Early diagenetic overprint in Caribbean sediment cores and its effect on the geochemical composition of planktonic foraminifera.

Regenberg, Marcus, Nürnberg, Dirk , Schönfeld, Joachim and Reichart, G.-J. (2007) Early diagenetic overprint in Caribbean sediment cores and its effect on the geochemical composition of planktonic foraminifera. Open Access Biogeosciences (BG), 4 . pp. 957-973. DOI 10.5194/bg-4-957-2007.

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Abstract

Early diagenetic features are noticed in the vicinity of carbonate platforms. Planktonic foraminifera of two tropical Atlantic deep-sea sediment cores show the strict relation between micro-scale euhydral crystallites of inorganic precipitates, higher oxygen isotope values and Mg/Ca ratios, and lower Sr/Ca ratios than expected for their pelagic environment in the time interval of ~100 000–550 000 calendar years before present. Laser ablation Mg/Ca (Sr/Ca) of crystallite-bearing foraminiferal chamber walls revealed 4–6 times elevated (2–3 times depleted) ratios, when ablating the diagenetic overgrowth. Crystalline overgrowth in proportion of 10–20% are estimated to cause the observed geochemical alteration. The extent of foraminiferal Mg/Ca alteration, moreover, seems to be controlled by the composition of the bulk sediment, especially the content of high-magnesium calcite. Anomalous ratios of >6 mmol/mol only occur, when high-magnesium calcite has dissolved within the sediment. The older parts (back to ~800 kyrs) of the records are characterized by similar trends of Mg/Ca and Sr/Ca. We discuss possible scenarios to accommodate the obtained geochemical information.

Document Type: Article
Keywords: Isotopes, Planktonic Foraminifera, Diagenesis
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-4-957-2007
ISSN: 1726-4170
Projects: Future Ocean
Date Deposited: 28 Apr 2009 13:59
Last Modified: 24 Sep 2019 00:15
URI: http://oceanrep.geomar.de/id/eprint/613

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