Crustal evolution of divergent and transform segments of the Brazilian Equatorial Margin derived from integrated geophysical data: Insights from basement grain heritage

The present comprehensive multidisciplinary geophysical study provides new insights into the structural ar-chitecture and tectonic development of the Brazilian Equatorial Margin during the transform opening of the Equatorial Atlantic Ocean. The study integrates magnetic, gravity, and seismic data and adds to the knowledge of the prebreakup geotectonic setting of West Gondwana, shedding light on the role of the Precambrian heritage in the crustal compartmentalization of the Equatorial Atlantic margins into divergent and transform segments. Additionally, we improved previous evolution models of the Brazilian Equatorial Margin, considering the nature of the crustal domains and processes related to the initial breakup of West Gondwana. Our geophysical datasets reveal that the Brazilian Equatorial Margin encompasses two crustal domains with distinct internal architecture and thermomechanical parameters divided by the Transbrasiliano Lineament. The western crustal block is composed of a thicker and older lithosphere, which acted as an obstacle to continental rupture. The resulting breakup occurred further north, while the crustal block east of the Transbrasiliano Lineament disrupted rela-tively further south. Two different rift systems thinned both crustal domains during a former rift phase before the subsequent and ultimate rift phase broke up the continental crust and initiated seafloor spreading under a transform regime. After the breakup between the South American and African continents, dextral strike-slip movements along oceanic fracture zones divided the Brazilian Equatorial Margin into divergent and transform segments, whose inner and outer intersections are identified in the present study. The marginal ridges represent basement uplifts separated from the continental hinterland by pull-apart basins deformed by negative structure -like flower structures. The prebreakup Precambrian structures played a key role in margin segmentation, behaving as crustal weakness zones and nucleating transform faults at the boundaries of the divergent margin segments.

Automated summary

This study provides new insights into the structural architecture and tectonic development of the Brazilian Equatorial Margin during the opening of the Equatorial Atlantic Ocean. It reveals the role of Precambrian heritage in the crustal compartmentalization and improves previous evolution models of the margin.