(Table 1) Organic geochemistry of sediments recovered from DSDP Leg 65 Holes@en

Pliocene-Pleistocene marls, muds, and hemipelagic clays with some beds of silt and sand were recovered on Leg 65 near the crest of the East Pacific Rise at the mouth of the Gulf of California. The organic matter in the sediments is mainly of marine origin for the upper Pleistocene sediments (0-0.61 m.y.), while the lower Pleistocene deposits (0.61- 1.80 m.y.) are characterized by continental organic matter except near the bottom of the sediment section in Hole 483A, where marine organic matter was found. The sediments belong to an early stage of geochemical evolution, except in Hole 482D, where hydrothermal effects are invoked to explain the maturity of the organic matter above the basement.