Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data: The SIMA experiment

P. Ayarza*, R. Carbonell, A. Teixell, I. Palomeras, D. Marti, A. Kchikach, M. Harnafi, A. Levander, J. Gallart, M. L. Arboleya, J. Alcalde, M. Fernandez, M. Charroud, M. Amrhar

*Corresponding author for this work

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

The crustal structure and topography of the Moho boundary beneath the Atlas Mountains of Morocco has been constrained by a controlled source, wide-angle seismic reflection transect: the SIMA experiment. This paper presents the first results of this project, consisting of an almost 700 km long, high-resolution seismic profile acquired from the Sahara craton across the High and the Middle Atlas and the Rif Mountains. The interpretation of this seismic data set is based on forward modeling by raytracing, and has resulted in a detailed crustal structure and velocity model for the Atlas Mountains. Results indicate that the High Atlas features a moderate crustal thickness, with the Moho located at a minimum depth of 35 km to the S and at around 31 km to the N, in the Middle Atlas. Upper crustal shortening is resolved at depth through a crustal root where the Saharan crust underthrusts the northern Moroccan crust. This feature defines a lower crust imbrication that, locally, places the Moho boundary at similar to 40-41 km depth in the northern part of the High Atlas. The P-wave velocity model is characterized by relatively low velocities, mostly in the lower crust and upper mantle, when compared to other active orogens and continental regions. These low deep crustal velocities together with other geophysical observables such as conductivity estimates derived from MT measurements, moderate Bouguer gravity anomaly, high heat flow, and surface exposures of recent alkaline volcanism lead to a model where partial melts are currently emplaced at deep crustal levels and in the upper mantle. The resulting model supports the existence of a mantle upwelling as mechanism that would contribute significantly to sustain the High Atlas topography. However, the detailed Moho geometry deduced in this work should lead to a revision of the exact geometry and position of this mantle feature and will require new modeling efforts.

Original languageEnglish
Pages (from-to)1698-1717
Number of pages20
JournalGeochemistry, Geophysics, Geosystems
Volume15
Issue number5
Early online date7 May 2014
DOIs
Publication statusPublished - May 2014

Keywords

  • quaternary deformation
  • tectonic implications
  • inversion tectonics
  • Mountains Morocco
  • wave velocities
  • Middle Atlas
  • lithosphere
  • beneath
  • mantle
  • neogene
  • wide-angle seismic reflection
  • Atlas Mountains of Morocco
  • crustal imbrication
  • low P-wave velocity
  • partial melt
  • asthenospheric upwelling

Cite this

Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data : The SIMA experiment. / Ayarza, P.; Carbonell, R.; Teixell, A.; Palomeras, I.; Marti, D.; Kchikach, A.; Harnafi, M.; Levander, A.; Gallart, J.; Arboleya, M. L.; Alcalde, J.; Fernandez, M.; Charroud, M.; Amrhar, M.

In: Geochemistry, Geophysics, Geosystems , Vol. 15, No. 5, 05.2014, p. 1698-1717.

Research output: Contribution to journalArticle

Ayarza, P, Carbonell, R, Teixell, A, Palomeras, I, Marti, D, Kchikach, A, Harnafi, M, Levander, A, Gallart, J, Arboleya, ML, Alcalde, J, Fernandez, M, Charroud, M & Amrhar, M 2014, 'Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data: The SIMA experiment', Geochemistry, Geophysics, Geosystems , vol. 15, no. 5, pp. 1698-1717. https://doi.org/10.1002/2013GC005164
Ayarza, P. ; Carbonell, R. ; Teixell, A. ; Palomeras, I. ; Marti, D. ; Kchikach, A. ; Harnafi, M. ; Levander, A. ; Gallart, J. ; Arboleya, M. L. ; Alcalde, J. ; Fernandez, M. ; Charroud, M. ; Amrhar, M. / Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data : The SIMA experiment. In: Geochemistry, Geophysics, Geosystems . 2014 ; Vol. 15, No. 5. pp. 1698-1717.
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title = "Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data: The SIMA experiment",
abstract = "The crustal structure and topography of the Moho boundary beneath the Atlas Mountains of Morocco has been constrained by a controlled source, wide-angle seismic reflection transect: the SIMA experiment. This paper presents the first results of this project, consisting of an almost 700 km long, high-resolution seismic profile acquired from the Sahara craton across the High and the Middle Atlas and the Rif Mountains. The interpretation of this seismic data set is based on forward modeling by raytracing, and has resulted in a detailed crustal structure and velocity model for the Atlas Mountains. Results indicate that the High Atlas features a moderate crustal thickness, with the Moho located at a minimum depth of 35 km to the S and at around 31 km to the N, in the Middle Atlas. Upper crustal shortening is resolved at depth through a crustal root where the Saharan crust underthrusts the northern Moroccan crust. This feature defines a lower crust imbrication that, locally, places the Moho boundary at similar to 40-41 km depth in the northern part of the High Atlas. The P-wave velocity model is characterized by relatively low velocities, mostly in the lower crust and upper mantle, when compared to other active orogens and continental regions. These low deep crustal velocities together with other geophysical observables such as conductivity estimates derived from MT measurements, moderate Bouguer gravity anomaly, high heat flow, and surface exposures of recent alkaline volcanism lead to a model where partial melts are currently emplaced at deep crustal levels and in the upper mantle. The resulting model supports the existence of a mantle upwelling as mechanism that would contribute significantly to sustain the High Atlas topography. However, the detailed Moho geometry deduced in this work should lead to a revision of the exact geometry and position of this mantle feature and will require new modeling efforts.",
keywords = "quaternary deformation, tectonic implications, inversion tectonics, Mountains Morocco, wave velocities, Middle Atlas, lithosphere, beneath, mantle, neogene, wide-angle seismic reflection, Atlas Mountains of Morocco, crustal imbrication, low P-wave velocity, partial melt, asthenospheric upwelling",
author = "P. Ayarza and R. Carbonell and A. Teixell and I. Palomeras and D. Marti and A. Kchikach and M. Harnafi and A. Levander and J. Gallart and Arboleya, {M. L.} and J. Alcalde and M. Fernandez and M. Charroud and M. Amrhar",
note = "Funded by: Spanish MEC . Grant Numbers: CGL2007–63889 , CGL2010–15416 , CSD2006-00041 , CGL2009–09727 , CGL2008–03474-E , EAR-0808939",
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T1 - Crustal thickness and velocity structure across the Moroccan Atlas from long offset wide-angle reflection seismic data

