluding the surface of the oceans - were covered with a thick blanket of ice. The Proterozoic atmosphere.? Several factors control the amount of oxygen in the atmosphere. Amongst them, a number of factors prevent the concentration of atmospheric oxygen from increasing to a significant de-

gree. Were oxygen to build up much beyond its present level, for example, weathering would become more in-tense and would consequently con-sume excess oxygen. Furthermore, if plants would markedly increase their bio-mass on Earth and thus would liberate more oxygen, animals and simpler respiring organisms, includ-ing bacteria, would also increase in bio-mass because more plant material would be available for them to feed on. The resulting increase in the rate of oxygen consumption would then offset the increase in oxygen produc-tion by plants.

Many geologists are con-vinced that the Archean atmosphere contained little or no free oxygen. Estimates were made that the free oxygen content of the atmosphere in-creased from about 1? 10% through the Proterozoic. It was not until 400 million yrs. ago that oxygen reached its present level. Most of the atmos-pheric oxygen was released as a waste product of photosynthesizing cyanobacteria. As indicated by fossil stromatolites, cyanobacteria became common about 2.3 billion yrs. ago.

Part B. Evolution and Extinction of Life Stromatolites.? In the course of the Proterozoic time, a great expansion of life issued from simple Archean bacteria. Stromato-lites first became abundant in the fos-sil record about 2.3 or 2.2 billion years ago. This perhaps because of an increase in the areal extent of conti-


nental shelves. Stromatolites re-mained abundant throughout the rest of the Precambrian time and did not decline in number until early in the Paleozoic Era, when animals that had stromatolites for breakfast, lunch, and dinner diversified. Fossil prokaryotic cells.? Remains of fossil cells were first identified in a formation of Ontario and Minnesota known as the Gun-flint Chert. The Gunflint fossils, which are about 1.9 billion years old, display a variety of shapes and appear to represent bacteria or cyanobact e-ria. The earliest eukaryotes.? All forms of life, except cyanobact e-ria and bacteria, are eukaryotes (forms whose cells contain chromo-somes, nuclei, and other advanced internal structures). Cells with a size of more than 20 microns (1/50 mil-limeter) are certainly eukaryotic. Only in rocks younger than 1.4 bil-lion years cells with diameters larger than 60 microns, become abundant. The most obvious records of eu-karyotic life in the Proterozoic are fossil cells called acritarchs. Acri-tarchs are rarely found in rocks older than about 850 or 900 million years. It is interesting that acritarchs suf-fered a mass extinction at the time of worldwide glaciation about 600 mil-lion years ago. Multicellular algae.? The multicellular algae differ from advanced land plants in that they lack multicellular reproductive struc-

tures to protect their eggs and em-bryos. Even the today’s largest forms of algae, the kelp, are fleshy struc-tures that decay easily and are thus unlikely to be fossilized. U-shaped fossils from the 0.9? 0.8 million-year-old Little Dal group of NW Canada, however, have outlines that may represent multicellular algae. Multicellular animals.? Multicellular animals evolved from animal-like protists rather than from multicellular plants. It is likely that certain mobile, predatory animal-like protists evolved into higher animals simply by developing multicellular body forms. In the beginning, the Earth’s ecosystem was relatively simple. This because the early photosynthetic producers did not suffer predation. The only limiting factor was the sup-ply of nutrients essential to their growth. The first animals to feed on algae must have been animal-like protists. Exactly when multicellular animals evolved remains uncertain, but we think that it was not before the Late Proterozoic that these organisms first appeared. An alternative way of finding evidence for organisms that do not have skeletons that might be fossil-ized is to search for fossil traces left by these creatures on the seafloors of Proterozoic oceans. Trace fossils have been found only in rocks less than about 1 billion yrs. old. In many regions, the oldest trace fossils are found above the youngest Pre-cambrian glacial sediments, which suggests that little multicellular ani-


mal life existed before the final gla-cial episode. The Ediacara fauna of Australia is the most famous of Late Precambrian soft-bodied faunas and was the first to be recognized. Probably before late in the Proterozoic Era, the concentration of oxygen in the atmosphere was high enough to support animal-like pro-tists, but too low to support multicel-lular animals. These cannot exist at levels of oxygen below about 10% of

the present level in the atmosphere . Animals that are more advanced than coelenterates were well established before the end of the Proterozoic time. Amongst these were the seg-mented worms the annelids, which include modern earthworms as well as many kinds of marine and fresh-water species. Also present were early members of the phylum Ar-thropods, which includes modern crabs, lobsters, insects, and spiders.

Important Terms • Animal-like protists • Annelids • Arthropods • Craton • Dropstones • Ediacara fauna • Ferric oxide

• Glaciation • Grenville Orogeny • Little Dal Group • Multicellular algae • Orogen • Photosynthesis • Red beds

• Skeleton • Slave Terrane • Snowball Earth • Stromatolites • Suture • Trace fossil • Varves

Review Questions 2.2.1 What are banded iron formations and how do they form? Describe the rela-tion between atmospheric oxygen, stromatolites, and the precipitation of ferric iron. 2.2.2 Name the period (in billion years) in the history of the Earth when the large majority of the banded iron formations formed. 2.2.3 Describe evidence for Proterozoic glaciations. 2.2.4 Describe the evolution of prokaryotic and eukaryotic cells in the Proterozoic. 2.2.5 Why is the Ediacara fauna in Australia famous? 2.2.6 Mention some of the more advanced forms of life that evolved towards the end of the Proterozoic.


3. THE EARLY PALEOZOIC WORLD (CAMBRIAN & ORDOVICIAN)

3.1 Introduction Chapter 3 summarizes the evolution of our planet through the Cambrian and Ordovician systems. These are the first two systems of the Phanero-zoic that encloses the remaining 12% of the Earth history. Both, the Cam-brian and the Ordovician systems have been established more than a century ago in Wales, Great Britain. The Cambrian includes ap-proximately the time from 545-495Ma. The Ordovician starts at 495 Ma and ends at 443 Ma.

Part A. Global Scale Paleo-geographic and Paleoenviron-mental Changes Paleogeography of the Cambrian world.? In Precambrian time, most cratons were fused into one giant super-continent (Laurentia, Gondwana, and Baltica). Gondwana and Laurentia separated by the end of the Protero-zoic and the Iapetus Ocean opened between them.

In Late Cambrian, the ar-rangement of continents was strik-ingly different. By that time, Gond-wana and several smaller landmasses occupied equatorial zones and no continent was close to the poles of

the Earth. This arrangement of land-masses near the equator explains why most Cambrian limestones accumu-lated in tropical or near-tropical climatic zones. The Cambrian Period was no-table for the progressive flooding of continental margins whereas near the end of the Precambrian time, most of the Earth’s cratons stood above sea level. As the Cambrian Period pro-gressed, many parts of Gond-wanaland remained above sea level, partially because of tectonic uplifts caused by orogenic activity between 800 and 400 Ma. This flooding repre-sents one of the largest and most per-sistent sea-level rises of the entire Phanerozoic Eon. This sea level and paleogeographic situation resulted in a characteristic pattern of sediment deposition and recorded several peri-odic mass extinctions of trilobites. At all times during the Middle and Late Cambrian, some parts of central Laurentia stood above sea level. These were the sites of erosion of topographic highs. Rivers trans-ported the erosional products towards the coastal regions where a belt of siliciclastic deposits formed. Sea-ward of these siliciclastic belts were broad carbonate platforms that were often fringed by reefs or stromatolites and that terminated along a steep slope. Muddy deposits and breccias


derived from the platform accumu-lated in deep water near the base of the steep continental slopes. Trilo-bites, the dominant skeletonized ani-mals of Mid-, and Late Cambrian oceans, were distributed around con-tinents in a pattern corresponding to the arrangement of sedimentary belts. Depending on the group of tri-lobites, they lived either on the warm, tropical shelf or in the deep-water setting. The trilobites that in-habited the warm shelf settings were the ones that suffered in the repeated mass extinctions of the Cambrian Pe-riod. These mass extinctions occurred over an interval of no more than few thousand of years and were fol-lowed by adaptive radiations of Cambrian trilobites that occupied several million yrs. It has been sug-gested that a sudden cooling of the seas was the agent of the trilobites’ periodic, massive death. This is sup-ported by the fact that those trilobites that lived in the cool, deep waters marginal to the continents were the group that issued the adaptive radi a-tion that followed the mass extinc-tions. Paleogeography of the Ordovician world.? Three major continents existed in the Early Ordovician. These were Gondwana (Armorica, Bohemian Massif, Africa, East Newfoundland, England, Ireland), Baltica, and Laurentia (N. America, W. New-foundland, Greenland, Scotland, N. Ireland, and small portions of Nor-way). Smaller continental fragments were China and Kazakhstania. The

ocean between Baltica in the south and Laurentia in the north is called Iapetus, or Iapetus Ocean (Fig. 3/2a). Note also the Panthalassic Ocean or Panthalassa and the early Tethys Ocean (Paleo-Tethys) in fig-ure 3/2a. These are important paleo-geographic names that you should know.

After the general rise that oc-curred during the Cambrian, sea level stood high during much of the Ordo-vician time, flooding broad cratonic areas. The movement of two major continents, Gondwana and Baltica, had profound provincial climatic consequences. As late as Mid-Ordovician, the center of Baltica lay far south of the equator. The Ordovician temperature gradient from equator to pole was nonetheless gentle enough to allow diverse marine faunas to occupy the shallow seas of Baltica. As Baltica and the microcontinent of England moved northwards toward Lauren-tia, the brachiopods, trilobites, and graptolites of these two landmasses became increasingly similar to those of Laurentia. It was not until the Si-luro-Devonian time, however, that the Iapetus Ocean closed and Bal-tica was united with Laurentia, Eng-land with Scotland, and the northern part of Ireland with the southern part. The northward movement of Baltica had other effects as well. In Middle Ordovician time, however, almost all of the limestone that accu-mulated in the area that today is oc-cupied by the Baltic Sea was com-posed of skeletal grains and car-bonate mud derived from skeletons


of marine life. In the latest Ordovi-cian, however, numerous carbonate grains started to form what resembles so-called ooids similar to the ones that now accumulate in the Bahamas. Even before geologists knew about plate tectonics, they recognized that Middle Ordovician limestones were probably typical for climatic condi-tions that were temperate or sub-tropical and that the latest Ordovi-cian change to Bahama-type carbon-ate deposition signaled a transition to tropical conditions. Before the ad-vent of the plate-tectonic theory, this unusual local pattern confused geolo-gists considerably. Whilst Baltica moved to the equator and came into the tropical realm, Gondwana experienced a ma-jor glacial episode near the end of the Ordovician. Gondwana glaciation and the end-Ordovician mass extinction.? The mass extinction at the close of the Ordovician was one of the most severe ever to strike life in the oceans, eliminating about a hundred families of marine animals. It devas-tated the tropical reef communities, which by this time was dominated by bryozoans, tabulates, and stro-matoporoids. The other groups that were diminished severely were trilo-bites, nautiloids , brachiopods , and crinoids. Plate movements seem to have played a major role in triggering the crisis. While Baltica moved to the equator, Gondwana moved to the South Pole. Thus, while Baltica be-came warmer, Gondwana became

colder. Several million yrs. before the end of the Ordovician period, glaciers grew in and around the south polar region of Gondwana. As the Ordovician came to its end, Gond-wana glaciation reached a climax that was accompanied by a mass extinc-tion in the marine realm. It has been suggested that the lowering of sea level at the end of the Ordovician Pe-riod contributed to the mass extinc-tion of marine life by reducing the area of shallow seafloor. Several patterns also suggest that cooling of the seas played an im-portant role in the Late Ordovician mass extinction. For one thing, ex-tinction was heaviest in the tropics (that is inhabited by the most tem-perature-sensitive animals), what is what we would expect to happen if seas cooled down on a global scale. In general, oceans tend to re-main warmer than the land in cold regions. This is partially attributable to the fact the albedo (the reflectance of sunlight) is usually higher for land than it is for water. This causes water to preserve more of the heat that comes from the sun than land. More-over, ocean waters from cold regions usually mix with waters from warmer regions. Thus, glaciers may accumu-late on a large body of land in cold polar regions while an ocean in the same region remains ice-free. Shallow seas in central Laurentia.? During Middle and Late Cambrian time, carbonate deposits accumulated in shallow seas and on tidal flats over large areas of the Laurentia craton, and stromatolites were widespread.


At all times during that period, how-ever, at least a small central area of the craton remained partly exposed. Late in Early Ordovician time, a ma-jor change took place. The marginal shelves of Laurentia persisted, but the central area became broadly ex-posed and eroded after the shallow seas moved out to occupy only a nar-row zone near the cratonic margin. This regression depicted a global lowering in sea level.

Part B. Evolution and Extinction of Life The story of early Paleozoic biota is essentially one of life in the sea. It is assumed that certain simple kinds of protists and fungi had made their way into freshwater habitats by this time, but no fossil record of early Paleozoic freshwater life is known. The terres-trial realm, too, was barren of all but the simplest living things. Before middle Paleozoic time, neither insects nor vertebrate animals occupied the land. However, the main reason why stratigraphers have drawn the line between the Proterozoic and the Phanerozoic biota is that in the Early Cambrian a conspicuous fossil re-cord is present. This because now a great variety of external shells and other kinds of skeletons made of du-rable minerals is found. During the earliest Cambrian, the seas became populated a fauna that consisted of small shelled animals. The Tommotian fauna.?

The first diverse biota of animals with skeletons is found in rocks of the Tommotian Stage, an interval representing about 15 Myr. The de-velopments of the types of skeletons that characterize Tommotian faunas constitute a major evolutionary event. It is still poorly understood why so suddenly so many different kinds of skeletons developed. It has been suggested that a chemical change within the oceans triggered the production of these skeletons. Nevertheless, this hypothesis does not explain why some of these skele-tons were composed of calcium car-bonate and others of calcium phos-phate, two compounds with different chemical properties. The evolution of external skeletons is at least understood in their context of protection against enemies. The first multicellular ani-mals must have fed on single-celled creatures and might have fed on lar-ger plants. The effective predation of some animals on others marks a change in the basic structure of eco-systems. The Later Cambrian marine life.? The brief Tommotian interval of Cambrian time was followed by the evolution of many larger marine ani-mals with hard parts, the most con-spicuous of which were the trilo-bites. These arthropods are by far the most conspicuous Cambrian fossils found above the Tommotian faunas. Most trilobites crawled or swam along the seafloor. Many of the trace fossils that are related to trilobites represent scratching or digging activi-


ties while others represent paths of locomotion. Due to the short survival period of many trilobites, 1 Myr. or less, in the Cambrian, trilobites have served as the principal index fossil for Cambrian strata. Algal stromatolites were also more abundant during the Cambrian and Ordovician intervals than in sub-sequent times. Other sessile organ-isms are suspension feeders known as brachiopods that are abundant in Cambrian strata as well. Mollusks are also common in Cambrian strata, but they are small and many of the advanced molluscan groups evolved later in Paleozoic time. Echinoderms were represented in the Cambrian by a remarkable variety of classes, but none of them resembles modern echinoderms such as starfishes, sea urchins, and sea cucumbers. A few other groups of fossils are present in small numbers in the Early Cambrian. These are conodonts, which are ap-parently toothlike structures belong-ing to a group of swimming animals and ostracods, a group of bivalved arthropods that has survived to recent times. Keep in mind that probably many important groups of soft-bodied animals flourished during the Cambrian Period without leaving fossil record. The presence of these soft-bodied animals is most impressively demonstrated in the Burgess shales in the Rocky Mountains of British Columbia. These shales represent an anoxic (no free oxygen) environment of deposition that resulted in the ab-sence of bacteria and predators that could possibly scavenge on death

animals. Therefore, soft-bodied ani-mals that were washed into this deep-water setting were preserved as im-pression and as carbonatization of soft tissues. Most of these creatures were probably plant eaters.

One group of predators that arose very late in the Cambrian Period was the nautiloids. Like the modern mol-lusks with which they are united in the class Cephalopda, nautiloids are predators whose tentacles were used to grasp prey and whose beaks served to tear the prey apart. Cambrian nau-tiloids are quite small, most measured between 2 and 6 cm in length.

Bony plates of very small fishes have been found in Cambrian rocks but they did not belong to biting fishes.

During Early Cambrian time, the archeocyathids flourished. These cone-shaped creatures were attached to the substratum by the tip of their skeletons and were suspension feed-ers. The archeocyathids were partly responsible for the world’s first or-ganic reefs.

The Cambrian adaptive radia-tion of marine animals with skeletons was not without interruption. During the later part of Cambrian time, sev-eral mass extinctions eliminated most of the trilobite species. The Ordovician adaptive radiation.? The last of the Cambrian mass ex-tinctions, at the very end of the Cambrian Period, eliminated large numbers of natiloid and trilobite genera. This is also an example of how and why stratigraphers place a physical boundary between the Cam-brian and the Ordovician: a major


mass extinction clearly and sharply changes the biota present above and below this line. The trilobites never fully recovered from this crisis. Tri-lobites are found in many Ordovician strata but not in abundances or diver-sities comparable to those of Cam-brian limestones. The Ordovician Pe-riod was instead characterized by the adaptive radiation of many other groups of animals. The Ordovician adaptive ra-diation populated the seas with many classes and orders of animals that continued to flourish in later Paleo-zoic periods. An interesting aspect of most of the skeletonized members of the Late Ordovician fauna was that animals that lived on the surface of the sediment rather than within it. Amongst these are the following es-pecially important Ordovician index fossils: the articulate brachiopods, the graptolites, and the conodonts. Articulate brachiopods are the most conspicuous group of well-preserved fossils both in Ordovician rocks and the younger Paleozoic as well. These animals were immobile suspension feeders that rested on sediment, were partially buried in sediment, or at-tached to solid objects.

Graptolites were especially common in Ordovician and Silurian times. They are most frequently found in black shales, partly because they were too fragile to be easily pre-served in sand and partially because many of them were oceanic plankton that sank to muddy deep-sea floors after death.

The wide distribution of cono-donts suggests that these toothlike

structures also represent elements of creatures that swam or floated. The discovery of a carbonized impression of the conodont animal reveals the presence of fins, which suggest eel-like creatures with a swimming mode of life.

Joining the brachiopods as im-portant sessile animals of the Ordovi-cian seafloors were the rugose corals, and the crinoids (sea lilies). Three groups of colonial animals with skeletons also attained importance on Ordovician seafloors. Of these, the bryozoans were the most conspicu-ous. The others, the stromatoporoids and the tabulates attained their greatest importance as reef builders in middle Paleozoic times.

In addition to trilobites, the mobile epifauna of Ordovician time included new varieties of snails (gas-tropod mollusks) as well as the first echinoids (or sea urchins). All five of the living orders of starfishes were already present in Ordovician time.

What is most striking about the post-Cambrian fauna is that it consisted of slightly more than 400 known families by the end of the Ordovician Period, approximately the same number that character-izes all subsequent intervals of Pa-leozoic time. At least three factors may have operated to accomplish this: a) environments might have be-come filled with life to the point where new forms could not have eas-ily evolved; b) the evolution of effec-tive predators might have made it difficult for new forms to evolve; and c) most of the animals that existed might have been too specialized to


give rise easily to other totally new types of life. Reefs of a new type.? By Middle Ordovician time, adaptive radiation had produced a number of new reef-building animals. Some of these Middle Ordovician reefs were built by bryozoans. Stromatoporoids and tabulates also contributed to reef building. These two groups subse-quently expanded to dominate or-ganic reefs during Silurian and De-vonian time. Many of these Ordovi-cian reefs were small, mounds or patch reefs similar to those of the Cambrian Period, other exceeded 100 m in length and 6 to 7 meter in height. The decline of stromatolites.? Stromatolites are only abundant in the Cambrian and Ordovician but by the end of the Ordovician interval, large stromatolites became rare . The types of algae that form stromatolites occur widely in modern seas, but they

only prosper well enough in su-pratidal areas and in hypersaline lagoons to form continuous stromato-litic structures. Marine animals, that feed on stromatolites (i.e. gastropods) are largely absent form both of these kinds of habitats. Ordovician land plants?? The evidence for Ordovician plants that probably invaded land is not yet conclusive. What we know consists of fossilized sheets of cells similar to those that cover the surfaces of mod-ern land plants as well as structures that closely resemble the spores re-leased by primitive land plants of the modern world. The terminal Ordovician mass extinc-tion.? The Ordovician Period concluded with one of the greatest mass extinc-tions in all of Phanerozoic time . In a global scale, 100 families of Ordovi-cian marine animals failed to survive into the Silurian Period.

Important Terms • Adaptive radiation • Albedo • Anoxic • Archeocyathids • Baltica • Brachiopods • Bryozoans • Burgess shale • Cambrian • Carbonate platform

• Cephalopods • Climatic cooling • Conodonts • Continental shelf • Continental slope • Echinoids • Ecosystem • Gondwana • Graptolites • Hypersaline

• Iapetus Ocean • Index fossil • Laurentia • Mass extinction • Mollusks • Mound/patch reef • Nautiloids • Ooids • Ordovician • Organic reef


• Ostracods • Sea-level rise • Skeleton

• Soft-bodied animals • Stromatoporoids • Supercontinent

• Tabulates • Tommotian • Trilobites

Review Questions 3.1 What made stratigraphers draw a boundary between the latest Proterozoic and the earliest Cambrian? 3.2 Describe the large-scale plate-tectonic evolution that took place between Late Proterozoic and Early Mesozoic. 3.3 Describe the relation between climate, sea-level, and the evolution/extinction of trilobites in the Early Paleozoic. 3.4 Describe the role of terrestrial life in the Early Paleozoic. 3.5 Why were soft-bodied animals preserved as imprints in the Burgess Shales? 3.6. Mention the main groups of Early Paleozoic marine life. 3.7 Mention some possible reasons why the number of families of marine life (~400) remained relatively constant throughout the Paleozoic.


