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März, Christian; Poulton, Simon W; Beckmann, Britta; Küster, Kathrin; Wagner, Thomas; Kasten, Sabine (2008): Geochemical analysis at ODP Site 207-1261 from the Demerara Rise in the western equatorial Atlantic. doi:10.1594/PANGAEA.732910,
Supplement to: März, C et al. (2008): Redox sensitivity of P cycling during black shale formation: Dynamics of sulfidic and anoxic, non-sulfidic bottom waters. Geochimica et Cosmochimica Acta, 72(15), 3703-3717, doi:10.1016/j.gca.2008.04.025

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Abstract:
A high-resolution geochemical record of a 120 cm black shale interval deposited during the Coniacian-Santonian Oceanic Anoxic Event 3 (ODP Leg 207, Site 1261, Demerara Rise) has been constructed to provide detailed insight into rapid changes in deep ocean and sediment paleo-redox conditions. High contents of organic matter, sulfur and redox-sensitive trace metals (Cd, Mo, V, Zn), as well as continuous lamination, point to deposition under consistently oxygen-free and largely sulfidic bottom water conditions. However, rapid and cyclic changes in deep ocean redox are documented by short-term (~15-20 ka) intervals with decreased total organic carbon (TOC), S and redox-sensitive trace metal contents, and in particular pronounced phosphorus peaks (up to 2.5 wt% P) associated with elevated Fe oxide contents. Sequential iron and phosphate extractions confirm that P is dominantly bound to iron oxides and incorporated into authigenic apatite. Preservation of this Fe-P coupling in an otherwise sulfidic depositional environment (as indicated by Fe speciation and high amounts of sulfurized organic matter) may be unexpected, and provides evidence for temporarily non-sulfidic bottom waters. However, there is no evidence for deposition under oxic conditions. Instead, sulfidic conditions were punctuated by periods of anoxic, non-sulfidic bottom waters. During these periods, phosphate was effectively scavenged during precipitation of iron (oxyhydr)oxides in the upper water column, and was subsequently deposited and largely preserved at the sea floor. After ~15-25 ka, sulfidic bottom water conditions were re-established, leading to the initial precipitation of CdS, ZnS and pyrite. Subsequently, increasing concentrations of H2S in the water column led to extensive formation of sulfurized organic matter, which effectively scavenged particle-reactive Mo complexes (thiomolybdates). At Site 1261, sulfidic bottom waters lasted for ?90-100 ka, followed by another period of anoxic, non-sulfidic conditions lasting for ~15-20 ka. The observed cyclicity at the lower end of the redox scale may have been triggered by repeated incursions of more oxygenated surface- to mid-waters from the South Atlantic resulting in a lowering of the oxic-anoxic chemocline in the water column. Alternatively, sea water sulfate might have been stripped by long-lasting high rates of sulfate reduction, removing the ultimate source for HS**- production.
Related to:
März, Christian; Beckmann, Britta; Franke, Christine; Vogt, Christoph; Wagner, Thomas; Kasten, Sabine (2009): Geochemical environment of the Coniacian-Santonian western tropical Atlantic at Demerara Rise. Palaeogeography, Palaeoclimatology, Palaeoecology, 273(3-4), 286-301, doi:10.1016/j.palaeo.2008.05.004
Project(s):
Coverage:
Latitude: 9.048617 * Longitude: -54.317400
Date/Time Start: 2003-02-16T00:00:00 * Date/Time End: 2003-02-23T00:00:00
Minimum DEPTH, sediment/rock: 570.210 m * Maximum DEPTH, sediment/rock: 571.360 m
Event(s):
207-1261 * Latitude: 9.048617 * Longitude: -54.317400 * Date/Time Start: 2003-02-16T00:00:00 * Date/Time End: 2003-02-23T00:00:00 * Elevation: -1899.7 m * Penetration: 1343.6 m * Recovery: 447.9 m * Location: North Atlantic Ocean * Campaign: Leg207 * Basis: Joides Resolution * Device: Composite Core (COMPCORE) * Comment: 67 cores; 632.8 m cored; 710.8 m drilled; 70.8 % recovery
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethodComment
1DEPTH, sediment/rockDepthmGeocode
2Depth, referenceDepth refmMärz, ChristianSection depth
3Depth, referenceDepth refmMärz, ChristianSection depth, corrected
4AluminiumAl%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
5BoronBmg/kgMärz, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
6BariumBamg/kgMärz, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
7CalciumCa%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
8CopperCu%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
9IronFe%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
10PotassiumK%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
11MagnesiumMg%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
12ManganeseMn%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
13SodiumNa%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
14PhosphorusP%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
15Sulfur, totalS%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
16StrontiumSr%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
17TitaniumTi%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
18VanadiumVmg/kgMärz, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
19ZincZn%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
20ZirconiumZrmg/kgMärz, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometry
21Barium/Aluminium ratioBa/AlMärz, ChristianCalculated
22Copper/Aluminium ratioCu/AlMärz, ChristianCalculated
23Iron/Aluminium ratioFe/AlMärz, ChristianCalculated
24Potassium/Aluminium ratioK/AlMärz, ChristianCalculated
25Magnesium/Aluminium ratioMg/AlMärz, ChristianCalculated
26Manganese/Aluminium ratioMn/AlMärz, ChristianCalculated
27Titanium/Aluminium ratioTi/AlMärz, ChristianCalculated
28Vanadium/Aluminium ratioV/AlMärz, ChristianCalculated
29Zinc/Aluminium ratioZn/AlMärz, ChristianCalculated
30Zirconium/Aluminium ratioZr/AlMärz, ChristianCalculated
31Strontium/Calcium ratioSr/CaMärz, ChristianCalculated
32Iron/sulfur ratioFe/SMärz, ChristianCalculated
33Phosphorus/Aluminium ratioP/AlMärz, ChristianCalculated
34Carbon, organic, totalTOC%März, ChristianElement analyser CS, LECO CS-200
35Calcium carbonateCaCO3%März, ChristianElement analyser CS, LECO CS-200
36Sulfur, totalS%März, ChristianICP-OES, Inductively coupled plasma - optical emission spectrometrytotal
37Carbon, organic total/Aluminium ratioTOC/AlMärz, ChristianCalculated
38Sulfur/Aluminium ratioS/AlMärz, ChristianCalculated
Size:
4292 data points

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