ALBERT

Description: Detrital provenance analyses in orogenic settings, in which sediments are collected at the outlet of a catchment, have become an important tool to es-timate how erosion varies in space and time. Here we present how Raman Spectroscopy on Carbonaceous Material (RSCM) can be used for provenance analysis. RSCM provides an estimate of the peak temperature (RSCM-T) experienced during metamorphism. We show that we can infer modern ero-sion patterns in a catchment by combining new measurements on detrital sands with previously acquired bedrock data. We focus on the Whataroa catch-ment in the Southern Alps of New Zealand and exploit the metamorphic gra-dient that runs parallel to the main drainage direction. To account for po-tential sampling biases, we also quantify abrasion properties using flume ex-periments and measure the total organic carbon content in the bedrock that produced the collected sands. Finally, we integrate these parameters into a mass-conservative model. Our results fist demonstrate that RSCM-T can be used for detrital studies. Second, we finnd that spatial variations in tracer concentration and erosion have a rst-order control on the RSCM-T distri-butions, even though our flume experiments reveal that weak lithologies pro-duce substantially more ne particles than do more durable lithologies. This result implies that sand specimens are good proxies for mapping spatial vari-ations in erosion when the bedrock concentration of the target mineral is quan-tied. The modeling suggests highest present-day erosion rates (in Whataroa catchment) are not situated at the range front, but around 10 km into the mountain belt.