Journal of Petroleum Geology, Vol.15,
No.4, pp. 435-450, 1992
©Copyright 2000 Scientific Press,
Ltd.
POTENTIAL PETROLEUM SOURCE
ROCKS IN TRIASSIC
LACUSTRINE-DELTA SEDIMENTS OF THE
GUNNEDAH BASIN, EASTERN AUSTRALIA
M. Smyth*, Feng Xu Jian** and C. R.
Ward**
* CSIRO Division of Exploration
Geoscience, P.O. Box 136, North Ryde, N.S.W., 2113, Australia.
** Department of Applied Geology,
University of New South Wales, P.O. Box 1, Kensington, N.S.W.,
2033, Australia.
Abstract
Integration of lithofacies, inferred
depositional environments and organic petrology of a lacustrine
delta sequence in the Permo-Triassic Gunnedah Basin of eastern
Australia has provided a logical explanation for the patterns of
distribution of the dispersed organic matter. The data show that:
(i) sedimentary processes, such as size sorting and
transportation, control the association of maceral assemblages in
the dispersed organic matter with depositional environments; (ii)
the extent of oxidation of organic matter increases downstream,
from floodplain lake to interdistributary bay, delta front,
prodelta and off-shore lake deposits; (iii) coarse, woody
material, mostly oxidised to semifusinite, is concentrated in the
delta-front environment; (iv) leaf material is transported
preferentially to the prodelta, via the delta front. On the basis
of organic matter type, the prodelta was probably the most
favourable environment in this depositional system for the
accumulation of oil-prone source beds.