Erosion rates inferred from cosmogenic 10Be concentrations in the Sierras Pampeanas, Argentina and their implications within the South Central Andes

90. NOBILE, J.C, MARTINI, M., DÁVILA, F.M.,

Congreso; XIV Congreso Geológico Chileno; 2015

Earth topography results from the interaction between tectonics, climate and bedrock strength, which together control the erosion rates. In this contribution we measure catchment-mean erosion rates at different scales using cosmogenic 10Be concentration from fluvial sands collected along streams across the eastern slope of the Ambato range, in the northern Sierras Pampeanas (also known as Argentine broken foreland). This area was selected given that it shows homogeneous lithology (mostly crystalline basement rocks) and climatic regime along strike, which simplify our landscape analyses (they might be considered relatively constant in the study region). The 10Be erosion rates range between ~38 and ~115 m Ma-1, which are typical values when they are compared with other results along the Andes. The mean erosion rates were, in turn, correlated with different geomorphometric parameters, like local relief, slope and hypsometric integrals, as well as with the catchment mean channel steepness index (Ksn). We found that relatively low values of erosion rates in the Ambato range might be attributed more directly to variations in the bedrock strength rather than to climate and/or tectonics.