Abdelfatah Tahiri

Andrés Pérez-Estaún

Antonio Azor

David Martínez-Poyatos

Francisco González-Lodeiro

Hassan El Hadi

José Fernando Simancas

Ramón Carbonell

Comptes Rendus Géoscience

C. R. Geoscience 342 (2010) 175–177ReplyReply to the comment by Michard et al. on ‘‘Tectonic relationships ofSouthwest Iberia with the allochthons of Northwest Iberia and theMoroccan Variscides’’Réponse au commentaire sur Relations tectoniques du Sud-Ouest de l’Ibérie avec lesallochtones du Nord-Ouest ibérique et le Maroc varisque par J.F. Simancas et al. [C. R.Geoscience 341 (2009) 103–113]José Fernando Simancas a,*, Antonio Azor a, David Martı́nez-Poyatos a, Abdelfatah Tahiri b,Hassan El Hadi c, Francisco González-Lodeiro a, Andrés Pérez-Estaún d, Ramón Carbonell da Departamento de Geodinámica, Universidad de Granada, Campus de Fuentenueva s/n, 18071 Granada, Spainb Institut scientifique, BP 703, Rabat-Agdal, Moroccoc Faculté des sciences Ben Msik-Sidi Othmane, BP 7955, Casablanca, Moroccod Instituto de Ciencias de la Tierra Jaume Almera, CSIC, 08028 Barcelona, SpainContents lists available at ScienceDirectComptes Rendus Geosciencewww.sciencedi rec t .comA R T I C L E I N F OArticle history:Received 11 September 2009Accepted after revision 12 January 2010Available online 6 March 2010Michard et al. (2010) comment on some aspects of theVariscan geology of Morocco that were briefly accountedfor in Simancas et al. (2009). In particular, they criticize ourinterpretation of the relationships between the Anti-Atlasand the Meseta domains, which we considered as beingseparated by a Late Carboniferous strike-slip shear zone.Based on the differences between these two geologicaldomains, Michard et al. (2010) conclude that thecorresponding crustal blocks would have been signifi-cantly separated in Early Palaeozoic times by an area ofthin crust, later on telescoped during the Variscan orogenyby a major lithospheric continental shear zone. Fortu-nately, our general interpretation of this Palaeozoicboundary as an intracontinental shear zone is endorsedby Michard et al. (2010), who concentrate their contentionDOI of original article: 10.1016/j.crte.2010.01.008* Corresponding author.E-mail address: simancas@ugr.es (J.F. Simancas).1631-0713/$ – see front matter  2010 Académie des sciences. Published by Edoi:10.1016/j.crte.2010.01.007on its relative importance and the timing when it startedto be shaped. In the following short sections we explainour view.1. TerminologyThere has been important discussion on the age, slipand geometry of the fault set running roughly between theMesetas and the Anti-Atlas, along the High Atlas (Houariand Hoepffner, 2003; Jacobshagen, 1992; Mattauer et al.,1972; Ouanaimi and Petit, 1992; Proust et al., 1977).Despite uncertainties due to discontinuous outcrop, weagree with the cartographic tracing and the terminologicaldistinction made by Michard et al. (2010) in their Fig. 1,retaining the name South Atlasic Fault for the set of Alpinefaults and renaming the shear zone between the Mesetasand the Anti-Atlas as South Meseta Fault Zone (SMFZ). Thislatter name is better than the previous one of AtlasPalaeozoic Transform (Piqué and Michard, 1989), whichwe avoided because of the plate-boundary significanceusually given to the word Transform.2. Interpretation of the South Meseta Fault ZoneThe geological differences between the Mesetas and theAnti-Atlas domain are clear, as summarized by Michardet al. (2010) [see also (Hoepffner et al., 2005; Michard et al.,lsevier Masson SAS. All rights reserved.J.F. Simancas et al. / C. R. Geoscience 342 (2010) 175–1771762008; Piqué and Michard, 1989)]. However, in our viewthese differences not necessarily ‘‘call for a basic role of theSMFZ as a major Variscan lithospheric discontinuity’’. Stronggeological contrast may exist in orogens between