Fault evolution in the Potiguar rift termination, equatorial margin of Brazil

摘要

The transform shearing between South American and African plates in theCretaceous generated a series of sedimentary basins on both plate margins.In this study, we use gravity, aeromagnetic, and resistivity surveys toidentify architecture of fault systems and to analyze the evolution of theeastern equatorial margin of Brazil. Our study area is the southern onshoretermination of the Potiguar rift, which is an aborted NE-trending rift armdeveloped during the breakup of Pangea. The basin is located along the NNEmargin of South America that faces the main transform zone that separatesthe North and the South Atlantic. The Potiguar rift is a Neocomianstructure located at the intersection of the equatorial and western SouthAtlantic and is composed of a series of NE-trending horsts and grabens. Thisstudy reveals new grabens in the Potiguar rift and indicates that stretchingin the southern rift termination created a WNW-trending, 10 km wide, and~ 40 km long right-lateral strike-slip fault zone. This zoneencompasses at least eight depocenters, which are bounded by aleft-stepping, en echelon system of NW–SE- to NS-striking normal faults.These depocenters form grabens up to 1200 m deep with a rhomb-shapedgeometry, which are filled with rift sedimentary units and capped bypostrift sedimentary sequences. The evolution of the rift termination isconsistent with the right-lateral shearing of the equatorial margin in theCretaceous and occurs not only at the rift termination but also as isolatedstructures away from the main rift. This study indicates that thestrike-slip shearing between two plates propagated to the interior of one ofthese plates, where faults with similar orientation, kinematics, geometry,and timing of the major transform are observed. These faults also influencerift geometry.