Organic geochemistry of recent sediments from Guaymas Basin, Gulf of California

Abstract

A 3.5-m gravity core taken from the Guaymas Basin, Gulf of California, was analyzed for lipids, humates, kerogens, and C 1 to C 8 hydrocarbons. The analyses were of interest due to the high geothermal gradient observed in the Guaymas Basin and the strong petroliferous odor of the sediment. Analyses were by gas chromatography (GC), GC-mass spectrometry, and stable isotope mass spectrometry. The bulk of the organic matter (humates and kerogens) was of marine origin and diagenetically immature. The molecular markers of the hydrocarbons, fatty acids, and ketones were of a predominantly marine autochthonous origin. A small and variable component of allochthonous lipids from terrestrial plants was also present. Methane was principally of biogenic origin, but the lower sections of the core contained significant concentrations (7 μg g −1 dry sediment) of petrogenic C 2 to C 8 hydrocarbons.