Deposition and deformation in the deepwater sediment of the offshore Barreirinhas Basin, Brazil

Abstract

The Barreirinhas Basin is an ideal location to study shale-dominated gravity-driven thrusting systems because of the limited areal extent of the deformed areas compared to other areas in the world. Regional seismic refl ection profi les across the Barreirinhas Basin on the Brazilian Equatorial margin show two major deepwater fold and thrust belts linked landward to extensional fault systems. Thrust faults are interpreted to be products of shortening caused by gravitydriven extension on the continental margin that involve rocks of both the shelf and the slope. Results show two main deformation events during the Cretaceous (between ca. 89 and 84 Ma) and several episodes during the Later Cenozoic (ca. 55-0 Ma). All events were characterized by displacement along a detachment fault linking a landward system of normal faults to a basinward system of folds and thrust faults. The Cretaceous deformation involved a <1.5-km-thick sequence deformed in a 30-km-wide set of listric normal faults (an extensional domain) on the outer continental shelf and upper slope. Those normal listric faults merge seaward into a bed-parallel detachment surface forming a 30-km-wide translational domain and a 30-km-wide zone of imbricate thrust faults (a compressional domain) at the toe of the slope. The Cenozoic structural system involves a thick (over 4 km) sedimentary sequence of Turonian to Miocene age, which cross-cuts the preexisting Cretaceous deformed sequence. The Cretaceous and Cenozoic deformational events formed two discrete bowl-shaped fault systems that are linked at different stratigraphic levels. Plots of displacement versus time show normaland thrust-fault movements during the same time intervals, confi rming the link between extension on the continental shelf and compression on the slope. Deformation increased dramatically during the past 10 m.y., with movement on all earlier and some newly formed faults. The increased deformation coincided with tectonic paleogeographic and topographic changes in northern South America during the Late Miocene that led to an increase in sediment supply to the Barreirinhas Basin.

Shallow Strata Expressions of Leakage and Seepage Structures Associated With Hydrocarbon Migration: a Seismic Analysis on Offshore Barreirinhas Basin, Brazilian Equatorial Margin

“…To the north of the RFZ, the deep-water basin developed as a classic passive margin inherited from thermal subsidence, with north-dipping normal faults (Montenegro et al, 2021). In the Cenozoic, systems of normal and thrust faults affected all the post-Cretaceous units and currently sediments in periods of relative tectonic quiescence (Trosdtorf Jr. et al, 2007;Krueger et al, 2012).…”

“…The Brazilian Equatorial Margin (BEM) (Fig. 1) comprises a sequence of divergent and transform continental margin segments that developed during the Pangea breakup, from Aptian to Albian (Krueger et al, 2012;de Castro et al, 2022). The Equatorial Atlantic opening-built pull-apart basins in the BEM (Foz do Amazonas, Pará-Maranhão, Barreirinhas, Ceará, and Potiguar Basin), and the African counterpart basins (Sierra Leone-Liberia, Saltpond-Central, Keta, Benin, and Deep Ivorian -sub-basins of Ivory Coast, Tano, and Grand Bassam) within the conjugate Ivory Coast-Ghana Margin in the Gulf of Guinea, West Africa (Azevedo, 1987;Lamarche et al, 1997;Zalán, 2004).…”

A Novel Regional-Residual Separation Approach for Gravity Data Through Crustal Modeling

“…Beyond that, gravity data mapped thrust faults that was interpreted as results of a shortening that was caused by extension activities. Moreover, gradient of free-air anomaly highlights many tectonic features, including the continental margin, Ceará Rise, zones of fracture and the seamount (Krueger et al, 2012).…”

Interpretação Sísmica E Modelagem 3d Estrutural Na Bacia De Barreirinhas (Maranhão, Brasil)

“…Notable examples of structures related to gravitational tectonics and for the gravitational fold-and-thrust belts in the Equatorial Margin Basins (Brazilian and African) were presented by Zalán (1998;2001, 2011, Oliveira et al (2012);Da Cruz et al (2009), Krueger et al, (2012), Perovano et al, (2009), Pellegrini and Ribeiro (2018); Corredor et al, (2005); Yang et al (2020). However, despite being known, there are still many studies that can be carried out to contribute to a more complete interpretation of different geological elements.…”