--> Abstract: Stratigraphic Comparisons Between the Post-Rift Section of the Campos and Santos Basins, Southeastern Brazilian Margin, by J. M. Macedo, J. A. Ricci, L. F. G. Caddah, and W. Winter; #90933 (1998).

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Abstract: Stratigraphic Comparisons Between the Post-Rift Section of the Campos and Santos Basins, Southeastern Brazilian Margin

Macedo, J. M. - Petrobras/Cenpes; Gamboa, L.A.P.; Ricci, J. A.; Caddah, L.F.G.; and Winter, W. - Petrobras/E&P

The Santos and Campos basins show remarkable stratigraphic differences in spite of their similar origin and proximity. Both basins are filled by Barremian to Aptian rift sediments and by the subsequent drift sequences. In this study, seismic lines and well data were used to contrast the Late Cretaceous and Tertiary stratigraphic and structural evolution of the two basins. The Santos Turonian section is formed by relatively shallow-water turbidites that are overlain by a thick Turonian/Maastrichtian prograding wedge composed of coarse clastics deposited in fluvial and shallow-marine environments (Fig.1). In contrast, the Upper Cretaceous succession of the Campos basin is mainly composed of deep-water shales and turbidite sandstones. The coastal and shallow-water environments of this basin are poorly preserved as they were mostly deposited onshore to the present coastline and are presently mostly eroded (Fig.1). In this basin the turbidite sandstones (from Turonian to the Maastrichtian) form a retrograding wedge with overlapping pattern, as usually found in correlative-age sections of other passive margin basins. The turbidite facies also show a backstepping style, as channel facies predominate in the Turonian section and lobe facies in the Santonian/Maastrichtian section. Therefore, the Upper Cretaceous section of the Santos Basin is progradational while the Campos Basin is retrogradational. This difference is interpreted to be a result of the uplift of the adjacent continental area of the Santos basin, the present-day Serra do Mar.

During the early Tertiary, the adjacent continental area of the two basins was subjected to renewed tectonic movements along the Serra do Mar region, responsible for the generation, on the onshore region, of half-graben basins that were mainly filled by lacustrine sediments (e.g., Taubaté basin). In the offshore region, erosion of the Upper Cretaceous section resulted in a thick Eocene prograding wedge that can be seen at the northern part of Santos basin (Fig. 1). New tectonic pulses along the Precambrian foldbelt in the Serra do Mar region established the present-day hydrographic basin of the Paraiba do Sul River. Although this river drainage starts adjacent to the Santos basin, it runs northeasterly parallel to the coast and only reaches the sea at the northern Campos basin. As a result, since the uppermost Eocene, the Campos basin received a large amount of sediments that enabled the development of a thick prograding wedge with well defined shelf-slope-basin clinoform profile. Meanwhile, the northern Santos basin was receiving a lesser amount of sediments resulting in relatively thin sedimentary sequences. Therefore, since the Upper Eocene, the Tertiary section of the Santos basin is retrogradational in contrast to the prograding style of the Campos basin. Major differences in the stratigraphic record of the Santos and Campos basins resulted from the tectonically controlled migration of the main source-area of sediments, that shifted from Santos to Campos basin from the Upper Cretaceous to the Tertiary.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil