HR: 0830h
AN: T31C-0853    [PDF]
TI: Late Quaternary Sedimentation and Erosion Rates Derived From Luminescence and Cosmogenic Nuclide Dating of Intermontane Basin Sediments, NW Argentine Cordillera
AU: * Robinson, R A
EM: rajr@st-and.ac.uk
AF: School of Geography and Geosciences, University of St Andrews, St Andrews, KY16 9AL United Kingdom
AU: Spencer, J Q
AF: School of Geography and Geosciences, University of St Andrews, St Andrews, KY16 9AL United Kingdom
AU: Phillips, W M
AF: School of Geosciences, University of Edinburgh, Edinburgh,, EH8 9XP United Kingdom
AU: Strecker, M R
AF: Institut f\"{u}r Geowissenschaften, Universit\"{a}t Potsdam, Postfach 60 15 53, 14415, Potsdam Germany
AU: Alonso, R N
AF: Universidad Nacional de Salta, Buenos Aires 177, 4400, Salta Argentina
AU: Kubik, P W
AF: Paul Scherrer Institut Institute of Particle Physics, HPK H30, ETH Hoenggerberg, CH-8093, Zurich Switzerland
AB: The easternmost basins of the central Andean cordillera (22$^{o}$-25$^{o}$S) are characterised by multiple Late Quaternary and Holocene alluvial fill-cut terraces. Humid phases in the central Andes, interpreted from cores of Late Pleistocene and Holocene lacustrine deposits, have been previously linked to periods of increased frequency of landsliding events. Large landslides lead to rapid increases in local base level and aggradation. Subsequent headward erosion propagates through the basin and produces a characteristic alluvial terrace, common to many active mountain belts. Although climate may be the predominant control on these events, small and young intra-basin faults could also be diverting fluvial systems and reorganising drainage basins and sediment pathways. We have integrated optically stimulated luminescence (OSL) with $^{10}$Be cosmogenic nuclide dating techniques to produce a chronology of three of these depositional and erosional sequences in the Quebrada de Humahuaca. From each sequence, multiple OSL samples were collected from the fluvial and (debris flow and stream dominated) alluvial fan deposits to quantify sedimentation rate; four cosmogenic samples were collected from a 1.5 m pit on each terrace surface to quantify surface exposure age, as well as basin-scale erosion rate. Integrating these two dating techniques allows us to test how episodic deposition-erosion events are linked to periods of pronounced climatic variability in the central Andes and to quantify landscape response time to incision events.
DE: 1035 Geochronology
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting