Constraints on the frontal crustal structure of a continental collision from an integrated geophysical research: The central‐western Betic Cordillera (SW Spain)

Abstract

Mélange rocks outcrop widely in the central and western frontal sectors of the Betic Cordillera, as in many other collisional orogens where they form part of the accretionary wedges. Extrusion of Triassic plastic clays and evaporites was favored by the progressive accretion of the Betic External Zones, mixing rocks of different provenance and forming a synorogenic frontal mélange unit. MT data coupled with gravity data are a valid combined methodology to characterize the geometry of these mélange units, since the characterization of plastic rocks geometry is usually uncertain using seismic techniques. The results correlate well with known geological features (sedimentary basins, calcareous ranges, evaporitic rocks) and reveal the deep geometry. A resistive body, slightly dipping toward the SE, points to the continuity of the Iberian Massif below the Guadalquivir basin (2°) and the External Zones (6–8°). To the south, gravity models show the Iberian continental crust subducting below the Internal Zones with a roughly 20–35° slope. The main conductive bodies are related to the location of evaporitic rocks involved in the frontal mélange. They overlie the Iberian Massif and, southwards, the frontal Jurassic and Cretaceous limestone sequences of the External and Median Subbetics. In this setting, thick plastic rock units placed above the foreland could act as a lubricant facilitating continental subduction, and being progressively accreted toward a frontal mélange.

From the North-Iberian Margin to the Alboran Basin: A lithosphere geo-transect across the Iberian Plate

“…In the southern segment, we used seismic data from different experiments (e.g., Banda et al, 1993;Carbonell et al, 1997;Comas et al, 1995;Gallart et al, 1995) and geological cross-sections (e.g., Banks and Warburton, 1991;Berástegui et al, 1998;Frizon de Lamotte et al, 2004;Michard et al, 2002;Platt et al, 2003 andRuiz-Constan et al, 2012). In addition to these data, we have also used for the whole transect the compilation of seismic data in Iberia by Díaz and Gallart (2009), and the recent receiver function data obtained in the TopoIberia project from the deployment of seismic stations (IberArray) covering the whole Iberian Peninsula (e.g., Mancilla et al, 2012, in this volume).…”

Shallow frontal deformation related to active continental subduction: structure and recent stresses in the westernmost Betic Cordillera

“…However, other researchers support subduction models (Doglioni et al ., ,b) – based on seismic tomography studies that imaged an oceanic subducted slab with SW–NE to N–S orientation (Blanco and Spakman, ; Gutscher et al ., , ; Piromallo and Morelli, ; Spakman and Wortel, ; Bezada et al ., ; Palomeras et al ., ) and E to SE‐dip – including slab roll‐back (Lonergan and White, ; Pedrera et al ., ) with partial or total slab break off and/or tearing (Blanco and Spakman, ; Spakman and Wortel, ; Garcia‐Castellanos and Villaseñor, ; van Hinsbergen et al ., ). Eastward (Gutscher et al ., , ) and south‐eastward (Ruiz‐Constán et al ., , , ) dipping slabs have been considered. The Alboran Basin may be interpreted as a backarc basin, although related to different proposed subduction slabs (Doglioni et al ., ; Gueguen et al ., ; Galindo‐Zaldivar et al ., ; Gueguen et al ., ; Doglioni et al ., ,b; Pedrera et al ., ; Carminati et al ., ; van Hinsbergen et al ., ).…”

“…To the west, however, there is widespread shallow seismicity in the Iberian basement beneath the Mor on de la Frontera area ( Fig. 1; Ruiz-Const an et al, 2009, 2012b. Farther west, seismic reflection profiles and Correspondence: Miss Lourdes Gonz alez-Castillo, Geodinamica, Universidad de Granada, Campus Fuentenueva S/N, Granada 18071, Spain.…”

Crustal structure beneath the Rif Cordillera, North Morocco, from the RIFSIS wide‐angle reflection seismic experiment

“…Within these initiatives special emphasis was placed on geophysical characterization of the crust with active seismic and magnetotelluric methods in specific areas coinciding with surface structural and petrological studies. These extended from the center of the Iberian Peninsula [ Gómez‐Ortiz et al ., ; Pous et al ., ; Martínez‐Poyatos et al ., ; Ruiz‐Costán et al ., ; Ehsan et al ., ; García‐Lobón et al ., ] to the Saharan craton, south of the Atlas Mountains. A unique high resolution wide‐angle reflection data set was acquired across the Atlas [ Ayarza et al ., ] and across the Rif (this manuscript).…”