Journal of Petroleum Geology, Vol.4, No.4, pp. 377-392, 1982

©Copyright 2000 Scientific Press, Ltd.

LOW-RANK SEQUENCES AND SCALES OF ORGANIC METAMORPHISM

R. P. Suggate*

*New Zealand Geological Survey, PO Box 30, 368 Lower Hutt, New Zealand.

Abstract

Degrees of alteration of carbonaceous material, when compared with scales of organic metamorphism, are used mainly by petroleum geologists for estimating conditions of development of sedimentary basins and for estimating the likelihood of oil and gas generation having taken place. For accurate estimation, especially of geological history, the scales need to be correctly designed, and low-rank sequences (lignite, sub-bituminous and high-volatile bituminous ranks of coal) are critical for this. Scales need review, and data from surface and drillhole sequences in New Zealand are valuable for this. The generally-accepted influence of time is considered unproved and unlikely to be significant.