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| Titel |
Early Paleogene variations in the calcite compensation depth: new constraints using old borehole sediments from across Ninetyeast Ridge, central Indian Ocean |
| VerfasserIn |
B. S. Slotnick, V. Lauretano, J. Backman, G. R. Dickens, A. Sluijs, L. Lourens |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 3 ; Nr. 11, no. 3 (2015-03-17), S.473-493 |
| Datensatznummer |
250117210
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| Publikation (Nr.) |
 copernicus.org/cp-11-473-2015.pdf |
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| Zusammenfassung |
| 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 δ13C records at Sites 213 and 215 are similar to those generated at
several locations in the Atlantic and Pacific, including the prominent high
in δ13C across the Paleocene carbon isotope maximum (PCIM) at Site
215, and the prominent low in δ13C 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 δ13C
(~52 Ma). This reflects a rapid shoaling of the CCD, and likely a
major decrease in the net flux of 13C-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. |
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