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Araripe Basin, NE : A basin implanted over a previous pull-apart system?

Tiago Siqueira de Miranda1; José Ricardo Gonçalves Magalhães1; José Antonio Barbosa1; Osvaldo Correia Filho1; Márcio Lima Alencar1

1Department of Geology, Federal University of , Recife, Pernambuco, Brazil. Correspondence: [email protected] dextral cinematic(BritoNeves et al., 2000). The main phase of sedimentary deposition in the Araripe Introduction Basin occurred between the and (Assine, 2007). However the basin also Studying the tectonic origin of the basins in Northeast contains an important Paleozoic (-) Brazil can provide important data to understand the sedimentary succession. continental processes related to the South Atlantic’s opening. These basins are located where the southern and The Araripe Basin can be divided in two main sub-basins, equatorial branch regions intersect with several yielding the Cariri (East) and the Feitoria (West), which are substantial structural data that constrain the temporal and separated by a regional structural high referred to as the spatial influence of the tectonic phases. The pre- Dom Leme (Assine, 1992; Neumann, 1999). and its structural framework have a strong influence on the formation of these intracontinental basins. There are three models proposed for the tectonic evolution It suggests that pre-existing crustal weakness zones, such as of the Araripe Basin. The first is based on a NW-SE initial the Neoproterozoic Pernambuco and Patos shear zones of extension (Matos, 1992, 1999), which reactivated the the Brazilian/Pan-African , controlled the Proterozoic shear zones. The second involves the development of intracrustal faults (De Castro et al., 2012). reactivation of the dextral E-W shear zones and the sinistral NE faults (Françolin et al., 1994). The third model, recently The Araripe Basin (ca. 8,000 km2) represents the largest proposed by Miranda et al. (2012), argues that the Araripe interior basin of NE Brazil, and is positioned between the Basin was formed as a pull-apart system between the two Patos and Pernambuco shear zones, which divide the shear zones, Pernambuco and Patos. Borborema Province in three (north, central and south) domains (Fig. 1). These shear zones strike E-W and have a Figure 1 - Simplified geological map of the Araripe Basin.

4th Atlantic Conjugate Margins Conference St. John’s, NL Canada August 20-22, 2014

Methodology Paleozoic, through the displacement at the step-overs of the Patos and Pernambuco shear zones. Stage 2 saw the We undertake a gravity and tectonic data analysis of the reactivation of the shear zones during the Cretaceous due to structural network of the Araripe Basin’s basement through the South Atlantic’s opening. satellite-derived gravity anomalies and the geological characterization in outcrops. For the gravity data we used a Acknowledgements 2' square grid of gravity/bathymetry, which is derived from satellite geodesic data (Scripps Institution of Financial support for this study was provided by a grant Oceanography, University of California San Diego) from the Project Turing – Petrobras/Federal University of measured with GEOSAT and ERS-1 satellites and the error Pernambuco (UFPE). We are grateful to the Department of in this gravity data is around 5 mGal (Sandwell and Smith, Geology/UFPE, Geosciences Graduate Program/UFPE, 1997). We then generated a Bouguer gravity anomaly and National Agency of Petroleum, Natural Gas and Biofuels of also performed a regional-residual separation of this map Brazil (ANP). using the Gaussian method. The residual component was selected in order to mitigate the gravity effect of the crust- References mantle interface. Assine, M.L., 1992. Análise estratigráfica da Bacia do During fieldwork we focused on collecting structural data Araripe, Nordeste do Brasil. Revista Brasileira de in order to perform the geological characterization of the Geociências 22 (3), 289-300. gravity anomalies. Assine, M.L., 2007. Bacia do Araripe. B. Geoci. Petrobras, 15: p. 371-389,. Results Brito Neves, B. B.; Santos, E. J.; Van Schmus, W. R., 2000. Tectonic history of the Borborema Province, Figs. 2 and 3 show the Bouguer and residual gravity Northeastern Brazil.In: Cordani, U. G.; Milani, E. J.; anomaly maps, respectively, for the Araripe Basin and Thomaz Filho, A.; Campos, D. A. (Ed.) Tectonic adjacent areas. The Bouguer anomaly documents the Evolution of .Rio de Janeiro effects of density variation whilst the residual gravity map International Geological Congress, p. 151-182. shows mostly the superficial anomalies. De Castro, D.L., Bezerra, F. H. R., Sousa, M. O. L., Fuck, R. A., 2012. Influence of Neoproterozoic tectonic Three main observations from the gravity maps and fabric on the origin of the Potiguar Basin, tectonics analysis stand out in our results. 1) The Araripe northeastern Brazil and its links with West Africa Basin is rhomb shaped, probably due to movement along based on gravity and magnetic data. Journal of the sandwiching Patos and Pernambuco shear zones. 2) Geodynamics.54: 29-42. NW and NNW gravity anomalies inside the basin are Françolin, J.B.L., Cobbold, P.R., Szatmari, P., 1994. suggestive of en echelon arrays, interpreted at Riedel Faulting in the Early Cretaceous Rio do Peixe Basin shears. 3) Other gravity anomalies trend E-W and NE-SW (NE Brazil) and its significance for the opening of in and around the basin, indicative of crustal extensional the Atlantic. Journal Structural Geology, 16: p. 647- deformation, strongly influenced by the Neoproterozoic 661. shear zones. This interpretation is substantiated by the fact Matos R.M.D., 1999. History of the Northeast Brazilian rift that the NW (R1) and NNW (R2) oriented structural trends system: kinematic implications for the break-up became reactivated as normal faults (Paleozoic pull-apart between Brazil and West Africa. In: N.R. Cameron, phase). The E-W and NE-SW gravity anomalies show R.H. Bate, V.S. Clure (eds.) The Oil and Gas potential sites for transfer faults or accommodation zones, Habitats of the South Atlantic. Geol. Soc., London, which could be associated with the Lower Cretaceous Spec. Publ., p. 153:55-73. rifting system. Matos, R.M.D., 1992. The NorthestBrasilian rift system.Tectonics, 11(4): p. 776-791. Conclusion Miranda, T.S., Magalhães, J.R., Barbosa, J.A., 2012b. Bacia do Araripe: Possível Sistema Pull-Apart? In: We concluded that the Araripe Basin had two main tectonic CONGRESSO BRASILEIRO DE GEOLOGIA, 47, phases: Stage one involved a pull-apart system, which 2012, Santos. Anais: Sociedade Brasileira de generated the rhomb-shaped configuration during the Geologia.

4th Atlantic Conjugate Margins Conference St. John’s, NL Canada August 20-22, 2014 Araripe Basin, NE Brazil: A rift basin implanted over a previous pull-apart system?

Neumann, V.H.M.L., 1999. Estratigrafía, Sedimentología, Sandwell, D.T. and Smith, W.H.F., 1997. Marine gravity Geoquímica y Diagénesis de los Sistemas Lacustres from Geosat and ERS-1 satelliteAltimetry. Journal Aptienses-Albienses de la Cuenca de Araripe of Geophysical Research 102 (B5), 10039e10054. (Noreste de Brasil). PhD Thesis. Universidad de Barcelona. Barcelona. 244p.

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Figure 2 - A) Bouguer gravity anomaly map of the Araripe Basin and adjacent areas showing the basin's rhomb shaped, gravity anomalies trend E-W and NW-SE in and around the basin. B) Residual gravity map of the Araripe Basin and adjacent areas showing the superficial structural anomalies which strike NW (R1) and NNW (R2) represent reactivated normal faults (Paleozoic pull-apart phase) and also the E-W and NE-SW trends show the influence of the Lower Cretaceous rifting system.