neigh-boring crustal domains, without these domains havingbeen far apart before orogenic telescoping. The IberianMassif provides a good example concerning this issue.Thus, the strong geological contrast between the WestAsturian-Leonese Zone (a very thick pile of LowerPalaeozoic metasediments, affected by recumbent folding,metamorphism and intruded to the west by Late Carbon-iferous granites) and the Cantabrian Zone [a comparativelythin and incomplete Cambrian to Early Carboniferous pre-orogenic sequence, subsequently affected by thin-skinnednon-metamorphic deformation (Pérez Estaún et al., 1990;Pérez Estaún et al., 1991)] does not imply at all a verydistant palaeogeographical position during the pre-oro-genic evolution. Concerning the Mesetas/Anti-Atlasboundary, we give credit to the suggestion made byOuanaimi and Petit, 1992 that the contrasting deformationin the Ouzellarh region might be explained by the presenceof a stiff Precambrian basement with a thin Palaeozoiccover (promontory of the Anti-Atlas domain) in contactwith a thicker Palaeozoic series (adjacent Meseta domain).Our view is that the contrasting features between thepoorly-deformed Anti-Atlas and the more deformed,variably metamorphic Mesetas do not prove the majorVariscan lithospheric discontinuity suggested by Michardet al. (2010) in their Fig. 2.We believe that the significance attributed to the SMFZmust take into account the analysis of its differentoutcrops. The Tizi n’Test Fault to the west is the biggestcontinuous outcrop of the SMFZ (Fig. 1 in Michard et al.,2010), having been characterized as a dextral strike-slipfault with a displacement of approximately 50 km (Proustet al., 1977). In a previous work, Mattauer et al., 1972 hadsuggested a dextral displacement of nearly 200 km, butthis figure is hardly compatible with the bend of the faultaround the Ouzellarh Massif [(Ouanaimi and Petit, 1992),Fig. 1 in Michard et al., 2010]. Contrary to the narrow faultzone in the Tizi n’Test outcrop, the SMFZ in the easternHigh Atlas appears as a wide shear zone [(Hoepffner et al.,2005; Michard et al., 2008), Fig. 1 in Michard et al., 2010].At Tamlelt, Houari and Hoepffner, 2003 have featured the60 km-wide shear zone as a ‘‘dextral wrench dominatedtranspression’’. Despite the difficulties assessing such awide strain-partitioned shear zone, the modeling made by(Houari and Hoepffner, 2003) has given a bulk shear strainof g = 1, thus suggesting a strike-slip displacement ofaround 60 km.Michard et al. (2010) indicate that the role of strike-sliptectonics along the SMFS must not be exaggerated to thedetriment of compression, this latter proved by a number ofthrust structures. However, all previous authors clearlyconclude that dextral strike-slip kinematics is dominant,though non-exclusive (Houari and Hoepffner, 2003; Mat-tauer et al., 1972; Proust et al., 1977). On the other hand,Michard et al. (2010) suggest that ‘‘the occurrence of theOuzellarh salient limited necessarily the importance of strike-slip displacements’’. This geometrical constraint argues, inour view, against a major tectonic significance of the SMFZ.3. Timing of the South Meseta Fault ZoneWe have pointed out (Simancas et al., 2009) that theregional shortening direction inferred from the first-phaseDevonian to Early Carboniferous folds in the Mesetas(Hoepffner et al., 2005) is not kinematically compatiblewith a dextral strike-slip displacement of the SMFZ. This isour main argument to sustain that this shear zone wouldhave been originated later, contemporaneously with theLate Carboniferous regional deformation in the Mesetas.4. ConclusionWe admit that the characterization of the boundarybetween the Mesetas and the Anti-Atlas is an openquestion and we do not reject the possibility of havingwrongly minimized its tectonic meaning. The geologicalcontrast