4. THE MIDDLE PALEOZOIC WORLD (SILURIAN AND DEVONIAN)

Introduction The Silurian was defined by Roderick Murchinson in 1835 in sec-tions in Wales, U.K. The Devonian was defined in 1839 by Murchinson and Adam Sedgwick in Devonshire, U.K. (you recognize that the Devo-nian is named after the county of De-von).

The world oceans stood high dur-ing most of the Silurian and Devo-nian time, leaving a widespread sedimentary record on every conti-nent. Marine deposition was inter-rupted during the most profound plate tectonic event of the Paleozoic, the suturing of Baltica to Laurentia along a zone of mountain building. This event produced the Caledonide mountains in Europe and the Arca-dian orogen of Northern America.

The broad, shallow epiconti-nental seas of Silurian and Devonian time teemed with life. In the tropical zone, a diverse community of organ-isms built reefs. The first jawed fishes reached the size of a modern-day shark and were advanced preda-tors. The Devonian was also marked by the progressive colonization of land habitats by new forms of ani-mals and plants. In Silurian time, plants were restricted to marshy envi-ronments but formed large forests by

Late Devonian time. Shortly before the end of the Devonian Period, a number of mass extinctions swept away a large numbers of aquatic taxa.

The Silurian contains the time between 443 and 417 Ma, whereas the Devonian starts at 417 Ma and ends at 354 Ma.

Part A. Global Scale Paleo-geographic and Paleoenviron-mental Changes Silurian and Devonian climate and sea-level history.? In general, the Silurian and Devonian were periods when sea level stood high. Early in Silurian time, sea level rose from its low position at the end of the Ordovician Period. This rise in sea level is probably the result of par-tial melting of the extensive polar glaciers that had formed late in Ordo-vician time. In many parts of the world regression occurred towards the end of the Silurian. The wide-spread occurrence of organic reefs, carbonates, and evaporites suggests that middle Paleozoic climates were relatively warm. Climates were not only warm but dry in some regions. Continents and oceans.? An important new paleogeographic feature to appear during Devonian time was the Old Red Sandstone con-


tinent, named for a well-known, largely Devonian sandstone unit of the British Isles. The Old Red Sand-stone continent had a high relief that formed when Laurentia and Baltica collided and the Iapetus Ocean disap-peared. This collision began in the north during the Silurian and pro-gressed southward, ending late in Devonian time. This suturing was probably followed by a rifting away of Gond-wanaland and then a second suturing event followed. This second event united the Old Red Sandstone conti-nent and Gondwana to form the bulk of the supercontinent Pangea. This supercontinent persisted into the Mesozoic Era. A new glacial interval.? No glacial deposits of Early Devo-nian age are known in Gondwana. It thus has been suggested that Gond-wana migrated away from the South Pole in Late Silurian time, so that its southern portions became warmer. In any case, near the end of the Devo-nian period, glacial deposits were laid down again in Gondwana. It thus ap-pears that a new of polar cooling and glaciation began in Late Devonian time, about when the mass extinction struck marine life in the tropics.

Part B. Evolution and Extinction of Life Recovery of aquatic life after the ter-minal Ordovician mass extinction.? Most of the marine taxa that had flourished during the Ordovician Pe-

riod re-diversified after the terminal Ordovician mass extinction. One group failed to recover fully, the tri-lobites. They were less conspicuous in middle Paleozoic than in early Pa-leozoic. Groups that recovered well during the middle Paleozoic were the bivalve and gastropod mollusks , and the brachiopods. The bivalves ex-panded their habitats by invading non-marine habitats as freshwater lakes and rivers. On the seafloor, bryozoans re-diversified and cri-noids increased in variety. Acri-tarchs were the dominant group of fossil phytoplankton in middle Paleo-zoic time. One of the most spectacu-lar Early Silurian adaptive radiations, however, was that of the graptolites. Silurian reefs.? Most of the Silurian radiation of ma-rine life did not vastly alter marine ecosystems but, instead, represented the refilling of niches. Builders of organic reefs did diversify in new ways, and in some of the shallow wa-ter settings, they produced reefs much greater than the Cambro-Ordovician ones. Reefs of the tabu-late-strome type diversified and per-sisted for about 120 my. until late in the Devonian Period. The success of these reefs was a result of mid-Paleozoic adaptive radiation of tabu-lates, colonial rugose corals, and stromatoporoids.

During the Silurian Period, tabulate-strome reefs attained heights of 10 m above seafloors and some were longer or wider than 3 km. Dur-ing the Devonian, tabulate-strome reefs assumed enormous propor-


tions. They took the form of elongate barriers, atolls with central lagoons, and platforms. The most spectacularly ex-posed tabulate-strome complex of Middle and Late Devonian age is found in the Canning basin in west-ern Australia. The outcrops of this reef complex ranges some 350 km along the northern margin of the Canning Basin. This reef is called, in analogy to the present-day one, the Devonian “Great Barrier Reef” of Australia. An unusual and unexplained fea-ture of those reefs, however, is that column-shaped stromatolites also contributed to their growth. As we have seen, few stroma-tolites have formed since Ordovician time except in environments that are hostile to other animals. New swimming animals.? Perhaps the greatest change in the na-ture of aquatic ecosystems during middle Paleozoic time resulted from the origin of nektonic (swimming) animals, many of which were preda-tors. The most important of these among the invertebrates were the ammonoids. These were the coiled cephalopod mollusks that evolved from straight-shelled nautiloids during Early De-vonian time. Ammonoids diversified rapidly were distinctive, widespread, and relatively short-lived. Thus, they serve as very important guide fossils in rocks ranging in age from Devonian to lat-est Mesozoic. The eurypterid arthropods were a second important group of in-vertebrate predators that proliferated during middle Paleozoic time. Unlike ammonoids, eurypterids ranged into brackish and freshwater habitats. Other swimmers that were adapted to both marine and freshwa-

ter conditions were the fishes. The Devonian Period has been called the “Age of Fishes” because fish skele-tons in marine settings, in lakes, and rivers are so widespread. This reflects the fact that there were no vertebrates on Earth other than fishes until the very end of the Devonian Period. One of the most conspicuous groups of the fishes was the ostracoderms (means “bony skin”). Late in Silurian, another, quite different group of small marine and freshwater fishes made their appear-ance. These were the acanthodians , elongate animals with numerous fins supported by sharp spines. Unlike os-tracoderms, many acanthodians were predators that fed on small aquatic animals.

During the Devonian Period, a great adaptive radiation added new jawed fishes and new levels to the food web of the aquatic habitats. At the top of this web were the largest representatives of this group, the pla-coderms. These heavily armored, jawed fishes almost disappeared be-fore the beginning of the Carbonifer-ous.

Sharks were amongst the most important groups of fishes in Devonian seas. They are the last major group of fishes to evolve. Other important groups of fishes that evolved were the ray-finned fishes (that today include most fishes as trout or tuna), lobe-finned fishes, and lungfishes that survived up to the present day. Invasion of land by plants.? It is difficult to imagine how the landscape looked in Precambrian and early Paleozoic times, before there were conspicuous terres-


trial plants. Certain environments must have been populated by algae and other simple plants and plant-like or-ganisms, but there were no forests or meadows, and there must have been large areas with barren rocks and soils. Thus, one of the most important events revealed by the fossil record of Silurian and Devonian life was the invasion of terrestrial habitats by higher plants. The first upright plants that made their way onto the land lacked roots, vascular systems (special tubes to carry water and nu-trients upward from their roots), and leaves that made their descendants so successful. These first plants were simple rigid stems. The horizontal por-tions stabilized them and the vertical por-tions transported materials and manufac-tured food without the benefit of vascular systems or leaves. These Silurian plants were rather semi-aquatic marsh dwellers than fully terrestrial plants. These plants were spore bearing , and spore-bearing plants are found up to the present day. The ferns are a familiar example. The first adaptive breakthrough for life on land was the evolution of vascular tissue. It is apparent that near the end of the Silurian Period vascular tissues evolved. Because of this, a great adaptive radiation took place in Early Devonian time. Plants also evolved roots for support and for effective absorption of nutrients as well as leaves for capturing large quantities of sunlight. As the Devonian Period pro-gressed, however, the appearance of a second adaptive “innovation”, the seeds, liberated land plants from their

dependence of moist conditions that are needed for the reproduction of spore-bearing plants. Today, most large plants grow from seeds. How-ever, advanced seed plants with flow-ers did not evolve until Cretaceous time. Flowers attract insects and birds, which carry pollen from flower to flower. More primitive, flowerless seed plants rely instead on primarily wind to carry pollen from plant to plant. Flowerless seed plants originated in Late Devonian time and soon became important elements of late Paleozoic terrestrial floras. During Late Devonian time, for the first time, dry land was in-vaded on a vast scale. Seed plants soon grew into trees with strong, woody stems. These were the worlds first forests. One of the consequences of the spread of landplants was that, for the first time in earth history, plants carpeted soils and stabilized it against erosion. This had clear influ-ences on the morphology of land-scape and the type of rivers. In the Precambrian and early Paleozoic time, braided rivers, reflecting rapid erosion, transported material to the oceans. In middle Paleozoic, when plants stabilized soils, rivers begin to meander. Invasion of land by animals.? The Rhynie Chert of Scotland yields some of the oldest known nonmarine arthropods , including scorpions and flightless insects. Arthropods probably invaded dry land in Late Silurian, but it was not until the Late Devonian interval


that vertebrate animals made a simi-lar transition. The amphibians, four-legged vertebrates as salamanders and frogs, are most closely related to fishes. These animals are also legless and aquatic early in life. They hatch from eggs in water, spend their juve-nile existence there and then usually metamorphose into air-breathing land-animals. In Greenland, fossils of maybe one of the first creatures (Ich-thyostega) that made the step from sea to land were found. Ichthyostega represents what commonly is termed a “missing link” (between fishes and land animals). Vascular plants colonized the land about 80 Myr before verte-brate animals. This because a food web must be built upward from the base. Animals cannot life on land in the absence of edible vegetation. Amphibians evolved so late in the Devonian Period that they played no signifi-cant role in the ecosystem of this time. It was the Carboniferous and Early Permian that might be called “Age of the Amphibi-ans”.

Late Devonian mass extinction.? One of the most devastating mass extinctions of marine life in all of Phanerozoic time took place near the end of the Devonian Period. Geologists divide the Upper Devonian Series into two stages, the Frasnian Stage, and the Famen-nian stage. The great extinction occurred late in Frasnian and early in Famennian time. On the land, vascular plants seem to be unaffected by this Late Devonian crisis. In the marine realm, brachiopods were hit hard, only about 15% survived. Ammonoids , gastropods , and trilobites also suf-fered. Two communities collapsed almost totally. These were the tabu-late-strome reefs, and the pelagic community (plankton and nekton). Acritarchs (phytoplankton) suffered heavy losses and placoderms almost disappeared. Again, tropical taxa were most severely affected. This again suggests that a global cooling was the agent of mass extinction.

Important Terms • Acanthodians • Acritarchs • Algae • Ammonoids • Amphibians • Arthropods • Caledonide moun-

tains • Canning Basin

• Crinoids • Devonian • First forests • Fishes • Flightless insects • Jawed fishes • Land animals • Land plants • Leaf

• Nekton • Ostracoderms • Pangea • Placoderms • Root • Scorpions • Seed • Sharks • Silurian


• Tabulate-strome reefs

• Vascular system • Wind

Review Questions 4.1 Describe the Silurian and Devonian climate. 4.2 Describe the Paleozoic evolution of the Old Red Sandstone Continent (Laurus-sia/Laurasia). 4.3 Describe the Paleozoic evolution of Pangea. 4.4 Why is the Canning Basin in western Australia famous amongst sedimentolo-gists? 4.5 Describe the evolution of nektonic animals in the Middle Paleozoic. 4.6 Describe the Middle Paleozoic invasion of terrestrial habitats by plants. 4.7 Describe the Middle Paleozoic invasion of terrestrial habitats by animals. 4.8 Name the biota that was most affected by the Late Devonian mass extinction.


5. THE LATE PALEOZOIC WORLD (CARBONIFEROUS AND PERMIAN)

Introduction The late Paleozoic interval of geo-logic time includes the Carbonifer-ous Period, when new groups of ani-mals and plants exerted influence over the accumulation of sediments, and the subsequent Permian Period, when many of these organisms died out in the greatest mass extinction in all of the Phanerozoic time. The Carboniferous System was for-mally recognized in Britain in 1822, early in the history of modern geology. The name “Carboniferous” was chosen to re-flect the system’s vast coal deposits, which had long been mined for fuel. Roderick Murchinson, who established the Silurian System and co-established the De-vonian, recognized and named the Permian in 1841 in Russia. He named it after Perm, a town on the western flank of the Ural Mountains, where an expedi-tion had taken him in 1840. The late Paleozoic world was marked by major climatic changes that today are reflected in the distri-bution of rocks and fossils. Glaciers, for example, spread over the South Polar Region of Gondwana during the Carboniferous period and the re-ceded during Permian times. Another major event took place near the end of the Paleozoic Era. This was the attachment of Gondwana to the Old Red Sand-

stone continent, accompanied by mountain building (Hercynian or Variscan orogens) in Europe and in Eastern North America. The Carbon-iferous starts at about 354 Ma and ends at 290 Ma. The Permian begins at 290 Ma and ends at 248.2 Ma.

Part A. Global Scale Paleo-geographic and Paleoenviron-mental Changes The Early Carboniferous (Mississip-pian, 354-323 Ma) climate.? Sea level, which had declined near the end of the Devonian Period, rose during Early Carboniferous time, so that warm shallow seas spread broadly across continental surfaces at low latitudes. Consequently, limestone accumulated over large areas, often with crinoid debris as their most important com-ponent.

Tillites (glacial deposits) found near the portions of Gondwana that were close to the South Pole in-dicate, that throughout Carboniferous time, large sheets of Gondwana were blanketed by ice sheets. Nearer the equator, warm moist con-ditions prevailed in some continental areas. Coal-swamp floras, for exam-ple, which first became established early in Carboniferous time, flour-


ished along the NE margin of the Old Red Sandstone continent. Middle Carboniferous boundary events.? The transition from Early to Late Carboniferous (Pennsylvanian – 323.0 to 290) time was marked by two very important events. These are: a global decline in sea level, and heavy extinction of marine life. In many parts of the world, the drop in sea level is evidenced by a discon-formity in shallow marine deposits. In North America, for example, the marine records that represent the Mississippian and the Pennsylvanian are separated by a hiatus that includes about 4 Myr. in some areas.

Among the marine groups that suffered heavy extinction during this interval were the crinoids and am-monoids , which lost more than 40 and 80% of their genera, respectively. Presumably, sea level fell because water was locked up in expanding ice shields.

During middle Carboniferous, the northward movement of Gond-wana caused that continent to collide with the Old Red Sandstone conti-nent. The mountains that formed dur-ing this collision are labeled Her-cynides, and the orogeny as a whole known as the Hercynian or Varis-can orogen. The Late Carboniferous period.? On the land, latitudinal temperature gradients steepened during Late Carboniferous time. Differences be-tween equator and polar regions were quite extreme. Continental gla-ciers pushed northward (from the South Pole) to within nearly 30° of the ancient

equator, a latitude where subtropical condi-tions have prevailed during most of the Phanerozoic time. It seems amazing that tropical coal swamps flourished in North America and Western Europe not much fur-ther north than the northernmost Carbonif-erous glaciers. The complex Permian climate.? Because of complex topographic conditions and steep climatic gradi-ents, the floras that characterized Permian time were probably more provincial than those of other Phan-erozoic periods. The Permian floras remained dis-tinct although they were not separated by vast oceans. In Permian time, the suturing of Siberia to Eastern Europe along the Ural Mountains resulted in the nearly complete assembly of Pangea. Southeast Asia re-mained as the only separate landmass of large size, and it would become attached during the Mesozoic Era. Contributing to the distinct separation of floral provinces were several mountain chains, including those of the Hercynian, which formed during the suturing of Gondwana to the Old Red Sandstone continent. Furthermore, polar regions remained quite cold and equatorial regions quite hot. As a result of this, the Late Per-mian floras of low latitudes remained dis-tinct from the Glossopteris flora to the south and also from the flora of Siberia, a cont i-nent that, although now attached to Europe, remained near the North Pole. Southeast Asia was still a separate continent, and its flora had become unique. The Euramerica flora had also broken down into more local floras separated by barriers such as moun-tain chains. The various floras had one thing in common: They changed dramatically in the course of the Permian. Terrestrial plants are highly


sensitive to climatic conditions, and it is believed that Permian floras changed in response to climatic changes. In general, plants adapted to moist conditions gave way to ones favored by drier habitats. In the north, the coal swamp floras were replaced by plant communities dominated by conifers such as Walchia. In the south, the Glossop-teris flora of Gondwana, which was adapted to moist conditions, gave way to the Di-croidium flora. The highly arid conditions of Permian time resulted in the deposi-tion of great thicknesses of evaporites in the SW United States and in N Europe. There is, in fact, a greater concentration of salt deposits in the Permian than in any other geo-logic system. In addition, dune de-posits are unusually common in the Permian System, where they record the locations of ancient deserts.

Part B. Evolution and Extinction of Life Marine life of the late Paleozoic in-terval did not differ markedly from that of Late Devonian time. An ex-ception is the absence of several groups of marine organisms that died out in the Late Devonian mass extinc-tion.

The changes that took place on land were much more profound. Numerous insects appeared and many new types of spore-bearing trees colonized swamps. Marine life.? Some groups of marine life never re-covered from the mass extinction of

Late Devonian time. Tabulates and stromatoporoids, for example never again played a major ecological role. The ammonoids rediversified quickly and assumed an important ecological position. Also persisting from the De-vonian time were sharks and ray-finned bony fishes. In general, heav-ily armored taxa such as the pla-coderms that ruled Devonian seas gave way to more mobile forms. The ability to swim rapidly became a ne-cessity. Following the decline of the tabulate-strome reefs, organic build-ups remain poorly developed throughout the Paleozoic time be-cause of the scarcity of effective, frame-building organisms. Corals of the type that build modern reefs did not evolve until the Triassic Period. Certain groups of animals (bryozoans, crinoids, and fo-raminifera) also contributed vast amounts of skeletal debris to the for-mation of bedded limestones. Pro-ductid brachiopods enjoyed particu-lar success. Crinoids expanded to their highest diversity early in the Carbon-iferous period. They formed mead-ows in many areas of the seafloor. Lacy bryozoans were sheet-like, colonial suspension feeders that stood above the seafloor. These or-ganisms not only contributed skeletal debris to limestones but also trapped sediment to form reeflike structures. The fusulinids, a group of benthic foraminifera underwent an enormous adaptive radiation during the Late Carboniferous and Permian.


Some of them exceed 10 cm in length. Terrestrial flora.? Plants gave the Carboniferous Period its name, and in no other geologic in-terval are plant fossils more con-spicuous. These swamp floras from the warm regions of Gondwana formed coal deposits that typically contain stems and leaves where it re-mained low-grade coal. Because it takes several m3 of wood to make one m3 of coal, it is evident that the vast Late Carboniferous coal beds repre-sent an enormous biomass of origi-nal plant material. The most impor-tant coal-swamp genera were Lepido-dendron and Sigillaria. Some of the species of these trees grew 30 m tall and measured 1 m across the base.

Coal deposits formed in the cool regions of Gondwana as well. Nonetheless, the Glossopteris flora that produced the coal deposits in Gondwana differed substantially from the so-called Euramerica flora (Europa and North America) of the equatorial region. The Glossopteris flora was adapted to the cool climates of the glacial regime in the south. Many cold climates are strongly seasonal, and seasonal growth of wood pro-duces distinctive tree rings. Carbon-iferous floras of Gondwana in the south and in the north (Siberia) are known for their distinctive tree rings. In contrast, the Euramerican fossil trees that grew near the Carbonifer-ous equator were of the tropical type: They lacked seaso nal rings.

Terrestrial and freshwater fauna.? In late Paleozoic freshwater habi-tats, ray-finned fishes continued to diversify and were joined by freshwa-ter sharks that have no modern rela-tives. For the first time, mollusks also became abundant in freshwater habitats. On land, the insects assumed a very important ecological role. The oldest known insects are from Devo-nian age, but these were wingless forms. By Late Carboniferous time, insects had evolved wings. The earliest flying insects differ from most modern in-sects in that they could not fold their wings back over their body. Insects underwent an extensive radiation before the beginning of the Permian Period. In Early Carboniferous time, the only vertebrates populating the landscape were amphibians, many of which retained aquatic or semi-aquatic. Early Permian amphibians, had the world largely to themselves and thus developed a much broader spectrum of shapes, sizes, and mode of live. Some Carboniferous am-phibians measured 6 m in body length. Amphibians continued to prosper into Early Permian time. Dur-ing the Permian, however, reptiles diversified and began to replace am-phibians in various ecological niches. The oldest known reptiles are found in deposits near the base of the Upper Carboniferous. Reptiles differ from amphibians in their mode of re-production. The key difference is, that whilst amphibians start their life in the aquatic environment and later become terrestrial or semi-terrestrial creatures, reptiles lay amniote eggs. In this egg, the embryo is provided


with a nutritious yolk and a sac that collects waste products. The embryo is also protected by a durable outer shell. This setting allows reptiles to life and reproduce away from water bodies. It is generally assumed that the amniote egg originated in Car-boniferous time, when reptiles evolved. Later reptiles developed an-other feature of great importance: an advanced jaw structure . Carboni f-erous amphibians and early reptiles could close their jaws quickly but they could apply little pressure. By Early Permian time, the pelycosaurs (finback reptiles) had become the top carnivores of wide-spread ecosystems. Dimetrodon was one such carnivore. It was about the size of a jaguar. Dimetrodon be-longed to a group known as mam-mal-like reptiles. In mid-Permian time, there evolved one particular group of mammal-like reptiles that were especially similar to mammals. These were the therapsids. Therap-sids seem to have represented an en-tirely new kind of animal, one so advanced that it was able to diversify very quickly. The terminal Permian mass extinc-tion.? The Paleozoic Era ended with what may have been the greatest mass ex-tinction in all of Earth history. Nearly 20 families of Permian

therapsids failed to survive into Tri-assic time. However, the extinction of therapsids did not occur as a single event in latest Permian. Rather, there were several pulses of extinction, with taxa of large body size suffering most of it and new taxa evolving from smaller survivors. It has been suggested that the extinction resulted from climatic changes that altered the terrestrial plant communities at the base of the therapsids’ food web. In the marine realm, the Per-mian crisis entirely swept away the fusulinids and the rugose corals , the tabulates, and trilobites. The am-monoids survived with a few species into the Triassic. The brachiopods , bryozoans, and stalked echinoderms suffered heavy losses. The bivalve and gastropod mollusks were struck moderately hard. Whatever caused the end Per-mian mass extinction, it obviously was not instantaneous in a geologic sense. In fact, it occurred in a series of steps and spanned several mil-lion years. The overall pattern ob-served suggests that climatic cooling played a major role in the crisis. In addition, sea level dropped substan-tially in Late Permian time, which eliminated the warm, shallow seas that had flooded the continental mar-gins and were home to countless ma-rine creatures.


