Small amounts of C1-C8 hydrocarbons were detected in continental rise sediments from DSDP Site 603. Organiccarbon- lean sections contained only C1-C3 compounds believed to have migrated from organic-carbon-rich sections. Heavier (C4-C8) hydrocarbons were found only in organic-carbon-rich sections. Restricted and sporadic distribution of C4-C6 compounds in 0-1100 m sub-bottom sediments suggest low-temperature (<20°C) biological/chemical generation processes. Increased C4-C8 concentrations and complexity, including unusually high levels of xylene, were detected in two deeper Cretaceous sections (603-34-2, 134 cm and 603-81-3, 120 cm). This behavior, which was not observed in 17 other samples from sub-bottom depths greater than 1100 m, is similar to that observed in immature surface sediments from the geothermally active Guaymas Basin (Gulf of California) area.
Supplement to: Whelan, Jean K; Burton, Christine (1987): C1-C8 hydrocarbons in sediments from the lower continental rise, Deep Sea Drilling Project Site 603. In: van Hinte, JE; Wise, SW Jr; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 93, 1231-1236, doi:10.2973/dsdp.proc.93.154.1987