GSC 111 Lecture Notes - Lecture 18: Western Interior Seaway, Tethys Ocean, Oceanic Crust
26 Nov 2017
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Document Summary
Circumtropical tethys current- caused rift between america and africa. Latest cretaceous- formation of caribbean plate- chicxulub impact site. Most ocean crust is cenozoic and mesozoic. Increased rate of western migration in north america. Decrease in angle of subducting slab- inland (east) migrations of volcanic (igneous activity) Warmer, less dense oceanic crust due to shallower angle. Dinosaurs and subtropical plants above the arctic circle. Sea level: up to 125 m higher than present day. Large foreland basin east of sevier orogenic uplift. Late cret. - seaway from arctic ocean to gulf of mexico. Cause: warming of seas and atmosphere- calcite sea. Radiation of diatoms- give phytoplankton a modern look. Calcareous nannoplankton- calcite tests (triassic to recent) Ammonoids and belemnoids persist as pelagic predators. Reflects the mesozoic marine revolution- arms race to survive. Very large because of symbiosis with algae. Still less common than gymnosperms (conifers, cycads, ginkos) Double fertilization- rapid manufacture of food supplies.
