Organic Petrography and Extractable Hydrocarbons of Sediments from the Eastern North Pacific Ocean, Deep Sea Drilling Project Leg 63

Abstract

Quantity, type, and maturity of the organic matter of middle Miocene to Quaternary sediments from the eastern North Pacific (Deep Sea Drilling Project Leg 63) were determined. Hydrocarbons and fatty acids in lipid extracts were analyzed by capillary column gas chromatography and combined gas chromatography/mass spectrometry. Kerogens were investigated by Rock-Eval pyrolysis and microscopy, and vitrinite reflectance values were determined. At Site 467, in the San Miguel Gap of the outer California Continental Borderland, organic carbon contents range from 1.46% to 5.40%. Normalized to organic carbon, total extracts increase from about 10 to 36 mg/g C org with depth. The organic matter is a mixture of both marine and terrestrial origin, with the marine organic matter representing a high proportion in some of the samples. Steroid hydrocarbons-sterenes and steradienes in the upper part of the section and steranes in the deepest sample-are the most abundant compounds in the nonaromatic hydrocarbon fractions. Perylene, alkylated thiophenes, and aromatic steroid hydrocarbons dominate in the aromatic hydrocarbon fractions of the shallower samples; increasing maturation is indicated by a more petroleumlike aromatic hydrocarbon distribution. Microscopy revealed a high amount of liptinitic organic matter and confirmed the maturation trend as observed from analysis of the extracts. The vitrinite reflectance may be extrapolated to a bottom-hole value of nearly 0.5% R o. The liquid hydrocarbon potential of the sediments at higher maturity levels is rated to be good to excellent. At Site 471, off Baja California, organic carbon values are between 0.70% and 1.12%. Extract values increase with depth, as at Site 467. The investigation of the soluble and insoluble organic matter, despite some compositional similarities, consistently revealed a more terrigenous influx compared with Site 467. Thus the potential for liquid hydrocarbon generation is lower, the organic matter being more gas-prone. The deepest sample analyzed indicates the onset of hydrocarbon generation. At this site, frequent sand intercalations offer pathways for migration and possibly reservoir formation.

Sources, Preservation, and Maturation of Organic Matter in Pliocene and Quaternary Sediments of the Gulf of California: A Synthesis of Organic Geochemical Studies from Deep Sea Drilling Project Leg 64

“…2). This may be misleading, as it is a common constituent of DSDP Leg 63 sediments (Louda and Baker, 1981;Rullkötter et al, 1981;Simoneit and Mazurek, 1981) and is generally ubiquitous in Recent sediments (Wakeham et al, 1979;LaFlamme and Hites, 1978;Hites et al, 1977Hites et al, , 1980. The presence of perylene in a sediment may indicate deposition under anoxic conditions, where it may form from precursors of either terrigenous or marine origin.…”

Geochemistry and Petrography of Organic Matter in Cretaceous Sediments from the Southeastern Gulf of Mexico, Deep Sea Drilling Project Hole 535—Preliminary Results

“…For a detailed description of the experimental procedures for organic carbon determination, Rock-Eval pyrolysis, solvent extraction, liquid chromatography, and computerized gas chromatography/mass spectrometry, we refer to an earlier report (Rullkötter et al, 1981). For details of the microscopic kerogen investigation see .…”

“…The cyclic compounds predominantly consist of 17ß (H)-hopanes and hopenes, which are probably of bacterial origin (Ourisson et al, 1979), and of 5 (H)-steranes, 5 (H)-steranes, and rearranged sterenes, which based on their relative abundance support the idea of a significant marine organic matter contribution to the sediment (cf. Rullkötter et al, 1981). The amount of regular sterenes present, in view of the low maturation level, is surprisingly low.…”

“…The cyclic hydrocarbons bear the characteristics of low maturation, i.e., 17/3 (H)-hopanes and 5/3-steranes, 5α (H)-steranes, 14a (H)-steranes, and 17α (H)-steranes with the 20R-configuration dominant (cf. Mackenzie and Maxwell, 1981;Rullkötter et al, 1981). The discrepancy between the w-alkane distribution without a distinct carbon number preference and the presence of biological marker compounds in their immature configuration clearly indicates the presence of nonindigenous hydrocarbons.…”

“…sample (Table 1), but unusually high in Sample 535-60-5, 120-150 cm (Hauterivian-Valanginian) and especially in the Valanginian sample from Section 535-66-5 (54.6 mg/g C org ; cf. Rullkötter et al, 1981). This either points to shipboard contamination with soluble organic matter, e.g., pipe dope (Brassell and Eglinton, 1981), or to an impregnation with migrated hydrocarbons, e.g., related to the tar-filled fractures in the Valanginian to Hauterivian interval at DSDP Site 535.…”