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Volume 30, issue 1
J. Micropalaeontol., 30, 33–74, 2011
https://doi.org/10.1144/0262-821X10-008
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 4.0 License.
J. Micropalaeontol., 30, 33–74, 2011
https://doi.org/10.1144/0262-821X10-008
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 4.0 License.

  01 May 2011

01 May 2011

Distribution of deep-sea benthic foraminifera in the Neogene of Blake Ridge, NW Atlantic Ocean

Kuppusamy Mohan1, Anil K. Gupta1, and Ajoy K. Bhaumik2 Kuppusamy Mohan et al.
  • 1Department of Geology & Geophysics, Indian Institute of Technology Kharagpur - 721 302, India
  • 2Department of Applied Geology, Indian School of Mines Dhanbad, Jharkhand – 826 004, India

Keywords: Benthic foraminifera, late Neogene, Blake Ridge, North Atlantic Deep Water

Abstract. This study describes and illustrates the evolution of deep-sea benthic foraminifera from the Blake Ridge during the late Neogene. In total, 305 species of benthic foraminifera belonging to 107 genera were identified. The Blake Ridge receives fine-grained nannofossil-bearing hemipelagic sediments, transported from the Canadian continental margin by the Deep Western Boundary Undercurrent (DWBUC). We thus presume that changes in benthic foraminifera at Ocean Drilling Program (ODP) sites 991A, 994C, 995A and B and 997A reflect mainly changes in the intensity of the DWBUC, which is closely related to North Atlantic Deep Water (NADW) production. However, the dominance of Uvigerina peregrina, U. proboscidea and Cassidulina carinata during the late Miocene in all the holes suggests an increased influence of Southern Component Waters in the Blake Ridge region. During the early Pliocene (4.8–2.8 Ma) in all the sites benthic faunal assemblages suggest that there was an increased transport of organic-rich sediments by the DWBUC from the Canadian margin to the Blake Ridge, driven by increased production of NADW. During this time the species diversity (Sanders' rarefied values) was low. In the younger interval (since 2.8 Ma), the faunal data suggest less transport of organic-rich sediments to the Blake Ridge, which appears to be related to weakening of the DWBUC during cold intervals. An increase in species diversity at 3 Ma probably resulted from decreased population of bacteria due to low organic matter and/or less competition. In the late Pleistocene (c. 0.6 Ma), Stilostomella lepidula became extinct in all the studied holes, suggesting that this species may have possessed a mode of feeding which no longer existed in the cold, well-oxygenated oceans of the present.

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