GEOL 102 Historical Geology
Spring Semester 2011
The Late Paleozoic Era II: Permian Geology
Paleogeography and Geology of the
Increase in continental climates (extreme summers and winters, arid conditions) in many
parts of the world, as Pangaea becomes more emergent.
In restricted basins, major evaporite deposits. Elsewhere, lots of eolian deposits.
CO2 levels begin to rise:
- Drier conditions cause major decline in the coal swamps, so less carbon is buried
- Drier conditions also means less chemical weathering
- Gondwanan glaciers shrink somewhat
Collision between Siberia and northeastern Pangaea (former eastern part of Euramerica/Laurussia);
Uralian Orogeny (Permian)
The Chinese blocks remain the only
large cratons not attached to Pangaea.
Latest Permian and earliest Triassic:
- Collision between microplate Sonomia and western Laurentian part of Pangaea
- Sonoman Orogeny:
part of the Cordilleran orogenies
- Sonomia is now southeastern Oregon, northern California, and northern Nevada
- The accretionary wedge formed during the orogeny is called the Golcanda terrane
basins in what is now west Texas were bordered by big
reef complexes (sponges, bryozoans, algae, brachiopds are main reef formers);
otherwise, very few reefs from the Permian.
At very end (last half million years?) of Permian: Siberian Traps:
- Largest flood basalt & largest volcanic episode in all of the Phanerozoic
- Presently covers 2.5 million km3; estimated original area 7 million km2
- Estimated original volume of 2-5 million km3! (including 250,000 km2 tuff!)
- Coincides with the Permo-Triassic extinction, the largest of the Phanerozoic
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Last modified: 14 January 2011