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Journal of Micropalaeontology An open-access journal of The Micropalaeontological Society
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Volume 9, issue 2
J. Micropalaeontol., 9, 153–158, 1991
https://doi.org/10.1144/jm.9.2.153
© Author(s) 1991. This work is distributed under
the Creative Commons Attribution 4.0 License.
J. Micropalaeontol., 9, 153–158, 1991
https://doi.org/10.1144/jm.9.2.153
© Author(s) 1991. This work is distributed under
the Creative Commons Attribution 4.0 License.

  01 Mar 1991

01 Mar 1991

Benthic Foraminifera from Middle to Late Pleistocene, coastal upwelling sediments of ODP Hole 686B, Pacific Ocean, off Peru

Kathryn A. Malmgren1 and Brian M. Funnell2 Kathryn A. Malmgren and Brian M. Funnell
  • 1(née YOUNG) Västertorp, Strömma, S-13900, Värmdo, Sweden
  • 2School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ

Abstract. Benthic Foraminifera from middle to late Pleistocene, (c. 600ka to 0ka), sediments of ODP Hole 686B, off Peru, show highest abundances and diversities during periods of cooler surface waters, (inferred from the Uk37 index), and enhanced upwelling, (inferred from the peridinacean/gonyaulacacean dinoflagellate cyst ratio). During the latest Pleistocene, (c. 160ka to 0ka), these periods are characterised by higher organic carbon contents in the bottom sediments, and occur during the odd-numbered, interglacial_18O stages. The benthic Foraminifera indicate deposition in 120 to 250 metres water depth for the earlier part of the record, (c. 600ka to c. 200ka), within the oxygen-minimum zone, with bottom water oxygen contents of <0.5 to 0.2 ml/l, (inferred from the dominance of Bolivinellina humilis). Deposition in water depths approaching those of the present day, (c. 450 metres), is indicated from c. 160ka onwards, with better oxygenated bottom water conditions, probably corresponding to the lower part of the oxygen-minimum zone.

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