Whiticar, Michael J; Suess, Erwin (1990): Characterization of sorbed volatile hydrocarbons from the Peru margin. PANGAEA, https://doi.org/10.1594/PANGAEA.753740, Supplement to: Whiticar, MJ; Suess, E (1990): Characterization of sorbed volatile hydrocarbons from the Peru margin, Leg 112, Sites 679, 680/681, 682, 684, and 686/687. In: Suess, E; von Huene, R; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 112, 527-538, https://doi.org/10.2973/odp.proc.sr.112.165.1990
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Bacterial and thermogenic hydrocarbons are present in the sorbed-gas fraction of Peru margin sediments. At Ocean Drilling Program (ODP) Sites 681, 682, 684, and 686, bacterial gases are restricted to the early diagenetic zones, where dissolved sulfate has been exhausted and methanogenesis occurs. Methane migrating into the sulfate zone at Sites 681, 684, 686, and possibly 682, has been consumed anaerobically by methanotrophs, maintaining the low concentrations and causing an isotope shift in d13C(CH4) to more positive values. Significant amounts of C2+ hydrocarbons occur at the shelf Sites 680/681, 684, and 686/687, where these hydrocarbons may be associated with hypersaline fluids. There is evidence at Site 679 that sorbed C2+ hydrocarbons may also have been transported by hypersaline fluids. This characteristic C2+ hydrocarbon signature in the sorbed-gas fractions of sediments at Site 679 is not reflected in data obtained using the conventional "free-," "canned-," or "headspace-gas" procedures. The molecular and isotope compositions of the sorbed-gas fraction indicate that this gas may have a thermogenic source and may have spilled over with the hypersaline fluids from the Salaverry Basin into the Lima Basin. These traces of thermogenic hydrocarbon gases are over-mature (about 1.5% Ro) and are discordant with the less-mature sediments in which they are found.
This observation supports the migration of these hydrocarbons, possibly from continental sources. Sorbed-gas analyses may provide important geochemical information, in addition to that of the free-gases. Sorbed-gases are less sensitive to activities in the interstitial fluids, such as methanogenesis and methanotrophy, and may faithfully record the migration of hydrocarbons associated with hypersaline fluids.
Median Latitude: -11.185643 * Median Longitude: -78.542595 * South-bound Latitude: -13.480167 * West-bound Longitude: -79.955830 * North-bound Latitude: -8.991500 * East-bound Longitude: -76.891500
Date/Time Start: 1986-11-01T12:45:00 * Date/Time End: 1986-12-05T06:00:00
112-679D * Latitude: -11.063830 * Longitude: -78.272170 * Date/Time Start: 1986-11-01T12:45:00 * Date/Time End: 1986-11-02T13:15:00 * Elevation: -462.0 m * Penetration: 245.4 m * Recovery: 116.03 m * Location: South Pacific Ocean * Campaign: Leg112 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 27 cores; 245.2 m cored; 0 m drilled; 47.3 % recovery
112-680B * Latitude: -11.065000 * Longitude: -78.077830 * Date/Time Start: 1986-11-05T20:30:00 * Date/Time End: 1986-11-06T14:30:00 * Elevation: -273.0 m * Penetration: 195.5 m * Recovery: 98.45 m * Location: South Pacific Ocean * Campaign: Leg112 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 22 cores; 195.5 m cored; 0 m drilled; 50.4 % recovery
112-681C * Latitude: -10.976660 * Longitude: -77.957670 * Date/Time Start: 1986-11-08T13:15:00 * Date/Time End: 1986-11-08T18:00:00 * Elevation: -162.0 m * Penetration: 91.4 m * Recovery: 86.24 m * Location: South Pacific Ocean * Campaign: Leg112 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 10 cores; 91.4 m cored; 0 m drilled; 94.4 % recovery
Datasets listed in this publication series
- Whiticar, MJ; Suess, E (1990): (Table 1) Molecular and isotope composition of sorbed gases of ODP Leg 112 samples. https://doi.org/10.1594/PANGAEA.753737
- Whiticar, MJ; Suess, E (1990): (Table 2) Molecular and isotope composition of free- and true sorbed gases of ODP Leg 112 samples. https://doi.org/10.1594/PANGAEA.753738