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Cyclic changes in Turonian to Coniacian planktic foraminiferal assemblages from the tropical Atlantic Ocean

Lookup NU author(s): Dr Britta Beckmann, Professor Thomas Wagner

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Abstract

Abundance patterns of planktic and benthic foraminifera from a tropical Atlantic drill site (Ocean Drilling Program Site 1259, Demerara Rise, Suriname margin) display a pronounced 400 kyr cyclicity, uninterrupted throughout our ∼ 87.8-92 Ma record, between two clearly distinguishable assemblages: (1) a pelagic foraminifer fauna, which represents a deep oxygen minimum zone, and (2) another assemblage representing a shallow oxygen minimum zone where the foraminifer fauna is dominated by a higher diversity population of mostly small clavate and biserial species common in epicontinental seas. The cyclic changes in the long eccentricity band (400 kyr) between these two assemblages are proposed to reflect changes in the mean latitudinal position of the Intertropical Convergence Zone (ITCZ). Associated fluctuations in precipitation and trade wind strength may have influenced the upwelling regime at Demerara Rise leading to the observed cyclicity of planktic foraminiferal assemblages. The severe Turonian to Coniacian paleoclimatic and paleoceanographic changes in the Atlantic Ocean (e.g., gateway opening, cooling, and glaciation), however, seem to have no influence on the composition of tropical planktic foraminiferal faunas. There is no apparent relationship between foraminifer abundances and a major deflection in the stable isotope record interpreted elsewhere as a sign of the growth and decay of a large polar ice sheet. © 2008 Elsevier B.V. All rights reserved.

Publication metadata

Author(s): Friedrich O, Norris RD, Bornemann A, Beckmann B, Palike H, Worstell P, Hofmann P, Wagner T

Publication type: Article

Publication status: Published

Journal: Marine Micropaleontology

Year: 2008

Volume: 68

Issue: 3-4

Pages: 299-313

Print publication date: 01/08/2008

ISSN (print): 0377-8398

ISSN (electronic): 1872-6186

Publisher: Elsevier BV

URL: http://dx.doi.org/10.1016/j.marmicro.2008.06.003

DOI: 10.1016/j.marmicro.2008.06.003

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