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In accordance with the lithosphere plate theory, the western part of the Pacific Ocean was occupied by an oceanic basin prior to the disintegration of Pangea. Linear magnetic anomalies and DSDP data indicate that the oldest oceanic crust is Late Jurassic in age. Little is known about the boundaries of the proto-Pacific plate and its fragments in the western part of the Pacific Ocean, but it is obvious that the oceanic crust fragments of this age occur along the western rim of the basin from the Koryak Mountains in Asia to eastern Australia as well as in various foldbelts on the east in Alaska and the Klamath Mountains. The most intensive tectonic movements and spreading within the Pacific Ocean, accompanied by subduction along both sides of the oceanic plate, occurred nea the end of the Jurassic (Kimmeridgian-Tithonian) and during Early Cretaceous time (Aptian-Albian). A result was the formation of the Kula plate with tectonic nappes which stand as such submarine dome rises as the Shatsky Rise, Manihiki Plateau, Hess Rise, and Campbell Plateau, characterized by double thicknesses of oceanic crust. By comparing differences in Albian-Aptian facies, between the east Pacific Ocean and the west, it is possible to assume that shallow-water depths characterized the east, while the west was the site of a deep-water abyssal plain. Albian subsidence, in the eastern part of the ocean, coincided with tectonic uplift in the west and with the initiation of subduction along the East Asian volcanic belt.
Island arcs and trenches, formed at the end of the Cretaceous, caused oceanward migration of the subduction zones. This detached the Bering Sea and Philippine plates from the margin of the oceanic plate. Tertiary spreading along the East Pacific Rise was compensated by subduction under South America and within the deep-water trenches. Spreading in marginal seas during Oligocene-Miocene time resulted in the formation of back-arch basins, compression within the framework of island arcs and thrusting of the arcs onto the oceanic crust. Convergence of arcs may be explained by rapid oceanward displacement within marginal seas, and local movement along transform faults significantly affected the evolution of the Pacific Ocean and the distribution of mineral deposits within the oceanic basin and on the continental shelf.
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