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Global Perspective: Geochronology and the Oceanic Record |
1 Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
2 Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
We have compiled deep water benthic
Our data show that the north Atlantic hole DSDP 384 was the most positive site for
13C data from the Paleocene portions of several DSDP and ODP holes and present it using the new timescale of Berggren et al. (1995). 13C in the late Cretaceous and the earliest Paleocene, suggesting that the sub-tropical north Atlantic was an important locus of deep water production during these intervals. Salinity and temperature comparisons do not support unequivocal deep water production by halothermal means in this region so we prefer to avoid the term Warm Saline Deep Water (WSDW) and employ instead the more neutral term ‘palaeo-North Atlantic Deep Water’ (palaeo-NADW). During K/T boundary time, the southern ocean apparently became the major producer of deep waters. Based on 13C comparisons both the North Atlantic and Southern Ocean were deep water producers during the early Paleocene to the late Paleocene interval. In the latest Paleocene (during the ‘Paleocene carbon isotope maximum’) Southern Ocean 13C was most positive, supporting a Southern Ocean deep water source. The earliest Eocene ocean was characterized by deep water production in the high southern latitudes with well developed interbasinal 13C gradients. 18O data show an overall decrease from the late Cretaceous into the Early Eocene interrupted by an increase between 64 and 57 Ma. This is interpreted as an overall warming trend with a superimposed, previously undocumented, cooling phase in the early to late Paleocene.
