DEM-based reconstruction of southern Basse-Terre volcanoes (Guadeloupe archipelago, FWI): Contribution to the Lesser Antilles Arc construction rates and magma production

We combine radiometric ages and geomorphologic investigations to quantify the relief creation of well preserved volcanic surfaces, applied to the volcanoes of southern Basse-Terre (Guadeloupe, Lesser Antilles Arc). The last 650 ka volcanic evolution of this island has been modeled using ten main stages constrained by K–Ar ages previously obtained on lava flows and domes from the volcanic massifs of the Axial Chain (1000–435 ka) and from the Grande Découverte Volcanic Complex (250 ka–present). Based on the construction of a 250,000-point database inferred from the analysis of the Guadeloupe Digital Elevation Model, 3D reconstructions of the successive volcanic stage landforms were calculated and the correlated geochronological maps drawn using ArcGIS software. Volumes and rates of construction were computed for each time span separating these ten stages. The average construction rates calculated here are 2.4 ± 0.3 × 10−4 km3/yr for the last million years, 0.9 ± 0.3 × 10−4 km3/yr for the last 100 ka, and 0.9 ± 0.2 × 10−4 km3/yr for the last 15 ka. Although Basse-Terre volcanism is characterized by a marked dominance of effusive products, our estimates should be considered as minimum values because the material that went into the sea during explosive events was not taken into account. However, we note that a relatively high construction rate of 4.5 ± 1.3 × 10−4 km3/yr has been obtained for the Icaques volcano, which was emplaced during the 630–600 ka time interval, within the depression formed by the first large-scale flank collapse having affected southern Basse-Terre. The sudden release of the lithostatic load induced by this mass-wasting event could explain this value, which is significantly higher than the average value of 0.8 ± 0.1 × 10−4 km3/yr obtained for the last 650 ka. Finally, the comparison with other analogous volcanic massifs from islands and continental arcs points to a relatively low magmatic production for southern Basse-Terre, which could be tentatively related to the relatively slow subduction rate of the Atlantic plate.