The Geology of the The Geology of the Paleozoic EraPaleozoic Era

7% of Earth’s history

PermianPennsylvanianMississippianDevonianSilurianOrdovicianCambrian

Boundaries are changes in the fossil record

Base of the Cambrian systemBase of the Cambrian system

Starts at appearance of first easily visible fossils

Boundaries changes in fossilsBoundaries changes in fossils

Prof Adam Sedgwick (Cambridge) studied the Cambrian (including the Ordovician) based on superposition and structural geology. Roderick Murchison described and mapped the Silurian based on fossils. Together they defined the Devonian System in Devon and Cornwall.Murchison established the Permian in Russian, then returned and split up Cambrian based on fossils. Later Charles Lapworth separated out the Ordovician.

Paleozoic OverviewPaleozoic Overview

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

• Deposition due to transgressions, and erosion - Deposition due to transgressions, and erosion - disconformities due to regressions.disconformities due to regressions.

• Transgressions caused shallow continental Transgressions caused shallow continental ((epeiricepeiric) seas. Interiors of continents were ) seas. Interiors of continents were frequently flooded.frequently flooded.

• Formation of mountain belts at edges: collisions Formation of mountain belts at edges: collisions with small and large landmasses with small and large landmasses

• Collisions resulted in assembly Collisions resulted in assembly of Pangaea.of Pangaea.

Rifting raises water, moves plates, which later collide, make foreland basins, water drops

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 , Laurentia and Baltica collide - Laurasia

Continues subduction Iapetus ; South docks w/ rest of AvaloniaOld Red SS

Catskill Clastic Wedge

Gondwana/Laurasia

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

Deep

Rifting raises water, moves plates, which later collide, make foreland basins, water drops

Notice: 3 orogenies, 4 transgressions, 2 glaciations, 1 huge mass extinction

Mass Extinction

Devonian Reconstruction

High sea levels mostly due large MORs and warm climates (no glaciers)

How can we reconstruct past How can we reconstruct past continent positions?continent positions?

• 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- until

200 mya Triassic\Jurassic 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

NOTE:

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 – 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 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. Note rotated 30o

Siberia moved from equatorial to northern temperate latitudes

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

Small piece of Avalonia hits in Ordovician

M. OrdovicianM. Ordovician

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

Saucrorthis

Mostly distinct faunasContinents were not close

Note land at South Pole

DevonianDevonian

– Acadian Orogeny in the Appalachians– Other orogenies: Antler (W. N.Am. 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.

Antler

Acadian

Caledonian

Devonian Faunal Similarities: CONTINENTS CLOSEDevonian Faunal Similarities: CONTINENTS CLOSE

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

DicranurusDicranurus

ReedopsReedops

Dalmanitidae Dalmanitidae

Looks like Oklahoma was close to Morocco

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 and to form Hercynian Mts. in Late Paleozoic. Hercynian collision forms Europe

Gondwana – Laurasia collision Gondwana – Laurasia collision Hercynian and Allegheny OrogeniesHercynian and Allegheny Orogenies

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

Allegheny

Hercynian

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

Tectonic DetailsTectonic Details

• That’s the overview

• Now let’s look in more detail at the collision, i.e. orogenies

Angular Unconformity between Martinsburg Fm (mid-Ordovician, folded by Taconic) and overlying Shawangunk Fm (Silurian, folded by Acadian and Allegheny Orogenies)

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

Rifting raises water, moves plates, which later collide, make foreland basins, water dropsAssembly 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, beginning 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

Development of the Taconic OrogenyDevelopment of the 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

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 filled the foreland basin. We saw the Shawangunk and High Falls – Bloomsburg Formations at the Delaware Water Gap.

Cambrian paleogeographyCambrian paleogeography

Pre –collisionsNote equator

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 Dolo., 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 - Early DevonianLate Silurian - Early DevonianCaledonian Orogeny-Laurasia formsCaledonian Orogeny-Laurasia forms

Caledonian Orogeny

To our North

Baltica sutured onto Laurentia

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 in 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 basin filled

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 docking, folding.By 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

Clastic Wedges fill Foreland BasinsClastic Wedges fill Foreland BasinsHighlands source of sediment

BIG 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 York to Alabama

Physiographic provinces Physiographic provinces AppalachiansAppalachians

• Piedmont Province: at collision suture, very metamorphosed and intruded

• Blue Ridge: Grenvillian rocks thrust toward craton.• Valley and Ridge: northwest thrust faults and northeast anticlines

and synclines Thin-skinned tectonics platform rx folded more than basement.

Resistant Ridges• Plateau: little deformation

Allegheny and Ouachita OrogeniesAllegheny and Ouachita Orogenies

Allegheny

Ouchita

Hercynian

Antler OrogenyAntler Orogeny

This is the beginning of Cordillera Construction

Antler Mts. are folded basin sediments, Devonian and Mississippian

• In the Devonian, a westward dipping subduction zone formed off Western Laurasia.An Island Arc formed, the Klamath Arc,ocean floor subducted as the arc approached and collided with the continent

• Late Devonian to Early Mississippian, 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 stressPennsylvanian – blocks push up along high angle faults, relieving the stress. PreCambrian basement exposed.Resulted in Front Range Uplift CO & WYUncompahgre Uplift CO & NM

Late Paleozoic also saw the beginnings of the Rockies

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

• 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

Rifting raises water, moves plates, which later collide, make foreland basins, water drops

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 Reflect Glacial sea-level var.

PERMIAN• 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 – less 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

Glacial Abrasion in BedrockGlacial Abrasion in Bedrock

Source: Tom Bean

Pennsylvanian Glacier -GondwanaPennsylvanian Glacier -GondwanaSea-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

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

due glacial melting)• 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