title: Clay mineral continental amplifier for marine carbon sequestration in a greenhouse ocean.
abstract: The majority of carbon sequestration at the Earth's surface occurs in marine continental margin settings within fine-grained sediments whose mineral properties are a function of continental climatic conditions. We report very high mineral surface area (MSA) values of 300 and 570 m(2) g in Late Cretaceous black shales from Ocean Drilling Program site 959 of the Deep Ivorian Basin that vary on subcentennial time scales corresponding with abrupt increases from approximately 3 to approximately 18% total organic carbon (TOC). The observed MSA changes with TOC across multiple scales of variability and on a sample-by-sample basis (centimeter scale), provides a rigorous test of a hypothesized influence on organic carbon burial by detrital clay mineral controlled MSA. Changes in TOC also correspond with geochemical and sedimentological evidence for water column anoxia. Bioturbated intervals show a lower organic carbon loading on mineral surface area of 0.1 mg-OC m(-2) when compared to 0.4 mg-OC m(-2) for laminated and sulfidic sediments. Although either anoxia or mineral surface protection may be capable of producing TOC of < 5%, when brought together they produced the very high TOC (10-18%) apparent in these sediments. This nonlinear response in carbon burial resulted from minor precession-driven changes of continental climate influencing clay mineral properties and runoff from the African continent. This study identifies a previously unrecognized land-sea connection among continental weathering, clay mineral production, and anoxia and a nonlinear effect on marine carbon sequestration during the Coniacian-Santonian Oceanic Anoxic Event 3 in the tropical eastern Atlantic.
authors.affiliation: School of Earth and Environmental Science, University of Adelaide, Adelaide 5005, Australia. martin.kennedy@adelaide
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Kennedy
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner
mesh_terms: D000349:Africa; D000538:Aluminum Silicates; D002244:Carbon / Q000032:analysis*; D057965:Carbon Sequestration; D000077215:Clay; D002980:Climate; D019015:Geologic Sediments / Q000737:chemistry*; D017752:Greenhouse Effect; D008903:Minerals / Q000032:analysis*; D009792:Oceans and Seas; D010100:Oxygen / Q000032:analysis; D012623:Seawater / Q000737:chemistry; D013997:Time Factors; D014872:Water Movements
chemical_list: D000538:Aluminum Silicates; D008903:Minerals; D002244:Carbon; D010100:Oxygen; D000077215:Clay