• Cambrian through Permian
- sediments on the platform - sedimentary sequences
- Major periods of sea level rise and fall
- Sauk, Tippecanoe, Kaskaskia, Absaroka
- Appalachian Orogenies
1. Taconic
2. Acadian
3. Alleghanian
Sloss Sequences - T/R Cycles
• 6 major periods of continental inundation - unconformities
• Megasequences - 100’s of millions of years
- Sequence stratigraphy - correlation of unconformities
The Early Paleozoic
• The Cambrian and Ordovician Marine Worlds
• high global sea levels
• tropical environments
• Sauk Sequence
• Passive margins
• Basins and arches
Cambrian History of North America
• Passive margins develop around the continent during the Proterozoic
- breakup of supercontinent
• Slowly-subsiding passive margins around the margins during Cambrian
• Thick packages of sediments near margins - thin over craton
Cambrian History of North America
• Basins and Arches
• Thickest Cambrian sediments on craton in basins
• Thinnest or eroded over arches - Transcontinetal Arch
Cambrian History of North America
• Cambrian Rocks
• Carbonates and shales near continent margins
• Sandstone on craton - mature
– Ex. Wisconsin Dells
Ordovician History
• Sauk sequence ends with a regression (E. Ord)
• M. Ord. = Tippecanoe Sequence
• North America = equatorial and flooded
Ordovician History
• Tippecanoe transgression expressed on craton by very mature sandstone
– St. Peter Sandstone
• Sandstones overlain by carbonates
Ordovician Life
• Cambrian Fauna replaced by Paleozoic Fauna
• Early Ordovician - recovery from extinction = Ordovician Radiation
• diversity of marine life triples
• complex communities - new lifestyles
• Burrowing & suspension feeding = “tiering”
Late Ordovician History
• M. Ord. - Subduction Zone - eastern margin of NA
• L. Ord. - island arcs collide = orogenic event
• Taconic Orogeny
• crustal loading creates Foreland Basin inland of mountains
– limestones in the midcontinent smothered by siliciclastics
Late Ordovician History
• Late Ordovician Glaciation
• southern continent near the poles
• lower atmospheric levels of CO2
– Burial of carbon; Mountain building
– Regression
Early Paleozoic Mass Extinctions
• Major extinction at the end of the Ordovician => 2 pulses
• 1) Climate Change (glaciation) & Sea Level fall
• 2) Climate Change & Sea Level rise