The Geology of the Paleozoic Era. The Paleozoic Era. Geologic periods in Paleozoic record 7% of...

The Geology of the The Geology of the Paleozoic EraPaleozoic Era

The Paleozoic Era.The Paleozoic Era.• Geologic periods in Paleozoic record 7% of

Earth’s history • Cambrian, Ordovician, Silurian, Devonian

Carboniferous (Miss., Penn.) Permian • Boundaries in the major divisions originally

defined by changes in the fossil record• Start of the Paleozoic used to be defined

by appearance of first easily visible fossils; later lowered to include small shelly fauna; then lowered further to first appearance of complex branching trace fossils.

Base of the Cambrian systemBase of the Cambrian system

Trace fossil Phycodes pedumNew modes of locomotion

Welsh Lower PaleozoicWelsh Lower Paleozoic

Prof Adam Sedgwick (Cambridge) studied the Cambrian (including the Ordovician) based on superposition and structural geology. Roderick Murchison described and mapped the Silurianbased on fossils. Together Sedgwick and Murchison defined the Devonian System in Devon and Cornwall.Murchison established the Permian in Russian.Charles Lapworth separated the Ordovician.Review: Origin of names

Paleozoic OverviewPaleozoic Overview

• Global tectonic theme of the Paleozoic - assembly of the supercontinent, Pangaea.

• Deposition due to transgressions (and disconformities due regressions) of shallow continental (epeiric) seas. Interiors of continents were frequently flooded.

• Formation of mountain belts at edges – Tectonic activities associated with the assembly of

Pangaea.

Paleozoic Global Geology Paleozoic Global Geology

• Six major Paleozoic continents are recognized after Rodinia breakup

• Gondwana - S. continents, India

• Laurentia - North America, Greenland, part Gr. Britain

• Baltica – Northern Europe

• Siberia – Most of Northern Asia

• Kazakhstania – part Central Asia

• China - All of SE Asia and SE China

Paleozoic Era key eventsPaleozoic Era key eventsTransgression and Regressions

Assembly of Pangea

Avalonia collides with Laurentia

Iapetus floor subducted Scotl Scan NE CanLauentia and Baltica collide - Laurasia

Continues subd Iapetus South docks rest AvaloniaOld Red SS

Catskill Clastic Wedge

Gondwana/Laurasia

Extinctions: http://www.fmnh.helsinki.fi/users/haaramo/Meteor_Impacts/Middle_Paleozoic_impacts.htm

Paleogeographic Paleogeographic Reconstructions and MapsReconstructions and Maps

• Geologists want to create maps of the Earth as it was in the past,

• correctly position the continents for different time periods, and

• reconstruct geography on the continents.

What data are used to do this as What data are used to do this as accurately as possible?accurately as possible?

• Paleomagnetism Latitude• Biogeography - Distribution of flora and fauna. • Climatology - Climate sensitive sediments

Glacial drift, desert pavement, laterite soils, etc. • Tectonic Patterns – continuation of mountains• Can’t use Magnetic Stripes on ocean floor-

Mesozoic and later

Global paleogeography for the Global paleogeography for the CambrianCambrian period period

All six continents occur at low paleolatitudes Ocean waters circulate freely/ poles appear ice-free Epeiric seas cover much of continents except Gondwana Highlands in N Gondwana, Eastern Siberia, Central Kazakhistan

Six major Paleozoic continents are recognized after Rodinia breakup Laurentia - North America, Greenland, Scotland Rotated 90o

Baltica - Russia (W of Urals), Scandinavia

Siberia - Russia (E of Urals), Part Asia Kazakhstania - Kazakhstan China - All of SE Asia and SE China

Gondwana - S. continents, India

Ordovician - SilurianOrdovician - Silurian

SILURIAN– Silurian collision of Baltica/Laurentia Caledonian Orogeny, suturing forms Laurasia- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ORDOVICIAN– Ordovician Gondwana moved 40o S to a South Pole

location (Glaciers formed, we find L. Ord. tillites) – Baltica moved S, then N – Avalonia collided with Laurentia (Taconic Orogeny)

How do we check our paleolatitude data?L. Ordovician biogeography of Carolinites genacinaca

Confirms paleomagnetic latitudes

Trilobite Paleogeography

From McCormick & Fortey 1999. From McCormick & Fortey 1999. J. Paleontol. 73(2):202-18.) J. Paleontol. 73(2):202-18.)