Important Terms • Amniote egg • Bryozoans • Carboniferous • Climatic cooling • Coal deposits • Coal swamp flora • Dunes • Equator • Euramerica flora • Floral provinces • Foraminifera

• Freshwater fauna and flora

• Fusulinids • Glossopteris flora • Hercynian or Varis-

can orogen • Ice sheet • Mammal-like reptile • Old Red Sandstone

Continent (Laurus-sia)

• Pelycosaurs

• Permian • Polar region • Ray-finned fishes • Reptiles • Rugose corals • Sea-level drop • Spore-bearing trees • Tabulate coral • Therapsids • Tillites • Tree ring

Review Questions 5.1 Why was the name “Carboniferous” chosen for the time interval between 362.5 and 290 Ma? 5.2 Describe the Early Carboniferous climate. 5.3 What happened at the boundary between the Early and Late Carboniferous? 5.4 Describe the Late Carboniferous climate. 5.5 During the Carboniferous, the ability to swim rapidly became more important. Which forms of marine life evolved that could swim more rapidly? 5.6 Why did two different floras, the Glossopteris and the Euramerica flora, evolved during the Carboniferous? 5.7 Why are reptiles, in terms of evolution, more successful than amphibians? 5.8 What are mammal -like reptiles?


6. THE EARLY AND MIDDLE MESOZOIC WORLD (TRIASSIC AND JURASSIC)

Introduction The Mesozoic Era (the interval of ‘middle life’) began with the Triassic Period. The Triassic and the subse-quent Jurassic Period constitute slightly more than half of the Meso-zoic Era. The Triassic System is bounded by the terminal Permian ex-tinction below and by another extinc-tion above. It was the unique fauna of this system that made Friedrich August von Al-berti to distinguish the Triassic in 1834. Von Alberti originally named the system the Trias for its natural division in Germany into three distinctive stratigraphic units (Bunt-sandstein, Muschelkalk, and Keuper). The Jurassic System is labeled after the Jura Mountains in Switzerland and France where the System is especially well exposed. The Jurassic was not formally established, in-stead it gradually became accepted as a valid system during the first half of the 19th cen-tury, when it’s many distinctive marine fos-sils were widely investigated. Life of Early Mesozoic time differentiated substantially from that of the Paleozoic Era. The marine eco-system was expanded by the addition of modern, reef-building corals and large reptiles, which joined fishes as swimming predators. The most dr a-matic event in the terrestrial ecosys-tem was the emergence and diversifi-cation of the dinosaurs. Near the transition of the Pa-leozoic Era to the Mesozoic Era, the great supercontinent Pangea took its

final form, encompassing virtually all of the segments of the Earth’s conti-nental crust. Then, later in the early Mesozoic, Pangea began to fragment again. Before the end of the Jurassic Period, Gondwana was again separate from the northern landmasses. The Triassic starts at 248.2 Ma and ends at 205.7 Ma. The Jurassic starts at 205.7 Ma and ends at 142 Ma.

Part A. Global Scale Paleo-geographic and Paleoenviron-mental Changes Sea level and climate in the Trias-sic.? Sea level rose slightly during the Early Triassic time. As in the Late Permian, however, the bulk of the continental crust stood high above sea level and formed the vast Pangea. The distributional pattern of floras (indicative of the climatic belts) remained much the same as it was in the latest Paleozoic. A Gond-wana flora existed in the south, and a Siberia flora existed in the north. The Euramerica flora grew under warmer, drier conditions at low lati-tudes. Unusually extensive deposition of evaporites indicates a dry climate. Due to the sheer size of Pangea,


many inland regions lay far from the lowstanding oceans. Sea level and climate in the Jura s-sic.? Although sea level underwent only minor changes during Late Triassic and Early Jurassic time, it subse-quently rose until Late Jurassic time. Late in the Jurassic, it remained at high level causing epicontinental seas to flood large areas of the conti-nental margins. The Navajo sandstone in (today) US North America, a thick deposit of wind-blown and accumulated dune sand, was situ-ated 190 Myr ago in a vast, low-latitude de-sert at Pangea’s western margin. Fossil slump masses within these dunes were inter-preted as triggered by heavy rainfall and thus form a rainfall periodicity proxy. Esti-mates of rainfall volumes from these out-crops may suggest that a pronounced annual monsoonal climate delivered at least 170 mm rain during monsoonal summer storms. During dry winter, dunes would have re-sumed their SE-ward migration. There were two biogeographic provinces of marine life in Europe during the Jurassic. The southern, tropical province of the Tethys, and the cooler, northern boreal province. There is little doubt, that tem-perature gradients from equator to pole were gentle throughout the Ju-rassic Period. Plants that appear to have required warmth occupied a broad belt extending to about 60° northern latitude. The breakup of Pangea.? The most spectacular geographic de-velopment of the Mesozoic Era was the fragmentation of Pangea, an event that began in the Tethyan re-

gion. As the Triassic period pro-gressed, the Tethyan Seaway spread farther and farther inland, and even-tually, the craton began to rift apart. The Tethyan ocean (called the ‘Tethys”) subsequently became a deep, narrow arm of the ocean sepa-rating what is now southern Europe from Africa. During the Triassic Pe-riod, this rifting propagated west-wards, ultimately separating North and South America. South America and Africa remained one continent until the Cretaceous Period when the South Atlantic opened. North Amer-ica began to break away from Africa in mid-Jurassic time. During Middle and Late Jurassic time, one arm of rifting passed westward between North and South America, giving rise to the modern Gulf of Mexico.

Part B. Evolution and Extinction of Life Life in the oceans.? Most common marine organisms in Lower Triassic rocks are mollusks (bivalves and gastropods). The am-monites made a dramatic recovery after almost total annihilation in the terminal Paleozoic extinction. Al-though only two ammonoid genera are though to have survived the Per-mian crisis, Lower Triassic rocks yield more than 100 genera of am-monoids. The adapt ive radiation that pro-duced these genera seems to have issued from the single genus Ophiceras, which probably was a descendent of Xenodiscus. The brachiopods also diversi-fied during the Triassic and Jurassic


periods but they subsequently de-clined. Today, they are very sparsely represented in the modern world. Sea urchins, which had ex-isted in limited variety during the Pa-leozoic Era, diversified greatly during the first half of the Mesozoic Era. Early in the Mesozoic, the place of the extinct Paleozoic corals was taken by a group that is still suc-cessful today, the hexacorals. Early reef-like structures of Middle Triassic age were low mounds that stood no more than 3 meters above the sea-floor. Some of the early coral mounds grew in relatively deep waters, suggesting that early hexacorals did not life in association with symbiontic algae. Late in the Triassic or Early in the Jurassic time, hexacorals be-gan to form large reefs. Many kinds of planktonic or-ganisms in Triassic and Jurassic seas left no fossil record, but a few types are well represented in early Meso-zoic rocks. Dinoflagellates under-went extensive diversification during mid-Jurassic time and remain an im-portant group of producers in modern seas. The calcareous nannoplank-ton, another important group of liv-ing algae, made their first appearance in early Jurassic times. The ammonoids and the bel-emnoids played an important as swimming predators. Individual am-monoid species, however, survived for relatively brief intervals. This has made them extremely useful index fossils for the Mesozoic rocks. Fishes developed an especially use-ful organ, the swim bladder. A sac of gas in the body of the animal that allows advanced fishes to regulate their buoyancy.

Sharks were also represented in early Mesozoic sea. The living Port Jackson shark of Australia, is a descendant of the hybodont sharks that evolved in Triassic times. Many of the reptiles that emerged in early Mesozoic seas were creatures that re-sembled ‘sea monsters’. Among these were the placodonts, they had the appearance of enormous turtles. Cousins of the placodonts were the nothosaurs, which seem to be the first reptiles that invade the oceanic realm (note how the amphibians first in-vaded the land, the reptiles then separated to become independent from water, and now the reptiles go back to the aquatic realm!) . A group of more fully aquatic reptiles evolved from these nothosaurs in mid-Triassic time, and these reptiles, known as the plesiosaurs, played an important ecological role for the re-minder of the Mesozoic. They reached the proportions of modern predatory wales, reaching some 12 m in length. By far the most fishlike rep-tiles of Mesozoic seas were the ich-thyosaurs. Ichthyosaurs were fully marine and thus could not easily lay eggs. Instead, they bore live young.

The last marine reptiles to evolve were the early crocodiles. Al-though crocodiles evolved in Triassic time as terrestrial animals, some were adapted to the marine environment by earliest Jurassic time. Terrestrial plant life.? Unlike terrestrial animals, land plants do not appear to have undergone a dramatic mass extinction at the close of the Paleozoic Era. In effect, the transition from the late Paleozoic to the early Mesozoic flora types began before the start of the Mesozoic (this is


an example for the “animal-centered” strati-graphic system that we use. If we would use a “plant-centered” stratigraphic system, many of the present boundaries would shift). The groups that decreased in diversity before the end of the Per-mian were the lycopod trees, which formed the coal swamp floras. Ferns persisted into the Mesozoic Era in greater numbers. Ferns, in fact domi-nate Triassic fossil floras. Most trees that stood above these ferns belonged to the group of gymnosperms (char-acterized by exposed seeds) that had become established during the Per-mian. Most gymnosperms rely pri-marily on wind to carry their pollen from tree to tree. The most diverse flora comprised the cycads, the cy-caeoids, the ginkgos, and the coni-fers. All of the modern conifer families (with exception of the pine family) were present in early Mesozoic time. The cycads, cycadeoids, coni-fers, and ginkgos formed the forests of the Jurassic Period. The cycads dominated to such an extent that the Jurassic interval might well be called the ‘Age of the Cycads’. Ferns of the Jurassic Period were less abundant than those of Triassic time. Generally, the absence of flowering plants such as grasses and hardwood trees would have made Mesozoic floras appear archaic to a modern observer. Terrestrial animal life: The rise of the dinosaurs.? Continuous fossil records of the time span between Late Permian and Early have only been found in the Karoo Basin of South Africa and near the Ural Mountains in Russia.

Just below the Permian-Triassic boundary in both regions, most of the dozens of genera of Late Permian mammal-like reptiles dis-appear. What remains at the start of the Triassic were a few predatory genera and the large herbivore Ly-strosaurus. In the Late Triassic, the dinosaurs quickly rose to domi-nance. Their massive presence was a problem for the early mammals , which did not grew larger than a house cat. Dinosaurs were small at first, but their advantage over the primitive mammals was that they were ex-tremely agile. Dinosaurs did not become gi-gantic before the end of the Triassic time when they reached lengths of more than 6 meters. Dinosaurs fall into two groups. The “bird-hipped” (ornitischian) di-nosaurs were all herbivores, whereas the “lizard-hipped” (saurischian) in-cluded herbivores and carnivores. The largest of all dinosaurs were the sauropods that moved on four legs. By Late Jurassic time, both bird-, and lizard-hipped dinosaurs were quite diverse. Late in the Triassic Period, vertebrate animals invaded the air for the first time as the pterosaurs came into being. These animals had hollow bones that spared weight and long wings.

The oldest known fossil birds are of Late Jurassic age. These feath-ered animals were named “Archae-opterix” which means ‘ancient wings’. This creature is the link be-


tween birds and their flightless ances-tors. Two other important groups also became established in Triassic time. One was the frogs (amphibians of small body size) and the other were the turtles. Mass extinctions.? The Triassic Period ended with one of the heaviest mass extinctions of all time. This crisis struck both on the land and in the sea. In the marine realm, about 20% of all families of animals suffered extinction. Cono-donts and placopod reptiles died out altogether. Also disappearing were most species of bivalves, ammon-oids , plesiosaurs, and ichthyosaurs, although all of these groups recov-ered in Jurassic time . The terrestrial victims included most genera of mammal-like reptiles and large amphibians.

The primary beneficiaries of the extinction on land were the dino-saurs, which radiated rapidly dur-ing the Jurassic and continued to dominate the terrestrial realm during the remainder of the Mesozoic Era. The cause of the Late Triassic extinctions remains unknown. Per-haps significant is that late in Norian time, conifers and other groups of gymnosperms replaced the Di-croidium flora . Some workers be-lieve that this floral transition sig-naled a climatic change. This cli-matic change, however, might have been an increase in aridity rather than a lowering of temperatures. In any case, the biosphere then remained relatively stable for mil-lions of years. At the end of the Ju-rassic Period, there was a moderately heavy extinction.

Important Terms • Ammonoids-

belemnoids • Archaeopterix • Boreal • Calcareous nanno-

plankton (coccoliths) • Crocodiles • Cycads • Dicroidium flora

• Dinoflagellates • Dinosaurs • Euramerica Flora • Evaporites • Ferns • Frogs • Ginkgos • Gondwana Flora

• Gymnosperms • Hexacorals • Ichthyosaurs • Jurassic • Mammals • Mesozoic • Nothosaurs • Ornitischian


• Pangea • Placodonts • Plankton • Plesiosaurs

• Pterosaurs • Saurischian • Sauropods • Siberia Flora

• Tethys • Triassic • Turtles

Review Questions 6.1 What made the stratigraphers draw a boundary between the Paleozoic and the Mesozoic? 6.2 What distinguishes the Tethyan from the Boreal realm? 6.3 Describe the planktonic life in Early Mesozoic oceans. 6.4 Aquatic reptiles were especially successful during the Jurassic. Why so? 6.5 Why would herbivore dinosaurs rather eat ferns than grass? 6.6 Describe the role of mammals in the Early Mesozoic. 6.7 Name the two main groups of dinosaurs. 6.8 In the Late Triassic, the conifers and other groups of gymnosperms replaced the Dicroidium flora. This had consequences for the herbivore and later, for the carnivore animals. Name these consequences.


7. THE CRETACEOUS WORLD

Introduction The Cretaceous Period was in many ways an interval of transition. Fossil biotas of the Cretaceous Period di s-play a mixture of archaic and modern features. They include members of important (nowadays) extinct taxa, such as dinosaurs and ammonoids, as well as important modern taxa, such as flowering plants and fishes that are most diverse in the world to-day. It was also during the Cret a-ceous period that continents moved toward their modern configuration. The Cretaceous System was first described formally in 1822 by a French sci-entist named d’Omalius D’Haloy. For many years before that, however, Cretaceous rocks had been recognized as constituting a strati-graphic interval distinct from the Jurassic rocks below and the sediments above, now labeled Cenozoic. The name ‘Creta-ceous’ derives from ‘creta’, the Latin word for chalk. Chalk is a soft, fine-grained kind of limestone that accu-mulated over broad areas of the Late Cretaceous seafloor. The Cretaceous comprises the time between 142 and 65 Ma.

Part A. Global Scale Paleo-geographic and Paleoenviron-mental Changes

Sea level and climate in the Creta-ceous.? Global sea level was high during the Cretaceous and continental margins were extensively blanketed with ma-rine deposits. During the first part of the Cretaceous, climates grew warmer. About 100 Myr. ago, the average temperature on Earth reached a level perhaps higher than it has ever been since. Temperatures then gen-erally declined during the Late Cre-taceous. The warm climates also re-sulted in the growth of coral reefs as far as 30° latitude. Further evidence of warm temperatures at high lati-tudes is the presence of fossil leaves of breadfruit trees in Cretaceous de-posits in Greenland. However, recent research shows that the concept of the Creta-ceous as a uniformly warm period is an oversimplification. There is clear record of short cool interludes with poles being glaciated. In summary, the Cretaceous climate is a very com-plex system with colder and warmer intervals. Oceanic anoxic events.? During the mid-Cretaceous, intervals of black, shaley muds covered large areas of the seafloor. An apparent connection exists between global temperature, water circulation and the presence or absence of these ‘black


shales’ in the sedimentary record. These shales are known to form where bottom waters are depleted of oxygen (anoxic conditions). It might be that laterally extensive black shales accumulated in shallow seas when unusually poor water circula-tion within ocean basins led to the stagnation of much of the water col-umn. Extensive black shale deposi-tion provides evidence that the Mi d-dle Cretaceous was a particularly warm interval, not even deep sea wa-ters were cold. New continents and oceans form.? Pangea had begun to break apart early in the Mesozoic Era. The smaller continents, however, that formed from this break-up remained tightly clustered at the beginning of the Cretaceous Period. The Cret a-ceous is the interval of a continued fragmentation of Pangea and the dispersion of its daughter continents. Especially significant is the fragmen-tation of Gondwana. At the start of the Cretaceous Epoch, Gondwana was barely attached to the northern continents. By the end of the Cret a-ceous, however, South America, Af-rica, and India had all become di s-crete entities. Only Antarctica and Australia remained attached to one another. This fragmentation and sepa-ration of continents caused new ocean basin to open and narrow ba-sins to grow wider. Most important are the Early Cretaceous opening of the South Atlantic, the Gulf of Mex-ico, and the Caribbean Sea.

A dominant feature of the Cre-taceous world was the great Tethys Seaway. Trade winds drove surface waters westward without obstruction by large landmasses. As in Jurassic time, the Tethys was an essentially tropical belt where carbonate pre-cipitation prevailed. As it had in the Jurassic Period, the largely non-tropical Boreal realm lay to the north of the tropical Tethys. Throughout the Cretaceous Period the North Atlantic ocean probably remained small.

Early in Cretaceous time, the Arctic Ocean remained largely iso-lated from the Atlantic and supported a distinct marine fauna. Later in the period, the huge landmass of the Northern Hemisphere was split into the modern continents of North America, Greenland, and Eurasia and the Arctic Ocean became connected to the North Atlantic.

Part B. Evolution and Extinction of Life Cretaceous pelagic life in the oceans.? Marine plankton had acquired a modern character by the end of the Cretaceous. The evolutionary expan-sion of the diatoms (solitary cells that lived within siliceous structures) was a primary change among the phytoplankton. Together with dinoflagellates and, in warm seas, calcareous nannoplankton (cocco-liths), diatoms must have accounted for most of the photosynthesis that


occurred in the pelagic realm of the Cretaceous seas. Higher in the pelagic food web, the modern planktonic fo-raminifera diversified greatly. This group is known as globigerinaceans . Since mid-Cretaceous time, both the globigerinid foraminifera and the cal-careous nannoplankton contributed vast quantities of calcareous sedi-ments in oceanic areas, whereas be-fore about 100 Myr. ago, little or no calcareous ooze was present on the deep seafloor. During the late Cretaceous time, the calcareous nannoplankton blossomed in warm seas to such an extent that the small plates that formed their outer cell protections accumulated in huge volumes as fine-grained limestone commonly known as ‘chalk’. Still higher in the food web of Late Cretaceous time were the am-monoids and belemnoids. They per-sisted as major swimming carnivores. New were the teleost fishes, a subclass today is the dominant group of marine and freshwater fishes. Reptiles were the largest ma-rine carnivores until the end of the Cretaceous time. Plesiosaurs ex-ceeded still 10 m in body length. Cretaceous seafloor life.? On the seafloor, life began to take a modern appearance during the Cret a-ceous period. Brachiopods declined whereas sea urchins and hexacorals diversified. Other important groups that survived to the present are: ben-thic (bottom dwelling) foraminif-era, bryozoans, burrowing bivalve

mollusks, gastropod mollusks, and crabs. Among new plants that inhab-ited the Cretaceous seafloors was sea grass. Some unique bivalve mollusks that are typical for the Cretaceous were the rudists. Rudists lived like corals, forming large tropical reef-like structures. In mid-Cretaceous time, rudist bivalves assumed the dominant role in tropical reef growth. Flowering plants conquer the land.? The greatest change in terrestrial eco-systems during the Cretaceous Period was the ascendancy of the flowering plants (angiosperms).

Early in Cretaceous time, conifers became the most numerous species and the Age of the Cycads came to a close. This change was short-lived. About 100 Myr. ago (mid-Cretaceous), the first angio-sperms made their appearance on Earth, and during the Late Cretaceous time, they surpassed the conifers in diversity. Today, there are about 200’000 species of flowering plants, whereas only about 550 modern conifer species are known.

The reason why angiosperms diver-sified during the Late Cretaceous while gymnosperms declined is quite evident. Most gymnosperms have reproductive cy-cles of 18 months or longer, whilst flower-ing plants grow from a seed and release seeds of their own in just a few weeks. The second reproductive mechanism of flower-ing plants that has contributed enormously to their success is that their flowers attract insects by color or smell. The insects carry pollen from one flower to another, which represents a much more efficient way to fer-tilize plants than the random transport of pollen by wind.


