Luminescence dating of alluvial fans in intramontane basins of NW Argentina
R. A. J. Robinson, J. Q. G. Spencer, M. R. Strecker, A. Richter, R. N. Alonso, 2005. "Luminescence dating of alluvial fans in intramontane basins of NW Argentina", Alluvial Fans: Geomorphology, Sedimentology, Dynamics, A. M. Harvey, A. E. Mather, M. Stokes
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Alluvial fans are sensitive recorders of both climatic change and tectonic activity. The ability to constrain the age of alluvial-fan sequences, individual sedimentary events and the rates of sediment accumulation are key for constraining which mechanisms most control their formation. Recent advances in optically stimulated luminescence (OSL) measurement and analysis have resulted in vast improvements in the dating technique and reliability of age determinations, particularly for OSL dating of quartz grains, and routine application to a wide variety of depositional environments is now possible. Here we apply OSL methods to date a variety of deposits within Late Pleistocene conglomeratic alluvial sequences in NW Argentina. The ages obtained range from 39 to 83 ka and were determined from debris-flow- and fluvial-dominated deposits and lacustrine sequences in intramontane basins bounded by tectonically active mountain ranges with as much as 2 km of relief. With careful choice of facies and sample collection, OSL techniques can be used to date Late Pleistocene, predominately matrix-supported, cobble–conglomerate alluvial deposits.
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Alluvial fans are important sedimentary environments. They trap sediment delivered from mountain source areas, and exert an important control on the delivery of sediment to downstream environments, to axial drainages and to sedimentary basins. They preserve a sensitive record of environmental change within the mountain source areas. Alluvial fan geomorphology and sedimentology reflect not only drainage basin size and geology, but change in response to tectonic, climatic and base-level controls. One of the challenges facing alluvial fan research is to resolve how these gross controls are reflected in alluvial fan dynamics and to apply the results of studies of modern fan processes and Quaternary fans to the understanding of sedimentary sequences in the rock record. This volume includes papers based on up-to-date research, and focuses on three themes: alluvial fan processes, dynamics of Quaternary alluvial fans and fan sedimentary sequences. Linking the papers is an emphasis on the controls of fan geomorphology, sedimentology and dynamics. This provides a basis for integration between geomorphological and sedimentological approaches, and an understanding how fluvial systems respond to tectonic, climatic and base-level changes.