Early/late Paleozoic Geology

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Early/late Paleozoic Geology

• Chapter 10 and 11

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Last time

• Phanerozoic Eon
• Paleozoic Era
• Cambrian
• Ordovician
• Silurian

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Last time

• Sequences

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Order of rock types

• Regression should have shale and sandstone as
  last rocks deposited.
• Where is the sandstone and shale on top in Sauk
  and Tippecanoe Sequences?

Limestone
Shale
Sandstone
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North American craton

• Appalachian mobile belt

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Rocks of the Appalachian mobile belt
mid to end of Ordovician
Volcanic ash in shales
Shales, no mud cracks, no stromatolites
mid-Ordovician- Silurian
Cambrian- Early Ordovician
Sandstone, stromatolites, Mud cracks, cross
bedding
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Appalachian mobile belt in Cambrian

• Passive margin and shallow water

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Appalachian mobile belt in Cambrian and Early
Ordovician

• Laurentia is still passive margin
• Iapetus ocean opens w/ divergent margin

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Appalachian mobile belt in middle
Ordovician-Silurian

• Deeper water deposition (Tippecanoe Sequence)

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Middle Ordovician

• Iapetus plate subducts under Laurentia
• Volcanoes form
• Onset of mountains
• Taconic orogeny
• Forms Taconic highlands
• New York, Mass., Vt.

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How to date Taconic orogeny

• Volcanic ash layers
• Intrusive igneous rocks
• 440-480 m.y.

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Evidence of Taconic orogen

• What happens with formation of new mountains
  (highlands?)
• Accumulation of detrital sediment
• Thickest near mountains (source area)
• Thinner, small particles away from source
• Queenston Delta

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Evidence of Taconic orogen

• What happens with formation of new mountains
  (highlands?)
• Accumulation of detrital sediment
• Thickest near mountains (source area)
• Thinner, small particles away from source
• Queenston Delta

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Early Paleozoic geology

• Sauk and Tippecanoe sequences
• Taconic orogeny

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Late Paleozoic

• Devonian, Carboniferous, Permian

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Late Paleozoic sed rocks
oldest

• Tippecanoe sequence (ends early Devonian)
• Unconformity/ erosion
• Middle Devonian transgression

youngest
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Late Paleozoic sed rocks

• Kaskaskia sequence
• What rock is deposited first?
• New York, Penn.

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Devonian Geography

• Above sandstone
• Shales, limestones/ evaporites

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Kaskaskia sed. rocks

• Devonian reefs of western Canada
• Barrier reefs, evaporite basins
• Sound familiar?

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New rock type in Kaskaskia black shales

• Black since organic-rich
• Need
• High organic activity
• Low oxygen water

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New rock type in Kaskaskia black shales

• Black since organic-rich
• Need
• High organic activity
• Low oxygen water

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End of Kaskaskia sequence

• Return to limestones in Mississippian
• Fossils of reefs!

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End of Kaskaskia sequence

• Return to limestones in Mississippian
• Fossils of reefs!

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Late Kaskaskia

• Return to limestones in Mississippian
• Fossils of reefs!

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Mississippian limestone
Grand Canyon
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Famous Mississippian limestone

• Indiana limestone
• Empire mine

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Pennsylvanian

• Late Mississippian Kaskaskia Sea regression
• Unconformity divides Mississippian
  Pennsylvanian
• Sea returns with Absaroka sequence

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New to Absaroka sequence

• Sequence of marine/nonmarine rocks
• What kind of sed. environment can we form these
  rocks?
• Called cyclothems

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Complete cyclothem

• Cyclothems contain coal
• Coal is dead plants

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Cyclothems coal

• Okefenokee Swamp, Georgia

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Pennsylvanian coal swamps

• How such widespread delta environments?
• How could sea level change over such large area?
• Glaciers in Gondwana

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End of Absaroka sequence

• Permian
• Lots of limestone!
• West Texas

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Sed. Sequences of N. America
Limestone
Coal
Sandstone
Absaroka Sequence
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Sed. Sequences of N. America
Limestone with evaporites
Limestone
Shale
Shale
Sandstone
Sandstone
Tippecanoe Sequence
Sauk Sequence
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Late Paleozoic sed rock summary

• Kaskaskia sandstone, limestone, black shale,
  limestone
• Absaroka sandstone, coal swamps, evaporites
  limestones