PROTEROZOIC, PERMO-CARBONIFEROUS AND PLEISTOCENE GLACIAL CYCLES AND CYCLIC SEDIMENTATION IN RELATION TO OIL SEARCH

Abstract

The Australian Upper Proterozoic, Permo-Carboniferous and Pleistocene glacial epochs were each notable for well -developed examples of glacially-induced, cyclical sedimentation. The Pennsylvanian (Upper Carboniferous) of North America was similarly characterized by cyclothems of probably related origin. Both the foregoing Pennsylvanian and the Australian Permain contain much of the world's coal. Both are significant sources also of hydrocarbons and constitute some of the more prolific hydrocarbon resources on both continents.

Around the world, Quaternary sea-floor and terrestrial sedimentary sequences reveal increasing evidence of comparable climatic fluctuations and related sea-level influenced sedimentary deposition. Such fluctuations relate primarily to alternate waxing and waning of contemporary continental ice sheets. Astronomic cycles influenced principally by the varying obliquity of the ecliptic (earth's axial tilt), and the precession of the equinoxes, appear to offer primary climatic controls. Milankovitch -type astronomic radiation cycles almost certainly apply.

Prominent sedimentary cycles characterising parts of the Australian Quaternary succession relate directly to repetitive climatic and sea-level changes. In turn, these are related back to Permo-Carboniferous sedimentary deposition as it influenced coal formation, the development of hydrocarbon source rock and a range of sand reservoirs as they bear on oil exploration.