Large dinosaurs and small mam-mals.? The fossil record suggests a contin-ued dominance of dinosaurs in the Early Cretaceous. Amongst the her-bivores were the duck-billed dino-saurs (Edmontosaurus), and amongst the carnivores the Albertosaurus and Tyrannosaurus. The horned dinosaur Triceratops appears to have been the last of the dinosaurs that survived to the very end of the Cretaceous Pe-riod. Terrestrial crocodiles grew to the remarkable length of 15 meters. The skies were populated by birds, and flying reptiles. The larg-est known species of flying reptiles had a wingspan of 11 meters. Less conspicuous were am-phibians (frogs and salamanders), reptiles (snakes, lizards, and turtles), and mammals. Mammals of the Cretaceous Period like those of the Triassic and Jurassic had small bodies. Several primitive groups died out but the two large modern groups came into being. These are the marsupials (today especially di-verse in Australia), and the placen-tals , a group that involves most living species of mammals. Cretaceous mass extinction.? About 90 Myr. ago (early Late Creta-ceous), a moderately severe episode of extinction eliminated many spe-cies in the marine realm. Compared to the mass extinction that brought the Cretaceous - and the Mesozoic – to an end, this episode is minor. The terminal Cretaceous mass extinction is especially intrigu-

ing because it has been suggested that its cause was the impact of a large meteorite or comet on Earth. A large crater that has a Creta-ceous/Paleogene boundary age and that fits in size to the impact of such a meteorite exists in the Gulf of Mex-ico.

The primary evidence for such an impact is the presence of a so-called iridium anomaly at the Creta-ceous-Paleogene boundary in many areas of the world. Iridium is an ele-ment that is generally very rare in the Earth’s crust, but is abundant in stony meteorites. A meteorite, about 10 km in diameter, exploding on impact, could have released the total amount of excessive iridium observed in the rock record. Another line of evidence for an impact is the presence of shocked quartz. These quartz grains display numerous shock lamellae. Shocked grains of this type are found in the debris of craters at the Earth’s surface.

Complicating the picture is the discovery of one or more small irid-ium anomalies stratigraphically less than a meter or two above or below the principal anomaly. This has led to the suggestion that not one but sev-eral impacts caused the final Creta-ceous mass extinction.

One likely result of such an impact would be that a huge volume of dust and smoke would be thrown up into the atmosphere to circle the Earth. Blocking out a large percent-age of sunlight, this global cloud would greatly lower temperatures at the earth’s surface for a year or longer. This kind of climatic event has


been termed an ‘impact winter’, just as a similar episode, anticipated for the aftermath of a nuclear war (nuclear winter). On land, the dinosaurs were the primary victims of the terminal Cretaceous crisis. Nevertheless, in the Maastrichtian, i.e. in the latest Cret a-ceous but before the final crisis, the dinosaur faunas were already impov-erished. Many seed plants, died out for a short period and ferns monopo-lized the landscape until a more var-ied flora reclaimed it. An interesting biologic pattern is also that plant spe-cies survived that shed their leaves in cold weather (winter). This sug-gests that temperatures remained cool much longer than an impact winter would have lasted.

In the seas, ammonoids, which had flourished throughout the

Mesozoic and the huge swimming reptiles (plesiosaurs and mosa-saurs), were extinct. The reef-building rudists also died out along with certain other groups of bivalves (rudists). Calcareous nannoplankton and planktonic foraminifera suffered heavy losses. The fossil record suggests that many taxonomic groups declined be-fore the end of the Cretaceous Period, but other taxa died out abruptly right at the very end. Extinction was, once more, heaviest in the tropical re-gions . The stratigraphic record sug-gests that seas at low latitudes cooled down during this crisis to the point at which many tropical species could not survive.

Important Terms • Black shales • Bottom water • Chalk • Conifers • Cretaceous • Diatoms • Dinoflagellates • Flowering plants

(angiosperms) • Globigerinaceans

• Impact winter • Iridium anomaly • Marsupials • Oceanic anoxic

events • Phytoplankton • Placentals • Planktonic fo-

raminifera • Rudists

• Sea grass • Sluggish water cir-

culation • Surface water • Teleost fishes • Terminal Cretaceous

mass extinction • Warm climate


Review Questions 7.1 The name for the Cretaceous derives from which term and why was this term chosen? 7.2 Describe the Cretaceous climate. 7.3 What are ‘oceanic anoxic events’ and what is their relation to so -called ‘black shales’? 7.4 Describe the evolution of Gondwana during the Cretaceous. 7.5 Describe the role of plankton during the Cretaceous. 7.6 The Cretaceous is unique for a group of mollusks that think they are corals. Name this group. 7.7 What is the most significant change in the terrestrial plant ecosystem that took place during the Cretaceous? 7.8 Summarize the arguments that suggest a meteorite impact as the main agent for a mass extinction at the Cretaceous/Paleogene transition.


8. THE PALEOGENE WORLD Introduction The close of the Cretaceous Period marked a major transition in earth history. Calcareous nannoplankton has never again abounded in such masses that they formed thick chalk deposits. Almost none of the belem-noids survived, and ammonoids , rudists, and marine reptiles were gone from the seas. On land, the flowering plants of the Paleogene resembled those of the latest Cret a-ceous, but animal life differed dr a-matically from that of the previous period. The mammals took over the space that was left by the dinosaurs. In terms of climate, the most profound change during Paleogene time was the cooling of the Earth’s polar regions . Cenozoic deposits are wide-spread in Europe, and the distinction between their fossil biotas and those of the Mesozoic was recognized long ago. The subdivision of the Cenozoic is less clear. Many geologists divide the era in two periods: the Paleogene Period (including the Paleocene, Eo-cene, and Oligocene epochs). Tradi-tionally, the Cenozoic has been sub-divided into Paleogene/Neogene (Pa-leocene to Pliocene) and the Quater-nary (Pleistocene and Holo-cene/Recent). The Paleogene Period, which will be summarized in this chapter, lasted 42 Myr. (65-23.8 Ma).

Part A. Global Scale Changes Paleogene climate, paleoceanogra-phy, and mass extinction.? During the second half of the Paleo-gene Period, a mass extinction struck both on the land and in the seas. This catastrophe was not as severe as some earlier biotic crises (e.g., the terminal Cretaceous one). The Paleogene in-terval of heavy extinction eliminated few higher taxa but many genera and species. The extinction came in sev-eral pulses that appear to be caused by climatic changes on land. Flowering plants are espe-cially sensitive to climate changes and used as proxy for the reconstruc-tion of the Paleogene climate. Bo-tanical data reveal that after early Eo-cene time, there were three pulses of cooling each more severe than the one before. This cooling was related to the first growth of glacial ice on Antarc-tica. The growth of glacial ice on Antarctica was a prelude to the greater expansion of ice sheets in this region that took place in near the end of the Cenozoic. It was during this late Eocene cooling that the psychrosphere , the cool bottom layer of the ocean, came into being as cold dense polar water began to sink to the deep sea. Deep-sea cores provide a re-cord of microfossils. Amongst them, planktonic foraminifera have been


especially carefully studied. Five successive pulses of change in plank-tonic foraminifera between about 40 and 31 Ma suggest again, that the cooling events were in fact a series of successive climatic events. The mammalian extinctions appear to coincide with the fourth and fifth pulses of heavy extinction of planktonic foraminifera in the marine realm. The first mammalian extinc-tion took place at about the end of the Eocene Epoch, about at 37 Ma. The second took place in mid-Oligocene time, about at 31 Ma. The first event eliminated many species and a mod-est number of genera. The second was less severe, but the huge, rhino-like titanotheres became extinct. It seems evident that climatic changes caused changes in the te r-restrial flora, and these flora changes (at the base of the food web) played a major role in the mammal-ian extinction. These floral changes may have resulted from cooling of the climate as well as from increased aridity. The effect of cooling and in-creased aridity was profound. The Eocene has been a time when moist tropical and subtropical forests covered much of North America and Eurasia. During the Oligocene, sa-vanna’s (grassy plains) spread across large areas of major continents.

Part B. Evolution of Life Marine life.? Perhaps the biggest beneficiaries of the terminal Cretaceous extinction

were the reef-building corals. They reclaimed their dominant reef-building role after they had lost it to the rudists in Middle Cretaceous time. The calcareous nannoplank-ton re-diversified somewhat during the Paleogene. These forms and the diatoms and dinoflagellates account for most of the ocean’s productivity throughout the Cenozoic. Some elements of marine life were new. Perhaps the most distinc-tive amongst these were the whales, which evolved during the Eocene from carnivorous land mammals. Joining the wales were enormous sharks. Other newcomers were pen-guins , a group of swimming birds that evolved during the Eocene, and probably animals such as walruses, seals , and sea lions . Terrestrial plants.? The transition to the Paleogene was apparently not marked by a dramatic change in the terrestrial flora. Instead, the great radiation of flowering plants simply continued. By the beginning of the Oligocene (~37 Myr. ago) about 50% of flowering plants be-longed to groups that are alive today. One major evolutionary event took place during the Paleogene: the grasses reached their full ecological potential until late Oligocene and Miocene times. Terrestrial and freshwater ani-mals.? At the start of the Paleocene Epoch, most mammals were small creatures that resembled modern rodents.


About 12 Myr. later, however, by the end of the early Eocene time, mam-mals had diversified to the point at which most of their modern orders were in existence. Included among the Paleocene mammals were bats, marsupials , and, insectivores. By the end of the Paleocene time, the earliest members of the horse family had evolved as well. In addition, the earliest mem-bers of the elephant order also ap-peared during early Eocene time. The rodents, which had originated in the Paleocene, continued to diversify as well. Other familiar modern carni-vore groups that arrived were the dogs, the cats, and the weasels. Huge flightless birds, the dia-trymas, evolved that are extinct to-

day. In general, flying birds were much less diverse than they are to-day. Most birds waded in shallow water when they were not in flight. The insects took on a modern appearance. During the Oligocene, many Eocene mammal families died out and there were important expansions of many living groups. The rhinoc-eros family included the largest land mammals of all times. Amongst them were the rhino-like titanotheres that stood about 5.5 m high at their shoul-ders. An especially important aspect of the modernization of the mammals during the Oligocene Epoch was the appearance of monkeys and apelike primates.

Important Terms • Antarctic ice shields • Diatrymas • Eocene • Grasses • Monkeys and ape-

like primates

• Neogene • Oligocene • Paleocene • Paleogene • Psychrosphere • Rodents

• Paleogene/Neogene • Titanotheres • Whales


Review Questions 8.1 Name the epochs that constitute the Paleogene. 8.2 Describe the mass extinctions that, during the second half of the Paleogene, struck both on land and in the seas. 8.3 Describe the evolution of the terrestrial floras during the Paleogene. 8.4 Name some of the marine mammals that evolved during the Paleogene.


9. THE NEOGENE WORLD Introduction The Neogene Period holds special interest because it includes the pre-sent, or Recent Epoch. The boundary between the Paleogene and the Neo-gene has no great historical signifi-cance inasmuch as no mass extinc-tion marks this boundary.

During the Neogene major changes in life and the physical fea-tures of the Earth have occurred, al-though the period has spanned only about 24 Myr. All four Neogene epochs, the Miocene, Pliocene, Pleistocene, and Recent (Holocene) were named by Charles Lyell in 1833. Lyell distin-guished the epochs of the Neogene Period based on his observations based on his observations of marine strata and fossils in France and Italy. He noted that Pleistocene strata were characterized by a molluscan fauna in which 90% of the species are still alive in modern oceans. Lyell found that Pliocene strata contained fewer surviving species and that Miocene contained again fewer. In the later 19th century, finally, glacial deposits were recognized on land and found to correlate with the marine Pleistocene record. The Neogene lasted from 23.8 Ma to the Present.

Part A. Global Scale Paleo-geographic and Paleoenviron-mental Changes Neogene climate and glaciations.? Neogene drier climates were, in part, the result of regional tectonic events. Mountain ranges formed that caused heavy rain to fall in the coastal re-gions whereas the land behind these moun-tain ranges received little meteoric water. The trend to drier climate was also in part due to global climatic changes. The presence of ice-rafted, coarse sediments in the SE Pacific shows that by this time Antarctic gla-ciers had begun to flow to the sea. Because of this polar cooling, the early Miocene age marked the begin-ning of a strong latitudinal gradient in the distribution of oceanic plankton. Species at high latitudes differed greatly from those at low latitudes. Analyses of floral composi-tions indicate only modest climatic fluctuations throughout the Neogene. This contrasts the dramatic drops in temperature that marked the Eocene-Oligocene interval.

The cooling and drying of climates that characterizes Oligocene and Miocene time caused grasses to expand their coverage of the land. In contrast, late Pliocene and Pleisto-cene time was marked by strong, rapid climatic fluctuations in the Northern Hemisphere. These


changes characterize the modern Ice Age. At the end of the Miocene, be-tween 5 and 6 Myr. ago, global sea level fell by about 50 m. This so-called Messinian event isolated the Mediterranean Sea from the worlds oceans. Causing the Mediterranean to dry out temporarily. During the Plio-cene Epoch, sea level rose again. This warm interval came to a sudden close with the start of the modern Ice Age, slightly more than 3 Myr. ago.

Part B. Evolution of Life Aquatic life.? As noted by Charles Darwin, inverte-brate life evolves less rapidly than vertebrate life. Thus, the short Neo-gene period has produced only mod-est evolutionary changes in the ma-rine invertebrate fauna . The most dramatic evolution-ary development in Neogene oceans has been the expansion of a group of vertebrate animals, the wales. Dol-phins, specialized small wales, made their first appearance early in Mio-cene time. At the other end of the size spectrum for pelagic life, the globi g-erinacean foraminifera, which barely survived the terminal Eocene mass extinction, expanded again early in the Miocene. On the seafloor, evolutionary changes from Paleogene time were relatively minor. An important devel-opment of the Miocene is the appear-ance of the first algal ridges on coral reefs. The algal ridges protect coral

reefs along coast that are pounded by heavy surf. Unlike the marine diatoms, which expanded in the Mesozoic, the dominant group of freshwater diatoms, the Pennales, did not evolve until early in Cenozoic time. By Miocene time, the Pennales comprised about 2000 known species. Terrestrial plant life.? Throughout the Neogene, climatic changes exerted a profound influence over terrestrial biota. As in Late Creta-ceous and Paleogene times, flowering plant fossils represent our best gauge of climatic shifts. In the world of plants, the Neogene Period might be described as the “Age of Herbs”. Herbs are small, non-woody plants that grow, release their seeds and die. They con-trast for example the trees that life many years. The success of herbs is mainly the result of the worldwide climatic change that took place dur-ing Oligocene and Miocene times, when cooler, drier conditions caused forests to shrink and opened new en-vironments to plants such as herbs and grasses, which prefer open habi-tats, and can survive under dry cli-mates. Terrestrial vertebrate life.? The Neogene Period might well be called the Age of Frogs, the Age of Rats and Mice, the Age of Snakes, or the Age of Songbirds. All four of these groups have undergone tremen-dous adaptive radiation over the past few million years. Rats and Mice dig burrows in dry ground and eat the seeds of grasses and herbs. The success of rodents during Neo-gene time is probably related to the overall


drier climate and the expansion of herbs. The snakes then obviously have flourished largely because of the prolifera tion of frogs and rodents. Also poorly represented before the Neogene time were the songbirds. Presumably, these birds have also profited from the diversification of seed-bearing herbs. Among the herbivore, the horse and rhinoceros family declined. Meanwhile, the Bovidae radiated. The Bovidae include cattle, ante-lopes, sheep, and goats. The giraffe family, the pig family, and the ele-phant family radiated during the Miocene but declined in number since then. The bear and hyena fami-lies were also important Miocene ad-ditions to the carnivore family. Monkeys were present by Oligocene time; the oldest group in-cludes the so-called Old World Monkeys, which now live in Africa and Eurasia. The New World mon-keys started to develop before the end of the Oligocene. Apes, which evolved in the Old World, flourished for a time but since then declined in number of spe-cies. Human evolution.? In addition to the species that now constitutes the human family, the Hominidae consists of just four spe-cies of the ape family. These are two types of chimpanzee, the gorilla, and the orangutan. The human family (Hominidae) did not evolve from the modern ape family (Pongidae). These two families have followed two independent lines of evolution.

We will not review the evolution of the Pongidae but focus on the Homi-nidae. The fossil record of the Homi-nidae was considered so poor for the later part of the Miocene Epoch that previously little was known of the history of the family during this in-terval. Nevertheless, recent findings from Chad, Central Africa have re-vealed six hominid species. The asso-ciated fauna suggests that the fossils are between 6 and 7 Myr. old. The finding of these fossils, 2500 km away from the East African rift, where previously the oldest hominid remains were found, suggests that the hominids were widely distributed and that the divergence between the hu-man and chimpanzee lineages was earlier than indicated by most mo-lecular studies.

The Pliocene yields numerous remains of the genus Australopith-ecus, the oldest known genus of the human family. These deposits range in age from about 1.3 to 4 Ma. This species averaged about 1.2 m in body size. Its average brain capacity ranged from 380 to 450 cm3. By comparison, the mo dern human brain averages about 1330 cm3. The most ancient fossils that have been assigned to Homo occur in strata about 2 Myr. old. The early fossils have been designated Homo habilis that had a relatively large brain capacity (650 to 800 cm3). Homo habilis made stone tools. The next species to follow was Homo erectus. Homo erectus was, in fact, a much larger and more advanced spe-


cies than Homo habilis. Homo erec-tus existed at least 1.6 Myr. ago. This species was widely traveled. It lived not only in Africa and Europe but also in China and in Java. Do to some differences in his skeleton, Homo erectus was superior to us in terms of endurance during walking and running. In effect, our evolution has sacrificed locomotory ability for brainpower. The brain capacity of Homo erectus ranges from about 800 to 1300cm3. The maximum size ap-proximates the average for modern humans (about 1300cm3) but the minimum size is much smaller. Sediments in Africa, repre-senting the interval above the young-est specimens of Homo erectus yielded a poor suite of fossil remains. We do not understand well the evolu-tion from Homo erectus to our spe-cies Homo sapiens. In sediments about 100’000 yrs. old, the well-preserved fossils of the creature known as Neanderthal is found. Its bones were first found in

the Neander Valley of Germany in 1856. Neanderthal did have religion. Burial sites reveal that Neanderthal prepared their death for a future live with flint tools and cooked meat. The record of this humanoid creature ex-tends from Spain to Central Asia, ranging in time up to about 35’000 yrs. ago. The distribution of the Ne-anderthal and the Homo erectus sug-gests that these two species repro-duced isolated. Neanderthals died out during the most recent glacial in-terval. They vanished from eastern Europe about 40’000 yrs. ago and from western Europe perhaps 5000 yrs. later.

At this time, the Cro-Magnon people, that were members of the species Homo sapiens and that were anatomically almost identical to modern humans spread throughout Europe. The Cro-Magnon culture emerged as the Late Neolithic culture in which a variety of specialized tools was invented. The Cro-Magnon painted magnificent cave paintings.

Important Terms • Australopithecus • Brain capacity • Cattle, antelopes,

sheep, goats, giraffe, pigs, elephants, bears, hyenas

• Cave painting • Chimpanzee • Cro-Magnon • Dolphins

• Frogs, rats, mice, snakes, songbirds

• Gorilla • Holocene • Hominidae • Homo erectus • Homo habilis • Homo sapiens • Messinian event • Miocene • Modern Ice Age

• Neanderthal • Neogene • New World Monkey • Old World Monkey • Orangutan • Pleistocene • Pliocene • Pongidae • Religion • Stone tools

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Review Questions 9.1 Describe the mass extinction that separates the Neogene from the Paleogene. 9.2 During the Miocene, the climate was cool and dry. As a consequence, one group of terrestrial plants expanded its coverage of the land. Which one? 9.3 Describe the climate during the late Pliocene and Pleistocene. 9.4 What is the so-called Messinian event? 9.5 The Neogene might be described as the “Age of herbs”. What are herbs in a botanical sense? 9.6 What is the relation between three so different groups of organisms as herbs, mice, and snakes? 9.7 Name some of the more common land mammals that evolved during the Neo-gene. 9.8 What are Pongidae and why was Charles Darwin no correct when he stated that the humans evolved from the apes? 9.9 Homo erectus had a brain capacity that approached the one of modern humans. In one respect, however, he was superior to the modern human. 9.10 Anthropologists believe that Neanderthal did have religion. How do they know?

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GLOSSARY OF IMPORTANT GEOLOGICAL TERMS USED IN THIS COMPILATION

Note: The Glossary below is based on many different sources. An important source with respect to the palaeontological terms is the homepage: Zoom-Diosaurs.com - Dinosaur and Paleontology Dictionary (URL: http://www.zoomdinosaurs.com/subjects/dinosaurs/glossary/indexa3.shtml).

Other important sources are: Bates, R. L., and J. A. Jackson, 1984, Dictionary of Geological Terms (third

edition) prepared by the American Geological Institute: New York, An-chor Books, Doubleday, 571 p.

Kearey, P., 1995, The Encyclopedia of the Solid Earth Sciences: Berlin,

Blackwell Science, 713 p. Acanthodians - Acanthodians were the earliest jawed vertebrates. These early fish (Class

acanthodii) lived from the Ordovician to the Carboniferous period. Although most Acanthodians were small, averaging roughly 5-6 inches (13-15 cm) long, some were much larger (for example, the genus Xylacanthus, known from its huge jaws, is thought to have been perhaps 3 feet (1 m) long). Some Acanthodians may have been primitive shark-like fish.

Acritarchs – Apparently unicellular, microscopic organism of unknown or uncertain bio-logic relationship. The range from Precambrian to Holocene but are especially abun-dant in the Precambrian and early Paleozoic.

Adaptive radiation - Adaptive radiation is the diversification of a species as it adapts to different ecological niches. If successful, the species become specialized for the new environments (the mechanism being natural selection), and they eventually evolve into different species.

Albedo – The percentage of the incoming radiation that is reflected by a natural surface such as the ground, ice, show, water, clouds, or particulates in the atmosphere.

