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Unformatted text preview: TOPIC 8 - THE PHYSICAL WORLD OF DINOSAURS THE PHYSICAL WORLD OF DINOSAURS Plate Tectonics and Dinosaur Dispersal • Dinosaurs evolved during the Late Triassic when the continents were still united as the supercontinent Pangaea was surrounded by the Panthalassa Ocean. • Plate tectonic events facilitated early dinosaur dispersal. • The Tethys Seaway separated Laurasian from Gondwana (northern and southern continents). Paleography of North America The Triassic Period • Rift basins - byproduct of Triassic rifting along the east coast (home to dinosaurs) • The Connecticut River Valley is a remnant of rift valleys and has abundant dinosaur footprints. • For most of the Mesozoic, subduction occurred along the western margin of North America causing the formation of volcanic arcs and numerous collisional events of volcanic arcs and microcontinents. The Jurassic Period • The paleogeography of the North American Jurassic was similar to that of the Triassic, except the topography was more subdued. The Cretaceous Period • The low relief, combined with the highest sea level of the Mesozoic, resulted in flooding of much of the continent (North America). CLIMATE, SEA LEVEL, AND VEGETATION Climate • The Mesozoic is characterized by a broad warming trend that reached its maximum during the Late Cretaceous. • Triassic ○ The existence of a single large continent caused dry regions in the interior because of the large distances to the moisture sources of the ocean. ○ Closer towards the margins of Pangaea, monsoonal climates of alternating wet and dry season were common. ○ Many dinosaurs were buried by flash floods caused by these summer monsoons. • Jurassic ○ Dry and hot desert conditions persisted in interior continental areas of Pangaea during the Early and Middle Jurassic. ○ Late Jurassic climate conditions were more hospitable to dinosaurs in most regions. ○ Epicontinental seas – shallow flooded portions of the continent ○ Climate was less monsoonal than during the Triassic. • Cretaceous ○ The rise of Late Jurassic sea level continued into the Cretaceous. ○ Cool temperate forests covered the polar regions where there was seasonal snowfall, but no ice sheets. Sea Level • Differences between periods of high and low stands of sea level can have a profound effect on the evolution of life. • Causes of sea level change ○ Glaciations Glacial ice is formed by the accumulation of snow as ice sheets or alpine glaciers. The accumulation of large ice sheets as large continental glaciers can lower sea level by hundreds of feet. Conversely, the melting of entire ice sheets can raise sea level significantly. ○ Changes in the hypsography (shape) of the ocean basins If the global average rate of seafloor spreading increases, ridge volume increases....
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This note was uploaded on 07/16/2008 for the course GLY 1102 taught by Professor Ciesielski during the Summer '08 term at University of Florida.
- Summer '08