TRITERPANE DISTRIBUTIONS IN DIAPIR-RELATED ASPHALTS

A gas chromatographic-mass spectrometric study of solvent-soluble extr acts from asphalt-rich sediments in a diapir-intruded crude oil reserv oir rock has demonstrated the extended biodegradation of the hydrocarb ons in the strata in contact with the diapir. The process has led to a sedimentary hydrocarbon composition dominated by unresolved complex m ixtures of aliphatic and aromatic hydrocarbons in which two main group s of resolved peaks in the gas chromatograms can be recognized. The do minant group encompasses the compounds preserved in these conditions a nd is composed of two distributions of hexacyclic hopanoids, a series of C32-C35 20,32-cyclobishomohopanes and a new series of C33-C35 homol ogues whose structure is not yet fully elucidated. The second group co rresponds to partly transformed aliphatic and aromatic structures, nam ely series of C27-C30 8,14-seco-hopanes and C27-C31 D-ring aromatic 8, 14-seco-hopanes.