Global paleogeography Global paleogeography MidMid Ordovician to SilurianOrdovician to Silurian

Baltica moved S, then N and collided with Laurentia, rotated 30o

Siberia moved from equatorial to northern temperate latitudes

Gondwana moved South , land in south high latitudes(Late Ord. tillites)

Small piece of Avalonia hits in Ordovician

M. OrdovicianM. Ordovicianhttp://www.gl.rhbnc.ac.uk/seasia/Biogeog_pdfs/Fortey_Cocks.pdf

http://www.geodynamics.no/Platemotions/500-400

Saucrorthis

Mostly distinct faunasContinents were not close

Paleogeography Early DevonianPaleogeography Early Devonian

Other orogenies: Antler (Cordillera) and Ellesmere (northwest margin of Laurentia) Gondwana moves to higher southern latitudes. All other continents at low northern latitudes.

Continued collision of Baltica/Laurentia formed Laurasia.Caledonian Orogeny finishes in E. DevAcadian Orogeny in the Appalachiansfolds older rocks M. Dev.

Late Devonian Faunal SimilaritiesLate Devonian Faunal Similarities

How close were Laurasia = Euramerica and Gondwana in How close were Laurasia = Euramerica and Gondwana in the Late Devonian?the Late Devonian?

DicranurusDicranurus

ReedopsReedops

Dalmanitidae Dalmanitidae

Looks like Oklahoma was close to Morocco

Euramerica is Laurentia plus Baltica

Final Assembly of PangeaFinal Assembly of Pangea• Permian – Kazakhstania collided with Baltica, forming the

Urals

• Single continent surrounded by Panthalassa Ocean w Tethys Sea

________________________________________• Pennsylvanian – Siberia collided with Kazakhstania,

forming Altai Mts.

• Laurasia collides with Gondwana to reform Appalachians Laurasia collides with Gondwana to reform Appalachians and to form Hercynian Mts. in Late Paleozoic. Hercynian and to form Hercynian Mts. in Late Paleozoic. Hercynian collision forms Europecollision forms Europe

Gondwana – Laurasia collision Gondwana – Laurasia collision Hercynian orogenyHercynian orogeny

North and South Europe sutureHercynian Orogeny continuous w Allegheny Orogeny about 300 mya

Final Assembly of PangaeaFinal Assembly of Pangaea

• After the suturing of Gondwana and Laurasia (includes Hercynian and Allegheny Orogenies),

• Then:

• Siberia collided with Kazakhstania in the Pennsylvanian, forming the Altai Mountains.

• Kazakhstania collided with Baltica in the Permian, forming the Ural Mountains.

Paleogeography Late PermianPaleogeography Late Permian

HercynianN Eur-S Eur

Allegheny Orogeny

Paleozoic Era key eventsPaleozoic Era key eventsNext let’s look closer at the Collisional Mountains

Rifting raises water, moves plates, which later collide.Assembly of Pangea

Avalonia collides with Laurentia

Iapetus floor subducted Scotl Scan NE CanLauentia and Baltica collide - Laurasia

Continues subd Iapetus South docks rest AvaloniaOld Red SS

Catskill Clastic Wedge

Gondwana/Laurasia

Tectonics Paleozoic North America Tectonics Paleozoic North America

• In the Cambrian, several small terranes lay to the south of Laurentia as it separated from Baltica. The shores were passive margins.

• In the Ordovician, about 500 mya, the direction of plate motion reversed and Iapetus began to close.

Global paleogeography for the Global paleogeography for the CambrianCambrian period period

Avalonia Terranes

The Taconic orogenyThe Taconic orogeny

Laurentia moves toward Avalonia Africa moves toward both

Rodinia breaking up

Avalonia Terrane E. Cambrian

Plates reverse, in E. Ordovician

Taconic orogeny (cont)Taconic orogeny (cont)

Mid – L. Ordovician, N.Avalonia

and an island arc dock with

Laurentia, beginning the Appalachians

Rocks thrust up over margin of Laurentia

Cambrian paleogeographyCambrian paleogeography

Pre –collisionsNote equator

Submerged

Submerged

Submerged

Submerged

Interior of Laurentia, Ord.-SilurianInterior of Laurentia, Ord.-Silurian

• Inland, the Taconic collisions caused the crust to be warped down, forming the Appalachian FORELAND BASIN

• Deep water sediments were deposited in the basin, until sediments eroded from the Taconic mountains filled the basin, and shallow water deposits prevailed.

• The Queenston Clastic Wedge.

