Preliminary results of molecular organic geochemical analyses of 26 samples from Hole 893A are reported in this paper. Detailed lipid analyses of 10 selected samples show a complex molecular composition of marine, terrestrial, and bacterial origin. Numerous steroidal alcohols of predominantly autochthonous origin form the major compound class in the bitumen. Higher plant-derived long-chain n-fatty acids, n-alcohols, and n-alkanes are also present in significant concentrations. The hydrocarbon fractions of all investigated samples contain a series of 17alpha(H)-hopanes that show a signature typical of biodegraded petroleum. These compounds are derived from eroded Monterey Formation petroleum source rocks or related oil seeps, or—considered less likely—from local migration of oil from greater depths. Several molecular parameters appear to distinguish laminated from nonlaminated sediments.

Date of initial receipt: 15 September 1994
Date of acceptance: 23 March 1995

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