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Wagner, Thomas; Pletsch, Thomas (1999): Rock eval analysis of organic matter in sediment core 159-959D. PANGAEA, https://doi.org/10.1594/PANGAEA.56133, Supplement to: Wagner, T; Pletsch, T (1999): Tectono-sedimentary controls on black shale deposition along the opening Equatorial Atlantic Gateway (ODP Leg 159). In: Camron, N (ed.), Oil and gas habitats of the South Atlantic. Geological Society of London, Special Publication, London, 241-265, https://doi.org/10.1144/GSL.SP.1999.153.01.15

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Abstract:
The Cretaceous Equatorial Atlantic Gateway between the Central and South Atlantic basins is of interest not only for paleoceanographic and paleoclimatic studies, but also because it provided particularly favourable conditions for the accumulation and preservation of organic-rich sediments. Deposition of carbonaceous sediments along the Côte d'Ivoire-Ghana Transform Margin (Ocean Drilling Program Leg 159) was intimately linked to the plate tectonic and paleoceanographic evolution of this gateway. Notably, the formation of a marginal basement ridge on the southeastern border of the transform margin provided an efficient shelter of the landward Deep Ivorian Basin against erosive and potentially oxidizing currents. Different subsidence histories across the transform margin were responsible for the development of distinct depositional settings on the crest and on both sides of the basement ridge. Whereas the southern, oceanward flank of the basement ridge was characterized by rapid, continuous deepening since last Albian-early Cenomanian, marine sedimentation on the northern, landward flank was interrupted by a period of uplift and erosion in the late Albian, and rapid subsidence started after the early Coniacian.
Organic-rich sediments occur throughout almost the entire Cretaceous section, but hydrogen-rich marine black shales were exclusively recovered from core sections above an uplift-related unconformity. These black shales formed when separation of Africa and South America was sufficient to allow permanent oceanic midwater exchange after the late Albian. Four periods of black shale accumulation are recovered, some of them are correlated with the global oceanic anoxic events: in the last Albian-earliest Cenomanian, at the Cenomanian-Turronian boundary, during the middle Coniacian-early Campanian, and in the mid-Maastrichtian. These periods were characterized by increasing carbon flux to the seafloor, induced by enhanced palaeoproductivity and intensified supply of terrestrial organic matter. Black shale depostion appears to be intimately linked to periods of rising or maximum eustatic sea level and to the expansion of the oxygen minimum zone, as indicated by foraminiferal biofacies. Intervals between black shales units, in contrast, indicate a shrinking oxygen minimum zone and enhanced detrital flux rates, probably related to lowering sea level.
Upper Cretaceous detritral limestones with high porosities may provide excellent hydrocarbon reservoirs, alsthough their areal extent appears to be limited. Palaeogene porcellanites, capped by Neogene pelagic marls and clays, extend over a wider area and max provide another target for hydrocarbon exploration.
Project(s):
Coverage:
Latitude: 3.627500 * Longitude: -2.735830
Date/Time Start: 1995-01-14T00:00:00 * Date/Time End: 1995-01-24T05:30:00
Minimum DEPTH, sediment/rock: 496.42 m * Maximum DEPTH, sediment/rock: 1158.30 m
Event(s):
159-959D * Latitude: 3.627500 * Longitude: -2.735830 * Date/Time Start: 1995-01-14T00:00:00 * Date/Time End: 1995-01-24T05:30:00 * Elevation: -2091.0 m * Penetration: 1158.9 m * Recovery: 429.03 m * Location: Gulf of Guinea * Campaign: Leg159 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 78 cores; 741.1 m cored; 0 m drilled; 57.9 % recovery
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1DEPTH, sediment/rockDepthmGeocode
2Carbon, organic, totalTOC%Wagner, ThomasElement analyser CHN, LECO
3Hydrogen index, mass HC per unit mass total organic carbonHI, HC/TOCmg/gWagner, ThomasRock eval pyrolysis (Behar et al., 2001)
4Pyrolysis temperature maximumTmax°CWagner, ThomasRock eval pyrolysis (Behar et al., 2001)
5Oxygen index, mass CO2 per unit mass total organic carbonOI, CO2/TOCmg/gWagner, ThomasRock eval pyrolysis (Behar et al., 2001)
6Hydrocarbon yield, S1 per unit sediment massS1/sedmg HC/gWagner, ThomasRock eval pyrolysis (Behar et al., 2001)
7Hydrocarbon yield, S2 per unit sediment massS2/sedmg HC/gWagner, ThomasRock eval pyrolysis (Behar et al., 2001)
8Carbon dioxide yield, S3 per unit sediment massS3/sedmg CO2/gWagner, ThomasRock eval pyrolysis (Behar et al., 2001)
9Sample code/labelSample labelWagner, ThomasODP sample designation
Size:
2178 data points

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