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 theCambrian (including the Ordovician) based on superposition and structural geology. Roderick Murchison described and mapped the Silurianbased on fossils. Together they defined the DevonianSystem 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 Era key eventsPaleozoic Era key eventsTransgression and Regressions

Rifting raises water, moves plates, which later collide.Assembly ofPangea

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

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

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

PaleogeographicPaleogeographicReconstructions 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 • 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 periodperiod

All six continents occur at low paleolatitudesOcean 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 90oBaltica - 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 Ordovician -- SilurianSilurianSILURIAN– Silurian collision of Baltica/LaurentiaCaledonian 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 – Microcontinent & Island Arcs collided with Laurentia

(led to Taconic Orogeny) narrowing Iapetus

How do we know?L. Ordovician biogeography of Carolinites genacinaca

Confirms paleomagnetic latitudes

Trilobite Trilobite PaleogeographyPaleogeography

From McCormick & From McCormick & ForteyFortey 1999. 1999. J. J. PaleontolPaleontol. 73(2):202. 73(2):202--18.) 18.)

http://www.trilobites.info/trilopaleogeo.htm

Global paleogeography Global paleogeography MidMid Ordovician to SilurianOrdovician to Silurian

Baltica moved S, then Nand collided with Laurentia, rotated 30o

Siberia moved from equatorialto northern temperate latitudes

Gondwana moved 40o S to a South Pole location (Late Ord. tillites)

Remember HawaiiansAnd Emperor ChainEvidence of changing directionsVarying rifting pushes

Small piece of Avalonia hits in Ordovician

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

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

Saucrorthis

Mostly distinct faunasContinents were not close

DevonianDevonian

– Acadian Orogeny in the Appalachian– Other orogenies: Antler (Cordillera) and

Ellesmere (north margin of Laurentia) – Gondwana moves to higher southern

latitudes. All other continents at low northern latitudes.

Paleogeography Early DevonianPaleogeography Early Devonian

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

Continued collision of Baltica/Laurentia formed Laurasia, closed Iapetus OceanCaledonian Orogeny in B/L finishes E. DevAcadian Orogeny in the Appalachiansfolds older rocks M. Dev.

Devonian Faunal SimilaritiesDevonian Faunal Similarities

Oklahoma and Morocco Trilobites from the DevonianOklahoma and Morocco Trilobites from the Devonian

DicranurusDicranurus

ReedopsReedops

DalmanitidaeDalmanitidae

Looks like Oklahoma was close to Morocco

http://www.trilobites.info/trilopaleogeo.htm

Final Assembly of PangeaFinal Assembly of Pangea• Laurasia collides with Gondwana to form

Hercynian Mts. Late Paleozoic forms Europe

• Pennsylvanian – Siberia collided with Kazakhstania, forming Altai Mts.

• Permian – Kazakhstania collided with Baltica, forming the Urals

• Single continent surrounded by Panthalassa Ocean w Tethys Sea

Gondwana Gondwana –– Laurasia collision 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 Orogenies

Rifting raises water, moves plates, which later collide.Assembly ofPangea

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 periodperiod

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.Avaloniaand an island arc dock with

Laurentia, beginning the Appalachians

Rocks thrust up over margin of Laurentia

Interior of Laurentia, Interior of Laurentia, OrdOrd..--SilurianSilurian

• 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.

Cambrian paleogeographyCambrian paleogeography

Pre –collisionsNote equator

Paleogeography N. Am. M Paleogeography N. Am. M OrdOrd--SilSil..

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 Laurasia

Late Silurian Late Silurian -- Early DevonianEarly DevonianCaledonian OrogenyCaledonian Orogeny--Laurasia formsLaurasia 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– Re-folding of Old Mountains – Virginia to Maritimes– Old rocks even more folded and metamorphosed– Erosion resulted Catskill clastic wedge– Facies change in foreland basin – shallow marine to

streams in Middle Devonian as basin fills– Field trip Marcellus to Mahantango Centerfield Reef– Catskill delta as push stopped and basin filled

Early Early -- Mid DevonianMid DevonianAcadian OrogenyAcadian Orogeny--Laurasia formsLaurasia forms

Acadian OrogenySouthern Avalonia into Laurasia

BIG Collision with GondwanaBIG Collision with GondwanaThe Allegheny OrogenyThe 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 York to Alabama

Paleozoic Era key eventsPaleozoic Era key eventsTransgression and Regressions

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

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 dueslowdown spreading, assembly of Pangaea, drained continent L Pm

HighLow

TimeTime--transgressive Cambrian 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

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 ofPangea

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 Pennsylvanian Glacier --GondwanaGondwanaSea-level falls/rises as glaciers grow/melt

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

PennsylvanianPennsylvanian--age coal depositsage coal deposits

Late Paleozoic Climates Late Paleozoic Climates -- 22(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

The Geology of the Paleozoic EraThe Paleozoic Era.�Base of the Cambrian systemWelsh Lower PaleozoicPaleozoic Overview�Paleozoic Era key eventsPaleozoic Global Geology �Paleogeographic Reconstructions and MapsWhat data are used to do this as accurately as possible?Global paleogeography for the Cambrian periodOrdovician - SilurianGlobal paleogeography �Mid Ordovician to SilurianDevonian �Paleogeography Early DevonianFinal Assembly of PangeaGondwana – Laurasia collision Hercynian orogenyFinal Assembly of PangaeaPaleogeography Late PermianPaleozoic Era key eventsTectonics Paleozoic North America Global paleogeography for the Cambrian periodThe Taconic orogenyTaconic orogeny (cont)Interior of Laurentia, Ord.-SilurianCambrian paleogeographyPaleogeography N. Am. M Ord-Sil.Queenston clastic wedgeThe Caledonian OrogenyLate Silurian - Early Devonian�Caledonian Orogeny-Laurasia formsThe Acadian OrogenyEarly - Mid Devonian�Acadian Orogeny-Laurasia formsBIG Collision with Gondwana� The Allegheny OrogenyPaleozoic Era key eventsTime-transgressive Cambrian rocks Grand CanyonPaleozoic Era key eventsNext: Paleozoic ClimatesLate Paleozoic ClimatesPennsylvanian Glacier -GondwanaPennsylvanian CyclothemsCoal formation Pennsylvania cyclothemsPennsylvanian-age coal depositsLate Paleozoic Climates - 2L. Permian PangaeaPERMIAN N. America