T2 - The SIMA experiment

AU - Ayarza, P.

AU - Carbonell, R.

AU - Teixell, A.

AU - Palomeras, I.

AU - Marti, D.

AU - Kchikach, A.

AU - Harnafi, M.

AU - Levander, A.

AU - Gallart, J.

AU - Arboleya, M. L.

AU - Alcalde, J.

AU - Fernandez, M.

AU - Charroud, M.

AU - Amrhar, M.

N1 - Funded by: Spanish MEC . Grant Numbers: CGL2007–63889 , CGL2010–15416 , CSD2006-00041 , CGL2009–09727 , CGL2008–03474-E , EAR-0808939

PY - 2014/5

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N2 - The crustal structure and topography of the Moho boundary beneath the Atlas Mountains of Morocco has been constrained by a controlled source, wide-angle seismic reflection transect: the SIMA experiment. This paper presents the first results of this project, consisting of an almost 700 km long, high-resolution seismic profile acquired from the Sahara craton across the High and the Middle Atlas and the Rif Mountains. The interpretation of this seismic data set is based on forward modeling by raytracing, and has resulted in a detailed crustal structure and velocity model for the Atlas Mountains. Results indicate that the High Atlas features a moderate crustal thickness, with the Moho located at a minimum depth of 35 km to the S and at around 31 km to the N, in the Middle Atlas. Upper crustal shortening is resolved at depth through a crustal root where the Saharan crust underthrusts the northern Moroccan crust. This feature defines a lower crust imbrication that, locally, places the Moho boundary at similar to 40-41 km depth in the northern part of the High Atlas. The P-wave velocity model is characterized by relatively low velocities, mostly in the lower crust and upper mantle, when compared to other active orogens and continental regions. These low deep crustal velocities together with other geophysical observables such as conductivity estimates derived from MT measurements, moderate Bouguer gravity anomaly, high heat flow, and surface exposures of recent alkaline volcanism lead to a model where partial melts are currently emplaced at deep crustal levels and in the upper mantle. The resulting model supports the existence of a mantle upwelling as mechanism that would contribute significantly to sustain the High Atlas topography. However, the detailed Moho geometry deduced in this work should lead to a revision of the exact geometry and position of this mantle feature and will require new modeling efforts.

AB - The crustal structure and topography of the Moho boundary beneath the Atlas Mountains of Morocco has been constrained by a controlled source, wide-angle seismic reflection transect: the SIMA experiment. This paper presents the first results of this project, consisting of an almost 700 km long, high-resolution seismic profile acquired from the Sahara craton across the High and the Middle Atlas and the Rif Mountains. The interpretation of this seismic data set is based on forward modeling by raytracing, and has resulted in a detailed crustal structure and velocity model for the Atlas Mountains. Results indicate that the High Atlas features a moderate crustal thickness, with the Moho located at a minimum depth of 35 km to the S and at around 31 km to the N, in the Middle Atlas. Upper crustal shortening is resolved at depth through a crustal root where the Saharan crust underthrusts the northern Moroccan crust. This feature defines a lower crust imbrication that, locally, places the Moho boundary at similar to 40-41 km depth in the northern part of the High Atlas. The P-wave velocity model is characterized by relatively low velocities, mostly in the lower crust and upper mantle, when compared to other active orogens and continental regions. These low deep crustal velocities together with other geophysical observables such as conductivity estimates derived from MT measurements, moderate Bouguer gravity anomaly, high heat flow, and surface exposures of recent alkaline volcanism lead to a model where partial melts are currently emplaced at deep crustal levels and in the upper mantle. The resulting model supports the existence of a mantle upwelling as mechanism that would contribute significantly to sustain the High Atlas topography. However, the detailed Moho geometry deduced in this work should lead to a revision of the exact geometry and position of this mantle feature and will require new modeling efforts.

KW - quaternary deformation

KW - tectonic implications

KW - inversion tectonics

KW - Mountains Morocco

KW - wave velocities

KW - Middle Atlas

KW - lithosphere

KW - beneath

KW - mantle

KW - neogene

KW - wide-angle seismic reflection

KW - Atlas Mountains of Morocco

KW - crustal imbrication

KW - low P-wave velocity

KW - partial melt

KW - asthenospheric upwelling

U2 - 10.1002/2013GC005164

DO - 10.1002/2013GC005164

M3 - Article

VL - 15

SP - 1698

EP - 1717

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 5

ER -