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Spatial variability of Quaternary denudation rates across a volcanic ocean island (Santo Antão, Cape Verde) from cosmogenic 3 He

Abstract : Denudation of volcanic ocean islands creates remarkable landscapes and contributes to Earth's carbon cycle, since the chemical alteration of basalts is a CO2 sink. Because many volcanic islands have large climate gradients and relatively low variations in lithology and tectonic history, they represent excellent natural laboratories for studying climatic effects on landscape evolution. However, little is known about the control of denudation rates in ocean islands and the respective influences of climatic gradients and morphological parameters. Here, we present new measurements of long-term denudation rates from Santo Antão Island, Cape Verde (17°N). In this 779 km 2 island, mean annual precipitation ranges from 40 mm.yr-1 in the southwest to 1100 mm.yr-1 in the north. To constrain the spatial distribution of denudation rates, we measured the cosmogenic 3 He concentration in river-transported pyroxene grains from 23 river bedload samples. We obtained basin wide denudation rates ranging from 2.7 ± 0.1 to 57.5 ± 0.3 m/Ma. The denudation rates display a significant spatial variability, with the highest rates in catchments located in the northeast side of the island where modern precipitation are the highest and low denudation rates in the southern and western dry basins. Our study shows that precipitation is the main control on denudation and landscape development of the Santo Antão volcanic island. This study provides for the first time the spatial distribution of denudation rates across a volcanic island located in a tropical zone.
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https://hal-cnrs.archives-ouvertes.fr/hal-03089201
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Submitted on : Monday, December 28, 2020 - 9:59:26 AM
Last modification on : Wednesday, January 20, 2021 - 11:11:50 AM

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Camille Litty, Julien Charreau, Pierre‐henri Blard, Raphaël Pik, Sébastien Nomade. Spatial variability of Quaternary denudation rates across a volcanic ocean island (Santo Antão, Cape Verde) from cosmogenic 3 He. Geomorphology, Elsevier, 2021, 375, pp.107557. ⟨10.1016/j.geomorph.2020.107557⟩. ⟨hal-03089201⟩

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