Global regularities in oil accumulation in the final light are the result of development of the sedimentary cover of the Earth. A working hypothesis here is that the change from epochs of intensive oil accumulation to epochs when rate and absolute mass of oil accumulation are low may be related to the main stages of formation and break up of super-cointinents and opening of oceans.
Formation of continental crust and the mechanism of plate tectonics began to function back in the Archean. At the end of the Archean about 2.7 billion years ago the first super-continent formed - Pangea I. The first of these epochs of intensive oil accumulation was at the time of break up Pangea I and the formation of sedimentary basins on the margins and within the newly formed continents.
At the end of the Early Proterozoic about 1.7 billion years ago a super-continent again formed - Pangea II. During its subsequent destruction a large umber of sedimentary basins formed - intra- cratonal sineklizes to peri-cratonal basins of passive and active continental margins. Oil-source beds in these basins yielded the first oil of super-giant Yurubchen-Tokhom field in the Riphean of East Siberia and shows in the MacArthur basin of Australia. The oil in the Vendian of East Siberia migrated from Riphean sediments.
The process of destruction of Pangea II appears to have continued to the end of the Middle Paleozoic. The paleo-Ural Ocean opened in the Ordovician, and the paleo-Asiatic Ocean in the Middle and possibly in the Early Paleozoic. In the Devonian and Early Carboniferous the paleo-Ural Ocean experienced a mature stage with deposition of oil-source sediments in that part adjacent to the European continent. These sediments include the Domanik deposits of Frasnian age. A similar situation existed on the North American craton.
In the Late Paleozoic the Early Proterozoic-Paleozoic ocean closed completely, and the Pangea III super-continent formed in this the third phase of Earth history. Destruction of this continent began with Early Triassic rifting but was particularly intensive in the Jurassic and Early Cretaceous, leading to formation of the Atlantic Ocean, Tethys Sea, Indian Ocean, and a whole series of Mesozoic and Cenozoic basins. One group of basins (West Siberian, Mesopotanian, North Sea, Amu-Dar'ya) formed largely in the initial phase of this cycle and predetermined the Jurassic-Cretaceous phase of intensive oil accumulation. These basins are classified as continental-margin of the Atlantic type and contain the main hydrocarbon resources of the Mesozoic. In a later stage when Tethys began to close, the Atlantic continued to open. Island arc formation and subduction of oceanic crust took place in the Pacific, and basins formed that were filled largely by Cenozoic sediment. The Eocene-Pliocene cycle of intensive oil formation was realized at this time.
These studies demonstrate that processes of oil formation have occurred in cycles, and that maximums of oil accumulation correspond with epochs of destruction of super-continents (Pangea I, II, and III) and initial stages of formation of oceans.
Taken from Vyshemirskiy and Kontorovich, 1997 (date incorrect in Part I);
digested in Petroleum Geology, vol. 35, no. 4, in preparation.
Copyright 2001 James Clarke. You are encouraged to print out this
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