Crustal and upper-mantle structure beneath the western Atlas Mountains in SW Morocco derived from receiver functions

Abstract

The High Atlas and the Anti Atlas are fold-belts linked to former and still ongoing continent–continent collisions. Despite their high elevation, studies indicate a lack of a deep crustal root (<40 km) while the lithosphere underneath is thinned (<100 km). Previous explanations for this thinning include asthenospheric upwelling due to small-scale convection or a small plume. We use data recorded at stations in SW Morocco to analyse teleseismic P- and S-wave receiver functions. Our study yields a crustal thickness ranging from 24 km near the Atlantic coast to 44 km beneath the High Atlas with an average crustal Vp/Vs ratio of 1.77 in the entire region. A crustal thickness of 40 km cannot entirely support the topography in this region. Furthermore, we find the lithosphere–asthenosphere boundary at ∼80 km depth. The lithosphere beneath SW Morocco is thinner than beneath northern Morocco (>150 km). This lithospheric thinning supports the theory of thermal compensation of the mountain ranges. The mantle transition zone thickness amounts to 240 ± 10 km. The transition zone seems to be slightly thinned which might indicate a higher mantle temperature in this region.