Depth profiles in a tropical, volcanic critical zone observatory: Basse-Terre, Guadeloupe

The Bras David watershed on the French island of Basse-Terre, Guadeloupe in the Lesser Antilles is located on a late Quaternary volcaniclastic debris flow of dominantly andesitic composition. The bedrock is mantled by more than 12 m of highly leached regolith. The regolith is depleted with respect to most primary minerals and weathering is dominated by the dissolution and precipitation of clays. Mineral nutrient cations such as Mg, K, and P are largely present as impurities or adsorbed to clays and iron oxides. Surface soils (<0.3 m depth) are enriched in feldspar, quartz, cristobalite, and solid state Fe(II), Ca, K, and Mg relative to the underlying regolith, likely reflecting atmospheric deposition, possibly related to volcanic activity.