Luminescence of quartz and feldspar fingerprints provenance and correlates with the source area denudation in the Amazon River basin

A.O. Sawakuchi*, M. Jain, T.D. Mineli, F. Nogueira, D.J. Bertassoli, C. Häggi, H.O. Sawakuchi, F.N. Pupim, C.H. Grohmann, C.M. Chiessi, M. Zabel, S. Mulitza, C.E.M. Mazoca, D.F. Cunha

*Corresponding author for this work

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    Abstract

    The Amazon region hosts the world's largest watershed spanning from high elevation Andean terrains to lowland cratonic shield areas in tropical South America. This study explores variations in optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) signals in suspended silt and riverbed sands retrieved from major Amazon rivers. These rivers drain Pre-Cambrian to Cenozoic source rocks in areas with contrasting denudation rates. In contrast to the previous studies, we do not observe an increase in the OSL sensitivity of quartz with transport distance; for example, Tapajós and Xingu Rivers show more sensitive quartz than Solimões and Madeira Rivers, even though the latter have a significantly larger catchment area and longer sediment transport distance. Interestingly, high sensitivity quartz is observed in rivers draining relatively stable Central Brazil and Guiana shield areas (denudation rate ξ=0.04 mmyr−1), while low sensitivity quartz occurs in less stable Andean terrains (ξ=0.24 mmyr−1). An apparent linear correlation between quartz OSL sensitivity and denudation rate suggests that OSL sensitivity may be used as a proxy for erosion rates in the Amazon basin. Furthermore, luminescence sensitivity measured in sand or silt arises from the same mineral components (quartz and feldspar) and clearly discriminates between Andean and shield sediments, avoiding the grain size bias in provenance analysis. These results have implications for using luminescence sensitivity as a proxy for Andean and shield contributions in the stratigraphic record, providing a new tool to reconstruct past drainage configurations within the Amazon basin.
    Original languageEnglish
    JournalEarth and Planetary Science Letters
    Volume492
    Pages (from-to)152-162
    Number of pages11
    ISSN0012-821X
    DOIs
    Publication statusPublished - 2018

    Keywords

    • Sediment provenance
    • Luminescence
    • Denudation
    • Tropical rivers
    • Amazon

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