Quartz luminescence sensitivity for estimation of denudation rates

Sawakuchi, A.O.1*, Pupim, F.N.2, del Rio, I.1, Jain, M.3, Rodrigues, F.C.G.1, Campos, M.C.1, Chiessi, C.M.4, Mendes, V.R.5, Mulitza, S.6, Parra, M.1 1Institute of Geosciences, University of Sao Paulo, Brazil 2Departament of Environmental Sciences, Federal University of Sao Paulo, Brazil 3Department of Physics, Technical University of Denmark, Denmark 4School of Arts, Sciences and Humanities, University of Sao Paulo, Brazil 5Institute of Marine Science, Federal University of Sao Paulo, Brazil 6MARUMCenter for Marine Environmental Sciences, University of Bremen, Germany *Presenting author: andreos@usp.br Denudation drives terrigenous sediment production, which in turn is crucial for the functioning of Earth surface systems. Quantifying present and past denudation rates over different spatial scales is therefore crticial for understanding Earth surface dynamics. Successive cycles of solar exposure and irradiation (due to burial) of quartz grains in soils and sedimentary systems increase their optically stimulated luminescence (OSL) sensitivity (light emitted per unit mass per unit radiation dose). The OSL sensitization is weak in sedimentary basins with large accommodation space, since subsidence inhibits repeated episodes of erosion and solar exposure. Instead, OSL sensitization would occur mainly in sediment source areas with low denudation rates because the stable surface promotes higher number of solar exposure-burial events. In areas with variable denudation rates, one expects, therefore, to observe a correlation between OSL sensitivity and denudation rate. Assuming that there is no change in OSL sensitivity after burial, it would be able to estimate past denudation rates using ancient sedimentary deposits. We tested the relationship between denudation rate and quartz OSL sensitivity using sediment samples from large South American rivers draining active orogenic and cratonic areas with varied denudation rates. Samples collected offshore the mouth of these rivers were used to obtain catchment integrated denudation rates. Laboratory experiments were also carried out to understand how light exposure and irradiation cycles determine rates and limits of OSL sensitization in nature. Keywords: sediment production; terrigenous sediments; large rivers; sediment routing system