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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.