Low-temperature diagenetic reactions (less than 50°C) are held responsible for the generation of small amounts of C1-C8 hydrocarbons (less than 100 ng hydrocarbon/g dry weight of sediment) at outer continental shelf Deep Sea Drilling Project Sites 468 and 469 (sub-bottom depths 415 m and 454 m, respectively). In contrast, Site 471 shows an exponential rise in hydrocarbon yields at depths greater than 500 meters. The high yields of C4-C8 hydrocarbons (up to 30 ng hydrocarbon/g dry weight of sediment) in this area of high geothermal and volcanic activity suggest the penetration of an active petroleum-generating zone. Similar arguments apply to Site 467, where relatively high levels (up to 3 µg hydrocarbon/g dry weight sediment) occurred in very shallow (250-600 m) sediments.

Sediment depth is given in mbsf. Empty cells = not determined.

Supplement to: Whelan, Jean K; Hunt, John M (1981): C1-C8 hydrocarbons in IPOD Leg 63 sediments from outer California and Baja California borderlands. In: Yeats, RS; Haq, BU; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 63, 775-784