Pisciotto, Kenneth A; Mahoney, John J (1981): Isotopic survey of diagenetic carbonates, at DSDP Leg 63 Holes [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.819172, Supplement to: Pisciotto, KA; Mahoney, JJ (1981): Isotopic survey of diagenetic carbonates, Deep Sea Drilling Project Leg 63. In: Yeats, RS; Haq, BU; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 63, 595-609, https://doi.org/10.2973/dsdp.proc.63.118.1981
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Abstract:
Authigenic carbonates, principally calcium-rich dolomites, with extremely variable isotopic compositions were recovered in organic-rich marine sediments during Leg 63 drilling off southern California and Baja California. These carbonates occur as thin layers in fine-grained, diatomaceous sediments and siliceous rocks, mostly deposited during the Neogene. A combination of textural, geochemical, and isotopic evidence indicates these dolomites formed as cements and precipitates in shallow subsurface zones of high alkalinity spawned by abundant CO2 and methane production during progressive microbial decay of organic matter. Depths and approximate temperatures of formation estimated from oxygen isotopes are 87 to 658 meters and 10°C to 50°C, respectively. Within any sedimentary section, dolomites may form simultaneously at several depths or at different times within the same interval. Highly variable carbon isotopes (-30 to +16 per mil) reflect the isotopic reservoir in which the carbonates formed. Oxidation of organic matter through microbial reduction of sulfate at shallow depths favors light-carbon carbonates such as those at Sites 468 and 471; heavy-carbon carbonates at Site 467 most likely formed below this zone where HC**12O3**- is preferentially removed by reduction of CO2 to methane during methanogenesis. An important controlling factor is the sedimentation rate, which dictates both the preservation of organic matter on the sea floor and depth distribution of subsurface zones of organic-matter decay.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 29.061300 * Median Longitude: -116.975695 * South-bound Latitude: 23.482200 * West-bound Longitude: -120.757800 * North-bound Latitude: 33.849500 * East-bound Longitude: -112.496300
Date/Time Start: 1978-10-10T00:00:00 * Date/Time End: 1978-11-08T00:00:00
Event(s):
63-467 * Latitude: 33.849500 * Longitude: -120.757800 * Date/Time: 1978-10-10T00:00:00 * Elevation: -2128.0 m * Penetration: 1041.5 m * Recovery: 399.1 m * Location: North Pacific/GAP * Campaign: Leg63 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 100 cores; 946.5 m cored; 38 m drilled; 42.2 % recovery
63-468 * Latitude: 32.617200 * Longitude: -120.117800 * Date/Time: 1978-10-21T00:00:00 * Elevation: -1849.0 m * Penetration: 241 m * Recovery: 81 m * Location: North Pacific/ESCARPMENT * Campaign: Leg63 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 25 cores; 237.5 m cored; 0 m drilled; 34.1 % recovery
63-468B * Latitude: 32.623500 * Longitude: -120.109200 * Date/Time: 1978-10-21T00:00:00 * Elevation: -1737.0 m * Penetration: 415.5 m * Recovery: 103.1 m * Location: North Pacific/ESCARPMENT * Campaign: Leg63 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 37 cores; 351.5 m cored; 0 m drilled; 29.3 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
2 datasets
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Datasets listed in this publication series
- Pisciotto, KA; Mahoney, JJ (1981): (Table 3) Estimated depths and temperatures of formation for DSDP Leg 63 Holes authigenic carbonates and computed δ¹³C equilibrium values for CO2 and CH4. https://doi.org/10.1594/PANGAEA.819171
- Pisciotto, KA; Mahoney, JJ (1981): (Table 1) Stratigraphy, composition, and isotopes at DSDP Leg 63 Holes carbonates. https://doi.org/10.1594/PANGAEA.819170