Evolution of the South Atlantic passive continental margin in southern Brazil derived from zircon and apatite (U–Th–Sm)/He and fission-track data Markus Karl a, ⁎, Ulrich A. Glasmacher a , Sebastian Kollenz a , Ana O.B. Franco-Magalhaes b , Daniel F. Stockli c , Peter C. Hackspacher d a Institute of Earth Sciences, University of Heidelberg, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany b Universidade Guarulhos, CEPPE, Centro do Pós-Graduação, Pequisa e Extensão, Praça Tereza Cristina, 229, Centro, 07011-040, Guarulhos, SP, Brazil c Department of Geological Sciences, Jackson School of Geosciences, The University of Texas, 2275 Speedway Stop C9000, Austin, TX 78712-1722, United States d Departamento de Petrologia e Metalogenia, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Av. 24-A, 1515, Bela Vista, 13506-900 Rio Claro, SP, Brazil abstract article info Article history: Received 9 June 2012 Received in revised form 12 June 2013 Accepted 19 June 2013 Available online 28 June 2013 Keywords: Low-temperature thermochronology Reactivation Fission-track (U–Th–Sm)/He Post-rift exhumation history Southeastern Brazil The area between São Paulo and Porto Alegre in southeastern Brazil plays a key area to understand and quan- tify the evolution of the South Atlantic passive continental margin (SAPCM) in Brazil. In this contribution, we present new thermochronological data attained by fission-track and (U–Th–Sm)/He analysis on apatites and zircons from metamorphic, sedimentary and intrusive rocks. The zircon fission-track ages range between 108.4 (15.0) and 539.9 (68.4) Ma, the zircon (U–Th–Sm)/He ages between 72.9 (5.8) and 525.1(2.4) Ma, whereas the apatite fission-track ages range between 40.0 (5.3) and 134.7 (8.0) Ma, and the apatite (U– Th–Sm)/He ages between 32.1 (1.5) and 93.0 (2.5) Ma. The spatial distribution of these ages shows three dis- tinct blocks with a different evolution cut by old fracture zones. While the central block exhibits an old stable block, the Northern and especially the Southern block underwent complex post-rift exhumation. The sample of the Northern block shows two distinct cooling phases in the Upper Cretaceous and the Paleogene to Neo- gene. After sedimentation of the Permian sandstones the samples of the Central block were never heated up over 100 °C with a following moderate to fast cooling phase in Cretaceous to Eocene time and a fast cooling between Oligocene to Miocene. The five thermal models obtained in the Southern block indicate a complex evolution with three cooling phases. The exhumation events of the three blocks correspond with the Paraná–Etendekka event, the alkaline intrusions due to the Trinidad hotspot, and the evolution of the conti- nental rift basins in SE Brazil and are, therefore, most likely to be the major force for the post-rift evolution of the passive continental margin in SE Brazil, which therefore corresponds to the three main phases of the Andean orogeny. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Passive continental margins are important geoarchives related to mantle dynamics, the break-up of continents, lithospheric dynamics, and other processes. The onshore–offshore transition between São Paulo and Porto Alegre therefore represents a key area for the evolution of the western margin of the South Atlantic with its complex history that involves rock uplift and erosion of the Precambrian basement and overlying Paleozoic and Mesozoic sedimentary units (Fig. 1). Since the break-up of the two lithosphere plates of South America and Africa the evolution of the margin has been complex. Following the intrusion, extrusion and partial erosion of the Paraná–Edendeka volcanic suite (including the dykes), the area was reactivated by the intrusion of alka- line magmas at around 80–90 Ma (Amaral et al., 1967; Cobbold et al., 2001; Herz, 1977). Thereafter, erosion and deposition lead to a thick (N 600 m) sequence of siliciclastic rocks in the Upper Cretaceous (Franco-Magalhães et al., 2010). South of Rio de Janeiro the evolution of the transtentional Taubaté graben (Cobbold et al., 2001; Riccomini et al., 1989, 2004), magma extrusion, and deposition of thick siliciclastic units (Almeida and Carneiro, 1998; Almeida et al., 2000; Cobbold et al., 2001; Meisling et al., 2001; Melo et al., 1985; Salamuni et al., 2003) changed the landscape dramatically in Eocene time. The extension of the graben reached the area around São Paulo in Oligocene to Mio- cene. Further to the South no distinct graben feature is known. The only relicts are patchy deposits of siliciclastic units of Eocene to Mio- cene. Furthermore, the area under investigation is characterized by metamorphic rocks and intrusions of Neoproterozoic, partly overlain by a thick sequence of Paleozoic to Mesozoic sedimentary rocks and more than 2000 m of Paraná volcanic rocks. Fault and fracture zones are known in the area but the timing of movement is still a major debate in the literature in Brazil. Thermochronological tools Tectonophysics 604 (2013) 224–244 ⁎ Corresponding author. Tel.: +49 6221 544843. E-mail address: markus.karl@geow.uni-heidelberg.de (M. Karl). 0040-1951/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.tecto.2013.06.017 Contents lists available at ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto