Luminiscence dating of alluvial fans in intramontane basins of NW Argentina

Abstract

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. Rere 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 froro debris-flow- and fluvial-dominated deposits and lacustrine sequences in intramontane basins bounded by tectonically active mountain ranges with as much as 2 km ofrelief. With careful choice offacies an<;l sample collection, OSL techniques can be used to date Late Pleistocene, predominately matrix-supported, cobble-conglomerate alluvial deposits.