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Tethys–Atlantic Interaction Along the Iberia–Africa Plate Boundary: the Betic–Rif Orogenic System

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Tethys–Atlantic Interaction Along the Iberia–Africa Plate Boundary: the Betic–Rif Orogenic System TECTO-125592; No of Pages 29 Tectonophysics xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto Review Article Tethys–Atlantic interaction along the Iberia–Africa plate boundary: The Betic–Rif orogenic system Jaume Vergés ⁎, Manel Fernàndez Group of Dynamics of the Lithosphere (GDL), Institute of Earth Sciences Jaume Almera, CSIC, Barcelona, Spain article info abstract Article history: Initial SE-dipping slow subduction of the Ligurian–Tethys lithosphere beneath Africa from Late Cretaceous to mid- Received 5 December 2011 dle Oligocene twisting to a later faster E-dipping subduction of the subcrustal lithosphere is proposed as an effi- Received in revised form 20 August 2012 cient geodynamic mechanism to structure the arcuate Betic–Rif orogenic system. This new subduction-related Accepted 27 August 2012 geodynamic scenario is supported by a kinematic model constrained by well-dated plate reconstructions, tectonic, Available online xxxx sedimentary and metamorphic data sets. The slow initial SE-dipping subduction of the Ligurian–Tethys realm be- neath the Malaguide upper plate unit is sufficient to subduct Alpujarride and Nevado-Filabride rocks to few tens of Keywords: – Africa–Iberia plate boundary kilometers of depth in middle Eocene times. The shift from SE- to E-dipping subduction during latest Oligocene SE-dipping subduction-related Betic–Rif early Miocene was possibly caused by both the inherited geometry of the highly segmented Ligurian–Tethys do- orogenic system main and by the fast roll-back of the subducted lithospheric slab. The early Miocene rather synchronous multiple Ligurian–Tethys domain crustal and subcrustal processes comprising the collision along the Betic front, the exhumation of the HP/LT meta- Alboran back-arc basin morphic complexes, the opening of the Alboran basin, its flooring by HP Alpujarride rocks and subsequent HT im- Subduction polarity shift print, can be explained by the fast NW- and W-directed roll-back of the Ligurian–Tethys subcrustal lithospheric Slab roll-back slab. The W retreat of the Ligurian–Tethys lithosphere in middle–late Miocene times could partly explain the ini- tiation of its lateral tear and consequent subcrustal processes. From latest Miocene onward the Betic–Rif system evolved under both the northerly push of Africa resulting in tightening at crustal and subcrustal levels and by the distinct current dynamics of the steep lithospheric slab. The SW-directed scape of the Rif fold belt is one of the most striking evidences linked to the recent evolution of the squeezed Betic–Rif system between Africa and Iberia. © 2012 Published by Elsevier B.V. Contents 1. Introduction .............................................................. 0 2. The Pyrenean orogenic system ...................................................... 0 3. The Betic–Rif orogenic system ...................................................... 0 3.1. Structure of the Betic–Rif orogenic system ............................................. 0 3.2. Kinematics of the Betic–Rif orogenic system ............................................ 0 4. Geological and geophysical key constraints on the kinematic model for the Betic–Rif orogenic system .................... 0 4.1. Large-scale plate reconstructions addressing the Africa–Iberia boundary during the Mesozoic and Cenozoic .............. 0 4.2. Spatial distribution of HP/LT metamorphic complexes related to the Alboran and Algerian basins ................... 0 4.3. Role of the mechanical stratigraphy in separating the external from the internal Betic–Rif units .................... 0 4.4. Timing for the onset of the compressional deformation along the Betic–Rif system .......................... 0 5. Betic–Rif kinematic evolution model ................................................... 0 5.1. Stage 1 — model set-up at the onset of the northern convergence of Africa during Late Cretaceous at ~85 Ma ............. 0 5.2. Stage 2 — SE-dipping subduction and related HP/LT metamorphism during middle Eocene at ~47–42Ma............... 0 5.3. Stage 3 — onset of slab roll-back and exhumation of Ligurian–Tethys HP/LT metamorphic rocks after middle Oligocene at ~30–25 Ma . 0 5.4. Stage 4 — shift to E-dipping subduction, opening of the Alboran back-arc basin and collision of the orogen during late Oligocene (?)–early Miocene times at ~27–20Ma................................................................... 0 5.5. Stage 5 — end of major Alboran extension during the middle Miocene at ~18–16Ma......................... 0 5.6. Stage 6 — tightening of the Betic–Rif orogenic system during the late Miocene after 9–8Ma ..................... 