Paleogeography N. Am. M Ord-Sil.Paleogeography N. Am. M Ord-Sil.

Post collisionsBarrier Reefs HighstandEvaporites Lowstand

Queenston Clastic Wedge

Queenston clastic wedgeQueenston clastic wedge

(Martinsburg Shale)

(Allentown Dm., Jacksonburg Ls.)

Hardyston Fmdownfolded

The Caledonian OrogenyThe Caledonian Orogeny

• Baltica sutured onto Laurentia– Mountains - Nova Scotia to Scandinavia– Erosion resulted clastic wedge– Devonian Old Red Sandstone

• Result called Euramerica or Laurasia

Late Silurian - Early DevonianLate Silurian - Early DevonianCaledonian Orogeny-Laurasia formsCaledonian Orogeny-Laurasia forms

Caledonian Orogeny

To our North

The Acadian OrogenyThe Acadian Orogeny• Continued subduction of Iapetus ocean floor in Devonian

• Additional parts of Avalonia docked with Laurentia

– Erosion resulted Catskill clastic wedge

– Facies change in foreland basin – shallow marine to streams in Middle Devonian as basin fills

– Field trip fossil collecting Marcellus to Mahantango Centerfield Reef

Early - Mid DevonianEarly - Mid DevonianAcadian Orogeny-Laurasia formsAcadian Orogeny-Laurasia forms

Acadian OrogenySouthern Avalonia into Laurasia

Accreted terranes Accreted terranes (Does this remind you of somewhere else?)(Does this remind you of somewhere else?)

Late Devonian paleogeography Late Devonian paleogeography of North Americaof North America

Catskill FormationCatskill Formation

Clastic Wedge from Acadian collision w rest of Avalonia

E-Mid Devonian dockingBy L. Dev. filled, mostly stream

deposits, floodplains have fossils of land plants and

amphibians

Oxidation state of Iron depended on oxygen levels

Catskill clastic wedge thicknessCatskill clastic wedge thickness

Coarse near sourceWedge thins away

CarboniferousCarboniferousBIG Collision with GondwanaBIG Collision with Gondwana

The Allegheny Orogeny The Allegheny Orogeny

• Initial contact Late Mississippian

• Northwest Africa collided

• Folding of Pennsylvanian rocks proves long duration

• Deformation much more extensive than the Taconic or Acadian – New England to Alabama

Physiographic provinces Physiographic provinces AppalachiansAppalachians

at collision suture, very metamorphosed and intruded

Grenvillian rocks thrust cratonward

Northwest thrust faults and northeast anticlines and synclines

little deformation

Allegheny and Ouachita OrogeniesAllegheny and Ouachita Orogenies

Allegheny

Ouchita

Hercynian

Ouchita hit by South America

Allegheny hit by Africa

Western: Antler OrogenyWestern: Antler Orogeny

Beginning of Cordillera Construction, Devonian to Mississippian

Antler Mts. are folded basin sediments

• In the Devonian, a westward dipping subduction zone formed off Western Laurasia.

• An Island Arc formed, the Klamath Arc• The ocean floor between subducted as

the arc approached and collided with the continent

• Late Devonian to Early Mississippian• Called the Antler Orogeny, basin thrust

East• Klamath Mts. and North Sierra Nevada

Late Devonian paleogeography Late Devonian paleogeography of North Americaof North America

Here it is

Paleozoic structure of the WestPaleozoic structure of the West

Exposed granite eroded as arkoses (feldspar-rich sandstones)

• Devonian – Ouachita Orogeny creates compressional stress

• Pennsylvanian – blocks push up along high angle faults, relieving the stress. PreCambrian basement exposed.

• Resulted in Front Range Uplift CO & WY

• Uncompahgre Uplift CO & NM

Pennsylvanian arkose, COPennsylvanian arkose, COFountain Arkose, CO, deposited northeast of Front Range Uplift

Next: Cratonic SequencesNext: Cratonic Sequences

• Laurence Sloss: Major transgressive-regressive cycles

• 4 in Paleozoic• Allow long range correlation “Sequence Stratigraphy”

• Transgression: nearshore sand covered by muds and/or carbonates “fining upward”

• Regression: – Nearshore: erosion and disconformity– Far offshore: sediments “coarsening upward”

