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ABSTRACT

A Cretaceous (Aptian) to Cenozoic composite oxygen isotope curve is presented and correlated to eustatic records and to global tectonic events. The curve was built using deep water benthonic foraminifera from DSDP/ODP sites. In addition, well-dated outcrop and subsurface whole rock samples were used. This composite record provides insight about the evolution of deep-water temperatures and/or ice volume changes from the Aptian to the present. Two important observations can be made from the isotope record. First, three low-frequency isotope cycles are recognized, encompassing most of the Upper Cretaceous (named Uki), most of the Paleogene (named Pi) and most of the Neogene (named Ni) period. These low-frequency cycles correspond well with the sequence stratigraphic supercycle sets Upper Zuni A, Tejas B and Tejas A, respectively. Second, oxygen isotope values for deep-water benthonic foraminifera during the Aptian to lower Albian and Campanian to Maastrichtian are similar to those observed during middle Eocene. Due to the evidence for middle Eocene Antarctic glaciation, similarity between Cretaceous and Eocene isotope values could indicate the presence of polar ice as early as the Aptian.

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