Crustal versus asthenospheric origin of relief of the Atlas Mountains of Morocco

Abstract

[1] We investigate the respective roles of crustal tectonic shortening and asthenospheric processes on the topography of the High Atlas and surrounding areas (Morocco). The lithospheric structure is modeled with a direct trial-and-error algorithm taking into account gravity (Bouguer and free air), geoid, heat flow, and topography. Three parallel cross sections, crossing the High Atlas and Anti-Atlas ranges, show that the lithosphere is thinned to 60 km below these mountain ranges. An analysis of the effect of the lithospheric thinning allows us to conclude that the whole topography of the Anti-Atlas, which belongs to the Sahara domain, is due to asthenospheric processes. In the High Atlas the lithospheric thinning explains a third of the relief of the western High Atlas, 500 m for a mean altitude of 1500 m, and half of the relief of the central High Atlas, 1000 m for a mean altitude of 2000 m. At the scale of Morocco the domain affected by lithospheric thinning forms an elongated NE-SW strip crossing not only the main structural zones but also the Atlantic margin to the south and the Africa-Eurasia plate boundary to the north. This major lithospheric thinning is associated with Miocene to recent alkaline volcanism and seismicity. We propose that this thermal anomaly is related to a shallow mantle plume, emplaced during middle to late Miocene time, during a period of relative tectonic quiescence.

Towards a de-carbonized energy system in north-eastern Morocco: Prospective geothermal resource

“…Their geochemical signature is similar to that of intra-oceanic island basalts, and suggests the role of an asthenospheric "hot lineament" [13]. Such interpretation is consistent with gravimetric and geodetic modeling of the lithosphere [14][15][16]. This MHL could extend from the Canary Islands to southeast Spain at least.…”

Flow of Canary mantle plume material through a subcontinental lithospheric corridor beneath Africa to the Mediterranean: REPLY

“…Elevated topography, high heat fl ow, and gravity and geoid anomalies point to the existence of an abnormally shallow lithosphereasthenosphere boundary beneath the western part of the Atlas system (60-80 km, compared to 130-160 km for normal northwest African lithospheric thickness), as illustrated on six lithospheric profi les across northwest Africa (Urchulutegui et al, 2006;Missenard et al, 2006;Teixell et al, 2005) (Fig. 1).…”

Reactivated lithospheric-scale discontinuities localize dynamic uplift of the Moroccan Atlas Mountains: COMMENT

“…They concluded that crustal thickness is insufficient to account for the observed elevations, and proposed a mantle-driven (upwelling) component of uplift, supported by low seismic velocities in the Atlas mantle reported already by Seber et al (1996). Subsequent efforts focused on modeling of gravity, the geoid, and topography that indicated a prominent lithospheric thinning, placing the lithosphere-asthenosphere boundary (LAB) at 70-90 km beneath the Atlas Mountains (e.g., Teixell et al, 2005;Missenard et al, 2006;Fullea et al, 2010). New contributions on the basis of active and passive seismology, partly under the Picasso project frame, are on their way (e.g., Bezada et al, 2013;Carbonell et al 2013;Palomeras et al, 2013;Miller and Becker, 2014).…”