earth history geol 2110
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Earth History GEOL 2110. The Paleozoic Era Late Ordovician Period Limestone, Limestone, and more Limestone and The Emergence of the Appalachians. Major Concepts. - PowerPoint PPT PresentationTRANSCRIPT
Earth History GEOL 2110
The Paleozoic EraLate Ordovician Period
Limestone, Limestone, and more Limestone and The Emergence of the Appalachians
Major Concepts• The great Sauk sea retreated to the edge of the NA craton about
480 Ma, when it transgressed the craton again (the Tippecanoe Transgression) over the next 50 million years, a whole new diversity of marine live came with it.
• While Cambrian sands were initially spread over the craton as the Tippecanoe beach trangressed over the land, creating another ultrapure quartz sandstone formation – the St. Peter, this was quickly followed extensive deposition of fossil-rich limestone.
• In the late Ordovician, the eastern margin of Laurentia transformed from a passive continental slope margin to a tectonically active volcanic arc – the Taconic.
• Immature sediments shed westward from this arc accumulated between the continent and the volcanic arc and eventually became deformed and metamorphosed when the arc eventually collided and was thrust onto the continental edge –Penokean-like.
The Tippecanoe TransgressionMid- to Late Ordovician
The Ordovician “Explosion”Changes in Ordovician from Cambrian Fauna
• more complex food chain
• extend higher above the seabed
• hard part made of calcite rather than phosphate
Ecological Diversification of Ordovician FaunaIncreasingly Complex Food Web
Multi-tiered Feeding Levels
Arrival of Classic “Paleozoic” FaunaArticulated
BrachiopodsBryzoans Crinoids
“Sea Lillies”
Sea Shells Twigs Cheerios
…and the world’s best Index fossils!
Conodonts Graptolites Ostracodes
New Kids on the BlockJa
wle
ss B
ony
Fish
Carniverous Nautiloid
Nautiloid fragment found last year on field trip
Why This Explosive Radiation?An Early Ordovician regression followed by the most extensive transgression up to that point in Earth historyEnormous areas of shallow marine environments - niches
Atmospheric oxygen reaches modern-day levels
The Tippecanoe Trangression
St Peter SS – Platteville LS, St. Paul
Capping the Craton in Limestone
Except Here
The Taconic Orogeny
The Taconic Orogeny
The Taconic Orogeny
Modern-Day Analog
Prior-Day Analog1.85 Ga Penokean Orogeny
Next Lecture
The Paleozoic EraCambrian and Ordovician History
of Minnesota and WisconsinHave a Great Spring Break!!!