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Pufahl, Peir K; Wefer, Gerold (2001): Petrographic, cathodoluminescent, and compositional characters of organic dolomites from ODP Leg 175 holes. PANGAEA, https://doi.org/10.1594/PANGAEA.735263, Supplement to: Pufahl, PK; Wefer, G (2001): Data report: Petrographic, cathodoluminescent, and compositional characteristics of organogenic dolomites from the southwest African margin. In: Wefer, G; Berger, WH; Richter, C (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 175, 1-17, https://doi.org/10.2973/odp.proc.sr.175.234.2001

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Abstract:
The main objective of Leg 175 was to reconstruct the Late Neogene paleoceanographic history of the Benguela Current and associated upwelling regimes along the southwest African margin between 5° and 32°S. This area is one of the great upwelling regions of the world and plays an important role in the global ocean-carbon cycle. It is characterized by organic-rich sediments that contain a high-resolution record of productivity history that is closely linked to changes in regional dynamics of circulation, mixing, and upwelling (Wefer et al., 1998, doi:10.2973/odp.proc.ir.175.1998). The Benguela Current region also provides an excellent setting to investigate the early diagenetic processes governing the formation of authigenic dolomite. Although unexpected, the discovery of widespread and pervasive dolomite horizons along the southwest African margin was one of the principal findings of Leg 175.
Dolomite precipitation within upwelling regimes is stimulated by the effects of high productivity and occurs early within the uppermost tens to hundreds of meters of sediment (Garrison et al., 1984; Hay, Sibuet, et al., 1984, doi:10.2973/dsdp.proc.75.1984; Kastner et al., 1990, doi:10.2973/odp.proc.sr.112.144.1990; Kelts and McKenzie, 1982, doi:10.2973/dsdp.proc.64.110.1982; Kulm et al., 1984; Lyle, Koizumi, Richter, et al., 1997, doi:10.2973/odp.proc.ir.167.1997; Middelburg et al., 1990, doi:10.1130/0091-7613(1990)018<0399:DFIASO>2.3.CO;2; Pisciotto and Mahoney, 1981, doi:10.2973/dsdp.proc.63.118.1981; Suess et al., 1988, doi:10.1130/0091-7613(1988)016<0939:ODPLPC>2.3.CO;2). Productivity must be sufficiently high to generate a favorable environment; the microbial respiration of sedimentary organic matter increases alkalinity and pH of pore waters and simultaneously alters Mg-Ca solution and crystal surface chemistries to promote dolomite precipitation (Baker and Burns, 1985; Baker and Kastner, 1981, doi:10.1126/science.213.4504.214; Compton and Siever, 1986; Compton, 1988, doi:10.1016/0016-7037(86)90057-8; Compton et al., 1994; Hardie, 1987; Mazzullo, 2000; Slaughter and Hill, 1990; Vasconcelos and McKenzie, 1997). These organogenic dolomites are distinguished from other types of authigenic carbonates by having a significant portion of their carbon derived from microbially degraded organic carbon (Froelich et al., 1979, doi:10.1016/0016-7037(79)90095-4) and are thus characterized by 13C values that deviate strongly from those of normal marine carbonates (Friedman and Murata, 1979, doi:10.1016/0016-7037(79)90126-1; Irwin et al., 1977, doi:10.1038/269209a0; Murata et al., 1972; Pisciotto and Mahoney, 1981, doi:10.2973/dsdp.proc.63.118.1981).
Here, we report the occurrence of organogenic dolomite horizons within organic-rich Neogene and Quaternary hemipelagic sediments from the southwest African margin. The purpose of this paper is to document the mineralogical, compositional, textural, and cathodoluminescent (CL) properties of dolomite horizons. It is not within the scope of this report to discuss horizon formation in detail. Aspects of horizon development based on the interpretation of these properties will be the focus of a subsequent paper.
Project(s):
Coverage:
Median Latitude: -20.716592 * Median Longitude: 12.175927 * South-bound Latitude: -25.513880 * West-bound Longitude: 10.820020 * North-bound Latitude: -11.920770 * East-bound Longitude: 13.400250
Date/Time Start: 1997-09-03T18:10:00 * Date/Time End: 1997-09-24T03:15:00
Event(s):
175-1078C * Latitude: -11.920770 * Longitude: 13.400250 * Date/Time Start: 1997-09-03T18:10:00 * Date/Time End: 1997-09-04T06:05:00 * Elevation: -426.0 m * Penetration: 165.2 m * Recovery: 149.58 m * Location: Benguela Current, South Atlantic Ocean * Campaign: Leg175 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 18 cores; 165.2 m cored; 0 m drilled; 90.5 % recovery
175-1080A * Latitude: -16.559660 * Longitude: 10.820020 * Date/Time Start: 1997-09-07T04:07:00 * Date/Time End: 1997-09-07T17:30:00 * Elevation: -2765.8 m * Penetration: 52.1 m * Recovery: 55.57 m * Location: Benguela Current, South Atlantic Ocean * Campaign: Leg175 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 7 cores; 52.1 m cored; 0 m drilled; 106.7 % recovery
175-1081A * Latitude: -19.619690 * Longitude: 11.319300 * Date/Time Start: 1997-09-09T02:00:00 * Date/Time End: 1997-09-11T21:15:00 * Elevation: -794.1 m * Penetration: 452.7 m * Recovery: 393.48 m * Location: Benguela Current, South Atlantic Ocean * Campaign: Leg175 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 49 cores; 452.7 m cored; 0 m drilled; 86.9 % recovery
Size:
9 datasets

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Datasets listed in this publication series

  1. Pufahl, PK; Wefer, G (2001): (Table T1) Stratigraphic, compositional, luminescent, and isotopic data for dolomite samples, ODP Hole 175-1078C. https://doi.org/10.1594/PANGAEA.204045
  2. Pufahl, PK; Wefer, G (2001): (Table T1) Stratigraphic, compositional, luminescent, and isotopic data for dolomite samples, ODP Hole 175-1080A. https://doi.org/10.1594/PANGAEA.204046
  3. Pufahl, PK; Wefer, G (2001): (Table T1) Stratigraphic, compositional, luminescent, and isotopic data for dolomite samples, ODP Hole 175-1081A. https://doi.org/10.1594/PANGAEA.204047
  4. Pufahl, PK; Wefer, G (2001): (Table T1) Stratigraphic, compositional, luminescent, and isotopic data for dolomite samples, ODP Hole 175-1082A. https://doi.org/10.1594/PANGAEA.204048
  5. Pufahl, PK; Wefer, G (2001): (Table T1) Stratigraphic, compositional, luminescent, and isotopic data for dolomite samples, ODP Hole 175-1084A. https://doi.org/10.1594/PANGAEA.204049
  6. Pufahl, PK; Wefer, G (2001): (Table T2) Electron microprobe analyses of iron concentrations within blocky dolomite, ODP Hole 175-1082A. https://doi.org/10.1594/PANGAEA.198839
  7. Pufahl, PK; Wefer, G (2001): (Table T2) Electron microprobe analyses of iron concentrations within blocky dolomite, ODP Hole 175-1084A. https://doi.org/10.1594/PANGAEA.198841
  8. Pufahl, PK; Wefer, G (2001): (Table T2) Electron microprobe analyses of iron concentrations within luminescent dolomite, ODP Hole 175-1081A. https://doi.org/10.1594/PANGAEA.198838
  9. Pufahl, PK; Wefer, G (2001): (Table T2) Electron microprobe analyses of iron concentrations within luminescent dolomite, ODP Hole 175-1084A. https://doi.org/10.1594/PANGAEA.198842