Abstract

The sedimentary evolution of pre-rift sequences in coastal and interior basins of northeastern Brazil is analysed through the understanding of paleoclimatic and tectonic changes that occurred in the region from Permian to Early Cretaceous. The history of that sedimentation began with a lacustrine environment in semi-arid conditions with associated fluvial and aeolian deposits (Alianca Formation in the Reconcavo Basin and Bananeiras-Candeeiro formations in the Sergipe-Alagoas Basin). This paleogeography was filled by braided fluvial systems coming from NNW and SSW (Sergi Formation in the Reconcavo Basin and Serraria Formation in the Sergipe-Alagoas Basin). The characterized sedimentary evolution allows definition of a new proposal in terms of the paleogeographic development of northeastern Brazil during Late Jurassic-Early Cretaceous. Paleogeography, provenance, depositional environment and diagenetic and burial histories of the Serraria Formation have been analysed to establish the principles for prospecting deep reservoirs (Garcia, 1992; Garcia et al., 1990). This unit was deposited by braided fluvial streams crossing a wide cratonic basin from NNW, before the Atlantic Rift rupture. The Serraria Formation shows lower and upper fine intervals of interbeded sandstones and lacustrine shales, and a coarser middle interval of high energy deposits and horizons of aeolian reworking. Provenance analysis has revealed a mature quartz-feldspathic assemblage that was deposited as a result of continuous weathering and transportation from distant source areas of essentially plutonic composition.