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Isotopic evidence of cool winter conditions in the mid-Piacenzian (Pliocene) of the southern North Sea Basin

By Annemarie Valentine, Andrew L.A. Johnson, Melanie J. Leng, Hilary J. Sloane and Peter S. Balson

Abstract

Oxygen isotope thermometry of Aequipecten opercularis and Atrina fragilis bivalves (which demonstrate all-year growth), provides quantitative evidence of cool-temperate winter conditions (below 10 °C) during deposition of the mid-Piacenzian Oorderen Sands and time-equivalent strata in the southern North Sea Basin (SNSB). Isotopic summer temperatures (seafloor) are within or only marginally above, the cool-temperate range (upper limit 20 °C). The occurrence of warm-temperate dinoflagellate cysts alongside (and presumably contemporaneous with) the bivalves, indicates the development of a correspondingly warm surface layer in summer (encystment allowing the dinoflagellates to survive cool winter conditions).This evidence of greater surface seasonality than now is consistent with greater global warmth and a reduction in the vigour of the Gulf Stream/North Atlantic Drift (GS/NAD), leading to a reduced supply of winter heat. This reduction in GS/NAD strength may be linked to breaching of the emerging Isthmus of Panama.\ud \u

Publisher: Elsevier
Year: 2011
DOI identifier: 10.1016/j.palaeo.2011.05.015
OAI identifier: oai:nora.nerc.ac.uk:14809
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