Print this pageBurial and Exhumation History of NE Brazil: Preliminary Results Based from Apatite Fission-Track Analysis, Landscape Analysis and the Stratigraphic Record
Peter Japsen1, Johan M. Bonow1, Paul F. Green2, Peter R. Cobbold3, Augusto Pedreira4, Ragnhild Lilletveit5, and Dario Chiossi5
1Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark
2Geotrack International, Victoria, VIC, Australia
3CNRS et Université de Rennes 1, Rennes, France
4Geological Survey of Brazil (CPRM), Salvador, Brazil
5Statoil do Brasil, Rio de Janeiro, Brazil
The burial and exhumation history of NE Brazil, including onshore and offshore areas, is the focus of an ongoing research project carried out for Statoil do Brasil by GEUS in collaboration with Geotrack International. Early Cretaceous rift systems are prominent along the Atlantic margin where the intracontinental Recôncavo-Tucano-Jatobá (RTJ) Rift is a mature hydrocarbon province whereas deep-water plays in the Camamu Basin along the continental margin are the target of frontier exploration. The post-rift sequence in the RTJ Rift is thin or absent but it has been estimated that up to 2 km of sedimentary cover was once present, but has been removed. The age of the cover and the time of its removal remain unknown, as does the timing of peak oil formation. In the Camamu Basin offshore, the Upper Cretaceous section is thin and separated from the rift sediments by a major unconformity and the Cenozoic succession is only about 1 km thick above a prominent Eocene unconformity. It is unknown how much section has been removed from these unconformities and when maximum burial of the rift sediments took place. Fieldwork in 2007 focussed on the RTJ Rift and the interior highlands, where remnants of a plateau are found at elevations of more than 1 km, and on the mountains outside Rio. Our interpretation is that the erosion surface that defines these plateaux was formed during the Palaeogene and that it was uplifted to the present elevation in the Neogene. The onshore denudation history will be discussed based on apatite fission-track analysis data from outcrop samples. First results indicate Cretaceous, Palaeogene and Neogene cooling episodes. The study will integrate the onshore denudation history with the burial and exhumation history offshore as estimated from palaeo-thermal, palaeo-burial and stratigraphic well data.
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