Clinton B. Foster1,
(1) Australian Geological Survey Organisation, Canberra, Australia
Abstract: Carbon isotopes, Tmax and EOM as environmental proxies: application to oil/source correlation – examples from the Permian-Triassic of Australia
The carbon isotopic composition of kerogens from the Permian–Triassic from eastern and western Australia appears to be controlled by the contribution of woody organic matter. Wood-dominated organics, as determined from palynological preparations, are typically isotopically enriched, 13C -24 %o; while non-woody material, comprising typically of spores, pollen and spinose acritarchs is significantly lighter (13C -30 %o). Tmax data, from standard Rock-Eval, for the same sample set, show patterns of reworking and can be associated with the amount of isotopically enriched, refractory woody tissue. Extractable organic matter (EOM) from the wood-dominated samples is, as might be expected, low. Evidence from Permian-Triassic boundary sections in Australia, China and Russia confirms that the primary control on organic carbon isotopic composition is its biological source; secular causes may also be present, but are difficult to isolate. These three data sets ( 13C, Tmax, and EOM) combine to give a proxy for sea level change, and biofacies. The kerogen 13C values can be modelled and used to predict biofacies, which in turn is correlated to the compound specific carbon isotopic analysis of oils (CSIA) and used to predict a likely organic source. This is a novel, relatively inexpensive, and useful tool for hydrocarbon exploration.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana