Effects of mantle upwelling in a compressional setting: the Atlas Mountains of Morocco

We discuss the implications of a lithospheric model of the Moroccan Atlas Mountains based on topography, heat flow, gravity and geoid anomalies, taking into account the regional geology. The NW African cratonic lithosphere, some 160‐ 180 km thick, thins to c. 80 km beneath the Atlas fold-thrust belts, in contrast with the shortening regime prevailing there since the early Cenozoic. This fact explains several geological and geophysical features as high topography with modest tectonic shortening, the occurrence of alkaline magmatism contemporaneous to compression, the absence of large crustal roots to support elevation, the scarce development of foreland basins, and a marked geoid high. The modelled lithosphere thinning is related to a thermal upwelling constrained between the Iberia‐Africa convergent plate boundary and the Saharan craton.

[1]  E. Mercier,et al.  The two main steps of the Atlas building and geodynamics of the western Mediterranean , 2000 .

[2]  M. Mattauer,et al.  Sur les mecanismes de formation des chaines intracontinentales; l'exemple des chaines atlasiques du Maroc , 1977 .

[3]  F. Chabaux,et al.  Carbonatite and Alkaline Magmatism in Taourirt (Morocco): Petrological, Geochemical and Sr-Nd Isotope Characteristics , 2003 .

[4]  A. Teixell,et al.  Crustal structure under the central High Atlas Mountains (Morocco) from geological and gravity data , 2005 .

[5]  Hermann Zeyen,et al.  Integrated lithospheric modeling combining thermal, gravity, and local isostasy analysis: Application to the NE Spanish Geotransect , 1994 .

[6]  P. Giese,et al.  Inversion tectonics of intracontinental ranges: High and Middle Atlas, Morocco , 1992 .

[7]  Ulrich R. Christensen,et al.  Dynamic Earth: Plates, Plumes and Mantle Convection , 2000 .

[8]  A. Rimi.  Mantle heat flow and geotherms for the main geologic domains in Morocco , 1999 .

[9]  Antonio Teixell,et al.  A structural transect through the High and Middle Atlas of Morocco , 2004 .

[10]  W. Spakman,et al.  A Lower Mantle Source for Central European Volcanism. , 1999, Science.

[11]  P. Renne,et al.  The Cameroon Volcanic Line Revisited: Petrogenesis of Continental Basaltic Magmas from Lithospheric and Asthenospheric Mantle Sources , 2000 .

[12]  H. Bellon,et al.  Évolution des sources du volcanisme marocain au cours du Néogène , 1999 .

[13]  Ulrich R. Christensen,et al.  Some effects of lateral viscosity variations on geoid and surface velocities induced by density anomalies in the mantle , 1993 .

[14]  F. Ramdani.  Geodynamic implications of intermediate-depth earthquakes and volcanism in the intraplate Atlas mountains (Morocco) , 1998 .

[15]  Jean Hernandez,et al.  Nouvelles données sur le volcanisme trachytique hyperalcalin du volcan du Siroua (Anti-Atlas, Maroc) , 1985 .

[16]  Dogan Seber,et al.  Grid search modeling of receiver functions: Implications for crustal structure in the Middle East and North Africa , 1998 .

[17]  L. Jolivet,et al.  Lateral slab deformation and the origin of the western Mediterranean arcs , 2004 .

[18]  Ramón Casillas,et al.  Cenozoic volcanism II: the Canary Islands , 2002 .

[19]  F. Anguita,et al.  The Canary Islands origin: a unifying model , 2000 .

[20]  Harmen Bijwaard,et al.  Non‐linear global P‐wave tomography by iterated linearized inversion , 2000 .

[21]  J. Warme.  Jurassic carbonate facies of the Central and Eastern High Atlas rift, Morocco , 1988 .

[22]  K. Hoernle,et al.  Seismic and geochemical evidence for large-scale mantle upwelling beneath the eastern Atlantic and western and central Europe , 1995, Nature.

[23]  Mark van der Meijde,et al.  Crustal structure beneath broad-band seismic stations in the Mediterranean region , 2003 .

[24]  A. Rimi,et al.  Lithospheric structure under the western African‐European plate boundary: A transect across the Atlas Mountains and the Gulf of Cadiz , 2005 .

[25]  P. Ayarzaa,et al.  Crustal structure under the central High Atlas Mountains ( Morocco ) from geological and gravity data , 2005 .

[26]  C. Harrison,et al.  Deep-imaging seismic and gravity results from the offshore Cameroon Volcanic Line, and speculation of African hotlines☆ , 1998 .

[27]  G. Davies,et al.  Dynamic Earth: Interior , 1999 .

[28]  Peter Giese,et al.  Crustal structure along a traverse across the Middle and High Atlas mountains derived from seismic refraction studies , 1992 .

[29]  C. Pin,et al.  Pétrogenèse des magnésio-carbonatites du complexe de Tamazert (Haut Atlas marocain) , 1997 .

[30]  Richard W. Allmendinger,et al.  Crustal shortening and vertical strain partitioning in the Middle Atlas Mountains of Morocco , 1998 .

[31]  M. Gurnis,et al.  Cenozoic subsidence and uplift of continents from time-varying dynamic topography , 1997 .

[32]  Samir Bouaziz,et al.  The Mesozoic–Cenozoic Atlas belt (North Africa): an overview , 2002 .

[33]  L. Rüpke,et al.  Deep roots of the Messinian salinity crisis , 2003, Nature.

[34]  Dogan Seber,et al.  Three‐dimensional upper mantle structure beneath the intraplate Atlas and interplate Rif mountains of Morocco , 1996 .

[35]  B. Goffé,et al.  How does the Alpine belt end between Spain and Morocco , 2002 .

[36]  Antonio Teixell,et al.  Tectonic shortening and topography in the central High Atlas (Morocco) , 2003 .

[37]  F. Gomez,et al.  Role of the Atlas Mountains (northwest Africa) within the African-Eurasian plate-boundary zone , 2000 .

[38]  J. Makris,et al.  Deep seismic soundings in Morocco and a crust and upper mantle model deduced from seismic and gravity data , 1985 .

[39]  R. D. Dresnay.  Recent data on the geology of the Middle-Atlas (Morocco) , 1988 .

[40]  O. Merle,et al.  The formation of the West European Rift; a new model as exemplified by the Massif Central area , 2001 .

[41]  D. Dhont,et al.  Paleostress evolution in the Moroccan African margin from Triassic to Present , 2002 .

[42]  J. Cantagrel,et al.  Le volcanisme alcalin tertiaire et quaternaire du moyen atlas (Maroc): chronologie K/Ar et cadre géodynamique , 1984 .

[43]  O. Merle,et al.  The evolution of the Massif Central Rift; spatio-temporal distribution of the volcanism , 2001 .