ABSTRACT.

Brazil has an area of 8,511,000 sq. km. of which 3,200,000 sq. km. are sedimcntary basin areas. Three large sedimentary basins, namely Paraná, Maranhão and Amazon are Paleozoic basins of large size. These basins appear to be sea arms of the Andean geosyncline and were probably interconnected. The Paleozoic basins are comparatively shallow and the Sediments indicate slow deposition and have never been affected by violent orogenie folding. The Brazilian Paleozoic basins are separated from the Andean trough by a low arch known as the Corumha Arch. The smaller Cretaceous basins are either graben or half-graben types with large marginal faults. The structures within these basins are of the horst and graben and tilted normal-fault-block type. The only commercial oil is in the Recôncavo basin where a reserve of over a billion barrels has been discovered. The producing foriuations are marinc Cretaceous rocks.

RESUME.

Le Brésil a une superficie de 8.511.000 km*, dont 3.200.000 sont des bassins sédimentaires. Trois grandes régions sédimentaires, à savoir Paraná, Maranháo et Amazone, sont des bassins Pal6ozoïques de grandes dimensions. Ces bassins semblent être des bras de mer du géosynclinal andien qui auraient autrefois été liés entre eux. Les bassins paléozoïques sont relativement peu profonds et tout indique que les sédiments ont été déposés lentement; aucune compression violente n'y a donné naissance à plissement ou relief pronond. Les bassins paléozoïques brésiliens sont séparés de la dépression andienne par un arc peu élevé connu sous le nom de "Voûte de Corumba".

Les bassins du Crétacé, de dimensions moindres, sont du type fosse ou demi-fosse avec des failles marginales. Les structures de ces bassins sont du type horst, fosse et bloc incliné de failles normales. Le pétrole n'existe commercialement que dans le bassin du Recôncavo où une réserve de plu, d'un milliard de barils a été découverte. Les formations productrices sont d'âge erétacé d'origine maritime.

Introduction:

The Sedimentary Basins of Brazil Brazil has an area of 8,511,000 sq.km. (3,244,246 sq.miles). Of this area approximately 3,200,000 sq.km. are sedimentary basin areas of various kinds or 37.8% of the total area of Brazil (Figure 1). There are three Paleozoic basins: Amazonas with an area of 1,200,000 sq.km., Maranhão with 600,000 sq.km., and Paraná with 1,200,000 sq.km. The Cretaceous basins of northeast Brazil cover 40,000 sq.km., Sergipe-Alagoas 16,000 sq.km., Tucano 40,000 sq.km., Recôncavo 15,000 sq.km and others 90,000 sq.km. The only commercially productive basin today is the Recôncavo, a Cretaceous basin. The Amazon basin will be presented in a separate report (Paper 51, Section I).

The Geological Framework of Brazil The geological framework of Brazil is controlled by the Brazilian and Guiana Pre-Cambrian Shields.

The large Paleozoic sediment

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