Constraints on the Velocity Structure and Accommodation of Shortening in the Atlas Mountains (Morocco) from Travel-Time Inversion of Refraction/Wide Angle Reflection Seismic Data
Abstract
The Atlas Mountains are an intra-continental Cenozoic orogenic belt located at the southern edge of the diffuse plate boundary zone separating Africa and Europe. Its western part, the Moroccan Atlas, has long been under the scope of geoscientists investigating the origin of its high topography, locally exceeding 4000 m. Geological studies indicate that this mountain belt has experienced low to moderate shortening (<24% from balanced sections) and that topography and shortening do not keep a direct relationship. Forward modelling of the SIMA (Seismic Imaging of the Moroccan Atlas) refraction/wide angle reflection seismic data suggests that the total orogenic shortening, is resolved at depth with a Moho offset and a limited lower crust duplication that defines a 40 km-deep root in the northern part of the central High Atlas. However, the shortening accomodated by this feature (50 km) exceeds that estimated with surface data, and the position of the root appears to the north of the highest topography. In order to achieve a better definition of the crust/mantle boundary and to outline a tectonic model more coherent with surface data, we have used the RAYINVR code to carry out travel-time inversion of the SIMA data set. Inversion results depict a small shift to the south of the crustal root, formerly positioned in the northern part of the High Atlas, and define a thrusted mantle wedge. A limited crustal imbrication also appears in the Middle Atlas. The new velocity model implies complex ray trajectories but provides a better travel-time fit between the observed and the calculated data. Also, the amount of shortening implied by the this model is in agreement with that estimated from geological cross-sections. The final crustal thickness, as yet not exceeding 40 km in the root zone and less than 35 km elsewhere, still implies the need of a significant contribution from the mantle to support the topography of the Atlas mountains
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.T43B2655A
- Keywords:
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- 8108 TECTONOPHYSICS Continental tectonics: compressional;
- 8180 TECTONOPHYSICS Tomography;
- 0935 EXPLORATION GEOPHYSICS Seismic methods