Algae – Photosynthetic, almost exclusively aquatic plants of a large and diverse group (the Algae). They range in size from simple unicellular forms to giant kelps several meters long. Algae range from the Precambrian.

Alpides – The greatest east-west orogenic belt that includes the Alps of Europe and the Himalayas and related mountains of Asia.

Ammonites - An early mollusk, a fast-moving predatory marine invertebrate (a cephalo-pod). These animals were protected by a shell (usually spiral-coiled) that contained many air filled chambers; the animal lived only in the outer chamber. Ammonites ranged in size from under an inch to about 3 m in diameter. They appeared during the Devonian and went extinct during the K-T extinction, 65 million years ago. The clos-est living relative of the ammonite is the chambered nautilus. Ammonites were named

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for ‘amun’ (also spelled Ammon), an ancient Egyptian God who is pictured as having ram's horns behind each ear (which look like ammonites). Ammonite fossils are found in great quantities and are used as an index fossil.

Amniote egg - A membrane that surrounds the embryo and helps retain fluids. This lets an animal lay eggs other than in the water (without having them dry out). Mammals, amphibians, birds, dinosaurs, turtles, and lizards are amniotes.

Amphibians - (meaning "double life") are vertebrate animals that live in the water during their early life (breathing through gills), but usually live on land as adults (and breathe with lungs). There are three groups (orders) of living amphibians: newts and salaman-ders (urodeles); frogs and toads (anurans); and caecilians (the worm-like gymno-phiones).

Annelids – Any wormlike invertebrate belonging to the phylum Annelida, characterized by a segmented body with a distinct head and appendages.

Angiosperms - (meaning "covered seed") are flowering plants. They produce seeds en-closed in fruit (an ovary). They are the dominant type of plant today; there are over 250,000 species. Their flowers are used in reproduction. Angiosperms evolved about 140 million years ago, during the late Jurassic period, and were eaten by dinosaurs. They became the dominant land plants about 100 million years ago (edging out coni-fers, a type of gymnosperm). Angiosperms are divided into the monocots (like corn) and dicots (like beans).

Anoxic – Oxygen free (suboxic = oxygen poor), commonly referring to the Oxygen con-tent of water.

Archaeopterix - (meaning "ancient wing") is a very old prehistoric bird dating from the Jurassic period, about 150 million years ago. It had teeth, feathers, three claws on each wing, a flat sternum (breastbone), and a long, bony tail.

Arthropods - Arthropods are a group of animals with exoskeletons made of chitin, seg-mented bodies, and jointed limbs. Insects, arachnids, trilobites, crustaceans, and others are arthropods.

Australopithecus - In 1924, Raymond Dart discovered a fossil in a limestone quarry in South Africa. This fossil was the remains of an immature primate. Raymond Dart named the fossil Australopithecus africanus, and this discovery was the beginning of the hominids, (humans). Throughout many years, skeletal fragments of the Australo-pithecus species have been found in Upper Pliocene or Lower Pleistocene deposits in Africa, Java and China. Scientist agree that the Australopithecines' belong to the same family, the Humans. Due to this conclusion, scientist divided the Australopithecus or "Southern Ape" into four species, the Afarensis, Africanus, Boisei and Robustus (source: http://www.dc.peachnet.edu/~pgore/students/f97/glenda/australopithecus.htm)

Baltic shield – A Proterozoic craton. Baltica – A landmass in the Middle Ordovician Iapetus ocean. Includes the Baltic shield. Big Bang - The prevailing theory about the origin and evolution of our Universe is the

so-called Big Bang theory. Black shales - Organic-rich intervals in ancient marine deposits, known as "black shales"

in basins and shelves, were formed and largely investigated through geological record. During the Lower Jurassic (Early Toarcian), black shales are distributed wide in many sectors of Tethys, constituting an "Oceanic Anoxic Event". Perhaps even more exten-sive black shales are known from the Middle Cretaceous.

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Boreal– Pertaining to the north, northern. Brachiopods - (meaning "arm feet") are a phylum of animals also known as lamp shells

(bottom-dwelling marine invertebrates that have two dissimilar protective shells held together with a hinge, and superficially look like mollusks). Brachiopods evolved dur-ing the Cambrian Period, roughly 570 million years ago. In the late Ordovician period mass extinction (about 438 million years ago), over half the Brachiopod species went extinct. There are about 260 living species of Brachiopods living worldwide.

Bryozoans - (meaning "moss life") are a phylum of small invertebrate animals that live in salt water (or occasionally in fresh or brackish water) and are also called moss ani-mals or sea mats. Bryozoans live in colonies of many polyps. They have ciliated tenta-cles and a hard, box-like, calcium carbonate skeleton. Bryozoans date from the Early Ordovician, roughly 400 million years ago. Fossil bryozoans are abundant and are im-portant in the rock-forming process.

Burgess shale - An incredibly fossil-rich area in the Canadian Rocky Mountains (in Brit-ish Columbia). This Lagerstätten (a geological fossil deposit rich with varied, well-preserved fossils) is replete with fossils from the Cambrian Period, roughly 500 mil-lion years old. The Burgess shale was discovered in 1909 by Charles Doolittle Wol-cott, who was the Secretary of the Smithsonian Institution in Washington, D.C. at the time. Fossils from this area include early representatives of most modern groups, in-cluding worms, sponges, shrimp-like crustaceans, and jellyfish.

Calcareous nannoplankton (coccoliths) – A general term applied to various micro-scopic plates having many different shapes and averaging about 3 microns in diameter. They form part of the outer aragonitic or calcitic skeleton of coccolithophores, minute planktonic flagellate organisms.

Caledonides – The orogenic belt extending from Ireland and Scotland NW-wards through Scandinavia, formed by the early Paleozoic Caledonian orogeny.

Canning Basin - The Ordovician period of the Paleozoic Era is an interval exhibiting increased animal diversity and an abundance of marine life. One of the many signifi-cant fossil sites from this time is the shallow Canning Basin in northwestern Australia (180 miles south-east of the present day city of Derby). The land portion of the Can-ning Basin covers approximately 430,000 km2. During the early Ordovician period, the Australian continent was located at the equator. Although the environment today is desert, evidence suggests that the basin was a deep water marine environment of high faunal diversity during the Ordovician period (Source: http://www.ucmp.berkeley.edu/ordovician/canning.html).

Cephalopods – (meaning "head foot") are mollusks with tentacles and a large head. These soft-bodied invertebrates include animals like squid, octopuses, cuttlefish, and the ammonites (extinct). They are fast-moving carnivores that catch prey with their tentacles and poison it with a bite from beak-like jaws. They move with by squirting water through a siphon, a type of jet propulsion. Many also squirt ink to help escape predators.

Chalk – Soft, white to gray limestone of marine origin, consisting almost wholly of cal-cite formed mainly by the calcareous tests of foraminifera and coccolithophores.

Chondrites – 1. Stony meteorites containing chondrules embedded in a fine-grained ma-trix of pyroxene, olivine, and nickel-iron with or without glass. 2. A common trace fossil probably a feeding burrow of a marine worm.

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Coal swamp flora - Early Permian and Carboniferous coals of Southern Laurasia (now in North America, western Europe and the Donetz Basin of the USSR) originated as peat bog accumulations of leaf and bark litter and fallen trees of the extinct genera Lepidodendron, Sigillaria, Calamites, and true-fern trees of the extinct genus Ganga-mopteris. These trees were all spore shedding. Leaves of the coal swamp flora are well known from museum exhibits. Significantly, however, even their largest trunks show no growth rings and this indicates for the coal accumulating areas of Laurasia an equa-torial climate. Modern analogs are the peats and mucks (histosols, which are soils de-fined as having at least 20-30% organic matter by weight and being more than 40 cm thick) of equatorial swamp forests of Indonesia. (Source: http://geowords.com/histbooknetscape/i19.htm)

Conifers - Most conifers are evergreen trees and shrubs that bear naked seeds in cones (a woody strobilus). Examples of modern-day conifers include pine, fir, and spruce trees. Mesozoic Era conifers included redwoods, yews, pines, the monkey puzzle tree (Araucaria), cypress, Pseudofrenelopsis (a Cheirolepidiacean). Towards the end of the Mesozoic, flowering plants evolved and began to overtake conifers as the domi-nant flora.

Conodonts – Small, disjunct fossil elements, phosphatic in composition and commonly tooth-like in form but not in function. Range Cambrian (possibly late Precambrian) to Upper Triassic, marine.

Craton – A part of Earth’s crust that has attained stability and has been deformed little for a long time.

Crinoids – An echinoderm of the class Crinoidea, characterized by a globular body en-closed by a calyx from which “arms” extend radially, and by a jointed flexible stem and a “root” by which it is attached to the sea bottom. Range: Ordovician to the Pre-sent.

Cro-Magnon - an early group of Homo sapiens (the species to which we belong) that lived about 40,000 years ago in what is now Europe. Skeletal remains of the Cro-Magnon were first found in caverns in Les Eyzies, Dordogne, France (in 1868).

Cycads - (Cycadophyta) are primitive seed plants that dominated the Jurassic period (cy-cads comprised 20% of the world flora). Cycads are palm-like trees that live in warm climates. Separate male and female plants exist (they are dioecious). These gymno-sperms have long, divided leaves and produce large cones. Cycads evolved during the Pennsylvanian, had their heyday during the Mesozoic, and only about 185 species (in 11 genera) still exist today. Leptocycas (shown above) and Ptilophyllum were Meso-zoic Era cycads. Later cycads had a more rounded, barrel-like base.

Diatoms – A microscopic single celled aquatic plant related to the algae. In grows in both fresh and saltwater. Diatoms secrete siliceous frustules in a great variety of forms, which may accumulate in sediments in enormous numbers.

Diatryma - Human-sized, heavily-built, flightless extinct birds that date from the Paleo-gene/Neogene to the early Eocene (38 Ma to 2 Ma). They were about 2.1 m tall, had thick legs with clawed feet, tiny wings, and huge, powerful, hooked beaks on a big head. They were probably carnivores (although there is some controversy about this) and perhaps the top predators in what is now western Europe and North America, in an environment that was a tree-covered plain. They nested on the ground. The small, fast, carnivorous mammal Cladosictis may have driven it to extinction by eating its

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eggs and chicks. Diatryma gigantea was named by paleontologist E.D. Cope in 1876 from a New Mexico fossil. (Subclass Neornithes, Order Gruiformes)

Dicroidium flora – Permian flora that was dominated for a genus of gymnosperms with forked, leaf-bearing branches. Dicroidium appeared first in tropical areas and then mi-grated into southern regions of the Gondwana region of Pangea, apparently tracking climatic changes.

Dinoflagellates – A one-celled microscopic flagellate organism, chiefly marine and usu-ally solitary, with resemblance to both animal and plant kingdoms. Range, Paleo-gene/Neogene to Present.

Dinosaurs - Land-dwelling reptiles that walked with an erect stance during the Mesozoic Era. Their unique hip structure caused their legs to stick out from under their bodies, and not sprawl out from the side (like other reptiles). They are extinct, but they evolved into the birds. The word dinosaur (meaning "fearfully great lizard") was coined by Sir Richard Owen in 1841.

Doppler shift - Light from moving objects will appear to have different wavelengths de-pending on the relative motion of the source and the observer. Observers looking at an object that is moving away from them see light that has a longer wavelength than it had when it was emitted (a red shift), while observers looking at an approaching source see light that is shifted to shorter wavelength (a blue shift). This relation is used to argue that the universe is expanding.

Dropstones – A clast which falls through a water column into soft or partly-unconsolidated sediment disrupting bedding and other structures. Clasts are typically released from melting icebergs and sea ice.

Echinoderms - (meaning "spiny skin") are a phylum of salt-water animals whose living members have five arms or rays (or multiples of five). They are mostly bottom-dwellers. These invertebrates include: starfish (sea stars), sea urchins, sand dollars, crinoids, sea squirts, sea cucumbers, etc.

Ediacara fauna - The animal life that lived during the Vendian or Ediacaran period (roughly 650 to 544 million years ago). The Vendian is when the earliest-known ani-mals evolved. Vendian biota (Ediacara fauna), included soft-bodied multi-cellular animals, like sponges, cnidarians, worms, and soft-bodied relatives of the arthropods. The Ediacara was named for the Ediacara Hills in Australia, north of Adelaide, where these early animal fossils were first found (in 1946, by the Australian mining geologist Reginald C. Sprigg). Other Vendian Period fossils have been found in Mistaken Point, Newfoundland and the White Sea off the northern coast of Russia.

Euramerica Flora – The plant life of the joined continents of Europe and the Americas (during parts of the Mesozoic Era).

Evaporites – Sediments which are deposited from aqueous solution as a result of exten-sive or total evaporation of a water body.

Ferns - Non-flowering plants that were plentiful during the Mesozoic Era and usually live in warm, moist areas. Ferns have fronds divided into leaflets.

Flowering plants (angiosperms) - Angiosperms (meaning "covered seed"). They pro-duce seeds enclosed in fruit (an ovary). They are the dominant type of plant today; there are over 250,000 species, including grasses, peas, etc. Their flowers are used in reproduction. Angiosperms evolved about 140 million years ago, during the late Juras-sic period, and were eaten by dinosaurs. They became the dominant land plants about

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100 million years ago (edging out conifers, a type of gymnosperm). Angiosperms are divided into the monocots (like corn) and dicots (like beans).

Foraminifera – Protozoan characterized by a test of one to many chambers composed of calcite or of agglutinated particles. Most foraminifera are marine. Range: Cambrian to Present.

Fusulinids – Ordovician to Triassic important guide fossils in the Carboniferous and Permian systems – belong to the foraminifera.

Ginkgos - or Gingko (also called the maidenhair tree) is a primitive seed-bearing tree (a gymnosperm) that was common during the Mesozoic Era, but has only one existing species now. Ginkgos peaked during the Jurassic and Cretaceous periods. This de-ciduous (losing its leaves in cold weather) tree has fan-shaped leaves divided into two lobes. Classification: Division Pinophyta (Gymnosperms) , Subdivision Pinicae, Class Pinopsida, Order Ginkgoales, Family Ginkgoaceae (Ginkgo).

Globigerinaceans – Foraminifera belonging to the genus Globigerina. Glossopteris flora - (from the Greek ‘glossa’, meaning tongue, because the leaves were

tongue shaped) is a genus of extinct seed fern (a Pteriosperm) whose fossils are found throughout India, South America, southern Africa, Australia, and Antarctica. Glossop-teris was about 12 ft (3.6 m) tall. The distribution of this fossil plant throughout the southern hemisphere led the Austrian geologist Eduard Suess to deduce that there had once been a land bridge between these areas. He named this large land mass Gond-wanaland (named after a district in India where the plant Glossopteris was found). This was the southern supercontinent formed after Pangaea broke up during the Juras-sic period. It included what are now the continents South America, Africa, India, Aus-tralia, and Antarctica. These deciduous (losing their leaves in the cool season) gymno-sperms arose during the late Permian period and became dominant, but went extinct by the end of the Triassic period.

Gondwana - was the southern supercontinent formed after Pangaea broke up during the Jurassic period. It included what are now the continents South America, Africa, India, Australia, and Antarctica. Gondwanaland was named for a district in India where the fossil plant Glossopteris was found; this plant led E. Suess to deduce that the southern continents were once joined, supporting Wegener's continental drift theory

Graptolites - A group of extinct marine colonial animals, most of which lived attached to the sea bed. Graptolites lived from the Cambrian period (roughly 540 to 505 million years ago) to the early to mid-Carboniferous (360 to 320 million years ago). These small sea animals had a soft body, tentacles, and a hard outer chitonous covering (similar to our fingernails); they were bilaterally symmetrical. These widespread fos-sils are often used as index fossils. Classification: Hemichordata (chordates lacking a backbone

Grenville Orogeny - About 1.1 billion years ago, subduction of the oceanic plate be-neath the North American continental plate had completed and collision of the previ-ously drifting continent began. This event is known as the Grenville Orogeny. The col-lision of the two continents formed a mountain range similar to that of the Himalay-ans. Over a period of about 360 million years little activity took place throughout the Grenville supercontinent other than relaxation of the formerly colliding plates, strike-slip faulting and erosion. The result was a flat landscape, which had been reduced in

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height by approximately 25 km to sea level. Subsequently, the removal of the original overlying weight caused the remaining rock to rebound and dome. (Source: http://info.hartwick.edu/geology/work/VFT-so-far/orogeny/gren.html).

Gymnosperms - (meaning "naked seeds") are seed-bearing plants that that don't produce flowers. They release pollen into the air to the female ovule, causing fertilization. Their seeds develop without a protective covering. The earliest gymnosperms were seed ferns from the Devonian period (408-360 million years ago). Conifers (like pines, redwoods, and fir), ginkgos, seed ferns, cycadeoids, and cycads are gymnosperms. These plants were very important to plant-eating dinosaurs.

Hercynian or Variscian orogen – The Late Paleozoic orogenic era of Europe, extending through the Carboniferous and Permian.

Hexacorals - Scleractinian ("hard-rayed") corals first appeared in the Middle Triassic and refilled the ecological niche once held by tabulate and rugose corals. They are proba-bly not closely related to the extinct tabulate or rugose corals, and probably arose in-dependently from a sea anemone-like ancestor. Their pattern of septa differs markedly from that of the Rugosa, being basically six-rayed. For this reason, scleractinians are sometimes referred to as hexacorals.

(Source: http://www.ucmp.berkeley.edu/cnidaria/scleractinia.html). Hominidae - Hominids (family Hominidae) are the group that includes people and our

close ancestors and relatives. Hominoidea - The Superfamily Hominoidea includes the apes and humans. It includes

the Family Hominidae (people and our close ancestors and relatives), Family Pongidae (orangutans, chimpanzees, and gorillas), and Family Hylobatidae (gibbons and sia-mangs).

Homo erectus - Homo erectus is one of several species of Homo generally recognized by most experts. Homo erectus has thick vault bones, the area over the eye sockets pro-trude quite prominently into the supraorbital (brow) ridges, the occipital region of the skull has a horizontal ridge known as the occipital torus, and the area along the sagital suture is raised into a low keel, called a sagital keel. This keel has flattened areas ex-tending laterally from it. Hominids with this type of morphology began to show up in Africa approximately 1.5 to 1.6 million years ago.

Homo habilis - (also known as "handy man") used primitive stone tools. The flat face and large molars of the Homo habilis resemble the Australopithecus lineage. The brain size of the Homo habilis is about 700 cc (larger than the Australopithecus). An "ape-like" (long arms and a small body) body structure was characteristic of the Homo ha-bilis. (Source: http://park.org/Canada/Museum/man/habilis2.html).

Homo sapiens - The evolution of Homo sapiens commenced approximately 200 000 - 300 000 years ago. The Homo sapiens structure is similar to that of the Homo erectus, yet Homo sapiens skulls were slightly rounder and larger. Their teeth and jaws were noticeably smaller, which corresponds with, they're fragile face. The Homo sapiens brain capacity averaged an impressive 1,350 cm3, surprisingly the same size of today’s humans. (Source: http://park.org/Canada/Museum/man/sapiens.html).

Hypersaline – Excessively saline; with a salinity substantially greater than that of normal seawater.

Iapetus – The hypothetical ocean that is assumed to have lain between North America and Europe-Africa some 500 Myr. ago. The closure of this ocean is considered the

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cause for the collision between these continents, resulting in the formation of the Caledonian orogen in Siluro-Devonian times.

Ichthyosaurs - a dolphin-like reptile about 2 m long. It could swim at 40 km/h. Ichthyo-saurs had a tall dorsal fin, a half-moon-shaped tail, paddle-like flippers and smooth skin. The nostrils were near the eyes on the top of the head. It had massive ear bones and large eyes, probably giving it acute hearing and sight. These marine reptiles gave birth to live young. Their diet was mostly fish, but also included cephalopods (like belemnites). Hundreds of Ichthyosaurus fossils have been found in England, Germany, Greenland, and Alberta, Canada. They lived during the early Jurassic to the early Cre-taceous periods. It was not a dinosaur, but another type of extinct reptile. Ichthyosau-rus, which means "fish lizard," was named by Charles Koenig in 1818.

Impact winter – Term related to the dust and ashes brought into the atmosphere due to the impact of a large meteorite body. The dust/ash cover is reducing the amount of sunlight reaching the surface of the Earth and causing a sharp climatic cooling.

Index fossils - are commonly found fossils that are limited in time span. They help in dating other fossils. For example: trilobites were common during the Paleozoic, but not found before the Cambrian period. Ammonites were common during the Mesozoic Era, but not found after the Cretaceous period. Another example: the oldest-known os-tracods are from the Cambrian period; they became widespread during the Ordovician and remain so.

Insubric Line – Tectonic lineament of the Swiss Alps. The insubric line separates the Southern Alps from the Eastern Alps (Paleo-Africa from Paleo-Europe).

Iridium anomaly - A layer of Earth's crust (the K-T layer, which is about 65 million years old) in which there is excess of iridium (a relatively rare element). The presence of this extra Iridium supports the Alvarez asteroid theory, since this iridium may have come from an asteroid.

Laurentia – A supercontinent comprising the Canadian shield and some other parts of North America, Greenland, and parts of NW Europe. The term usually refers to the western “Atlantic” continent during and subsequent to the formation of the Variscian Mountains.

Laurentia (Laurasia)- The northern supercontinent formed after Pangaea broke up dur-ing the Jurassic period. Laurasia included what are now North America, Europe, Asia, Greenland, and Iceland.

Little Dal Group – 0.8 or 0.9 Byr. old stratigraphic unit of NW Canada. Contains possi-bly multicellular algae.

Mammal-like reptiles (synapsids) - Dimetrodon was a prehistoric animal with a large sail; it was not a dinosaur but a pelycosaur, an early synapsid.

Mammals - Hairy warm-blooded animals that nourish their young with milk. Mammals evolved during the Triassic period. People are mammals.

