CYCLIC CHARACTER OF OIL ACCUMULATION IN T HE EARTHS HISTORY

Scales of petroleum formation in various geological epochs were compar ately estimated From initial proved reserves of recoverable oil in 45 well-studied largest oil- and gas-bearing basins. The related paleogeo logical reconstructions are required to take into account inter-reserv oir migration of oil. The oil reserves were estimated separately in 25 stratigraphic subdivisions of various ranks and durations; according to them intensity of oil accumulation was determined in tons of the pr oved recoverable reserves a year. It varies from 1.4 t/year in the Cam brian to 2250 t/year in the Upper Jurassic. The stratigraphic localiza tion of largest accumulations of bitumens is also taken into account. Nearly all large deposits of solid bitumens originated from the oils g enetically related to the deposits corresponding to peaks of oil forma tion. Representativeness of the sample studied is under discussion. Th ere are five peaks of the intensity of oil accumulation: Early Protero zoic, Late Proterozoic, Late Devinian--Early Carboniferous, Late Juras sic--Late Cretaceous, and Eocene-Pliocene peaks. A hypothesis is propo sed that the oil Formation cycling is connected with cycles of accreti on and decomposition of supercontinents (Wilson geodynamic cycles), se veral times occurring in the Earth's history.