Exploring spatial variations in geomorphic features of a young intracontinental orogenic belt: A case study of the High Atlas range

Abstract

Morphotectonic parameters are sensitive to crustal and/or mantle dynamics, especially in young convergent margins and contractional orogenic systems. In northwest Africa, the High Atlas orogen is a natural example where tectonics interact with mantle dynamics to shape the orogen's topography.The High Atlas Mountains are an intracontinental segment of the peri-Mediterranean belt in northwest Africa, formed during the Late Cretaceous-Cenozoic period as part of the Alpine orogeny. An important aspect in the evolutionary history of the High Atlas belt is the presence of uplifted asthenosphere beneath the range, overlaying the Late Cretaceous-Cenozoic crustal shortening. This study aims to investigate the geomorphic and topographic features that reflect the influence of tectonics and mantle dynamics in the High Atlas orogen. A morphotectonic approach is employed, utilizing analysis of geomorphic indices such as relief, slope, channel steepness index, and stream length gradient. Additionally, eleven 30 km wide and 150 to 230 km long swath profiles are constructed to illustrate the variations in topography and geomorphology along the range.The geomorphic indices display a similar pattern of evolution across the High Atlas, with higher values of these indices associated with the primary faults that control the structure of the range. By combining the geomorphic indices and swath profiles, it is evident that the eastern part of the orogen exhibits geomorphic asymmetry, with the northern border experiencing greater neotectonic activity and surface uplift. The central part of the range displays more geomorphic symmetry, while the western part is asymmetrical, characterized by higher elevations and elevated values of geomorphic indices along the southern border. This variation in geomorphology is attributed to the oblique intersection of the High Atlas orogen and a region of thinned lithosphere, which facilitated increased neotectonic activity and surface uplift in the northern part of the Eastern High Atlas and the southern part of the Western High Atlas. In the westernmost portion of the range, the role of structural inheritance is critical in the neotectonic activity. At a local scale, the role of lithology in the drainage reorganization is evident especially in basement exposures such as Mougueur inlier, Skoura inlier and Ouzellarh salient.This study underscores the robustness of tectonic geomorphology as a tool to understand the complex interplay between crustal processes and mantle dynamics, together with surface processes, in young orogenic belts like the High Atlas.