Cosmogenic Erosion Rate Estimation from Detrital Olivine without Soil Characterization: The Case of the Matatia Basin (Tahiti Island)

Erosion rate studies conducted in volcanic islands bring key information about landscape dynamics and also for risk assessment and management policies. In this study we discuss how inadequate characterization of soils in volcanic island could lead to an underestimation of cosmogenic 3He erosion rates inferred from river sediments. Measurements in the Matatia basin (Tahiti) show that detrital olivine provides an average erosion rate of 252±37 t/km2/yr in good agreement with the erosion rate of 310±9t/km2/yr inferred from initial topography reconstruction. Additional measurements along the river allowed us to locate the zones of fastest erosional. However, soils olivine abundance measurements in the Matatia basin are planned in order to better constrain erosion rates inferred from cosmogenic 3He measurements in detrital olivine, and in order to quantify catastrophic erosion processes like landslide, rock falls etc.