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

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.

Introduction

“…This study gives insights into the complex transform components of passive margins as also seen in the Ghana -Cote d' Ivoire margin on the equatorial margin of West Africa (cf. as well as on the Brasilian margin (Tamara et al, 2020).…”

“…The Atlantic margins have long been studied as type examples of passive margins particularly in the context of the formation of conjugate margins such as those offshore Iberia offshore Newfoundland (Peron-Vinvidic et al, 2013). Papers in this section focus mainly on the Equatorial Atlantic margins (Kuznir et al 2018;Tamara et al, 2020), but also include the development of palaeo-bathymetry in the South Atlantic realm (Perez-Diaz & Eagles, 2018), and the shale tectonics of the Niger delta system (Restrepo-Pace; 2018) (see Figure 1). Kuznir et al (2018) use regional scale gravity inversion of the equatorial Atlantic region to map the 3D crustal thickness from the continental margins to the oceanic basins.…”

“…The crustal architecture of the central equatorial margin of north-eastern Brasil is documented by Tamara et al (2020) (Fig. 1).…”

Sequence stratigraphy and organic geochemistry: An integrated approach to understand the anoxic events and paleoenvironmental evolution of the Ceará basin, Brazilian Equatorial margin

“…The process started with thinning of the continental lithosphere and mantle exhumation. Plate tectonics at this stage is characterized by rifting, block faulting, subsidence and pulling apart of the crystalline basement, which created a series of horsts and grabens and deposition settings controlled by the Romanche Fracture Zone (Mascle et al, 1997;Matos, 2000;Tamara et al, 2020). This stage started in the Barremian (?…”