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Abstract: Phanerozoic Plate Tectonic
Reconstructions: Insights into the
Driving Mechanism of Plate Tectonics
Plate tectonic models describing the development of the Atlantic Ocean (Srivastava, Rowley, and Cande), Indian Ocean (Patriat, Royer) and Pacific Ocean have been combined with preliminary plate tectonic models for Asia (Rowley), Tethys (Sengor, Dercourt et al. ), the Soviet Union (Zonenshain et al.) and the Paleozoic (Scotese, McKerrow) to produce a global model of Phanerozoic plate motions. Fifty plate tectonic reconstructions will be presented illustrating the movement of the continents and the development of the world's ocean basins since the late Precambrian. The maps are the preliminary draft of the PALEOMAP Phanerozoic Atlas Project, a jointly sponsored IUGG/IUGS program.
The pattern of plate motion during the last 600 million years can be characterized as "episodic". Long intervals of steady state plate motion (lasting 20-50 million years) have been interrupted at irregular intervals by tectonic events that have triggered global changes in the rates and directions of plate movement. At least 12 times of global plate reorganization can be recognized during the Phanerozoic. These events took place during the: latest Precambrian, middle Ordovician, early Devonian, early-late Carboniferous, early Permian, late Triassic, middle Jurassic, early Cretaceous (Valanginian), early Eocene, and early Miocene.
It appears that these global plate reorganizations arise from interactions between the plates and are not the result of deep-seated events in the asthenosphere. The loss of a major subduction zone due to continent-continent collision, or the loss of a spreading center due to subduction of a ridge, are the two principal events that trigger global plate reorganizations. From the pattern of plate motion during the last 600 million years, it is clear that the forces that drive the plates are concentrated in the lithosphere (slab pull and ridge push) and that the pattern of convection in the Earth's interior does not play an active role in determining the movement of the plates.
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