Mountain Front Development by Folding and Crustal Thickening in the Internal Zone of the Betic Cordillera-Alboran Sea Boundary

The boundary between the Alboran Sea and Betic Cordillera is a good example of a fold related mountain front in the Internal Zone of an alpine mountain range. Since the late Miocene, NNW-SSE convergence between the Eurasian and African plates has produced shortening and related orthogonal extension. To improve the characterisation of the geometry of the deep structure in the region and to establish the recent tectonic evolution of the mountain front, well logs and newly acquired geophysical data (multichannel reflection seismic and gravimetric surveys) have been interpreted and integrated with available surface data. The most marked tectonic structure corresponds to large antiforms and synforms of ENE-WSW trend which are related to mountain ranges and basins, respectively. The fold belt continues toward the northern continental shelf of the Alboran Sea. The fold vergence is generally northwards and its amplitude decreases progressively towards SSE, until disappearring in a sharp boundary where the reflectors are undeformed. The deep geometry suggests that fold growth started during upper Tortonian times and continued its activity up to Pliocene or even Quaternary times. The NNW-SSE compression produces crustal thickening and a regional and progressive southwards emersion. The location of main present-day deformation fronts in the Internal Zones contrasts with classical models where the deformation progresses towards the frontal part of External Zones of cordilleras. In addition, this fold-related deformation mountain front has features different from fault related fronts, as it does not show a sharp boundary, and folds that determine rectilinear mountain boundaries decrease progressively in amplitude or in wavelength up to undeformed areas.

[1]  E. S. Robinson,et al.  Basic exploration geophysics , 1988 .

[2]  F. Lucchi.  The Oligocene to Recent Foreland Basins of the Northern Apennines , 2009 .

[3]  Pedro Alfaro,et al.  Tectonic significance of the present relief of the Betic Cordillera , 2004 .

[4]  J. Galindo‐Zaldívar,et al.  Recent Tectonic Deformations and Stresses in the Frontal Part of the Rif Cordillera and the Saïss Basin (Fes and Rabat Regions, Morocco) , 2004 .

[5]  Pierre Bordet,et al.  The Betic segment of the lithospheric Trans-Alboran shear zone during the Late Miocene , 1988 .

[6]  M. Comas,et al.  Well log interpretation and seismic character of the cenozoic sequence in the northern Alboran Sea , 1992 .

[7]  C. Thanassoulas,et al.  A simple BASIC program for computing terrain corrections on a microcomputer , 1984 .

[8]  Timothy P. Loomis,et al.  Tertiary mantle diapirism, orogeny, and plate tectonics east of the Strait of Gibraltar , 1975 .

[9]  Enric Banda,et al.  Evidence for the eastward migration of the Alboran Sea based on regional subsidence analysis: A case for basin formation by delamination of the subcrustal lithosphere? , 1995 .

[10]  S. Kokkalas,et al.  Stress and deformation patterns in the Aegean region , 2001 .

[11]  Deep structure of the Betic Cordillera derived from the interpretation of a complete Bouguer anomaly map , 1990 .

[12]  Carlos Marín-Lechado,et al.  Active faulting in the internal zones of the central Betic Cordilleras (SE, Spain) , 2003 .

[13]  J. Braga,et al.  Patterns and average rates of late Neogene-Recent uplift of the Betic Cordillera, SE Spain , 2003 .

[14]  J. Platt,et al.  44. THE ORIGIN AND TECTONIC HISTORY OF THE ALBORAN BASIN: INSIGHTS FROM LEG 161 RESULTS 1 , 1999 .

[15]  John P. Platt,et al.  Extensional collapse of thickened continental lithosphere: A working hypothesis for the Alboran Sea and Gibraltar arc , 1989 .

[16]  N. Pinter,et al.  Active Tectonics: Earthquakes, Uplift, and Landscape , 1995 .

[17]  M. Torné,et al.  Crustal thinning from the Betic Cordillera to the Alboran Sea , 1992 .

[18]  J. Galindo‐Zaldívar,et al.  Recent Tectonic Structures in a Transect of the Central Betic Cordillera , 2004 .

[19]  R. Weijermars,et al.  Uplift history of a Betic fold nappe inferred from Neogene-Quaternary sedimentation and tectonics (in the Sierra Alhamilla and Almeria, Sorbas and Tabernas Basins of the Betic Cordilleras, SE Spain) , 2007 .

[20]  J. Galindo‐Zaldívar,et al.  40Ar/39Ar geochronology of Alpine tectonism in the Betic Cordilleras (southern Spain) , 1991, Journal of the Geological Society.

[21]  C. Biermann,et al.  Palaeostress analysis of the northern Nijar and southern Vera basins: constraints for the Neogene displacement history of major strike-slip faults in the Betic Cordilleras, SE Spain , 1998 .

[22]  J. Goy,et al.  Synthesis of the quaternary in the almeria littoral neotectonic activity and its morphologic features, western betics, Spain , 1986 .

[23]  S. Kelley,et al.  Thermal evolution, rate of exhumation, and tectonic significance of metamorphic rocks from the floor of the Alboran extensional basin, western Mediterranean , 1998 .

[24]  A. Maldonado,et al.  Alboran Sea late cenozoic tectonic and stratigraphic evolution , 1992 .

[25]  W. Spakman,et al.  The P-wave velocity structure of the mantle below the Iberian Peninsula: evidence for subducted lithosphere below southern Spain , 1993 .

[26]  J. Galindo‐Zaldívar,et al.  Progressive extensional shear structures in a detachment contact in the Western Sierra Nevada (Betic Cordilleras, Spain) , 1989 .

[27]  Richard G. Gordon,et al.  Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions , 1994 .

[28]  W. Frisch,et al.  Balancing lateral orogenic float of the Eastern Alps , 2002 .

[29]  Claude Hillaire-Marcel,et al.  Pleistocene raised marine terraces of the Spanish Mediterranean and Atlantic coasts: records of coastal uplift, sea-level highstands and climate changes , 2003 .

[30]  A. Chalouan,et al.  Neogene Tectonic Evolution of the Southwestern Alboran Basin as Inferred from Seismic Data Off Morocco , 1997 .