Mass extinction - The process in which huge numbers of species die out suddenly. The dinosaurs (and many other species) went extinct during the K-T extinction, probably because of an asteroid that hit the Earth.

Messinian event – Refers to an interval of near total or total desiccation of the Mediter-ranean Sea, some 6 Myr. ago. The Messinian event left thick successions of evaporitic minerals.

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Mollusks – Solitary invertebrate belonging to the phylum Mollusca. Among the classes included in the mollusks are the gastropods, pelecypods, and cephalopods.

Mound/patch reef - A patch reef (or bioherm) forms mounds of isolated coral (or other reef-forming organisms) colonies.

Nautiloids - Primitive, thick-shelled, carnivorous marine invertebrates, cephalopod. The shell is divided into chambers. The nautiloid head has well-developed eyes and tenta-cles that can grasp prey. They swim by jet-propulsion; they squirt water out from the body cavity. They evolved during the Silurian and are still around today, but are un-common (only a single genus survives). They were most abundant during the Paleo-zoic Era, roughly 400 million years ago. Some Nautiloids evolved into Ammonoids.

Neanderthal - or Neandertal man, a subspecies of Homo sapiens, the species to which contemporary humans belong, known as H. sapiens neandertalensis after Neanderthal, Germany, the valley where the first specimen was found. Many scientists classify Ne-anderthal as its own species (H. neandertalensis), pointing to the large number of ana-tomical differences between it and H. sapiens.

(Source: http://www.bartleby.com/65/nn/Nndrtlmn.html) Nekton – Organisms that actively swim (as opposed to plankton). Nothosaurs - A reptile with flipper-like limbs that lived both on land and in the water

(like a modern-day seal). It was about 10 feet (3 m) long and had a long, thin, pointed tail with a fin on its upper portion. This tail must have been used for swimming. It had five long, webbed toes. The forelimbs were shorter than the rear limbs. The jaws were long, thin and full of pointed, interlocking teeth (good fish traps). Nothosaurus lived during the entire Triassic period. Fossils have been found in what is now Europe (Germany, the Netherlands, and Switzerland), North Africa, and Asia (China, Israel, and Russia). It was not dinosaur, but another type of reptile. Classification: Order Nothosauria, Family Nothosauridae.

Oceanic anoxic event - Black shale-like deposits on the ocean beds, formed from or-ganic-rich black muds, indicate that during the mid Cretaceous (and Jurassic) the deep oceans went through a number of phases of anoxia. The cause of these oceanic anoxic events (OAEs) remains uncertain despite over two decades of intense study.

Ooids – Small round accretionary bodies in a sedimentary rock, resembling fish eggs with a diameter of usually 0.25 to 2 mm. Ooids are generally formed of calcite or ara-gonite in concentric layers around a nucleus such as a sand grain.

Ornitischian hip - The hip or pelvis of dinosaurs is composed of three bones, the Pubis, Ilium, and Ischium. Based on hip structure, the British paleontologist H. G. Seeley di-vided the dinosaurs into the orders Saurischia (or "Lizard-hipped") and Ornithischia (or "Bird-Hipped").

Orogen – A linear or arcuate region that has been subjected to folding and deformation during an orogenic cycle. A mountain belt.

Ostracoderms - (also called Agnaths) are extinct, primitive, armored, jawless fish that lived during from the Ordovician period to the Devonian period. These vertebrates had bodies that were protected by bony plates and scales. Fossils have been found in North America and Europe. Some ostracoderms include the Pteraspids.

Ostracods - (meaning "shell like") are also called seed shrimp or mussel shrimp. These tiny freshwater and marine crustaceans belong to the subclass Ostracoda. They are scavenger that have a shrimp-like body plus two hard shells connected by a hinge; they have one or two appendages. Ostracods range in size from micoscopic to about an

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inch (2.5 cm) long. There are about 20,000 species of living ostracods and many more extinct species. These very common animals are used as index fossils, helping to date rock layers. The oldest-known ostracods are from the Cambrian period; they became widespread during the Ordovician and remain so.

Paleo-Tethys - The Tethys was named in 1893 by the Austrian geologist Eduard Suess after the sister and consort of Oceanus, the ancient Greek god of the ocean. As pres-ently understood, there were actually at least two Tethys Seas. In Permian times, the continents were - roughly speaking - assembled into one, enormous, 'C'-shaped land-mass, known as Pangea. The Paleo-Tethys was the body of water enclosed on three sides (and at times, almost four sides) by Pangea. By the Early Triassic, a long sea-floor spreading ridge developed along the southern shore of the Paleo-Tethys. This extended all the way from Australia, at the extreme southeast end of Pangaea, north-west to the point where the plates of Europe, North America and Africa met roughly at the center of the 'C'. As the sea floor spread, it created a basin bordered on the south and west by the Gondwana continental plates of the Pangean landmass (the bottom half of the 'C') and on the north and east by the new microplates of Tibet, Iran and Turkey. These microplates were pushed rapidly northward towards Eurasia and China, eventually closing the Paleo-Tethys. The new Tethys basin expanded behind them to become the Mesozoic Tethys Sea. The Tethys Sea also expanded westward, splitting Pangaea into the supercontinents of Gondwana (in the South) and Laurasia (in the North). By Late Triassic and Jurassic times, the Tethys extended a long, shallow arm through what is now Central Asia and Southern Europe, known as the Tethys Seaway (yet a third "Tethys"). (Source: http://www.palaeos.com/Earth/Geography/Tethys.htm)

Pangea - A supercontinent consisting of all of Earth's land masses. It existed during the Permian through the Jurassic period. It began breaking up during the Jurassic, forming the continents Gondwanaland and Laurasia.

Panthalassa - (meaning "All seas") was the super-ocean that existed on Earth during the time of the super-continent Pangaea. Panthalassa existed during the Permian through the Jurassic period, when Pangaea began to break up; the Tethys sea formed between the northern and southern parts of Pangaea as they drifted apart.

Pelycosaurs - (meaning "basin lizards") were the earliest synapsids; they were not dino-saurs. These quadrupeds appeared during the upper Carboniferous and went extinct during the Permian period (before the Triassic period when the dinosaurs evolved). Pelycosaurs began as small, lizard-like animals and evolved into larger, more differen-tiated types. Some were carnivores, some were herbivores; some had sailbacks like Dimetrodon), some did not. These swamp dwellers with a sprawling gait were likely the ancestors of the therapsids, which led to the mammals. Pelycosaurs are divided in to the suborders Eupelycosauria and Caseasauria.

Photosynthesis - process by which green plants and certain other organisms use the en-ergy of light to convert carbon dioxide and water into the simple sugar glucose. In so doing, photosynthesis provides the basic energy source for virtually all organisms. An extremely important byproduct of photosynthesis is oxygen, on which most organisms depend. (Source: http://encarta.msn.com/encnet/refpages/refarticle.aspx?refid=761572911)

Phytoplankton – The portion of the passively swimming organisms in an ocean/lake that belong to the plants (usually algae).

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Placental mammals - Placental mammals all bear live young, which are nourished be-fore birth in the mother's uterus through a specialized embryonic organ attached to the uterus wall, the placenta. The placenta is derived from the same membranes that sur-round the embryos in the amniote eggs of reptiles, birds, and monotreme, mammals. The term "placental mammals" is somewhat of a misnomer because marsupials also have placentae. The difference is that the placenta of marsupials is very short-lived and does not make as much of a contribution to fetal nourishment as it does in eutheri-ans, as "placental mammals" are known scientifically. (Source: http://www.ucmp.berkeley.edu/mammal/eutheria/placental.html)

Placoderms - (meaning "plated skin") were armored fish that evolved during the Silurian Period, about 420 million years ago. They diversified and came to dominate the seas by the Devonian. They went extinct bout 355 million years ago. They had hinged bony armor on their head and thorax. They had no teeth, but did have bony ridges that acted like teeth. Some placoderms included the Antiarchi (like Bothriolepis), Dunkleosteus (the largest placoderm), Groenlandapsis, and Phyllolepis. Placoderms were early fish, not dinosaurs.

Placodonts - meaning "plate-like or flat teeth" were chunky, relatively-sedentary marine reptiles that lived in shallow seas during the Triassic period, going extinct at the end of the Triassic. Many of these sauropterygian diapsids had turtle-like shells (dermal ar-mor) and sprawling legs. Placodonts ate shellfish which were crushed between their strong, flat teeth. Placodonts included Placodus, Placochelys, the armored Henodus, and Claudiosaurus. They were not dinosaurs.

Planktonic foraminifera – Floating and drifting foraminifera as opposed to bentonic (bottom dwelling foraminifera).

Pongidae - The family Pongidae, generally referred to as the "great apes" contains three genuses, Pongo. Gorilla, and Pan, and four species: Pongo pygmaeus (orangutans), Gorilla gorilla (gorillas), Pan troglodytes (chimpanzees), and Pan paniscus (bonobos, also known as pygy chimpanzees).

Precambrian shield - A Precambrian shield is a largely Precambrian portion of a craton that is exposed as the earth’s surface. The largest of these is the vast Canadian shield.

Cladogram - Branching diagrams that depict species divergence from common ances-tors. They show the distribution and origins of shared characteristics. Cladograms are testable hypotheses of phylogenetic relationships.

Protozoa - (meaning "first animals") are a phylum of primitive animals that include the following classes: Mastigophora (flagellates), Sarcodina (amoebas), Sporozoa (Para-sites), and Ciliata (Ciliates).

Psychrosphere – Cool waters in depths below about 500 m in the world oceans form an environment called psychrosphere (a portion of the hydrosphere). The species that live in the psychrosphere are unique and well adapted.

Pterosaurs - (meaning "winged lizard") were flying, prehistoric reptiles. They were not dinosaurs, but were closely related to them. Pterosaurs were named by Kaup in 1834.

Radiogenic isotopes – Isotopes that decay from instable mother isotopes to (stable or instable) daughter isotopes.

Ray-finned fishes - (class Actinopterygii) are the largest group of fish. These bony fish evolved during the very end of the Silurian, about 408 million years ago. These fish dominate the seas today. Sharks are not ray-finned fish.

Red beds - Used to describe red sedimentary rocks, usually sandstone or shale.

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Red giants - After the main sequence life of a main sequence star, it next goes to the red giant stage. Eventually the core of a main sequence star starts to run out of hydrogen. The core is now composed mostly of helium nuclei and electrons, and begins to col-lapse, driving up the core temperature, and increasing the rate at which the remaining hydrogen is consumed. The outer portions of the star expand and cool, producing the Red Giant phase. At this stage the Sun will become large enough to swallow Mercury, and bright enough to boil away the Earth's oceans. There is however a limit to the con-traction of the core. Eventually the core is supported by the resistance of the electrons to being squeezed together, known as electron degeneracy . We say that the core is now degenerate. This core will soon become the object known as a white dwarf. (Source: http://plabpc.csustan.edu/astro/stars/giant.htm).

Reptiles - (meaning "to creep") are a group of animals that have scales (or modified scales), breathe air, and usually lay eggs. The term reptile is loosely defined in every-day English to mean scaly, cold-blooded, egg-laying animals. In cladistics (a way of classifying life forms), the reptiles are more strictly defined and include the descen-dants of the most recent common ancestor of the turtles, lepidosaurs (lizards, snakes, tuataras), and archosaurs (crocodilians, dinosaurs, and birds). The maintenance of body temperature (cold vs. warm-blooded) is not a factor in this classification, but skull and egg structure are.

Rodents – Group of small mammals that include for instance mice, rats, hamsters, ger-bils.

Rudists - Rudist are a group of bivalves, which evolved during the Late Jurassic to Cre-taceous and lived in warm, shallow oceans of low latitudes. They became extinct at the Cretaceous/Paleogene boundary. Most rudists have not much in common with 'normal' bivalves and developed bizarre, occasionally large shells. (Source: http://www.ruhr-uni-bochum.de/sediment/rudinet/rudipal.htm).

Rugose corals - The Rugosa are an extinct group of corals that were abundant in Middle Ordovician to Late Permian seas. Solitary rugosans are often referred to as "horn cor-als" because of their characteristic shape; two Paleozoic rugose corals are shown at the top of this page. Some solitary rugosans reached nearly a meter in length. However, some species of rugose corals could form large colonies. (Source: http://www.ucmp.berkeley.edu/cnidaria/rugosa.html).

Saurischian - The "Lizard-Hipped" dinosaurs (Saurischians) had a hip structure similar to that of lizards. Oddly enough, these dinosaurs were the ancestors of the birds. They are divided into the theropods (bipedal carnivores like Allosaurus) and sauropodo-morphs (huge, quadrupedal herbivores like Apatosaurus).

Sauropods - Were huge, quadrupedal, herbivorous dinosaurs with long necks, small heads, and long tails.

Seed ferns - Seed ferns (Pteridosperms) were primitive seed plants (not ferns at all) that lived in swampy areas from the Mississippian Epoch through the Mesozoic Era. They had woody stems studded with dried out leaf bases. The tops had fern-like fronds which bore seeds. Some seed ferns include Glossopteris (pictured above), Dicroidium, Caytonia, Denkania, and Lidgettonia.

Shocked quartz - is quartz that has undergone deformation due to extreme pressure and heat. It has been found in the layer that marks the K-T boundary, lending credence to the Alvarez impact theory.

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Skeleton - the supporting structure of an animal's body. Dinosaur skeletons were made of bones and cartilage.

Slave Terrane/Province – An Archean province of North America. Forms part of Can-ada.

Snowball Earth – A theory that suggests that the Earth was frozen solid (a snowball) in the Late Precambrian. According to this hypothesis, the Cambrian explosion of life is the result of the melting of the ice shields.

Spore-bearing trees – Spores are reproductive structures that can grow into a new adult plant when released into the environment. Spore bearing plants are present in the mod-ern world, ferns are a familiar example. Upright spore-bearing plants might go back at least into the Silurian.

Stromatolites - Stromatolites are fossils which show the life processes of cyanobacteria (formerly called blue-green algae). The primitive cells (Prokaryotic type), lived in huge masses that could form floating mats or extensive reefs. Masses of cyanobacteria on the sea floor deposited calcium carbonate in layers or domes. These layered depos-its, which have a distinctive "signature”, are called laminar stromatolites. This is an example of a layered stromatolite from the Ozark Precambrian. Most often, stromato-lites appear as variously-sized arches, spheres, or domes. Ozarkcollenia, a distinctive type of layered Precambrian stromatolite, pushes the appearance of life in the Ozarks to well over a billion and a half years ago.

Stromatoporoids - An extinct group of massive colonial marine organisms that were im-portant Paleozoic and Mesozoic reef builders. For a long time it was not even clear what sort of organisms they are. Affinities were suggested with sponges (Phylum Po-rifera), corals (Phylum Cnidaria), and even Algae. It is now generally accepted that they represent perhaps two distinct groups of demosponges or sclerosponges. However some paleontologists still consider stromatoporoids to belong to their own phylum. with either sheet-like or hemispherical skeletons. On structure they have horizontal partitions called laminae and vertical partitions called pillars. (Source: http://www.palaeos.com/Invertebrates/Porifera/Stromatoporoidea.htm).

Tabulate coral - Tabulate corals were common from the Ordovician to the Permian. Very recently, a Lower Cambrian coral, Moorowipora chamberensis, has been found in southern Australia; it appears to be a tabulate coral, although this is not absolutely certain. If it is a true tabulate, this find extends the history of tabulate corals consid-erably. (Sorauf and Savarese, 1995). Tabulate corals receive their name from horizon-tal internal partitions known as tabulae, as seen on this large specimen. Most tabulates were colonial, with some forming substantial reefs. Tabulate corals, as well as rugose corals, went extinct at the end of the Permian, about 245 million years ago, victims of the heaviest mass extinction ever.

(Source: http://www.ucmp.berkeley.edu/cnidaria/tabulata.html). Teleost fishes - (meaning "perfect-boned") fish are advanced fish with bones that

evolved during the Jurassic period. They are the most abundant fishes today. Tethys – see Paleotethys. Therapsids - Advanced synapsid animals from the late Permian period. They had teeth

that were differentiated into post-canines and incisors. Dominant among the early therapsids were the large dinocephalians. The clade of therapsids includes the mam-mals, some close relatives, and their recent common ancestors. Some therapsids in-clude the Eotitanosuchids , herbivorous dicynodonts (like Boreogomphodon, Lystro-

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saurus, Kannemeyeria, Estemmenosuchus, and Ischigualastia), and the cynodonts (like Cynognathus, Probainognathus, and Thrinaxodon).

Till - Debris deposited directly by melting ice in a glacier. Tillite - Glacial till cemented into a solid rock Titanotheres - (also known as brontotheres) are extinct family of large, rhinoceros-like

mammals that were ancestors of the horse, rhinoceros, and tapir. Titanotheres had horn-like structures on their snout; bony knobs protruded from their skull and were covered with thick skin. Males had larger knobs than females. These herbivores ate soft forest vegetation and were up to 8 feet (2.5 m) tall at the shoulder. Titanotheres each had a tiny brain, only as big as a fist. They had four hoofed toes on each front foot and three hoofed toes on each rear foot They lived from the early Eocene until the middle Oligocene (from 58-30 million years ago). Some titanotheres include Brontops (3 m tall, from North America), Brontotherium (3 m tall, from North America), Dolichorhinus (1.5 tall, from North America), Eotitanops (0.5 m tall, from North America and Asia), and Embolotherium (3 m tall, from Mongolia).

Tommotian - The Tommotian Age, which began about 530 million years ago, is a subdi-vision of the early Cambrian. Named for rock exposures in Siberia, the Tommotian saw the first major radiation of the animals, or metazoans, including the first appear-ance of a great many mineralized taxa such as brachiopods, trilobites, archaeocyathids, mollusks, echinoderms, and more problematic forms. Soft-bodied members of many other phyla were also appearing and diversifying at this time.

Trace fossil - Also known as ichnofossils, these are fossilized footprints, nests, dung, gastroliths, etc., but not actual body parts. They record the movement and behavior of animals.

Trilobites - Early invertebrates with a segmented body and an exoskeleton. Trilobites dominated the environment during the Cambrian Period (540 to 500 Ma).

Variscides – see Hercynides. Varves - Varves are found in the deposits of glacial lakes. Each varve consists of two

distinct layers of sediment, a lower layer of light colored sandy material and an upper layer of darker silt. Most melting of the glacier occurs in spring and early summer, so at these times the meltwater streams flow fastest and carry their greatest loads. Fine material is held in suspension in the lake whilst heavier material is deposited. As au-tumn and winter approach, the capacity and competence of the meltwater streams is reduced because there is less melting and less meltwater. This allows the finer material that has been kept in suspension, to settle out and be deposited. Thus, each year, a new set of coarse and fine beds are formed.

Vascular plant - A vascular plant has specialized pipelines that carry water and nutrients around the plant. Club mosses, ferns, horsetails, gymnosperms, and flowering plants are vascular plants.

Zechstein - The Zechstein is a complex of evaporite and carbonate rocks of late Permian age, thought to have been deposited over a time period of 5 million years. The Zech-stein evaporites filled a broad basin, measuring 600km by 1500km extending from the British Isles across the North Sea, the Netherlands, Denmark, Germany, eastern Po-land and Lithuania. The basin can be divided into southern and northern sub-basins, separated by the Mid North Sea – Ringkobing –Fyn High. Thick salt occupies the ba-

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sin centers, whilst carbonates and anhydrites are more abundant around the edges and over the high.

(Source: http://www.dur.ac.uk/r.j.simmons/zechsteinevaporites.html#Zechstein)

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10. APPENDIX - SPECIAL CHAPTERS 10.1 Some remarks on the Geologic framework of Western Europe Introduction Present day Europe forms part of the large Eurasian plate which is sur-rounded by 12 large and at least as many small plates. This plate con-figuration is quite young, actually of Late Mesozoic? Cenozoic origin. In earlier geological times quite differ-ent plate configurations existed. Some of the former plate borders can still be recognized as sutures in the continental crust, other boundaries have been obliterated. Because all the pre-Mesozoic oceans that once sur-rounded Europe have been consumed by subduction, the answers as how Europe was formed and evolved through time must be sought in the continental lithosphere and remnants of these oceans that are built in oro-gens.

One possible approach to subdi-vide the geologic history of Europe is shown below. 10.1.1 Proto-Europe (Baltica) Proto-Europe (termed Baltica throughout this course or Fennosar-mantia by other authors) consists of all European crustal fragments that were last deformed prior to the Cambrian. Europas crustal evolution started ca. 3.5 billion yrs. ago in what

presently is the Russian Karelia, north of Lake Onega. Throughout the Middle and most of the Late Archean time, accretion of greenstone and granite gneiss terranes was main-tained. Towards the close of the Ar-chean, a continental nucleus of Ar-chean Europe had evolved. This nu-cleus subsequently was rifted and broke apart at the Archean-Proterozoic transition.

Fragments of proto-Europa are mainly the Russian platform, the Bal-tic shield, and the Ukrainian shield (shields are exposed Precambrian rocks, platforms are Precambrian rocks covered by younger sediments). The Russian platform is bor-dered in the North, by the Baltic shield, to the SW by the Ukrainian shield, and to the E by a younger Variscian orogen (Ural). It consists of a metamorphic crystalline basement overlain by Precambrian to Paleo-gene/Neogene sediments. The Baltic shield consists mainly of high-grade metamorphic rocks overlain by sedimentary units. The Baltic shield probably consists of an archaic nucleus in the NE (2600-2800Ma) and two Lower to Middle Proterozoic accretion zones. The Ukrainian shield is also formed by a high-grade metamorphic crystalline basement (mainly volcanic

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rocks) and overlying volcanic and sedimentary units. Around 750 Ma, Proterozoic Europa began to drift towards high southern latitudes where the Gondwana conti-nent was assembled during the Cadomian and Pan-African oro-genies. Africa, S. America, Australia, and India all then belonged to the great “Southern Continent” Gond-wana. Proterozoic Europe remained at high southern latitudes during Cambrian time but at the end of Early Ordovician those parts that now con-stitute the Baltic shield broke off and drifted away as an independent plate (Baltica).

