Clay mineral continental amplifier for marine carbon sequestration in a greenhouse ocean

Martin J. Kennedy, Thomas Wagner

Research output: Contribution to journalArticle

78 Citations (Scopus)

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 m2 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-OCm-2 when compared to 0.4 mg-OCm-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.

Original languageEnglish
Pages (from-to)9776-9781
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number24
DOIs
Publication statusPublished - 14 Jun 2011
Externally publishedYes

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