The Geology of 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 system Trace fossil Phycodes pedum New modes of locomotion

Welsh Lower Paleozoic 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 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 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 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 events Transgression and Regressions Extinctions: http://www.fmnh.helsinki.fi/users/haaramo/Meteor_Impacts/Middle_Paleozoic_impacts.htm Assembly of Pangea Gondwana/Laurasia Catskill Clastic Wedge Continues subd Iapetus South docks rest Avalonia Old Red SS Iapetus floor subducted Scotl Scan NE Can Lauentia and Baltica collide - Laurasia Avalonia collides with Laurentia

Paleogeographic Reconstructions 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 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 Cambrian 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 Siberia - Russia (E of Urals), Part Asia Kazakhstania - Kazakhstan China - All of SE Asia and SE China Gondwana - S. continents, India Six major Paleozoic continents are recognized after Rodinia breakup Laurentia - North America, Greenland, Scotland Rotated 90o Baltica - Russia (W of Urals), Scandinavia

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

Global paleogeography Mid Ordovician to Silurian Siberia moved from equatorial to northern temperate latitudes Small piece of Avalonia hits in Ordovician Baltica moved S, then N and collided with Laurentia, rotated 30o Gondwana moved South , land in south high latitudes(Late Ord. tillites)

http://www.geodynamics.no/Platemotions/500-400 M. Ordovician http://www.gl.rhbnc.ac.uk/seasia/Biogeog_pdfs/Fortey_Cocks.pdf Saucrorthis Mostly distinct faunas Continents were not close

Paleogeography Early Devonian Continued collision of Baltica/Laurentia formed Laurasia. Caledonian Orogeny finishes in E. Dev Acadian Orogeny in the Appalachians folds older rocks M. Dev. Other orogenies: Antler (Cordillera) and Ellesmere (northwest margin of Laurentia) Gondwana moves to higher southern latitudes. All other continents at low northern latitudes.

How close were Laurasia = Euramerica and Gondwana in the Late Devonian? Euramerica is Laurentia plus Baltica Dalmanitidae Looks like Oklahoma was close to Morocco Reedops Dicranurus Late Devonian Faunal Similarities

Final 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 Hercynian orogeny North and South Europe suture Hercynian Orogeny continuous w Allegheny Orogeny about 300 mya

Final 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 Permian Hercynian N Eur-S Eur Allegheny Orogeny

Paleozoic Era key events Next let’s look closer at the Collisional Mountains Rifting raises water, moves plates, which later collide. Assembly of Pangea Gondwana/Laurasia Catskill Clastic Wedge Continues subd Iapetus South docks rest Avalonia Old Red SS Iapetus floor subducted Scotl Scan NE Can Lauentia and Baltica collide - Laurasia Avalonia collides with Laurentia

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 Cambrian period Avalonia Terranes

The Taconic orogeny Rodinia breaking up Avalonia Terrane E. Cambrian Plates reverse, in E. Ordovician Laurentia moves toward Avalonia Africa moves toward both

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 paleogeography Submerged Pre –collisions Note equator Submerged Submerged Submerged

Interior 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. Post collisions Queenston Clastic Wedge Barrier Reefs Highstand Evaporites Lowstand

Queenston clastic wedge (Martinsburg Shale) Hardyston Fm downfolded (Allentown Dm., Jacksonburg Ls.)

The 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 Devonian Caledonian Orogeny-Laurasia forms To our North

The 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 Devonian Acadian Orogeny-Laurasia forms Southern Avalonia into Laurasia

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

Late Devonian paleogeography of North America

Catskill Formation Clastic Wedge from Acadian collision w rest of Avalonia E-Mid Devonian docking 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 thickness Coarse near source Wedge thins away

Carboniferous BIG Collision with Gondwana 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 Appalachians little deformation at collision suture, very metamorphosed and intruded Northwest thrust faults and northeast anticlines and synclines Grenvillian rocks thrust cratonward

Allegheny and Ouachita Orogenies Hercynian Allegheny Allegheny hit by Africa Ouchita Ouchita hit by South America

Western: Antler Orogeny 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 Antler Mts. are folded basin sediments Beginning of Cordillera Construction, Devonian to Mississippian

Late Devonian paleogeography of North America Here it is

Paleozoic structure of the West 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 Exposed granite eroded as arkoses (feldspar-rich sandstones)

Pennsylvanian arkose, CO Fountain Arkose, CO, deposited northeast of Front Range Uplift

Next: 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 events Transgression and Regressions Assembly of Pangea Low High ABS: Sea level rise (cyclic) due Gondwana glaciation Penn-Pm regression due slowdown spreading, assembly of Pangaea, drained continent L Pm KS: filling in of the Appalachian foreland basin by Late Devonian time TC: glacial melting and accelerated sea-floor spreading Sauk: High rates of sea-floor spreading

Cambrian – E Ord Sauk Sequence Pre-collision, dramatic transgression due active MORs Note extensive shallow carbonates and equator

Time-transgressive Cambrian rocks Grand Canyon Sauk Sequence WEST EAST Transgression Middle Cambrian http://www.geo-tools.com/trilobites.htm Lower Cambrian http://www.wmrs.edu/projects/trilobites/images/trilo7-2.jpg Note how western BAS is older than eastern BAS

Tippecanoe Transgression M Ord-Sil. Reworking of Sauk sands gives pure sands useful in glass manufacture. Sands covered by carbonates as transgression advances Michigan Basin surrounded by reefs Restricted circulation caused evaporite precipitation Source of Rock Salt About 5 smaller T-R Pulses

Late Devonian Kaskasia Transgression Carbonates over pure sands Williston Basin surrounded by reefs Restricted circulation caused evaporite precipitation

Absoroka 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 events Climate/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 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 Climates 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 -Gondwana Sea-level falls as glaciers grow, inland seas retreat

Pennsylvanian Cyclothems Rapid transgressions cover swamp as ice melts Coal Swamp swamp estuary Slow regression as ice sheet grows

Coal formation Pennsylvania cyclothems Melting glacier Highland source to east

Pennsylvanian-age coal deposits

Late 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 Pangaea Ice-free, dry interiors, no coal Much of land +/- 30 degrees Hot, dry climate Note evaporites Pangaea is assembled, sea-level low

PERMIAN N. America Inland sea limited to w Texas & s NM Extensive evaporite deposits KS – OK Redbeds over interior – strong seasons

Next Time A survey of Paleozoic Life, and Latest Permian Mass Extinction Most profound in history of life.