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A uniform lithospheric extension model has been applied to the subsidence and thermal history of the Santos and Sergipe-Alagoas basins. Thermal subsidence curves were derived from more than 40 exploratory wells, complemented by seismic and gravity sections.
In the Santos basin, the region landward of the hinge zone is dominated by Tertiary marine onlapping sediments. Seaward, rift (continental) and postrift (transitional and marine) sequences are present with predominance of the latter. Crustal thinning by 35% exists just east of the hinge zone and increases to 70% at the shelf break.
Likewise, the hinge zone in the Sergipe-Alagoas basin overlies the largest gradient in crustal thinning, but unlike the Santos basin, rift-stage sediments dominate landward of this hinge zone. Seaward, the ratio of rift to postrift sediments is larger than in the Santos basin. Crustal thinning ranges from 20% to 60%, but this transition occurs over a short distance.
Thermal and burial histories were used to estimate oil windows for potential source rocks in various parts of these basins. Maturation profiles are in good agreement with observed vitrinite reflectance and hydrocarbon maturity data. The areal distribution of maturation stages through time is variable and largely controlled by crustal thinning. Information on timing of hydrocarbon generation was applied to the prediction and evaluation of hydrocarbon accumulation.
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