Abstract The South Atlantic presalt petroleum system has unique elements which are related to the basin bounding structural fabric, accommodation space and climatic conditions. The development of both high total organic carbon lacustrine source rocks and hypersaline/hyperal-kaline microbial carbonates requires sequestration of these basins from marine conditions. Sequestration is accomplished by an outer-high which was isostatically elevated by magmatic under-plating. This magmatic under-plating is occurs along the margin from the Santos Basin to the Espírito Santo Basin and the conjugate Kwanza Basin. Where the outer high is absent, such as in the Brazilian Pelotas Basin and Namibian basins, the presalt petroleum system fails to develop. In Gabon where under-plating and basin sequestration occurs, a Brazilian style presalt system fails to develop due to high clastic influx. Gabon lacks the microbial hypersaline carbonate reservoir. Similar Brazilian style presalt petroleum systems are likely however, to occur on other passive margins where similar structural styles create a sequestered basin. These basins should occur in regions which are transitional from classic volcanic margins to true nonvolcanic margins. Through better understanding of the Brazilian presalt geodynamic setting we can position ourselves to identify new basins with similar petroleum systems which have created the giant Brazilian presalt discoveries.

Abstract Recent and very important oil discoveries in Albian carbonate reservoirs from the shallow to deep waters in the marginal basins off the eastern coast of Brazil have led Petrobras to develop work flows for the geological characterization and modeling of these complex reservoirs. The Albian carbonate reservoirs are often elongated shoals that are mainly composed of grainstones and packstones containing oncolites, peloids, oolites, and rare bioclasts. The sedimentation occurred in a high temperature hypersaline environment ( Spadini et al. , 1988 ). The geological controlling factors on reservoir quality are different in each of the Albian fields. Blauth (1993) and Blauth and Carvalho (1994) document the effect of depositional and diagenetic features on pore geometry and permeability of the Albian carbonate reservoirs of the Santos Basin, Brazil. Guimarães (1995) gives a complete reservoir characterization and geostatistical modeling of an Albian carbonate reservoir from the Campos Basin in his master’s degree.

This paper summarizes the research efforts devoted over the years to the understanding of the origin and evolution of brines in the Dead Sea basin. These brines are characterized by a unique Ca-Chloride composition, which evolved from interaction of evaporated seawater filling the late Neogene Sedom lagoon with the Cretaceous carbonate rocks exposed at the basin-bounding escarpments. Following the disconnection of the lagoon from the open sea and the development of inland lakes, the composition of the ancient Sedom brine changed due to precipitation of evaporites and addition of salts from incoming fresh water. Relative to highly evaporated seawater, these processes led to enrichment of the brines in Cl, Br, Mg, Ca, and K and depletion in Na and SO 4 . The modern Dead Sea, representing a recent product of these evolutionary processes, derived its ingredients from residual brines that remained after the desiccation of the late Pleistocene Lake Lisan, from incoming fresh water, and from saline springs that emerge along the western shores of the Dead Sea. Similar sources probably dictated the composition of the Pleistocene lakes (Amora, Lisan), though their relative contribution changed through time, reflecting the control of climate on the hydrological system (e.g., the activity of saline springs).