C1-C5 hydrocarbons from DSDP Legs 56 and 57 sediment gas pockets were analyzed on board ship. Results suggest that the C2-C5 hydrocarbons accompanied biogenic methane and were generated at low temperatures - less than 50° C - either by microorganisms or by low-temperature chemical reactions. Neopentane, a rare constituent of petroleum, is the major C5 component (about 80%) in much of the sediment at Site 438. This compound, which appeared in smaller amounts at Sites 434, 439, 440, and 441, seems to correlate with either fractured or coarse-grained sediments. Scatter in C4 and C5 isomer ratios and generally good correlation between C3, C4 and C5 components suggest local sources for these molecules.

Supplement to: Whelan, Jean K; Sato, S (1980): C1-C5 hydrocarbons from core gas pockets, Deep Sea Drilling Project Legs 56 and 57, Japan Trench transect. In: Scientific Party, Initial Reports of the Deep Sea Drilling Project, 56/57, Initial Reports of the Deep Sea Drilling Project, 56/57, U.S. Government Printing Office, 56-57, 1335-1347