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

JULIETA NOBILE; MATEO MARTINI; FEDERICO DAVILA

La Serena

Congreso; XIV Congreso Geológico Chileno; 2015

Earth topographyresults from the interaction between tectonics, climate and bedrock strength,which together control the erosion rates. In this contribution we measurecatchment-mean erosion rates at different scales using cosmogenic 10Beconcentration from fluvial sands collected along streams across the easternslope of the Ambato range, in the northern Sierras Pampeanas (also known asArgentine broken foreland). This area was selected given that it showshomogeneous lithology (mostly crystalline basement rocks) and climatic regimealong strike, which simplify our landscape analyses (they might be consideredrelatively constant in the study region). The 10Be erosion ratesrange between ~38 and ~115 m Ma-1, which are typical values whenthey are compared with other results along the Andes. The mean erosion rateswere, in turn, correlated with different geomorphometric parameters, like localrelief, slope and hypsometric integrals, as well as with the catchment meanchannel steepness index (Ksn). We found that relatively low valuesof erosion rates in the Ambato range might be attributed more directly tovariations in the bedrock strength rather than to climate and/or tectonics.