Quantitative morphometric analysis of the Jama River profile in a tectonically active margin (Northwestern Ecuador) Quantitative morphometric analysis of the Jama River profile in a tectonically active margin (Northwestern Ecuador)

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Vol15 No.5: 966-975

Title】Quantitative morphometric analysis of the Jama River profile in a tectonically active margin (Northwestern Ecuador)

Author】Pedro S.B. REYES1*; Mauricio E. VALAREZO1,2; Jenry CÓRDOVA3; François A. MICHAUD4; Camilo ZAPATA1

Addresses】1 Department of Geology, Escuela Politécnica Nacional, Ladrón de Guevara, E11-253, PO.Box 17-01-2759, Quito, Ecuador; 2 Geostrat S.A., Jorge Drom N39-188 y Gaspar de Villaroel, Quito, Ecuador; 3 Department of Civil and Environmental Engineering, Escuela Politécnica Nacional, Ladrón de Guevara, E11-253, PO.Box 17-01-2759, Quito, Ecuador; 4 Sorbonne Université, Université Côte d’Azur, IRD, CNRS, Observatoire de la Côte d’Azur, Geoazur, 250 rue A. Einstein, Sophia Antipolis, 06560 Valbonne, France

Corresponding author】Pedro S.B. REYES

Citation】Reyes PSB, Valarezo M, Córdova J, et al. (2018) Quantitative morphometric analysis of the Jama River profile in a tectonically active margin (Northwestern Ecuador). Journal of Mountain Science 15(5). https://doi.org/10.1007/s11629-017-4751-y

DOI】https://doi.org/10.1007/s11629-017-4751-y

Abstract】The longitudinal profile of a river channel can be described in function of mathematical expressions. The logarithmic fit is the most used method to describe the relative equilibrium of a channel elevation profile. Rivers showing zones of high channel gradient and convex-upward profiles can be evaluated in function of the offset distance with respect to the logarithmic curve. The Jama River profile has been constructed using differential GPS data for the downstream reach and 4-m-grid DEM data base for the remaining headward profile. The resulting longitudinal profile shows a prominent knickpoint of about 80 m in elevation characterized by sharp local convexity. The offset distance in vertical direction from the logarithmic plot is interpreted as the successive accumulation of multiple uplift episodes associated with the Jama Fault System activity. The horizontal offset is suggested to represent the remaining retreated distance for the upstream propagation of the Jama knickpoint. The highly resistant Cretaceous rocks outcropping along the Jama knickpoint reach acts as an inflection point between two subprofiles that show well-fitted logarithmic curves, thereby representing a temporary partitioned equilibrium along the Jama River profile.

Keywords】Morphometry; Jama River; Stream profile; Active tectonics