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Early Paleozoic.

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Presentation on theme: "Early Paleozoic."— Presentation transcript:

1 Early Paleozoic

2 Periods of the Early Paleozoic
Cambrian: mya Ordovician: mya Silurian: mya

3 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

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

5 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

6 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

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

8 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


10 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

11 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

12 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)

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

14 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

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

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

17 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

18 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)

19 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)

20 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

21 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


23 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)

24 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)

25 Taconic Orogeny


27 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)

28 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)

29 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

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

31 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

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

33 Late Paleozoic Devonian (480-360 m.y.a.)
Mississippian ( m.y.a.) Pennsylvanian ( m.y.a.) Permian ( m.y.a.)

34 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

35 Forming Pangea Pennsylvannian Silurian Mississippian Devonian Permian

36 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

37 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.

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

39 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

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