After the Cadomian orogeny, sedimentary rift basins developed across those parts of Proterozoic Europe that had become part of Gondwana. During the Late Ordovi-cian, they experienced, like neighbor-ing areas a major glaciation. Mean-while, a wide ocean, the Tornquist Sea was opening between those ice-covered portions of former Proto-Europa that now were welded to Gondwana and the northward drifting Baltica. 10.1.2 Paleo-Europe (Caledon-ides) In contrast to the East European Plat-form, Baltica underwent a different geological evolution. The margin that later would collide with Laurentia was originally passive when Late Proterozoic Baltica separated from N.

America, Greenland, and NW–Scotland (Laurentia in this course). It also remained passive when Baltica paid its visit to Gondwana as de-scribed in the last chapter. An anti-clockwise rotation 520-500 Ma ago made it face and approach Lauren-tia. The ocean in-between, Iapetus (the Proto-Atlantic) as termed in this course, was closing in the Cambrian whilst Baltica drifted towards the north and milder climates.

After the Cambro-Ordovician transition, and collision between Northern America (Laurentia) and Northern Europe starts. In Late Cam-brian to Silurian the Iapetus Ocean is closed and Europe (Baltica) collided with Laurentia and the two continents united in the supercontinent Laurus-sia (also termed “Old Red Sandstone continent” in this course). This colli-sion created the Caledonian orogens.

In the suturing zone , oceanic lithosphere (ophiolites), sediments, and volcanic rocks are pushed on the continental margins and up-folded to form the Caledonian orogens. In the Silurian, the suturing zones becomes fragmented, folded, metamor-phosed, and thrust in nappes. To-day, the suture of the former Iapetus Ocean runs e.g. through Ireland and Great Britain. The main Caledonian orogens extend from Britain via Norway, mid- and northern Sweden, northern Finland, and Spitsbergen.

After the Caledonian orogen marine sediment deposition ends at the Silurian/Devonian boundary. Younger deposits are now mainly continental (Old Red-Sandstone). These sediments are indicative for a

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continental setting and relatively dry climate. This change in deposition was mainly a consequence of the Caledonian collision and uplift of the landmass that we termed “Old Red-Continent”. At the End of the Devonian, the Old Red-Continent started to dis-integrate. Baltica (the Caledonides and the Baltic Shield) remained highs. The area of the British Isles recorded partly shallow marine, partly terrestrial sedimentation. 10.1.3 Meso-Europe (Variscides) The Variscides (Hercynides) are a mountain belt that extends from Mo-rocco and Northern Algeria via Western, Middle, and Southern Europe to the Ural. A large part of the Variscides in Europe was later overprinted by the alpine deforma-tion. The Variscides are the result of the collision between the conti-nents in the North (Laurentia and Baltica) and Gondwana in the South during the Carboniferous. In fact the Variscan orogens form the sutures of the assemblage of Pangea.

Variscan massifs are mainly the Cantabrian Mountains, the Iberian Massive, the Armoricanian Massive, the Montagnes-Noires, SW England and South Ireland, the Ardennes, the Rhenish-Bohemain High, and the Harz, the Thueringian and Frankian High, South Sardinia, and the Antiat-las.

In Europe, the Variscides are subdivided into several main zones

that are characterized by their compa-rable sediment facies, magmatism, and tectonic evolution. These are the:

• Sub-Hercynian Basin. The Sub-

Hercynian basin is the “molasse” trough of the Hercynides, i.e. the depression in front of an orogen in which the weathering deposits of the rising orogen accumulate. This basin was rapidly filled with coal-bearing molasse deposits and folded prior to the latest Carbon-iferous.

• Rhenohercynian Basin. The Rhenohercynian basin is mainly filled with Devonian and Lower Carboniferous deposits. The main sediment type is flysch, i.e. tur-bidites that represent relative deepwater sedimentation. The sediments were folded during the Late Carboniferous. Synorogenic (i.e., “during” the orogenic phase) volcanism is rare.

• Saxothuringian Basin. The Saxothuringian comprises Pre-cambrian crystalline rocks, over-lain by Paleozoic to Permian sediments. The entire succession is overprinted during metamor-phism, intruded by granitic plu-tons, and intercalated with vol-canic deposits.

• Moldanubian Zone. The Molda-nubian Zone occupies the axial (middle) position of the Variscian zones. It comprises high-grade metamorphic rocks such as mig-matites, gneisses, amphibolites etc. Folding of the Moldanubian zone started in the Lower Carbon-

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iferous and ended in the middle of the Lower Carboniferous.

In terms of plate tectonic models, the Variscides are difficult to interpret. The main problem is that the ocean(s) that opened and later closed during convergence were de-stroyed. Remnants of these oceans are poorly exposed, fragmented, and metamorphosed. Paleomagnetic data, however, document that a huge ocean basin was destroyed when the conti-nents in the north (Laurentia and Bal-tica) and those in the south (Gond-wana) converged. This ocean is termed Paleo-Tethys. The Paleo-tethys opened probably already in the Late Proterozoic and most likely ex-isted in the Cambrian. The regional extension of the Paleotethys in the Silurian and Devonian is unclear. The Paleo-Tethys closed in the Carboni f-erous.

Similar to the post-Caledonian phase, continental conditions domi-nated after the Variscian collision. The European Variscides formed part of the giant continent Pangea that consolidated due to the varisican col-lisions. The Variscian orogens were situated in the middle of Pangea. The Tethyan seaway extended from the east into Pangea. The continental sediments that characterize the post-orogenic phase are Late Carboniferous to Permian in age. The type of sedimentation is also the result of the climatic change from humid-tropical to dry climate that took place when Pangea moved to the north.

The Permian sediments (Rot-liegendes) are the typical continental types of deposition that characterizes this semi-aridic continental climate. In Germany, the Netherlands, Great Britain, Denmark, and Poland, the Rotliegendes is overlain by the depo-sition of the Zechstein transgression. Rotliegendes sediments alternate with volcanic intercalations that are the result of igneous activity starting in the Upper Carboniferous and continu-ing throughout the Permian. 10.1.4 Neo-Europe (Alpides) In Early Jurassic time, Gondwana and Laurussia were still assembled to-gether into the megacontinent Pangea. During the Jurassic, the southern half of Pangea began to shear. A new ocean, the Tethys, opened in the east and grew in size. In the west, early Jurassic transten-sion produced rifting between Africa and America and, as the continents split apart, lead to the opening of the central Atlantic Ocean by the Late Jurassic. In Mid to Late Jurassic times, western Europe had been feel-ing the influences of stress from the opening of the central Atlantic which resulted in updoming of the central North Sea and then rifting.

The Late Cretaceous and earli-est Cenozoic evolution of Western and Central Europe reflects a funda-mental new plate tectonic setting. New is the gradual opening of the Arctic-North Atlantic domain and the onset of convergence between Africa (Adriatic Plate) and the southern

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margin of Europe. Convergence be-tween Africa and Europe finally lead to the collision of those two litho-spheric units and to the formation of the Alpine orogen during latest Cre-taceous and Paleocene. The boundary (suture) between southern Europe and the Adriatic plate is termed ‘Insubric Line’.

In Europe and Northern Af-rica, three main alpine systems are recognized: • Dinarides-Hellenides-Taurides

fold belt • Alps-Carpathian fold belt • Appenine-Atlas-Betides-Baleares

fold belt The opening of the Northern

Atlantic occurred in three stages that evolved from South to North. This had three consequences: firstly, it caused the fragmentation of he sur-rounding continental plates, secondly, small ocean basins opened in the Mediterranean realm, and thirdly, Af-rica and Europa converged. Crustal separation in the Arctic and North Atlantic domain was accompanied by the development of a major hot spot that was centered on Iceland.

The organization of the alpine orogen is complex. It consists of four units termed Helvetic nappes, Pen-ninic nappes, East Alpine, and South Alpine. The first three are al-lochthonous units that were thrusted northwards, whereas the South Al-pine units mainly show south-vergent imbrication.

These four tectono-stratigraphic units represent four pa-leogeographic domains.

The East (Austroalpine) and South Alpine facies realm belongs to the PermoTriassic continent Pangea, more specifically to the Adriatic domain. This domain was closest to the Tethys seaway. There-fore, the East and South Alpine re-corded marine deposits as early as latest Carboniferous. During the Tri-assic, the Tethys transgressed into the East Alpine facies realm (docu-mented impressively in the Northern “Kalkalpen”). In the Jurassic, the opening of the south-alpine ocean leads to a dramatic change in the sedimentation pattern. Deepwater de-posits cover the Triassic shoalwater carbonates. During the second stage of the opening of the Northern Atlan-tic, the sedimentation changed again and the molasse and flysch deposits of the “Gosau” were deposited. Sub-sequently, the East Alpine became stepwise uplifted whereas the South Alpine subsided further.

The Penninic facies realm constitutes primarily the inner do-mains of the Western Alps. The Penninic nappes are extremely thin slivers made up detached units from (1) subducted European lithosphere (European margin), (2) the Valais Ocean (a deepwater domain), (3) the Piedmont-Liguria Ocean (remnants of the South Penninic Ocean), and (4) the Briançonnais ribbon continent (or terrane). The Briançonnais zone was actually a continental high.

During the Triassic, the influ-ence of the Tethys seaway reached as far north as the Briançonnais. As for the East and South Alpine realm, the facies pattern changes drastically dur-

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ing the Jurassic. North and South Penninic basins formed where argil-laceous deposits were laid down (“Bündner Schiefer”). In the Late Cretaceous, the Briançonnais sub-sided to depths were red foramini f-eral marls were deposited (“couches rouges”). In the neighboring South and North Penninic domains flysch deposits, an indicator of the advanc-ing alpine nappes were shed.

The Helvetic facies realm originally occupied a region within the megacontinent Pangea during the

Triassic. In the Jurassic and Creta-ceous the newly opening Penninic Ocean caused a change in sedimenta-tion pattern. In the northern Helvetic domain sedimentation was largely shallow marine (“Schrattenkalk”, whereas in the south, deposition re-flected a more open marine deepwa-ter environment (“Drusberg mer-gel”). During transgression in the Eo-cene subsidence and the advancing nappes lead to flysch deposition.

10.1.4.1 Southern Alps and Adri-atic indenter Note: Much of this chapter and the following ones summarizing the tec-tonic architecture of the Alpine oro-gen are extracts from the excellent review paper by Schmid, Fügen-schuh, Kissling and Schuster (Ec-logae Geologicae, Helvetiae, 2004, 97, 93-117). The term ‘Apulian plate’ denotes all continental palaeogeographic do-mains situated south of the Alpine Tethys (Piedmont-Liguria Ocean) and north of the Neo-Tethys. This also includes the southern foreland of the Alps. Moreover, Apulia was bor-dered to the east by a westwards clos-ing oceanic embayment that formed in Triassic times (Meliata Ocean). Only after closure of the Meliata Ocean during the Cretaceous orogeny, did Apulia behave as coher-ent block.

Together with the external Di-narides, the Southern Alps represent that part of the Apulian plate, which is located south of the Periadriatic lineament (Adriatic microplate or Adriatic indenter). The southern Alps are charac-terized by a dominantly south-verging fold-and-thrust belt. This young (Miocene) 10 to 15 km-thick retro-wedge consists of upper crustal slices. The Adriatic indentor caused WNW-directed thrusting along the Penninic front of the Western Alps. During the late orogenic stages, WNW-directed indentation of the Adriatic micro-plate affected also the European foreland, finally causing the formation of the Molasse Basin and folding of the arcuate Jura Mountains.

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10.1. 4.2 Apulian plate north of the Periadriatic line: Austrolapine nappe system To the north of the Periadriatic Line, remnants of the southern margin of the Piedmont-Liguria Ocean (i.e. the Apulian Plate) are only preserved in the form of basement and cover slices (Austroalpine nappes). Most of them are completely detached from their former deep crust and mantle lithosphere. Around the Tauern window, along a thrust formed during the Pa-leogene/Neogene orogeny, the Au s-troalpine nappes are seen to overlie Penninic units that consist of slivers derived form the Alpine Tethys and the distal European margin. The Austroalpine nappes were affected by a Cretaceous orogenic cycle, related to the closure of the Meliata Ocean and its adjacent conti-nental margin. The tectono-metamorphic events that affected these units are subdivided into a first Cretaceous, followed by a second Paleogene-Neogene orogenic cycle. The two events are separated by Late Creta-ceous extension. Flysch deposits found in parts of the Southern Alps (Lombardi ba-sin), and possibly the pre-Adamello deformation indicate orogenic activ-ity in parts of the southern Alps at this time. The Cretaceous (Eoalpine) orogenic cycle, however, was pro-ceeded by Late Jurassic thrusting of the distal passive margin onto Au s-troalpine units derived from Apulia. This Jurassic event is well-developed

in the Dinarides where it leads to the obduction of parts of the Jurassic Vardar Ocean (Dinaridic ophiolites during the Late Jurassic onto an ac-cretionary wedge that contains rem-nants of the former Meliata Ocean and onto the Apulian margin. The Cretaceous (Eoalpine) orogeny is interpreted to be related to a collisional event that led to the clo-sure of the Meliata Ocean. 10.1.4.3 Meliata Ocean and its dis-tal passive margin Late Paleozoic to Meozoic oceans, whose opening is kinematically unre-lated to the opening of the Atlantic Ocean and the ‘Alpine Tehtys’, in-clude ‘Neotethys’, the Triassic Meliata Ocean and the Jurassic Vardar Ocean. No remnants of the Vardar and only extremely scarce of the Triassic Meliata Ocean are found in the Alps. There they form tectonic slices containing very low-grade metamorphic serpentinites, Triassic radiolarites, olistoliths and Jurassic flysch-type sediments. In contrast, units attributed to the distal passive margin of Apulia adjacent to the Meliata Ocean are more widespread in the Alps. They are preserved in parts of the Austro-alpine nappes (Hallstatt-facies or parts of the Juvavic nappes of the Northern Calcareous Alps. In the western Carpathians, ophiolitic remnants of the Meliata Ocean are preserved as olistoliths in Jurassic mélange formation.

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In spite of the rare occurrences of remnants of this paleo-geographical realm, the Triassic Meliata Ocean plays a crucial role for the understanding of the Cretaceous orogeny. 10.1.4.4 Tiza unit The Tiza unit forms the innermost parts of the Western Dinarides and the Romanian Carpathians. It is sepa-rated by the Mid-Hungarian Line from the northerly adjacent eastern extension of the Southern Alps into Slovenia and the SW-NE-striking continuation of the internal Dinarides situated NE of Zagreb. 10.1.4.5 Margna-Sesia fragment Small fragments off the Apulian dis-tal margin during mid-Jurassic open-ing of the Piedmont-Liguria Ocean, were incorporated during the Late Cretaceous into the accretionary wedge along the active northern and western margin of Apulia, facing the still open Alpine Tethys. In the Gri-sons area, such fragments are partly caught within ophiolitic units. The Sesia unit was incorpo-rated into the accretionary prism dur-ing the Late Cretaceous to the Paleo-gene below the Dent Blanche nap-pes, while the Austroalpine nappes always remained in an upper plate setting after the termination of the Cretaceous. The pre-Alpine basement of the units assigned to the Margna-Sesi fragment, including that of the Dent

Blanche unit, comprises substantial pieces of lower crust. 10.1.4.6 Piedmont-Liguria Ocean The Piedmont-Liguria Ocean was located directly adjacent to the Apulian margin and south of the Bri-ançonnais ribbon continent . Tec-tonic units derived from the Pied-mont-Liguria Ocean (Alpine Tethys) and immediately adjacent distal con-tinental margins are also referred to as “Upper Penninic Nappes”. They occupy the structurally highest posi-tion within the Penninic nappe stack, unless their original position was se-verely modified by large-scale post-nappe folding. Units belonging to this ocean are made of relicts of oceanic litho-sphere and/or exhumed sub-continental material. Drifting started during the Middle Jurassic, in the context of the opening of the Central Atlantic. The onset of sea-floor spreading was followed by deposition of radiolarites and ap-tychus limestones, lithologies that are rather diagnostic for the Pied-mont-Liguria Ocean and neighboring parts of Apulia. This facies is not found in the Valais Ocean (the north-ern branch of the Alpine Tethys. During the Cretaceous, deposi-tion of trench deposits (Avers Bünd-nerschiefer of Eastern Switzerland, schistes lustrés of western Switzer-land and France, parts of the cal-cescisti of Italian authors) indicates that that the southern (Apulian) mar-gin of this basin had been converted into an active margin.

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In eastern Switzerland, units derived from those parts of the Pied-mont-Liguria unit that are immedi-ately adjacent to the Apulian margin (Arosa and Platta units) were al-ready accreted to the Austroalpine units during the Cretaceous orogeny. Other tectonic units attributed to this branch of the Alpine Tethys, particu-larly those of the Western Alps, com-prise parts of the Piedmont-Liguria Ocean that stayed open until the onset of the Paleogene/Neogene collision, when the accretionary wedge of the Alpine subduction system collided with the Briançonnais ribbon conti-nent. In the Eastern and Western Alps, Cretaceous orogeny only af-fected the most internal parts of the Piedmont-Liguria Ocean. This lead to the accretion of internal Piedmont-Liguria-derived slices with the Apulian margin. The final suturing occurred in the context of the Paleo-gene/Neogene orogeny. At this time, all units of the Eastern Alps already stacked during the Cretaceous orogeny, were trusted together over the rest of the Penninic, and in case of the Tauern window, also over the Subpenninic units. 10.1.4.7 Briançonnais terrane Tectonic units derived from the con-tinental Briançonnais Terrane or micro-continent constitute the ‘Mid-dle Penninic nappes’. Before the opening of the Valais Ocean this pa-laeogeographic realm represented the passive continental margin of Europe

in respect to the Piedmont-Liguria Ocean. Later the Briançonnais micro-continent, i.e. the eastern tip of the Iberia block, was separated from Europe in conjunction with the open-ing of the Valais Ocean in Early Cre-taceous times. The basement of the Mesozoic sediments of the Briançonnais Ter-rane is preserved in the ‘Zone Houillère’ (Upper Carboniferous sediments detached from their former Variscan basement), and in basement nappes such as the Gran Paradiso and Monte Rosa nappes of France, Italy and Western Switzerland. Some, but not all of these basement nappes preserved at least part of theirs of their Mesozoic cover. 10.1.4.8 Valais Ocean The Valais Ocean represent a sec-ond, more northerly located branch of the Alpine Tethys. Remnants of this oceanic domain and/or immediately adjacent distal margin units for the ‘Lower Penninic Nappes’. Units considered as derived from this ocean are referred to as “Bündnerschiefer”, “Schistes Lustrés”, or “Calcescisti”. Note, the same or similar types of sedimentary rocks are found in units derived from the Piedmont-Liguria Ocean. Sedimentation of the Valais Bündnerschiefer most probably started near the Jurassic-Cretaceous boundary and evolved into deposition of flysch during the Paleo-gene/Neogene. It remains unclear if all of these deposits were sedimented upon oceanic lithosphere and it is as-

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sumed that some of the indeed rested on distal continental crust. 10.1.4.9 European margin The European margin constitutes the northern and western foreland of the Alps. Paleogene/Neogene rift-ing in this foreland during the forma-tion of the European Cenozoic rift system stated in the Late Eocene and occurred contemporaneously with crustal shortening in the Alps and Pyrenees. The Oligo-Miocene Mo-lasse Basin, representing the northern flexural foreland basin of the Alps, is not developed in front of the western Alpine arc, where the internal parts of this foreland basin were involved in W-directed thrusting of the Penninic units during the Oligocene. In con-trast, its external parts were affected by Miocene thick-skinned thrust propagation (External massifs and the Chaînes Subalpines), followed by thin-skinned deformation of the European margin (Late Miocene to Pliocene deformation of the Jura Mountains). The Molasse Basin is, how-ever, well-developed in Switzerland and Bavaria. This foreland Basin be-gan to subside during the late Eocene, orogen-derived continental clastics were deposited during the late Oligo-cene to late Miocene, directly follow-ing a stage of accretionary-wedge formation. In eastern Austria, the Molasse Basin is considerably narrower and shallower as compared to Switzerland and Bavaria. Moreover, its sedimen-

tary infill is dominated by orogen-derived Oligocene to Early Miocene deepwater clastics. The external massifs of the Western Alps and their sedimentary cover (Chaînes Subalpines of the French Alps) were strongly affected by Neogene thick-skinned thrusting. By contrast, the Eastern Alps are de-void of external massifs. Correspond-ingly, the European foreland is seen to either uniformly dip southward be-neath a flat-lying stack of Alpine nappes, or, to rise steep in a more in-ternal position, as it is the case in the Tauern window. The completely detached Hel-vetic cover nappes are also part of the European margin but in the strict sense (thin-skinned sedimentary thrust-and-fold belts, detached from their former pre-Mesozoic basement) only exist in the Swiss and the westernmost Austrian Alps. The pre-Mesozoic basement, onto which the sediments now exposed in the Helvetic cover nappes were de-posited, form part of the so-called Penninic nappes, but are also referred to as ‘Subpenninic nappes’. These nappes predominantly consist of Variscan basement . Occasionally, the Mesozoic cover of these distal units was not detached. The Sub-penninic basement nappes, which were detached from their deeper crustal underpinnings (lower crust and upper mantle) during subduction, are presently exposed in the Lepon-tine dome. In case of the Lepontine dome, all units structurally located below the trace of the Valais suture zone,

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including the Gotthard and Tavetsch ‘massifs’, as well as the eclogitic Adula nappe, are attributed to the European margin. Parts of

these basement nappes, particularly the small ‘Tavetsch Massif’, are con-sidered to represent the basement of the Helvetic nappes.

