Early Paleozoic

Periods of the Early Paleozoic Cambrian: 570-505 mya Ordovician: 505-438 mya Silurian: 438-408 mya

Overview of Paleozoic Broad Sequence of Events Gradual Marine invasion of low continents Wide epeiric (shallow) seas; moderated climate Wide shallow habitats for marine organisms Epeiric seas retreated; instability occurred Thick sedimentary layers and Volcanic deposits developed Collisional Mountain ranges built

Plate Tectonic Events Break-up of Rodinia Oceanic closing and orogeny to form Pangaea Taconic orogeny Acadia orogeny Alleghenian orogeny Caledonian Orogeny Hercynian Orogeny

Clues to Paleogeography Paleomagnetic evidence Lithologic evidence Limestone Evaporites Lithic Sandstone and greywacke Arkose Tillites Quartz sandstone Shales Shallow Sea Equatorial Drying conditions Mountain Building Arid conditions-deserts

Laurentia (N. America) and Gondwanaland (first stage of Pangaea ) formed in southern hemisphere consists of S. America, Africa, and other shields Drifter south to polar position Laurentia Lay on equator rotated counter clockwise

Continental framework Stable interior Arches Synclines Basins Domes Orogenic Belts Cordilleran Mtn Franklin Mtn Appalachian Mtn Caledonian mnt

Paleogeography of Laurentia Equator: North-central Mexico to Ellsmere Island, Canada Vast epeiric Sea (30o Latitude; vast carbonate deposits) Vast lowlands of Canada Shield were exposed (desert) Volcanic Mnts: Texas and New England

Seaways Appalachians (on east) Cordilleran (on west) Franklinian (on north) Caledonian (on northwest) Extensive Sediment belts Shales in seaways limestone in empieric seas Quartz sand on shoreline and deserts

Cratonic Sequence of Paleozoic Sauk Sequence: Late Proterozoic to early Ordovician Tippecanoe Sequence: Early Ordovician to early Devonian Kaskakia Sequence: Early Devonian to end of Mississippian Absaroka Sequence: Pennsylvanian to Early Jurassic

Early Paleozoic History Synopsis of Sauk Transgression Canadian Shield eroded for 50 my prior to transgression Gradual transgression covered shield Transcontinental Arch (highlands) became island chain in shallow epeiric sea Transcontinental Arch: Ontario to Mexico, parallel to Cambrian equator As a Result: Late Cambrian seas: MT to NY Cordilleran deposits of Grand Canyon Tapeat Sandstone (oldest) Bright Angel Shale Mauv Limestone (youngest)

Back to the Sauk Sequence By the early Ordovician sea regresses and deposition ends Vast continental-scale uncomformity Karst topography on carbonates rocks

Tippecanoe Sequence Massive unconformity separates the Tippecanoe from the Sauk Sequence Known for: the “Super Mature” Sandstone, St. Peter Sandstone What could “Super Mature” mean? Carbonate deposits contain abundant marine fauna

Fauna found in Tippecanoe Shallow Marine limestones with vast fauna Brachiopods Bryozoans Echinoderms Mollusks Corals Algae

Close of the Tippecanoe Landlocked, reef-fringed basins develop in Great Lake region

Evaporite region In some areas evaporites accumulated to 750 meters If this occurred due to evaporation of a single body of water, the water would have to have been ~1000 kilometers deep Barred Basin

Cordilleran Region History Sauk Interval Passive Margin on opening ocean; deep marine basin on west Western ocean opened; block rotated out; included Siberian region of Asian continent Arms of rift filled with thick sediments Belt supergroup (MT, ID, BC) Uinta Series (UT) Pahrump Series (CA) Canadian Rockies (BC, Alberta)

Tippecanoe Interval Conversion to active margin with subduction (Wilson Cycle) Volcanic Chain formed along western trench Trench deposits; greywacke and volcanics Western ocean deposits: Siliceous black shales and bedded cherts with graptolites (graptolite facies) East of subduction zone: shelly facies- deposited in back arch basins (fossiliferous carbonates)

