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Early Paleogene variations in the calcite compensation depth: new constraints using old borehole sediments from across Ninetyeast Ridge, central Indian Ocean
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences. Rice University, USA.
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2015 (English)In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, no 3, 473-493 p.Article in journal (Refereed) Published
Abstract [en]

Major variations in global carbon cycling occurred between 62 and 48 Ma, and these very likely related to changes in the total carbon inventory of the ocean-atmosphere system. Based on carbon cycle theory, variations in the mass of the ocean carbon should be reflected in contemporaneous global ocean carbonate accumulation on the seafloor and, thereby, the depth of the calcite compensation depth (CCD). To better constrain the cause and magnitude of these changes, the community needs early Paleogene carbon isotope and carbonate accumulation records from widely separated deep-sea sediment sections, especially including the Indian Ocean. Several CCD reconstructions for this time interval have been generated using scientific drill sites in the Atlantic and Pacific oceans; however, corresponding information from the Indian Ocean has been extremely limited. To assess the depth of the CCD and the potential for renewed scientific drilling of Paleogene sequences in the Indian Ocean, we examine lithologic, nannofossil, carbon isotope, and carbonate content records for late Paleocene - early Eocene sediments recovered at three sites spanning Ninetyeast Ridge: Deep Sea Drilling Project (DSDP) Sites 213 (deep, east), 214 (shallow, central), and 215 (deep, west). The disturbed, discontinuous sediment sections are not ideal, because they were recovered in single holes using rotary coring methods, but remain the best Paleogene sediments available from the central Indian Ocean. The delta C-13 records at Sites 213 and 215 are similar to those generated at several locations in the Atlantic and Pacific, including the prominent high in delta C-13 across the Paleocene carbon isotope maximum (PCIM) at Site 215, and the prominent low in delta C-13 across the early Eocene Climatic Optimum (EECO) at both Site 213 and Site 215. The Paleocene-Eocene thermal maximum (PETM) and the K/X event are found at Site 213 but not at Site 215, presumably because of coring gaps. Carbonate content at both Sites 213 and 215 drops to < 5% shortly after the first occurrence of Discoaster lodoensis and the early Eocene rise in delta C-13 (similar to 52 Ma). This reflects a rapid shoaling of the CCD, and likely a major decrease in the net flux of C-13-depleted carbon to the ocean. Our results support ideas that major changes in net fluxes of organic carbon to and from the exogenic carbon cycle occurred during the early Paleogene. Moreover, we conclude that excellent early Paleogene carbonate accumulation records might be recovered from the central Indian Ocean with future scientific drilling.

Place, publisher, year, edition, pages
2015. Vol. 11, no 3, 473-493 p.
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:su:diva-117054DOI: 10.5194/cp-11-473-2015ISI: 000352159900007OAI: diva2:811306


Available from: 2015-05-11 Created: 2015-05-06 Last updated: 2015-05-11Bibliographically approved

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Backman, Jan
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