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Crustal structure of the central sector of the NE Brazilian equatorial margin

2019; Geological Society of London; Volume: 476; Issue: 1 Linguagem: Inglês

10.1144/sp476-2019-54

2041-4927

Javier Tamara, Ken McClay, Neil Hodgson,

earthquake and tectonic studies

Abstract The central equatorial Brazilian margin is divided into the Amazon and Barreirinhas divergent segments separated by the Pará-Maranhão transform segment. Analysis of regional 2D seismic lines allowed the definition of the crustal architecture of the margin. In the study area, the Barreirinhas segment has a proximal domain with a 30–35 km-thick continental crust, a 20–40 km-wide necked domain where the crust thins to 10 km, and an outboard domain with hyperextended continental crust. The Pará-Maranhão and Amazon segments consist of exhumation domains and their transition to ocean crust. Their structural styles indicate that this is a magma-poor passive margin with oceanic crust formed in a slow spreading centre. The Pará-Maranhão segment is bounded by two branches of the Saint Paul Fracture Zone that displace crustal domains with structures that document the transition from the distal part of a transform margin to an oceanic fracture zone. Two groups of post-rift volcanic complexes have been identified in the exhumation and oceanic domains, and whose distribution is controlled by the fracture zones. Late Cretaceous–Recent gravitationally-driven slide systems and mass-transport deposits indicate long-lived margin collapse and sediment redistribution fundamentally controlled by the underlying crustal structure of this part of the northeastern Brasilian passive margin.