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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Gondwana Research 20 (2011) 782–797 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr Paleomagnetism and rock magnetism of the Neoproterozoic Itajaí Basin of the Rio de la Plata craton (Brazil): Cambrian to Cretaceous widespread remagnetizations of South America E. Font a,⁎, C.F. Ponte Neto b,1, M. Ernesto b a Instituo Dom Luiz, Universidade de Lisboa, Campo Grande,1749-016, Lisbon, Portugal b Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil article info abstract Article history: A detailed rock magnetic and paleomagnetic study was performed on samples from the Neoproterozoic Itajaí Received 8 July 2010 Basin in the state of Santa Catarina, Brazil, in order to better constrain the paleogeographic evolution of the Rio Received in revised form 27 April 2011 de la Plata craton between 600 and 550 Ma. However, rock magnetic properties typical of remagnetized rocks Accepted 28 April 2011 and negative response in the fold test indicated that these rocks carried a secondary chemical remanent Available online 6 May 2011 magnetization. After detailed AF and thermal cleaning, almost all samples showed a normal polarity fi Handling Editor: E. Tohver characteristic remanent magnetization component close to the present geomagnetic eld. The main magnetic carriers are magnetite and hematite, probably of authigenic origin. The mean paleomagnetic pole of the Itajaí Keywords: Basin is located at Plat=−84°, Plong=97.5° (A95=2°) and overlaps the lower Cretaceous segment of the Remagnetization apparent polar wander path of South America, suggesting a cause and effect with the opening of the South Paleomagnetism Atlantic Ocean. A compilation of remagnetized paleomagnetic poles from South America is presented that Rock magnetism highlights the superposition of several large-scale remagnetization events between the Cambrian and the West Gondwana Cretaceous. It is suggested that some paleomagnetic poles used to calibrate the APWP of Gondwana at Rio de la Plata Precambrian times need to be revised; the indication of remagnetized areas in southern South America may Neoproterozoic offer some help in the selection of sites for future paleomagnetic investigations in Precambrian rocks. © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction components (e.g. Trindade et al., 2004; Rapalini and Sánchez Bettucci, 2008; Tohver et al., 2010, 2011). The timing and kinematic models of the Gondwana superconti- The APWP of Gondwana is well documented from 550 to 500 Ma nent assemblage at the end of the Neoproterozoic is still a matter of (see review in Trindade et al., 2006), the latter representing the time debate (e.g., Yoshida, 1995; Torsvik et al., 2001; Stern, 2002; Meert, of the final assemblage of the supercontinent. However, the 2003; Veevers, 2004; Collins and Pisarevsky, 2005; Squire et al., 2006; 600–550 Ma interval is still poorly constrained (Tohver et al., 2006). Trindade et al., 2006; Yoshida and Upreti, 2006; Paulsen et al., 2007; Recently, a high quality but secondary origin paleomagnetic pole has Yoshida, 2007; Meert and Lieberman, 2008; Vaughan and Pankhurst, been obtained from the Nola dolerite, Central Africa (Moloto-A- 2008; Cordani et al., 2009; Santosh et al., 2009). Several models are Kenguemba et al., 2008) satisfying six of the seven criteria of the Q proposed in the literature but they still deserve more high-quality index of Van der Voo (1990). The remagnetization is associated to paleomagnetic poles to be tested, particularly for South America metamorphism and dated by 40Ar/39Ar on amphibole to 571±6 Ma. cratons. A principal limitation resides in the superposition of This pole gives clues to Gondwana APWP, however only two poles successive large-scale deformational events (from Cambrian to from the South American plate (Fig. 9), namely the Sierra de las Cretaceous) that affected the area causing overprints of secondary Animas (SA1, Sánchez-Bettucci and Rapalini, 2002) and Sierra de los magnetization, or the complete resetting of primary magnetic Barrientos (LB, Rapalini, 2006) contribute to the curve. In this way, additional efforts are needed to better constrain the APWP of Gondwana at 600–550 Ma. In this way, in this paper we investigated the Neoproterozoic rocks from the Itajaí