0 ⁎ Corresponding author. Fax: +34 93 4110012. E-mail address: [email protected] (J. Vergés). 0040-1951/$ – see front matter © 2012 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.tecto.2012.08.032 Please cite this article as: Vergés, J., Fernàndez, M., Tethys–Atlantic interaction along the Iberia–Africa plate boundary: The Betic–Rif orogenic system, Tectonophysics (2012), http://dx.doi.org/10.1016/j.tecto.2012.08.032 2 J. Vergés, M. Fernàndez / Tectonophysics xxx (2012) xxx–xxx 5.7. Stage 7 — Pliocene–Quaternary evolution of the Betic–Rif orogenic system . ............................ 0 6. Discussion ............................................................... 0 6.1. Current models and present-day lithospheric structure ....................................... 0 6.2. Geodynamic implications of an initial SE-dipping subduction beneath the Betic–Riforogenicsystem................... 0 6.3. Lateral change of subduction polarity and position of the Africa–Iberiapaleo-suture............................ 0 7. Conclusions ............................................................... 0 Acknowledgments .............................................................. 0 References .................................................................. 0 1. Introduction ~150 km (e.g., Choukroune and E.C.O.R.S. Team, 1989; Muñoz, 1992; Roure et al., 1989). As a consequence of this Iberian continental under- Assessing the detailed movements of tectonic micro-plates in- thrusting, the Ebro and Aquitaine foreland basins were formed by the volves serious difficulties because of their ability to move indepen- downward flexure of the Iberian and European plates, respectively. dently from the large limiting plates and due to the large-scale The combination of limited shortening and the endorheic (closed) vertical axis rotations they can experience. The Iberian plate located post-tectonic evolution of the Pyrenees up to early late Miocene caused at the western boundary of the Tethys Ocean in Mesozoic and early– the preservation of most of the syntectonic deposits providing an accurate mid Tertiary times, is one of these puzzling micro-plates (e.g., Vissers time control for the Pyrenean fold belt evolution (e.g., Puigdefàbregas and and Meijer, 2011). The combined study of large scale plate motions to- Souquet, 1986; Vergés et al., 2002). gether with geological observations constrains the evolution of the Ibe- On the contrary, the Betic–Rif orogen shows an arcuate geometry, rian plate despite arguable areas and time periods that need to be which is the result of a more intricate geological history, comprising refined (e.g., Roest and Srivastava, 1991; Rosenbaum et al., 2002a). an outer zone formed by the Guadalquivir and Gharb (Rharb) fore- In late Paleozoic times, after the Hercynian orogeny, the Iberian land basins, the Gulf of Cadiz accretionary complex, the External plate was part of Europe and Africa. Soon after the Triassic rifting ep- Betic and Rif thrust systems and the Internal Betic and Rif HP meta- isode (c. 250 million years ago [Ma]), propagation of the Central At- morphic complexes (Fig. 4). The hinterland of this arcuate compres- lantic Ocean toward the north produced the eastward movement of sive belt is cut by the extensional system related to the back-arc Africa relative to Iberia–Europe, opening the transtensional Atlas Alboran basin development. and Betic–Rif basins in early and middle Jurassic times, respectively. Despite the large amount of literature published on this region The transtensional corridor along the future Betic–Rif segment devel- since the first explicative model by Andrieux et al. (1971), the com- oped during ∼20 million years (m.y.) connecting the Atlantic to the plexity of the Betic–Rif orogenic system remains. At a large scale Ligurian–Tethys oceanic domains (Fig. 1A). This corridor was charac- there is a general consensus that the Betic–Rif orogen was formed terized by segmented domains possibly composed of thinned conti- as a consequence of the southwest slab roll-back of lithosphere nental crust with strong evidences of upper mantle exhumation and subducting beneath the large and over-thickened Alkapeca tectonic oceanization (e.g., Jiménez-Munt et al., 2010; Puga et al., 2011; domain (Bouillin et al., 1986). This domain, originally located south Schettino and Turco, 2010). In early Cretaceous times, northward of the present Balearic domain, was dismembered in several blocks propagation of the Atlantic Ocean spreading along the western mar- (Alboran–Kabylies–Peloritan–Calabria), which drifted radially, produc- gin of Iberia produced the abandonment of the Ligurian–Tethys corri- ing the closure of the Ligurian–Tethys oceanic domains (e.g., Michard et dor and the opening of the Bay of Biscay along the already rifted al., 2002; Ricou, 1994). In this context,
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