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Patton, J W; Choquette, P W; Guennel, G K; Kaltenback, A J; Moore, Andrew (1984): Organic geochemistry and sedimentology of lower to mid-Cretaceous at DSDP Leg 77 Holes [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.809297, Supplement to: Patton, JW et al. (1984): Organic geochemistry and sedimentology of lower to mid-Cretaceous Deep-Sea Carbonates, Sites 535 and 540, Leg 77. In: Buffler, RT; Schlager, W; et al. (eds.), Initial Reports of the Deep Sea Drilling Project, Washington (U.S. Govt. Printing Office), 77, 417-443, https://doi.org/10.2973/dsdp.proc.77.110.1984

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Abstract:
Analyses of 40 carbonate core samples - 27 from Site 535, 12 from Site 540, and 1 from Site 538A - have confirmed many of the findings of the Shipboard Scientific Party. The samples, all but one Early to mid-Cretaceous in age (Berriasian to Cenomanian), reflect sequences of cyclically anoxic and oxic depositional environments. They are moderately to very dark colored, dominantly planar-parallel, laminated lime mudstones. Most show the effects of intense mechanical compaction.
Visual kerogen characteristics and conventional Rock-Eval parameters indicate that these deep basinal carbonates contain varying mixtures of thermally immature kerogen derived from both marine and terrigenous precursors. However, variations in kerogen chemistry are evident upon analysis of the pyrolysis mass spectral data in conjunction with the other geochemical analyses. Particularly diagnostic is the reduction index, Rl, a measure of H2S produced during pyrolysis. Total organic carbon, TOC, ranges from 0.6 to 6.6%, with an overall average of 2.4%. Average TOCs for these fine-grained mudstones are: late Eocene 2.5% (1 sample), Cenomanian 2.2% (6), Albian 2.0% (10), Aptian 1.3% (1), Barremian-Hauterivian 2.8% (11), late Valanginian 4.8% (3), Berriasian-early Valanginian 1.6% (7).
Most of the carbonates have source-potential ratings of fair to very good of predominantly oil-prone to mixed kerogen, with only a few gas-prone samples. The ratings correlate well with the inferred depositional environments, i.e., whether oxic or anoxic. Several new organic-geochemical parameters, especially Rl, based on pyrolysis mass spectrometry of powdered whole-rock samples, support this view.
Tar from fractures in laminated to bioturbated limestones of Unit IV (late Valanginian) at 535-58-4, 19-20 cm (530 m sub-bottom) appears to be mature, biodegraded, and of migrated rather than on site indigenous origin.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 23.806107 * Median Longitude: -84.780433 * South-bound Latitude: 23.708000 * West-bound Longitude: -85.165500 * North-bound Latitude: 23.849200 * East-bound Longitude: -84.370800
Date/Time Start: 1980-12-29T00:00:00 * Date/Time End: 1981-01-19T00:00:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
6 datasets

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Datasets listed in this publication series

  1. Patton, JW; Choquette, PW; Guennel, GK et al. (1984): (Appendix A) Carbon analyses and Rock-Eval geochemistry at DSDP Leg 77 Holes. https://doi.org/10.1594/PANGAEA.809291
  2. Patton, JW; Choquette, PW; Guennel, GK et al. (1984): (Appendix C) Hydrocarbons and pyrolysis indexes at DSDP Leg 77 Holes. https://doi.org/10.1594/PANGAEA.809293
  3. Patton, JW; Choquette, PW; Guennel, GK et al. (1984): (Appendix D) Semiquantitative compositions of kerogen constitutents and inorganic constituents at DSDP Leg 77 Holes. https://doi.org/10.1594/PANGAEA.809294
  4. Patton, JW; Choquette, PW; Guennel, GK et al. (1984): (Appendix E) Semiquantitative mineralogy at DSDP Leg 77 Holes. https://doi.org/10.1594/PANGAEA.809296
  5. Patton, JW; Choquette, PW; Guennel, GK et al. (1984): (Table 1) Petrographic descriptions grouped by age and lithostratigraphic unit at DSDP Leg 77 Holes. https://doi.org/10.1594/PANGAEA.809290
  6. Patton, JW; Choquette, PW; Guennel, GK et al. (1984): (Appendix B) Rock-Eval characteristics at DSDP Leg 77 Holes. https://doi.org/10.1594/PANGAEA.809292