Research paper Anatomy of a basin-controlled foreland fold-thrust belt curve: The Tr ^ es Marias salient, S ~ ao Francisco basin, Brazil Humberto L.S. Reis a, b, * , Fernando F. Alkmim a a Departamento de Geologia, Escola de Minas, Universidade Federal de Ouro Preto, Morro do Cruzeiro, 35.400-000 Ouro Preto, MG, Brazil b Petra Energia S.A. Alameda Oscar Niemeyer, 500- Vila da Serra, 34.000-000 Nova Lima, MG, Brazil article info Article history: Received 31 October 2014 Received in revised form 18 June 2015 Accepted 13 July 2015 Available online xxx Keywords: Tr^ es Marias salient S~ ao Francisco basin Ediacaran Basin-controlled curve Low friction detachment Hydrocarbon exploration Brazil abstract Salients, as common features of fold-thrust belts, correspond to convex-to-foreland map-view curves. Hosting sedimentary sequences younger than 1,8 Ga., the intracratonic S~ ao Francisco basin of south- eastern Brazil encompasses two foreland fold-thrust belts of opposite vergences: the Brasília, on the west, and the Araçuaí, on the east. These belts culminate in the central portion of the basin in form of two almost touching antitaxial curves developed in response to diachronic orogenic events affecting the basin fill-units during the Ediacaran Brasiliano/Pan-African assembly of West Gondwana. Located in the external sector of the thin-skinned Brasília foreland fold-thrust belt, the ca. 130 km long and 80 km wide Tr^ es Marias salient involves the up to 2500 m-thick Ediacaran Bambuí sequence. In order to characterize the overall architecture and processes involved in the generation of the Tr^ es Marias salient, we con- ducted a detailed structural investigation of the southern segment of the Brasília foreland fold-thrust belt, based on surface, seismic, well and aerogeophysical data interpretation. The salient is frankly dominated by monotonous trains of upright chevron folds, bounded by a small number west-dipping thrust faults. The structural traces of thrusts and fold hinges on maps trend preferentially NS in the central portion of the salient, curving progressively toward NE and NW in its southern and northern limbs, respectively. The entire system is linked to a spoon-shaped detachment zone located near the base of the Ediacaran Bambuí strata, whose maximum thickness roughly coincides with the salient culmi- nation. Our analysis led to the conclusion that the Tr^ es Marias salient corresponds to a basin-controlled curve, generated during a single and progressive deformational episode. Its fold-dominated character and the high symmetry of its internal fabrics can be explained by the low friction of the associated detachment (located along a lower Bambuí sequence black shale) and the mechanical behavior of the pelite-dominated deposits incorporated in the fold-thrust wedge. The occurrence of seepages and recent gas discoveries in the Tr^ es Marias salient area point toward its potential for unconventional hydrocarbon resources. Our investigation suggests that the main basin controls that led to the development of the salient might have controlled the quality and distribution of Proterozoic petroleum system elements. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Map-view curves are common features of fold-thrust belts (f-t- belts). Intensively studied, these structures are discriminated with basis on their geometry and development processes (e.g.: Guti errez-Alonso et al., 2012; Hnat et al., 2009; Johnston et al., 2013; Li et al., 2012; Marshak, 1988, 2004; Marshak and Fl€ ottmann, 1996; Macedo and Marshak, 1999; Pastor-Gal an et al., 2011; Paulsen and Marshak, 1999; Prasad et al., 2011; Silva and Oliveira, 2009; Tull and Holm, 2005; Weil and Sussman, 2004). Antitaxial curves or salients correspond to convex-to-foreland structures, whereas syntaxial curves or recesses are concave-to- foreland structures. From a kinematic point of view, two basic types of orogenic curvatures are currently discriminated (Marshak, 2004; Weil and Sussman, 2004): (1) rotational curves or oroclines, and (2) non-rotational curves or primary arcs. Rotational curves form by bending or buckling of originally straight or curved fold- thrust belts. Differently from oroclines, primary arcs initiate as * Corresponding author. Departamento de Geologia, Escola de Minas, Uni- versidade Federal de Ouro Preto, Morro do Cruzeiro, 35.400-000 Ouro Preto, MG, Brazil. E-mail addresses: humbertosiqueira@gmail.com (H.L.S. Reis), hr@petraenergia. com.br (F.F. Alkmim). Contents lists available at ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo http://dx.doi.org/10.1016/j.marpetgeo.2015.07.013 0264-8172/© 2015 Elsevier Ltd. All rights reserved. Marine and Petroleum Geology xxx (2015) 1e21 Please cite this article in press as: Reis, H.L.S., Alkmim, F.F., Anatomy of a basin-controlled foreland fold-thrust belt curve: The Tr^ es Marias salient, S~ ao Francisco basin, Brazil, Marine and Petroleum Geology (2015), http://dx.doi.org/10.1016/j.marpetgeo.2015.07.013