Journal
EARTH AND PLANETARY SCIENCE LETTERS
Volume 369, Issue -, Pages 169-177Publisher
ELSEVIER
DOI: 10.1016/j.epsl.2013.03.019
Keywords
cretaceous; ocean circulation; neodymium isotopes; gateways
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Funding
- US National Science Foundation
- German Research Foundation DFG [VO687/10-1, VO687/10-2, FR2544/2-1, FR1198/7-1]
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The evolution of global ocean circulation toward deep-water production in the high southern latitudes is thought to have been closely linked to the transition from extreme mid-Cretaceous warmth to the cooler Cenozoic climate. The relative influences of climate cooling and the opening and closure of oceanic gateways on the mode of deep-ocean circulation are, however, still unresolved. Here we reconstruct intermediate- to deep-water circulation for the latest Cretaceous based on new high-resolution radiogenic neodymium (Nd) isotope data from several sites and for different water depths in the South Atlantic, Southern Ocean, and proto-Indian Ocean. Our data document the presence of markedly different intermediate water Nd-isotopic compositions in the South Atlantic and Southern Ocean. In particular, a water mass with a highly radiogenic Nd isotope signature most likely originating from intense hotspot-related volcanic activity bathed the crest of Walvis Ridge between 71 and 69 Ma, which formed a barrier that prevented deep-water exchange between the Southern Ocean and the North Atlantic basins. We suggest that the Cenozoic mode of global deep-ocean circulation was still suppressed by tectonic barriers in the latest Cretaceous, and that numerous, mostly regionally-formed and sourced intermediate to deep waters supplied the deep ocean prior to 68 million yr ago. (C) 2013 Elsevier B.V. All rights reserved.
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