basin (Santa Catarina) recently dated at 563±3 Ma and 549±4 Ma (U–Pb dating, ⁎ Corresponding author at: Instituto Dom Luiz, Universidade de Lisboa, Edifício C8, Guadagnin et al., 2010). However, as will be discussed, rock magnetic Campo Grande, 1749-016, Lisbon, Portugal. Tel.: +351 21 75 00 811. E-mail address: [email protected] (E. Font). properties typical of remagnetized rocks and negative response in the 1 Presently at Observatorio Nacional, ON/MCT, Rio de Janeiro, Brazil. fold test indicated that these rocks carried a post-folding remanent 1342-937X/$ – see front matter © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2011.04.005 Author's personal copy E. Font et al. / Gondwana Research 20 (2011) 782–797 783 Fig. 1. A) Map of South America and location of the Mantiqueira Province; Geological and structural maps of B) main tectonic terranes in southern Brazil and northeastern Uruguay (modified from Rostirolla et al., 1999); C) eastern Santa Catarina and southernmost Paraná with emphasis on the Itajaí, Camaquã and Campo Alegre basins (modified from Hartmann et al., 2003); D) the Itajaí basin (modified from Rostirolla et al., 1999). Author's personal copy 784 E. Font et al. / Gondwana Research 20 (2011) 782–797 magnetization. In view of these results, and considering that this is a Guaratubinha basins which date 598±29 Ma and 604±5 Ma (U–Pb persistent problem in the Gondwana Neoproterozoic, we then extend zircon; Basei et al., 1998) respectively. our discussion to a larger-scale perspective by presenting a review of According to Macedo et al. (1984) the sedimentary rocks of the remagnetized paleomagnetic poles from South America and by Apiúna region were weakly metamorphosed as indicated by illite discussing the possible mechanisms responsible for the widespread crystallinity data. The Itajaí sediments were silicified without any remagnetization events. Our results question the reliability of the metamorphic foliation, thus preserving their original sedimentary Precambrian paleomagnetic database in South America and identify features (Rostirolla et al., 1999). According to Rigon (1993), early unsuitable geographical areas for future paleomagnetic investigations diagenesis is evidenced by mechanical compaction, hydration and in Precambrian rocks. carbonation reactions and by precipitation of iron and titanium oxides. Mesodiagenesis is characterized by chemical compaction, 2. Geological setting calcite precipitation, illitization, chloritization and late cements (pyrite and titanium oxides). According to Rostirolla et al. (1999), In southeastern Brazil the collision that sutured the Congo, the basin underwent a main late-collisional compressional deforma- Kalahari and Rio de la Plata cratons produced the Ribeira and Dom tion phase followed by an extensional post-orogenic relaxation. The Feliciano orogenic belts. These belts consist mainly of syn- to post- same authors reported that the Perimbó Fault Zone (PFZ), a orogenic magmatic and volcanic rocks with local metasedimentary Precambrian dextral-reverse fault separating the Itajaí foreland successions. A series of isolated ‘basins’, some possibly remnants of a basin from the Brusque Metamorphic Fold Belt, was reactivated as a much larger basin, is found inboard of the older orogenic belts. The left-lateral strike-slip fault during the Paleozoic (Rostirolla et al., Castro, Guaratubinha and Camarinha basins in the Paraná state, and 2003). At the scale of the Dom Felicano Belt, Almeida et al. (in press) the Campo Alegre and Corupá basins in the Santa Catarina state, discriminate at least three deformational events in the Itajaí, Camaquã southern Brazil, record the evolution of the volcanic activity and and Castro basins based on fault orientation data. The first event is sedimentary deposition in the region at the end of the Proterozoic characterized by strike-slip and oblique faults generated by a NE–SW (Fig. 1). compression at the Precambrian–Cambrian boundary in relation to The Itajaí Basin is located in the northeastern portion of the state of the Brasiliano orogeny. The second deformational event, more Santa Catarina, and represents an area of 50×25 km elongated in the intense, occurred between the Cambrian and Permian and is N60°E direction. It is limited by thrusts and shear zones from the Santa characterized by a NW–SE compression that