Appalachian History Appalachian Trough: Deformed three times during Paleozoic Subdivisions of trough: Eastern sediment belt: greywacke, volcanic siliceous shale Western sediment belt: Shale, sandstone, limestone Physiographic region of today Eastern belt: Blue Ridge and Piedmont Western Belt: Valley and Ridge and Plateau

Sauk Interval Trough was a passive margin on opening ocean Shelf sediments: sandstone and limestone Oceanic sediments: shales Transgression spread deposits westward across craton; thick carbonates formed on subsiding shelf Abrupt end with onset of subduction and ocean closure during Middle Ordovician

Tippecanoe Interval Carbonate sedimentation ceased; platform downwarped by subduction Thick graptolite black shale and shoreline immature sands spread west Volcanic flows and pyroclastic beds formed when volcanoes emerged on coast Rapid closing of eastern ocean (Iapetus); coastal and volcanic arc developed Millerburg Volcanic ash bed formed (454 my; 1-2 m thick)

Taconic Orogeny Appalachian Mountains built in collision with part of western Europe Compression folded shelf sediments into mnt and Logan’s Thrust formed (48 km displacement)

Taconic Orogeny

Giant granitic batholiths produced by Taconic melting Taconic Mountains weathered to form vast sandstones of PA, WY, OH, and NY Great clastic wedges spread westward (age tracts deformation)

Climates Transgressions= Mild Climates, windswept low terrains Regressions and Orogenic Episodes= Harsher more diverse climates; winds diverted by mountains Earth Rotation was faster (shorter days, greater tidal effects)

Climate No land Plants Solar Radiation reflected, not absorbed Sever temperature differences resulting End of Late Proterozoic Glacial Cycle: Cool beginning for Early Paleozoic Melting Polar Caps= Rising sea levels and warming Equitorial Position= tropical climates for Laurentia, Baltica, and Antarctica No Ice caps= warm polar seas

Climate Cross Bedding in Desert Sand Deposits Shows wind blew NE to SW across eastern

Ordovician Sea Levels and Biotic Extinctions African Glaciation lowered sea levels and cooled global temperatures End-Ordovician extinctions in many families Bryozoans Tabulate corals Brachiopods Sponges Nautiloid cephalopods Crinoids

Silurian Climate Temperature Zonation Glacial deposits above 65o latitude Reefs, evaporates, eolian sands below 40o latitude

Late Paleozoic Devonian (480-360 m.y.a.) Mississippian (360-320 m.y.a.) Pennsylvanian (320-286 m.y.a.) Permian (286-245 m.y.a.)

Pangea During Silurian Iapetus sea closes - joins Baltica and Lauretia (Caledonian Orogeny) Devonian-Orogeny continues to south forming Laurussia Pennsylvanian collision joins Gondwanna Land and Laurussia (Hercynian in Europe, the Alleghenian in N. America By the Late Permian Pangea is complete

Forming Pangea Pennsylvannian Silurian Mississippian Devonian Permian

Kaskaskia Sequence Oriskany sandstone- initial transgression Devonian Clastics- material shed off rising Appalachians Upper Devonian-Mississippian Massive marine deposits Late Mississippian- Regression Widespread erosion and development of Karst topography

Absaroka Sequence Yet another transgression Unique cyclical sediments Cyclothems Shale Limestone Coal Caused by either eustatic rise in sea level (Glacial melting) or by subsidence.

Climate Zonation paralled latitude Warm to hot within 40o of equator Reduced CO2 in late Paleozoic causes cooling and then late Paleozoic Ice Age

Mineral Deposits Fossil Fuels Limestone- used to produce cement’ Coal Present in all post Devonian rocks Limestone- used to produce cement’ Silica- glass production Silver, gold- mountain building events