Sediment generation on a volcanic island with arid tropical climate: A perspective based on geochemical maps of topsoils and stream sediments from Santiago Island,Cape Verde |
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| Institution: | 1. Department of Patología Animal, Producción Animal, Bromatología y Tecnología de los Alimentos, Universidad de Las Palmas de Gran Canaria, Autovia Las Palmas Arucas km 6.5 35413, Canary Islands, Spain;2. Department of Edafología y Geología, Av. Astrofísico F. Sánchez, s/n Universidad de La Laguna, 38203 La Laguna, Spain;4. Laboratorio Agroalimentario y Fitopatológico del Cabildo Insular de Gran Canaria, Spain;1. Department of Materials Science and Engineering, Ghent University, Tech Lane Ghent Science Park - Campus A, Technologiepark Zwijnaarde 903, 9052, Belgium;2. Department of Architectural Engineering, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium;3. Department of Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium |
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| Abstract: | The present research tests the application of geochemical atlas of soils and stream sediments in the investigation of weathering and erosion processes on volcanic islands. The composition of surface soils collected in six catchments from Santiago Island (Cape Verde) are compared with bedload stream deposits sourced by these catchment areas in order to evaluate the spatial variability of these exogenous processes. The geochemistry of bedload stream deposits is between that of the fresh rocks and the topsoils of their source areas. Relative to average soil composition, bedload deposits are depleted in most of less-mobile elements (e.g., Al, Fe, La, Sc) and strongly enriched in Na and, usually, Ca. When the topsoil weathering intensity in the catchment areas is highly variable and the composition of bedload deposits is substantially different from the average soil composition, bedload deposits should incorporate significant amounts of poorly-weathered rocks and sectors from erosion occur within the drainage basin. Ratios of non-mobile elements allow the identification of highly vulnerable and erosion-protected sectors within the catchments. It is proposed that the catchments of the rivers in the SW flanking side of Santiago Island include sectors where lava shields formed during the post-erosional eruptive phases are capable of an effective protection to erosion. Conversely, the NE-facing part of the island is highly dissected and any younger post-erosional cover was either completely eroded away, or never existed in the first place. Simple compositional parameters derived from the databases of geochemical maps of soil and stream sediments provide important information for the analyses of weathering, erosion and denudation processes at the catchment scale. |
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| Keywords: | Volcanic island Santiago Island (Cape Verde) Topsoils Bedload stream sediments Weathering Erosion |
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