Recôncavo Basin, Brazil: A Prolific Intracontinental Rift Basin
Published:January 01, 1994
A.M.F. de Figueiredo, J.A.E. Braga, J.C. Zabalaga, J.J. Oliveira, G.A. Aguiar, O.B. Silva, L.F. Mato, L.M.F. Daniel, L.P. Magnavita, C.H.L. Bruhn, 1994. "Recôncavo Basin, Brazil: A Prolific Intracontinental Rift Basin", Interior Rift Basins, Susan M. Landon, Anny B. Coury
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The Recôncavo basin is located in northeastern Brazil, and occupies an area of 11,500 km2. It corresponds to the southern portion of an elongated intracontinental aulacogen that extends to the north, encompassing the Tucano and Jatobá basins (Figure 1). The basin is limited to the east by the Salvador fault, with a maximum dip slip of around 5000 m, and to the west by the Maragogipe fault, with an average vertical displacement of 200 m. To the north, the basin is separated from the Tucano basin by the Aporá high, while to the south its exposed portion is delimited by the Itacaré high (Figure 2). This asymmetric graben is basically filled with Upper Jurassic and Lower Cretaceous sediments, which characterize two major sedimentary sequences: the first, prerift, is composed of an arid alluvial fan system and associated facies; the second, synrift, is composed of alluvial, fluvial, and deltaic lacustrine sediments representing the complete record of infilling of a tectonically active lake basin. A thin package of Upper Cretaceous and Tertiary postrift coarse clastics partially covers the present-day basin. As a whole, the sedimentary section reaches a maximum thickness of about 6000 m, deposited over Archean granulites and, locally, over slightly metamorphosed Proterozoic rocks and Permian-Carboniferous sediments.
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Interior Rift Basins
Not only are rift basins the foundation for much of the geologic history of the earth, but they also are very attractive areas for hydrocarbon accumulations. Klemme stated that this geographic area has provided significant hydrocarbon reserves: "By area, these basins represent slightly over 5% of the world's basins (50% productive). However, high recovery has resulted, as they contain 10% of the world's present reserves (12% of the oil reserves and 4% of the gas reserves)." The rift basins discussed in this volume are only a few of the productive and, more importantly, potentially productive rift basins in the world. The term "rift" was coined by Gregory (1896) for the graben that now bears his name in the Kenyan portion of the East African rift system. The study of geology of rift basins began in the Rhine graben. The discovery of hydrocarbons in rift basins about the turn of the century provided new motivation for understanding these basins. This publication was initiated by the AAPG Publications Committee in 1985 and contributors were invited to write. AAPG designed their "World Petroleum Basins" series and sought to publish the definitive volume on each of several basin types. In this volume, "Interior Rift Basins," a detailed, 3-paper overview was written about the Suez Rift basin as representative of interior rift basins. The key papers were followed by less detailed reviews of three other selected interior basins: Pripyat and Dnieper-Donets Basins; Reconcavo Basin, Brazil; Albuquerque Basin Segment of the Rio Grande Rift.