The Western Cameroon Highland margin: Is there any geomorphometric evidence of active tectonics?

Abstract

The Western Cameroon Highland margin (WCHM) within the West African margin displays an uneven high relief. Its evolutionary model in vogue suggests the tectonic activity of the Cameroon Volcanic Line (CVL). An evident question in this regard is whether there is any geomorphometric evidence in support of what is this widespread view? We evaluate this question using field controls and geomorphometric indices of active tectonics derived for 13 main river basins with the help of digital elevation model (DEM)‐30 m data. The WCHM is developed on Proterozoic granite‐gneissic basement and the Cretaceous to Recent volcano‐sedimentary cover and was affected by regional active tectonic features. It is marked by transient signs of different landscape evolutionary stages recorded by the relief and drainage network; shown by gradual adjustment of rivers to equilibrium stages; and cautioned by a greatest variation of DEM‐based geomorphic indices. These indices, hypsometric integral (HI = 0.10–0.35), topography relief (TR = 595–2,710), topography dissection (TD = 114–829), valley floor width to valley height ratio (Vf arg = 0.61–14.91), transverse topographic symmetric factor (T‐index = 0.18–0.49), and basin asymmetric factor (AF = 1.08–24.37) highlight elevated and roughness character of that margin, from the Benue Trough and culminating to the CVL. River longitudinal profiles reveal variably and deeply incised WCHM by the drainage network, reinforced by ongoing tectonic activities. Knickpoints (Kps), stream length‐gradient (SL), uplift (U = 1.17–2.0), and a variety of normalized steepness (Ksn = 11.63–635.16) evidence the diversity and preeminent tectonic controls. The above results show that the WCHM is widely considered to be the consequence of the mantle dynamisms and regional tectonics since Proterozoic, the CVL activities, and the erosional processes.