Crustal Structure and Tectonic Evolution of the Potiguar Basin--Northeast Brazil

Abstract

The combined analysis of potential field and seismic reflection data suggest that the Potiguar basin of northeast Brazil developed as a consequence of northwest-southeast extension, resolved in the upper crust by hanging-wall block rotation along a system of linked faults. This extension developed during the Early Cretaceous rifting associated with the separation of South America and Africa. The basic basin architecture includes two main parallel northeast-trending half-grabens (Umbuzeiro and Boa Vista) separated by intervening basement highs and northwest-trending transfer faults. A three-dimensional crustal-scale model of the basin was generated by combining deep and shallow seismic reflection data, borehole and outcrop information, and potential field data. The deep seismic profiles reveal a highly reflective crust underlain by a high-amplitude reflection Moho around 10 seconds (roughly 30 km depth). Moreover, it seems that the basin-bounding normal faults terminate at a mid-crustal detachment surface, suggesting that the basin architecture is mainly controlled by two parallel listric normal fault ones that follow pre-existing upepr crustal weaknesses, partially reactived during the main rift episode (Neocomian). Whereas the pre-existing northeast-trending planar fabrics within the basement (schistosities, gneissosity, and shear zones) apparently controlled the main normal faults, internal conjugate and synthetic transfer faults are probably related tomore » major discontinuities in basement rock fabrics. Seismic reflection data together with gravity and magnetic modeling, show that the basin architecture is directly related to a linked system of northeast-trending listric normal faults and a mid-crustal detachment surface.« less