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Contact
Email
Thilo Bechstädt (Info)
Rainer Zühlke (Info)
Phone
+49 6221 54-8292
+49 6221 54-6055
Fax
+49 6221 54-5503
Thilo Bechstädt (Info)
Rainer Zühlke (Info)
Phone
+49 6221 54-8292
+49 6221 54-6055
Fax
+49 6221 54-5503
Project Login
Seismic Stratigraphy and Numerical Modeling of the Western Southern Atlantic Continental Margin (Cretaceous-Quarternary, Brazil, Uruguay) |
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| Abstract | ||
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| Scientists Jorham Contreras, GeoResources and University of Heidelberg Rainer Zühlke, GeoResources and University of Heidelberg Scott Bowman, BHP Billiton Inc. and Petrodynamics Inc., Houston Thilo Bechstädt, GeoResources and University of Heidelberg |
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| Abstract The project addresses a multidisciplinary approach integrating seismo-stratigraphy, 2D numerical reverse and stratigraphic forward basin modeling. The dataset includes three regional seismic profiles, each 300 to 340 km long, located in the Campos, Santos and Pelotas basins as well as lithological and biostratigraphic well information. Key objectives are to: (i) interpret large-scale seismo-stratigraphic second order sequences from the continental to oceanic crust domains; (ii) quantitatively analyze the subsidence history (i.e., thermo-tectonic, flexure- and compaction-induced subsidence) and sediment flux concerning changes in accommodation space and depositional trends; (iii) estimate depositional geometries and quantify its physical factors determining deposition; (iv) evaluate the interplay between facies distribution and structural deformation in terms of favorable location for potential reservoirs, source rock distribution and synchronization traps-migration. The basin fill from middle Barremian to Holocene has been subdivided into 12 to 14 seismic units. During the basin development, four main subsidence trends of 8 to 51.5 my duration, closely related to the rift-to-drift basin evolution stages, controlled the basin architecture. The Barremian to early Aptian rift phase is characterized by high rates of subsidence (80-120 m/my) during crustal rupture and stretching. From the last rift phase, a depth-dependent extensional model (Driscoll and Karner, 1998) governed the basin development and resulting heat flow influenced the high hydrocarbon generation of the lacustrine source rocks. The break-up unconformity of middle Aptian age (117 my) marks the onset of a long-term phase of thermal subsidence (sag basin stage). A thick transitional sequence composed by evaporites and shallow-marine carbonates in the Campos and Santos basins was deposited, while the time-equivalent succession in the Pelotas Basin is mainly composed by fine-grained siliciclastic sediments. High subsidence rates (70-100 m/my) in the Aptian decreased until the middle Albian. The initial drift stage is defined by continuous decreasing subsidence controlled by thermal crustal contraction until the Maastrichtian. In the Late Cretaceous a retrogradational pattern in the Campos Basin dominated, while in the Santos Basin progradation occurred. In the Pelotas Basin predominant retrogradation prevailed from the Late Cretaceous until the Holocene. Basin tilting, positives pulses of sediment flux and eustatic sea-level falls facilitated the deposition of great thicknesses of turbidite sandstones, which represent important hydrocarbon reservoirs. In the Campos and Santos Basins these deposits are confined to troughs limited by impermeable salt layers, which in addition to listric faults and rollover structures represent potential structural traps. The lowest subsidence rates recognized in the Maastrichtian ((20-30 m/my) mark the onset of the third trend. In the Tertiary, previous architectural styles were reversed, and since the Paleogene a prograding pattern in the Campos Basin contrasts with overall retrogradation in the Santos Basin. During the Eocene subsidence increased continuously along the whole margin and large volumes of sediments accumulated. These thicknesses variations have thermal relevance in the maturation of post-salt marine source rocks as well as in the distribution of the reservoirs. The fourth subsidence trend extends from the Miocene to recent times. Distinctive subsidence/uplift patterns in each of the studied basins are result of the interplay between tectonism, sediment supply and flexural response of the crust. Remainder accommodation space was filled and salt structures were completely capped. Important events of bypass, submarine erosion and redistribution of sediments are clearly recognized, which triggered further variations in the subsidence rates and accommodation space. |
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| Publications Contreras, J., Zühlke, R., Bowman, S. and Bechstädt, T., (accepted) Seismo-stratigraphic interpretation and subsidence analysis for key segments of the southern Brazilian passive continental margin: Marine and Petroleum Geology. |
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| Presentations Seismo-stratigraphic interpretation and subsidence modeling for key segments of the southern Brazilian passive continental margin, 2009, SEPM-CES, Sediment, Kraków, Poland (oral presentation). 71st EAGE Conference & Exhibition incorporating SPE EUROPEC, Amsterdam 2009. Poster Presentation. “Seismo-stratigraphic interpretation and basin modeling for key segments of the southern Brazilian passive continental margin” IAS-SEPM Central European Section 2008. Bochum-Germany. Poster Presentation. “Basin Analysis and Numerical Modeling of Brazilian and Uruguayan passive continental margins” SEPM-CES, Sediment 2007. Brixen/Bressanone-Italy. Oral Presentation. “Basin Analysis and Numerical Modeling of South Atlantic conjugate passive continental margins” SEPM-CES, Sediment 2006. Göttingen-Germany. Poster Presentation. “Basin Analysis and Numerical Modeling of the South American and South African passive continental margins: First Results” |
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| References Driscoll, N.W. and Karner, G.D., 1998, Lower crustal extension along the Northern Carnarvon Basin, Australia: Evidence for an eastward dipping detachment: Journal of Geophysical Research, v. 103, p. 4975-4992. |
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| Funding Organizations German Academic Exchange Service (DAAD) German Research Fund (DFG) |
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