Tectonically driven changes in the Indian Ocean circulation over the last 25 Ma:: Neodymium isotope evidence

Changes in ancient oceanic current patterns have been strongly influenced by plate tectonics, particularly by the opening or closing of gateways between different oceans. Such modifications of oceanic circulation have important consequences on climate. We studied the Nd seawater isotopic composition of Indian and Pacific Ocean cores using Nd isotopes, which are good paleo-oceanographic tracers. We focused on the past 25 Ma which are marked by the closure of the Indonesian gateway as well as the Mediterranean connection. We show that a strong westerly oceanic surface current, which we refer to the Miocene Indian Ocean Equatorial Jet (MIOJet), linked the eastern and western Indian Ocean from 14 Ma to 3 Ma and infer that this major change in oceanic circulation probably induced important variations of global climate. (C) 2007 Elsevier B.V. All rights reserved.