Along-strike segmentation of the northeastern Brazilian margins controlled by geodynamics and lithospheric inheritance

• Published in: Journal of South American earth sciences Vol. 128; p. 104479
• Main Authors: Evain, Mikael, Schnürle, Philippe, Loureiro, Afonso, Gallais, Flora, Pinheiro, Joao, Afilhado, Alexandra, Klingelhoefer, Frauke, Dias, Nuno, Soares, José Eduardo, Fuck, Reinhardt, Cupertino, J.A., Viana, Adriano, Aslanian, Daniel, Moulin, Maryline
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2023; Elsevier
• Subjects: Crustal structure; Geodynamics; Lithospheric inheritance; Margins' segmentation; Northeastern Brazilian margins; Plate kinematics; Sciences of the Universe; Wide-angle seismic; Margins' segmentation; Northeastern Brazilian margins; Plate kinematics; Lithospheric inheritance; Geodynamics; Crustal structure; Wide-angle seismic
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2023.104479

Passive continental margins depict a wide range of crustal architectures. Such observation mainly come from wide-angle seismic that has proven to be a valuable tool to constrain margins’ onshore and offshore crustal structures. Yet, it is still unclear what are the main drivers of such diversity and whether some more general processes do also control their formation. Here, by analyzing coincident marine seismic reflection and refraction data acquired parallel to the coast of northeast Brazil we shed a unique view on the along-strike segmentation of its passive margins. Our two P-wave velocity models add up to 10 other wide-angle velocity models build in the scope of the SALSA (Sergipe ALagoas Seismic Acquisition) project to provide a coherent picture of the crustal and upper mantle architecture of the offshore domains of the Jequitinhonha, Almada, Camamu, Jacuípe, Sergipe and Alagoas margins. In the Camamu-Jacuípe segment, both crustal necking and the continent to ocean transition were shown to be sharp. Along strike, our models show extremely thin crust above a thick anomalous velocity layer and a relatively low density mantle. This architecture is interpreted as made of collapsed continental blocks above either highly intruded lower continental crust and/or serpentinized mantle that is locally exhumed. It greatly differs from the crustal structure imaged to the south, within the Jequitinhonha and Almada segments, where our models support the existence of a vast and homogeneous domain of exhumed lower continental crust. It also considerably contrasts with the offshore architecture of the Sergipe-Alagoas segment to the north. There, the necking and transition to normal oceanic crust was shown to be narrow but gradual and dominated by middle to lower continental crust. On our along-strike models, it is characterized by a thicker but also highly intruded continental crust. Crustal architecture evolves brutally at the frontiers of these segments which coincides precisely with the Camamu Triple Junction and the offshore prolongation of the Vaza Barris fault zone. The former is one of the major geodynamic features in the development of the Central Segment of the South-Atlantic Ocean while the later marks the suture between the São-Francisco Craton and the northeastern Brazilian Orogenic Belt. Therefore, we clearly evidence the first-order control of both geodynamics and lithospheric inheritance on the along-strike segmentation of the northeastern Brazilian passive margins. Our results emphasize the crucial role of plate kinematics and lithospheric strength in shaping their architectures and the exhumation of middle/lower continental crust as a more general process of their formation.
•Northeastern Brazilian margins' segmentation is investigated using along-strike wide-angle seismic profiles•Velocity models reveal strong variations in offshore margin's crustal structure.•Changes in architecture occur at the Camamu Triple Junction and the offshore Vaza-Barris Fault Zone.•We argue that the lithospheric inheritance and the geodynamic context controlled this segmentation.