Paleozoic Era key eventsPaleozoic Era key eventsTransgression and Regressions

Assembly of Pangea

Sauk: High rates of sea-floor

spreading

TC: glacial melting and accelerated sea-floor spreading

KS: filling in of the Appalachian foreland basin by Late Devonian time

ABS: Sea level rise (cyclic) due Gondwana glaciation Penn-Pm regression due slowdown spreading, assembly of Pangaea, drained continent L Pm

HighLow

Cambrian – E Ord Sauk SequenceCambrian – E Ord Sauk Sequence

Pre-collision, dramatic transgression due active MORsNote extensive shallow carbonates and equator

Time-transgressive Cambrian Time-transgressive Cambrian rocks Grand Canyonrocks Grand Canyon

Sauk SequenceSauk Sequence

Transgression

Note how western BAS is older than eastern BAS

LowerCambrian

MiddleCambrian

http://www.wmrs.edu/projects/trilobites/images/trilo7-2.jpg

http://www.geo-tools.com/trilobites.htm

WEST EAST

Tippecanoe Transgression M Ord-Sil.Tippecanoe Transgression M Ord-Sil.

Reworking of Sauk sands gives pure sands Reworking of Sauk sands gives pure sands useful in glass manufacture.useful in glass manufacture.

Sands covered by carbonates Sands covered by carbonates as transgression advancesas transgression advances

Michigan Basin surrounded by reefsMichigan Basin surrounded by reefsRestricted circulation causedRestricted circulation caused

evaporite precipitationevaporite precipitationSource of Rock SaltSource of Rock Salt

About 5 smaller T-R PulsesAbout 5 smaller T-R Pulses

Late Devonian Kaskasia Late Devonian Kaskasia TransgressionTransgression

Williston Basin surrounded by reefsWilliston Basin surrounded by reefsRestricted circulation causedRestricted circulation caused evaporite precipitationevaporite precipitation

Carbonates over pure sandsCarbonates over pure sands

Absoroka SequenceAbsoroka Sequence

• Transgression starts M Pennsylvanian• Regression starts L Pennsylvanian• Cyclothems (pulses) reflect Glacial sea-

level var. PERMIAN dry interior• Inland sea limited to w Texas & s NM• Extensive evaporite deposits KS – OK• Redbeds over interior

Paleozoic Era key eventsPaleozoic Era key eventsClimate/Sedimentation

Rifting raises water, moves plates, which later collide and fold. Folding makes deep basin. If fold basin sediments, uplift.

Assembly of Pangea

Next: Paleozoic ClimatesNext: Paleozoic Climates• Paleozoic mostly warm, but two glacial times,

Ordovician and Pennsylvanian to Late Permian.

• Cool Middle Ordovician– CO2 tied up in carbonates – no greenhouse

– Extensive Gondwana tillites and striations

– Sea level retreats as glacier holds water

Late Paleozoic ClimatesLate Paleozoic Climates(1) Cool Pennsylvanian – M Permian

– CO2 tied up in carbonates

– Extensive Gondwana tillites and striations – sea-level fluctuations due glacial (slow regression) and interglacial (fast melt) “cyclothems”

– Generated Coal deposits, carbon reservoirs, low CO2

Pennsylvanian Glacier -GondwanaPennsylvanian Glacier -GondwanaSea-level falls as glaciers grow, inland seas retreat

Pennsylvanian CyclothemsPennsylvanian Cyclothems

Rapid transgressions cover swamp as ice

melts

Slow regression as ice sheet grows

estuary

swampCoal Swamp

Coal formation Pennsylvania cyclothemsCoal formation Pennsylvania cyclothems

Highland source to east

Melting glacier

Pennsylvanian-age coal depositsPennsylvanian-age coal deposits

Late Paleozoic Climates - 2Late Paleozoic Climates - 2(2) The Late Permian WARM• Pangaea was ice-free• Warm equatorial waters from the Panthalassa

Ocean reached both poles. • No glaciers = no coal (need rapid transgression)• The Gondwana landmass had drifted north into

warmer climates.• reduced coal formation caused carbon dioxide

levels to rise • Greenhouse effect

L. Permian PangaeaL. Permian Pangaea

Pangaea is assembled, sea-level low

Ice-free, dry interiors, no coalMuch of land +/- 30 degrees

Hot, dry climateNote evaporites

PERMIAN N. AmericaPERMIAN N. America

• Inland sea limited to w Texas & s NM

• Extensive evaporite deposits KS – OK

• Redbeds over interior – strong seasons

Next TimeNext Time

• A survey of Paleozoic Life, and

• Latest Permian Mass Extinction– Most profound in history of life.