Discussion ‘‘Proterozoic–Early Paleozoic evolution in western South America—a discussion’’ in: Tectonophysics, 354: 121–137 (2002) $ Ricardo A. Astini a, * , Augusto E. Rapalini b a Ca´tedra de Estratigrafı ´a y Geologı ´a Histo´rica, Facultad de Ciencias Exactas, Fı ´sicas y Naturales, Universidad Nacional de Co´rdoba, Av. Velez Sarsfield 299, 5000, Co´rdoba, Argentina b Instituto de Geofı ´sica Daniel Valencio (INGEODAV), Departamento de Ciencias Geolo´gicas, FCEyN, Universidad de Buenos Aires, Pabello´n 2, Ciudad Universitaria, 1428, Buenos Aires, Argentina Received 11 December 2002; accepted 28 February 2003 Paleogeographic reconstructions and terrane track- ing are essentially supported by two major lines of evidence: (a) paleomagnetism and (b) biogeographic development. Other elements like basement isotopic studies and lithologic indicators of climate are also frequently used in paleogeographic reconstructions. Stratigraphy and structure do not say much about any particular time slice, but do mean a lot when consid- ering a time-dependent paleogeographic sequence, particularly regarding paleoenvironmental reconstruc- tions and geologic setting. Unfortunately, no strati- graphic bases for a true alternative comparison to the existing hypothesis of the Laurentian origin for the Argentine Precordillera has been put forward in the recent paper by Acen˜olaza et al. (2002), from now on AMT. Appropriate data sets and details of several different lines of evidence supporting a Laurentian origin for the Argentine Precordillera have been published in numerous papers (e.g. Astini et al., 1995, 1996; Astini, 1998a,b; Astini and Thomas, 1999; Benedetto 1993, 1998; Benedetto et al., 1995, 1999; Can˜ as, 1999; Casquet et al., 2001; Dalziel et al., 1996; Kay et al., 1996; Keller et al., 1998; Lehnert et al., 1995; Rapalini and Astini, 1998; Rapalini et al., 1999; Thomas and Astini, 1996, 1999; Thomas et al., 2001, 2002). It is therefore most striking that AMT (p. 131) ignor the existence of paleomagnetic data sup- porting the Laurentian origin of the Argentine Pre- cordillera, when a high-quality Early Cambrian pale- omagnetic pole confirming the Laurentian origin of this terrane is available since few years ago (see Rapalini and Astini, 1998; Rapalini et al., 1999). The successful paleomagnetic study was reported from the Cerro Totora Formation (northern Precordil- lera), which is dated Early Cambrian (Bonnia-Ollene- lus Zone) and considered to be part of the rift-related facies assemblage (Astini and Vaccari, 1996; Thomas et al., 2001). A positive fold test indicated a pre- tectonic (pre-Tertiary) magnetization. The position of the Cerro Totora paleomagnetic pole is not consistent with any expected pole position for South America in the Phanerozoic, suggesting that a post-Cambrian remagnetization of the rocks is unlikely. Because it disagrees with the Cambrian path for the already assembled Gondwana (Meert and Van del Voo, 1996; Meert, 2001), but it is perfectly consistent in position and age with the Cambrian segment of the Laurentian APWP, when the Precordillera is placed in the Ouachita embayment as suggested by Thomas and Astini (1996), the paleomagnetic result strongly sup- 0040-1951/03/$ - see front matter D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0040-1951(03)00073-8 $ doi of original article S0040-1951(03)00074-X. * Corresponding author. E-mail addresses: raastini@com.uncor.edu (R.A. Astini), rapalini@gl.fcen.uba.ar (A.E. Rapalini). www.elsevier.com/locate/tecto Tectonophysics 366 (2003) 143– 148