THE ORIGINS OF COASTAL BITUMENS FROM WESTERN AUSTRALIA

Abstract

A total of 83 samples of stranded bitumens collected from the western and southern coasts of Western Australia have been classified into eight groups on the basis of their biomarker compositions. The source rock characteristics inferred for these bitumens, in terms of organic matter type and depositional setting indicated by the biomarkers, suggest strongly that the bitumens originate from a variety of areas in SE Asia in the vicinity of the Indonesian archipelago. In fact, in seven of the eight cases a good correlation is observed between biomarker composition of each bitumen group and a produced crude oil or oil seep from this region. The bitumens are transported to and around the Australian coastline by a system of ocean currents.