GEO 103 Lecture 26: Mesozoic Life
19 Apr 2017
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Document Summary
During permian, island arc and ocean basin formed off western north american craton. Followed by subduction of oceanic plate beneath island arc. Thrusting of oceanic and island arc rocks eastward against craton margin. There is subduction here where we take cool surface material and push it down underneath other plates. When this is done fast enough, the rock does not get hot enough to metamorphose normally which creates unique rocks such as blue schist. (nevadan orogeny) Franciscan complex - up to 7000m thick unusual rock unit. Consists of chaotic mixture of late jurassic - cretaceous rocks. Graywacke, volcanic breccia, siltstone, black shale, chert, pillow-basalt, and blueschist. Low temperature, high pressure metamorphic rock - termed blueschist metamorphic facies. Continental shelf - slope - deep-sea sediments brought together in submarine trench as north. To east, separated by thrust fault is >16 km of continental shelf-slope sediment - great valley. Large volumes of granitic magma generated beneath western edge of north america.
