Vol18 No.1: 68-87
【Title】Lithostructural controls in Douala-Buea Region landscape (SW Cameroon margin): Insights from morphometric analysis
【Author】Christian BALLA ATEBA1; Sébastien OWONA1*; Moussa NSANGOU NGAPNA1; Véronique MANGA TSIMI1; Dieudonné MINYEM2,3; Joseph MVONDO ONDOA
【Addresses】1 Department of Earth Sciences, Faculty of Science, the University of Douala, Douala 24157, Cameroon; 2 Department of Earth Sciences, Faculty of Science, the University of Yaounde I, Yaounde 812, Cameroon; 3 Department of Mines and Quarries, Faculty of Mining and Petroleum Industries, the University of Maroua, Maroua 814, Cameroon
【Corresponding author】Sébastien OWONA
【Citation】Balla Ateba C, Owona S, Nsangou Ngapna M, et al. (2021) Lithostructural controls in Douala-Buea Region landscape (SW Cameroon margin): Insights from morphometric analysis. Journal of Mountain Science 18(1). https://doi.org/10.1007/s11629-020-6085-4
【Abstract】The Douala-Buea Region (DBR; 4° - 5°N, 9° - 10°30'E), a portion of the southern Cameroon passive margin, developed on the Proterozoic granito-gneissic basement and the Cretaceous to Recent volcano-sedimentary cover, was explored in order to evaluate the lithology and tectonics controls on its landscape using the qualitative and quantitative geomorphological analyses based on 30 m resolution Digital Elevation Models (DEM) and field evidences. This area displays an uneven and complex landscape differentiated into four morphological units: Douala, Nkondjock, Kumba and Buea Units. The Douala Unit corresponds to the Coastal Plain and is extended on the Douala-Kribi/Campo sedimentary basin. The Nkondjock Unit represents a middle plateau developed on a Proterozoic granito-gneissic basement. The Kumba Unit matches with the southernmost volcanic Western Cameroon High Plateau. The Buea Unit corresponds to the Mount Cameroon stratovolcano. The relief analysis through mountain-front sinuosity (Smf, 1.19–1.43) and relative relief ratio (Rr, 0.10–2.31) vary from one unit to another. The drainage network analysis including drainage patterns, stepped longitudinal river profiles, the associated morphometric indexes, notably the concavity index (IC, 0.56–0.88), deviation (D, 267–2912 m), basin asymmetry factor (AF, 6.37–42.12), hypsometric integral (HI, 0.10–0.29), valley floor width to valley height ratio (Vf, 0.36–2.75), elongation ratio (Re, 0.30–0.50), watershed slope (S, 6.88–88.88) and stream length gradient index (SL, 0–3332) vary from one basin to another too. These results also show the heterogeneous and uneven DBR landscape controlled by its lithology and active tectonics. The drainage system reveals concave to concavo-convex longitudinal river profile shapes with knick points, asymmetric basins, and fault reactivations, and highlights the tectonics activity that used to occur through the time and their control on the morphology. Together, they document the lithostructural controls on the DBR landscape evolution, extendable in the whole SW Cameroon margin.
【Keywords】Morphometric indices; Lithological control; Structural control; Morphological units; Douala-Buea Region; SW Cameroon margin.