A SUB-SURFACE SURVEY OF NORTH EASTERN BRAZIL; SPECIFICALLY THE RECONCAVO BASIN

Extensional stress caused Africa and South America to break up about 130 m.a. The Reconcavo basin, located in northeastern Brazil (north of Salvador), is the result of a failed rift which occurred during this time period. The majority of the faults along the Brazilian coastline are parallel to the coastal margin, but in this area the faults are transverse to the coastline. The Reconcavo Basin is bounded by faults on the eastern and the western sides (the Salvador fault on the east and the Maragopipe fault on the left). These faults correspond to a basin on the continental slope, and the slope basin corresponds to significant magnetic and gravity anomalies. The basin is filled with sedimentary material, most of which is alluvial fan deposits. The sediments in this basin have been used to outline the geological history of the area. The coastal baseline in this area has undergone three major stages of tectonic evolution; a continental interval, an evaporate interval, and a marine interval. Several other sedimentary basins are also located in northeastern Brazil. Much like the Reconcavo basin, these basins are underlain by seaward-facing half grabens which extend 20-50 km onto the shore and dip 3 km seaward.

In this study we model the gravity and magnetic anomalies on the Continental Margin to understand the fault pattern along the North Eastern coast of Brazil. Understanding the relation between the Reconcavo basin, the faults surrounding the basin, and the corresponding offshore basin will help facilitate the gravity and magnetic modeling. Describing the offshore anomalies and the fault complexes along the Brazilian coastline help to better describe the current evolution models of the coastline.