10.1.4.10 Major tectonic units of the Alps Dinarides: The continental Tiza unit is part of the larger Tiza block, and makes the innermost parts of the northwestern Dinarides and the Ro-manian Carpathians. The Internal Dinarides unit includes the distal continental margin of Apulia adjacent to a branch of Neoththys as well as mélange formations and/or ophiolitic slivers. Some mélange of Jurassic age contain ophiolitic fragments of the Triassic Meliata Ocean. The bound-ary between external Dinarides and the adjacent southern Alps is not a sharp one. Both units belong to the Apulian plate south of the Periadri-atic line and both are characterized by an interference of Eocene (‘Di-naridic’) and Neogene to recent de-formations. Appennine: The Ligurian nappes unit comprises units that paleo-geographically belong to the Pied-mont-Liguria ocean. However, in contrast to the situation in the Alps, in the Apennines the remnants of this ocean presently form the upper plate in relation to units attributed to the Apulian plate. This because the Lig-urides were ‘back-thrust’, i.e. thrust north to northeastward onto the Po Plain during Mid-Miocene and later times. The underlying Tuscan nap-pes unit, is exposed in windows sur-

rounded by thrusts that formed during early stages of deformation in the Northern Apennines. Southern Alps: The Lower crust unit of the Southern Alps corre-sponds to the Ivrea zone. The Ivrea zone, structured during the Paleozoic, formerly represented the westernmost part of the passive continental margin of Apulia adjacent to the Piedmont-Liguria ocean and later formed the tip of the Adriatic indenter. The Upper crustal basement of the Southern Alps comprises pre-Late Carbonifer-ous basement units affected by Varis-can deformation and metamorphism, unconformably overlain by Late Car-boniferous to Permian sedimentary or volcanic and sub-volcanic units. The Late Paleozoic to Paleogene/Neogene sediments constitute the post-Variscan volcanic and sedimentary cover of the Southern Alps. The Late Paleozoic to Paleogene/Neogene sediments constitute the post-Variscan volcanic and sedimentary cover of the Southern Alps unit . These sediments, together with parts of the unit ‘Upper crustal basement of the Southern Alps’ are affected by Neogene top-S thrusting over unit ‘little deformed parts of the Adriatic micro-plate’ and/or unit ‘external Di-narides’ in the Southern Foreland of

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the Alps. The unit Adriatic micro-plate forms paleogeographically a part of the Apulian plate south of the Insubric Line. It represent the little deformed rigid foreland of the South-ern Alps, Apennines and northern-most external Dinarides. Northern Calcareous Alps and Grauwackenzone (Upper Austroal-pine): Detached Paleozoic (Grau-wackenzone) and Mesozoic (North-ern Calcareous Alps) cover units presently form a thin-skinned fold-and thrust belt positioned at the northern front of the Austroalpine nappes. The sediments arte non- to weakly metamorphic and they were stacked in a transpressional top-NW tectonic scenario during the Cret a-ceous. The Juvavic nappes unit com-prises a series of Mesozoic cover nappes that presently occupy the tec-tonically highest position within the Northern Calcareous Alps. Hence these different units, mostly detached along Permian evaporites may be re-garded as a nappe system. Deforma-tion within the Juvavic nappes is poly-phase. Part of the Juvavic nap-pes are characterized by Hallstatt fa-cies and hence attributed to the distal passive margin of Apulia, facing the Meliata Ocean further to the south. The Tirolian Nappes are observed to represent the cover of the Grau-wackenzone. These two units origi-nally occupied the same paleo-geographic position within the pas-sive margin north of the Meliata Ocean, a position that is more proxi-mal (or external), as compared to the Hallstatt realm. The Bavarian Nap-

pes form the lowermost nappe system within the Northern Calcareous Alps and consist of detached Mesozoic cover. At the northern rim of the Alps these nappes directly overly Penninic units, derived from the Alpine Tethys. Hence, their palaeo-geographic origin is distal in respect to the passive margin that was south-erly adjacent to the Piedmont-Liguria Ocean. The Grauwackenzone repre-sents the former substratum of the Tirolian nappes. This unit was de-tached from an unknown older sub-stratum and has been paleo-geographically positioned north of the Meliata Ocean. Upper Austroalpine basement nap-pes: The Mesozoic cover of the Up-per Austroalpine basement nappes denotes Mesozoic cover of Upper Austroalpine basement nappes pres-ently still found in direct stratigraphic contact with these nappes in areas situated south of the Northern Cal-careous Alps. The structurally higher Drauzug-Gurktal nappe system comprises basement units located south of the southern border of alpine metamorphism. The Ötztal-Bundschuh nappe system occupies an intermediate tectonic position be-tween Drauzug-Gurktal nappe system in its hanging wall, and Koralpe-Wölz high-pressure nappe system in its footwall. The unit is characterized by a strong field metamorphic gradi-ent regarding Eoalpine metamor-phism: grade of metamorphism rap-idly increases towards the base of the nappe system. The Koralpe-Wölz high-pressure nappe system com-

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prises a series of basement units that are characterized by significant, often pressure dominated, Eoalpine meta-morphic overprint and which include eclogite MORB-type gabbros yield-ing Permian protolith ages. The Silvretta-Seckau nappe system comprises all Upper Austroalpine basement nappes found near the western margin of the Austroalpine nappes in eastern Switzerland. These units were thrusted towards the WNW and over the Lower Austroal-pine units of Eastern Switzerland dur-ing Eoalpine deformation. Lower Austroalpine nappes: Units that were derived from a very distal palaeogeographic position within the passive margin of Apulia adjacent to the Piedmont-Liguria Ocean. Such units are widespread in Eastern Swit-zerland, particularly along the south-western margin of the Austroalpine nappe system. The unit nappes de-rived from Margna-Sesia frag-ments are somewhat special in that they are derived from fragments that are interpreted to have been rifted off the most distal part of the Apulian margin as extensional allochthons during mid-Jurassic opening of the Piedmont-Liguria Ocean. Upper Penninic nappes: The Upper Penninic Nappes are predominantly derived from the Piedmont-Liguria Ocean (Alpine Tethys) and pieces of exhumed sub-continental of the im-mediately adjacent distal margin of Apulia. These units normally occupy the structurally highest position within the Alpine nappe stack, unless

the original position was severely modified by large-scale post-nappe folding. The units consist of ophio-lites, Bündnerschiefer, metamorphic cover nappes of very internal but not exclusively oceanic origin. Middle Penninic nappes: These units are part of the Briançonnais terrane. The units are mapped as Sedimentary cover of Middle Penninic basement nappes comprise Mesozoic cover at-tributed to the Briançonnais terrane. In many cases this Mesozoic cover is complete and only comprises those Triassic sediments that were situated below a principle detachment hori-zon. The Middle Penninic basement nappes partly consist of pre-Pennsylvanian (Late Carboniferous) basement exhibiting pre-alpine metamorphism, and partly of mono-metamorphic Permo-Carboniferous fill. The detached Middle Penninic cover nappes of the Western Alps are found at the front of the Western Alps, together with the upper Penninic cover nappes (Préalpes Ro-mandes, ‘Klippen’ of Central Swit-zerland). Detached Permo-Carboniferous sediments (Zone Houillère) and their Mesozoic cover were mapped separately. These units were detached at the base of a volu-minous Permian trough, referred to as Zone Houillère. The Zone Houillère, whose pre-Carboniferous substratum remains unknown, forms the back-bone of the Western Alps. Lower Penninic nappes: This unit comprises sequences derived from the Valais Ocean and/or the immedi-

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ately adjacent distal continental mar-gin units. The Tertiary flysch seal-ing Lower Penninic accretionary prism is attributed to the Ultra-Dauphinois. The bulk of the Lower Penninic units are made up of North-Penninic ophiolites and Bündner-schiefer. These Bündnerschiefer-dominated sediments represent a Cre-taceous to Paleogene/Neogene-age post-rift sequence. Sub-Penninic nappes: These units form the structurally lowest parts of the Lepontine dome and the Tauern window. They are interpreted as de-rived from the distal European mar-gin. Some of these basement-dominated units, together with the basement of the Tavetsch massif, rep-resent the former crystalline substra-tum of the Helvetic and the Ultrahel-vetic nappes, detached before the on-set of Paleogene/Neogene-age meta-morphism with the lowermost Sub-Penninic nappes. The Mesozoic cover of Sub-Penninic basement nappes represent those cover units of the Sub-Penninic basement units that remained within the metamorphic core of the Alps and which suffered Alpine metamorphism. This cover delineates nappe boundaries within the deepest Lepontine nappes. The Non-eclogitic Sub-penninic base-ment nappes, are overprinted by Pa-leogene/Neogene-age Barrowian-type metamorphism. In the Lepontine dome, these nappes include, from base to top: Gotthard ‘Massif’ (in reality a back-folded nappe), Veram-pio and Leventina gneisses, Simano-Antigorio and Monte Leone nappes.

The intensely sliced Eclogite Sub-Penninic basement units are occa-sionally found at the top of the Sub-Penninic nappes, i.e. at the immediate base of the Lower Penninic Nappes. Northern Alpine foreland and Hel-vetic nappes: The Helvetic and Ul-tra-Helvetic nappes are limestone-dominated cover nappes derived from the more proximal European margin. These units are restricted to the Al-pine foreland of Switzerland and western most Austria. The base of the Helvetic nappes is drawn along the Glarus overthrust and its equivalent in Western Switzerland, i.e. the base of the Diablerets nappe. A thin my-lonitic slice of basement, referred to as Tavetsch Massif, positioned be-tween Aar and Gotthard ‘Massif’ is also considered as part of the Helve-tic. The Helvetic flysch mostly com-prises Upper Eocene to Lower Oligo-cene flysch (including nummulitic limestone) deposited in the internal part of the Alpine foreland basin. Of-ten this flysch un-conformably over-lies the Mesozoic cover of the autochthonous to para-autochtohonous external massifs of the Northern Alpine foreland. The Subalpine Molasse unit is made of conglomeratic molasse. These thrust sheets, that root below the external massifs in Eastern Switzerland can be followed all along the northern rim of the Swiss and Austrian Alps. The de-formed autochthonous and para-autochthonous pre-Tertiary cover of the Northern Alpine foreland is restricted to the Western Alps where late stage thrusting propagated far

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into the foreland in Miocene to Re-cent times. These units contain thick- and thin-skinned thrust sheets. The thick-skinned thrust sheets comprise the ‘External Massifs’ and their cover also referred to as Chaînes Subalpi-nes. The Undeformed pre-Tertiary cover of the Northern Alpine fore-

land comprises the rift flanks of Rhine and Bresse Graben. The base-ment outcropping in unit External massifs of the Alps and Variscan basement of the Northern Alpine foreland is connected below the Mo-lasse basin and the Jura Mountains.

Important Terms

• Adriatic indentor/plate • Alpinides • Aptychus limestones • Apulian plate • Atlantic Ocean • Austroalpine nappes • Baltic shield • Baltica • Briançonnais ribbon continent • Bündnerschiefer • Caledonides • Chaînes Subalpines • Eoalpine • External massifs • Fennosarmantia • Flysch deposits • Hallstatt-facies • Helvetic, Penninic, East-alpine,

South-alpine • Iapetus • Insubric Line • Jura Mountains • Laurussia/Old Red Sandstone

Continent

• Lower Penninic Nappes • Molasse Basin • Neotethys • North Sea • Olistoliths • Paleo-Tethys • Pangea • Piedmont-Liguria Ocean • Precambrian platform • Precambrian shield • Radiolarites • Russian platform • Serpentinites • Subpenninic nappes • Tauern window • Tiza unit • Tornquist Sea • Ukrainian shield • Valais Ocean • Vardar Ocean • Variscides - Hercynides • Zechstein

Page 90 – Vs. 4.0 - winter 2005

Review Question 10.1.1 Show a possible subdivision of the geologic history of Europe. 10.1.2 Name some of the fragments that form Proto-Europe. 10.1.3 How did Laurussia (Old Red Sandstone Continent) formed? 10.1.4 What was the Tornquist Sea? 10.1.5 The Variscan/Hercynian orogens are the suture that delineates which plate tectonic event? 10.1.6 Describe the plate tectonic setting that lead to the buildup of the Alpine orogenic belt. 10.1.7 Name some of the alpine fold belts in Europe. Sources used and references for further study Blundell, D., Freeman, R., and Mueller, S., 1992, A continent revealed - The European Geotraverse: Cambridge, Cambridge University Press, 275 p. Pluijm, B.v.d., and Marshak, S., 1997, Earth Structure: USA, WCB/McGraw-Hill, 495 p. Schmid, S.M., Fugenschuh, B., Kissling, E. & Schuster, R., 2004, Tectonic map and over-all architecture of the Alpine orogen: Eclogae Geologicae Helvetiae, vol. 97/1, 93-117. Schönenberg, R., and Neugebauer, J., 1987, Einführung in die Geologie Europas: Frei-burg im Breisgau, Rombach GMBH, 294 p.


10.2 Some basics of Plate Tectonics The theory of new global tectonics (plate tectonics) has largely been developed since 1967. This uniformitarian view of continents drift was first suggested by F.B. Taylor, an American physicist, in 1910, and by Alfred Wegener, a German meteorologist in 1912.

The concept of plate tectonics is based on the observation that ca. 80% of the Earth’s seismic activity was concentrated in narrow, continuous zones, com-monly less than 10km wide. These zones are the crests of the ocean ridges, transform faults, and subduction zones. This observation suggested that vast ar-eas of the Earth’s surface were in relative motion to each other. Today we know that some 10 to 12 major lithospheric plates can be defined. In addition, there are numerous microplates within present and past subduction and collision zones. The plates within the Pacific consist entirely of oceanic lithosphere , but all other plates are composed of both, oceanic and continental lithosphere . All plates, oceanic, or mixed continental-oceanic (the lithosphere) float on the asthenosphere.

New oceanic lithosphere is produced along mid-ocean ridges and de-stroyed in subduction zones. Lithosphere that dives into a subduction zone under-goes metamorphism under increased pressure and temperature. This metamor-phism (transformation) causes the growth of minerals with a heavier specific weight (e.g., garnet). These heavy minerals increase the net weight of the sub-ducted lithosphere. It is believed that this weight drags the lithosphere down into the subduction zone. This mechanism is called “slab pull” and it is supported by “ridge push”. Ridge push is the term for the force of the upwelling (and pushing) magma that forms new oceanic lithosphere along mid-ocean ridges. Because the Earth is a sphere, motion of pieces of the surface of this sphere must be accommodated along fracture zones. These fracture zones are called “transform faults”. Where continents collide, orogens (mountain chains) form. Much of the continental lithosphere is built by the old cratons and small plates sutured against them. The sutures are marked by orogenic zones. The orogenic phases discussed in this hand-out reflect major collision phases of continental plates. The main differences between oceanic and continental lithosphere are: • Layering. The large-scale layering of the continental crust is poorly defined

and highly variable. It generally reflects a complex and long geologic history. By contrast, the layering of oceanic lithosphere is well defined.

• Thickness. The thickness of continental crust averages about 35-40 km but it is quite variable thinning to only few kilometers beneath rifts and thickening to up to 80 km beneath young mountain belts (orogens). The oceanic crust main-


tains a relatively constant thickness of about 7 km, although its thickness de-creases along transform faults and increases towards the continental margins.

• Age. Continental crust may be as old as 3960 Ma consisting of Precambrian cratons or shields, which are surrounded by younger orogenic belts. Oceanic crust however, is nowhere older than 200 Ma. It progressively becomes older when traced away from mid ocean ridges.

• Tectonic activity. Continental crust may be extensively folded and faulted and may have undergone multiple orogenic events. Oceanic crust, however, ap-pears to be very stable and has suffered little deformation except along plate boundaries.

• Igneous activity. Very little igneous activity occurs on the great majority of the continental crust. The only present-day localities of activity are the mountain belts of the Andean type. The activity within the oceans is much larger. Ocean ridges and island arcs are the location of the Earth’s most active areas of vol-canic and plutonic activity.

Important Terms • Continental and oce-

anic lithosphere • Crust • Lithosphere plate • Mantle

• Mid-ocean ridge • Seismic activity • Slab pull – ridge

push • Subduction zone

• Transform fault • Wegener


10.3 Classification of life

Until comparatively recently, living organisms were divided into two kingdoms: animal and vegetable, or the Animalia and the Plantae. In the 19th century, evidence began to ac-cumulate that these were insufficient to express the diversity of life, and various schemes were proposed with three, four, or more kingdoms. The scheme most often used currently di-vides all living organisms into five kingdoms: Monera (bacteria), Pro-tista, Fungi, Plantae, and Animalia. This coexisted with a scheme divid-ing life into two main divisions: the Prokaryotae (bacteria, etc.) and the Eukaryotae (animals, plants, fungi, and protists).

Recent work, however, has shown that what were once called ‘prokaryo-tes’ are far more diverse than anyone had suspected. The Prokaryotae are now divided into two domains, the Bacteria and the Archaea, as differ-ent from each other as either is from the Eukaryota, or eukaryotes. No one of these groups is ancestral to the others, and each shares certain fea-tures with the others as well as hav-ing unique characteristics of its own.

Within the last two decades, a great deal of additional work has been done to resolve relationships within the Eukaryota. It now appears that most of the biological diversity of eukaryo-tes lies among the protists, and many scientists feel it is just as inappropri-ate to lump all protists into a single kingdom as it was to group all pro-karyotes. Although many revised sys-tems have been proposed, no single one of them has yet gained a wide acceptance.

The Eukaryota include the organisms that most people are most familiar with - all animals, plants, fungi, and protists. They also include the vast majority of the organisms that pale-ontologists work with. Although they show unbelievable diversity in form, they share fundamental characteris-tics of cellular organization, bio-chemistry, and molecular biology. Note this text and figure 10.3/1 are based on:

http://www.ucmp.berkeley.edu/alllife/threedomains.html To show the full range of classifica-tion for animals within the Eukaryota we use the coyote, Canis latrans.

Kingdom – Animalia, Phylum – Chordata, Subphylum – Vertebrata, Class – Mammalia, Order – Carnivora, Family – Canidae, Genus – Canis, Species – la-trans.


10.4 Stratigraphic stages In many parts of the world, the geologic record has been divided into stages. Stages are time-stratigraphic units. For the most part, the stages recognized in Europe have become the standard stages with which stages are correlated that have been defined elsewhere. Correlation of different systems of stages remains imperfect. The same accounts for the radiometric ages of stage boundaries. Prior to the rise of life in the late Precambrian, our chronostratigraphic framework is based on radiometric dating. With the Cambrian explosion of live the relative stratigraphic succession of fossil hardparts provides a relative biostratigraphic framework. The stratigraphic system is subdivided into a number of hierarchical units. These are: • EON (Archean, Proterozoic, Phanerozoic) • ERA (Paleoproterozoic, Mesoproterozoic, Neoproterozoic, Precambrian, Pa-

leozoic, Mesozoic, Cenozoic. • PERIOD (Vendian, Cambrian, Ordovizian, Silurian, Devonian, Carboniferous,

Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene, Quaternary) • EPOCH (e.g., Scythian (early Triassic), Middle Triassic, Late Triassic, Liassic

etc.). • STAGES (e.g., the Triassic epoch is subdivided into Anisian, Ladinian,

Carnian, Norian, Rhaetian stages etc.). • SUB-STAGES (e.g., the Ladinian is subdivided into Early and Late Ladinian

substages). • BIOZONES (e.g., the Late Ladinian substage is divided into three ammonite

biozones Megnioceras meginae, Maclaernoceras maclaerni , Frankites suther-landi etc.).


Main references used A. Books Best, M. G., 1982, Igneous and Metamorphic Petrology: New York, W.H. Free-

man and Company, 630 p. Faure, G., 1977, Principles of Isotope Geology: Singapore, John Wiley & Sons,

Inc., 589 p. Kearey, P., and F. J. Vine, 1994, Global Tectonics: London, Blackwell, 302 p. Kearey, P., 1995, The Encyclopedia of the Solid Earth Sciences: Berlin, Blackwell

Science, 713 p. Monroe, J. S., and R. Wicander, 1993, The Changing Earth: St. Paul, West Pub-

lishing Company, 731 p. Murray, J. W., 1985, Atlas of Invertebrate Macrofossils: London, Halsted Press,

241 p. Schönenberg, R., and J. Neugebauer, 1987, Einführung in die Geologie Europas:

Freiburg im Breisgau, Rombach GMBH, 294 p. Stanley, S. M., 1986, Earth and Life through time: New York, W. H. Freeman and

Company, 689 p. Ziegler, P.A., 1990, Geological Atlas of Western and Central Europe: Avon, Eng-

land, Shell Internationale Petroleum Maatschappij BV. 239 p. B. Papers Dercourt, J., L. P. Zonenshain, L.-E. Ricou, V. G. Kazmin, X. Le Pichon, A. L.

Knipper, C. Grandjacquet, I. M. Sborttshikov, J. Geyssant, C. Lepvrier, D. H. Dechersky, J. Boulin, J.-C. Sibuet, L. A. Savostin, O. Sorkokhtin, M. Westphal, M. L. Bazhenov, J. P. Lauer, and B. Biju-Duval, 1986, Geological evolution of the Tethys belt from the Atlantic to the Pamirs since Lias: Tectonophysics, v. 123, p. 241-315.

Schmid, S.M., Fugenschuh, B., Kissling, E. & Schuster, R., 2004, Tectonic map and overall architecture of the Alpine orogen: Eclogae Geologicae Helvetiae, v. 97/1, 93-117.

Stampfli, G., J. Marcoux, and A. Baud, 1991, Tethyan margins in space and time: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 87, p. 373-409.

Weijmars, R., 1989, Global tectonics since the breakup of Pangea 180 Million years ago: evolution maps and lithospheric budget: Earth-Science Reviews, v. 26, p. 113-162.

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