between the Mesetas and the Anti-Atlas iscertainly strong and sudden, but looking at the faultsystem that constitutes the boundary, we do not findpieces of evidence supporting the interpretation envisagedby Michard et al. (2010) as a long-lived major lithospherictectonic contact. Instead, the SMFZ might be a LateCarboniferous, transpressional shear zone dominated bydextral strike-slip, with a displacement of less than orequal to 100 km and lesser shortening component.Fortunately, Michard et al. (2010) support our view thatthe SMFZ must not be interpreted as a transform boundarylinked to an orogenic suture, this being the real crucialpoint in our tectonic model (Simancas et al., 2009).AcknowledgementsThis research has been financed by the AgenciaEspañola de Cooperación Internacional, the AcadémieHassan II des sciences et techniques, and the SpanishMinistry of Science and Innovation through grantsCGL2007-63101/BTE and TOPO-IBERIA CONSOLIDER-INGENIO CSD2006-00041.ReferencesHoepffner, C., Soulaimani, A., Piqué, A., 2005. The Moroccan Hercynides. J.Afr. Earth Sci. 43, 144–165.Houari, M.-R., Hoepffner, C., 2003. Late Carboniferous dextral wrench-dominated transpression along the North African craton margin(Eastern High-Atlas, Morocco). J. Afr. Earth Sci. 37, 11–24.Jacobshagen, V., 1992. Major fracture zones of Morocco: the South Atlasand the Transalboran fault systems. Geol. Rundsch. 81, 185–197.Mattauer, M., Proust, F., Tapponnier, P., 1972. Major strike-slip faults ofLate Hercynian age in Morocco. Nature 237, 160–162.Michard, A., Hoepffner, C., Soulaimani, A., Baidder, L., 2008. The VariscanBelt. In: Michard, A., Saddiqi, O., Chalouan, A., Frizon de Lamotte, D.(Eds.), Continental Evolution: the Geology of Morocco. SpringerVerlag, pp. 65–131.Michard, A., Ouanaimi, H., Hoepffner, C., Soulaimani, A., Baidder, L., 2010.Comment on ‘‘Tectonic relationships of Southwest Iberia with theallochthons of Northwest Iberia and the Moroccan Variscides’’ by J.F.Simancas et al. C. R. Geoscience 341 (2009), 103–113. C.R. Geoscience342, 170–174.Ouanaimi, H., Petit, J.P., 1992. La limite sud de la chaı̂ne hercynienne dansle Haut Atlas marocain : reconstitution d’un saillant non-déformé.Bull. Soc. Geol. France 163, 63–72.Pérez Estaún, A., Bastida, F., Martı́nez-Catalán, J.R., Gutiérrez Marco, J.C.,Marcos, A., Pulgar, J.A., 1990. West Asturian-Leonese zone: Stratigra-phy. In: Dallmeyer, R.D., Martı́nez Garcı́a, E. (Eds.), Pre-MesozoicGeology of Iberia. Springer Verlag, pp. 92–102.J.F. Simancas et al. / C. R. Geoscience 342 (2010) 175–177 177Pérez Estaún, A., Martı́nez-Catalán, J.R., Bastida, F., 1991. Crustal thick-ening and deformation sequence in the footwall to the sutureof the Variscan belt of northwest Spain. Tectonophysics 191,243–253.Piqué, A., Michard, A., 1989. Moroccan Hercynides, a synopsis The Paleo-zoic sedimentary and tectonic evolution at the northern margin ofWest Africa. Am. J. Sci. 289, 286–330.Proust, F., Petit, J.P., Tapponnier, P., 1977. L’accident de Tizi n’Test et le rôledes décrochements dans la tectonique du Haut Atlas occidental(Maroc). Bull. Soc. Geol. France 19, 541–551.Simancas, J.F., Azor, A., Martı́nez Poyatos, D.J., Tahiri, A., El Hadi, H.,González Lodeiro, F., Pérez-Estaún, A., Carbonell, R., 2009. Tectonicrelationships of Southwest Iberia with the allochthons of NorthwestIberia and the Moroccan Variscides. C. R. Geoscience 341, 103–113.

Reply to the comment by Michard et al. on “Tectonic relationships of Southwest Iberia with the allochthons of Northwest Iberia and the Moroccan Variscides”

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Reply to the comment by Michard et al. on “Tectonic relationships of Southwest Iberia with the allochthons of Northwest Iberia and the Moroccan Variscides”

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