Abreu, Vitor S.; Droxler, A. W.; Vail, P. R. (1997): Towards a pre-Pleistocene sea-level calibration; sequence stratigraphy and oxygen isotope stratigraphy of Pelotas Basin, offshore Southeast Brazil. Geological Society of America (GSA), Boulder, CO, United States, In: Anonymous, Geological Society of America, 1997 annual meeting, 29 (6), 413, georefid:1998-043127
Abstract:
We compare two eustatic Upper Cretaceous and Cenozoic records, developed in Pelotas Basin based upon the sequence stratigraphic interpretation of industry seismic lines and well-log information and oxygen isotope analyses of benthonic foraminifera and bulk rock. Pelotas Basin is one of the nine large sedimentary basins distributed along the eastern Brazilian continental margin and explored for hydrocarbons since the '70s. The sedimentary infill of these basins directly resulted from the Jurassic to Lower Cretaceous break-up of Pangea. Forty one depositional sequences were identified based upon the analysis of 3,000 km of 2D reflection seismic profiles and 4 hydrocarbon exploration wells. These sequences form the sequence stratigraphic framework for the Lower Cretaceous (Albian) to Cenozoic sedimentary succession. The age control was given by calcareous nannofossils and planktonic foraminifera biostratigraphies. This local sequence stratigraphic framework is compared with the global chart (Haq et al., 1987) and the new cycle chart of Hardenbol et al. (in press). Oxygen isotope analyses were based upon benthonic foraminifera (Bulimina sp. and Uvigerina sp.) in the Miocene and Quaternary sections and in bulk rock samples in the Upper Cretaceous and Cenozoic sections from one industry well. The stable isotope record of Pelotas Basin is compared with the deep-sea record from ODP/DSDP sites.The sequence boundaries defined in the Upper Cretaceous of Pelotas Basin seem to be related to second order transgressive-regressive cycles. Higher frequency sequence boundaries are shown in the Cenozoic section, more likely related to third and fourth order cyclicity. From the sequence stratigraphic analyses, a chronostratigraphic chart and an onlap curve were built. We estimate the magnitude of sea-level fluctuations in measuring the downward shift of coastal onlap in seismic lines for each sequence boundary and tentatively built an eustatic curve. This curve is compared with the oxygen isotope records, another proxy for eustasy. Results from this study are compared with the New Jersey and Bahamas ODP Legs, whose main objective is to address sea-level changes during the Cenozoic.
Coverage:
West: -74.0000 East: -34.0000 North: 5.1500 South: -34.0000
West: NaN East: NaN North: NaN South: NaN
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