HR: 1340h
AN: T23D-1646    [Abstracts]
TI: Rates of Fluvial Incision and Exhumation in an Active Mountain Belt, Lahul Himalaya, Northern India
AU: * Adams, B A
EM: Byron.A.Adams@asu.edu
AF: Arizona State University, School of Earth and Space Exploration 550 Tyler Mall PSF 638, Tempe, AZ 85287-1404, United States
AU: Dietsch, C
EM: craig.dietsch@uc.edu
AF: University of Cincinnati, Department of Geology 500 Geology/Physics Building, Cincinnati, OH 45221-0013, United States
AU: Owen, L A
EM: lewis.owen@uc.ed
AF: University of Cincinnati, Department of Geology 500 Geology/Physics Building, Cincinnati, OH 45221-0013, United States
AU: Spotila, J A
EM: spotila@vt.edu
AF: Virginia Tech, Department of Geosciences 4044 Derring Hall, Blacksburg, VA 24061, United States
AU: Caffee, M
EM: mcaffee@physics.purdue.edu
AF: Purdue University, Purdue Rare Isotope Measurement Laboratory 525 Northwestern Avenue, West Lafayette, IN 47907-2036, United States
AU: van Soest, M
AF: Arizona State University, School of Earth and Space Exploration 550 Tyler Mall PSF 638, Tempe, AZ 85287-1404, United States
AB: The Lahul Himalaya of northern India provides an excellent natural laboratory to define rates of denudation and exhumation in an active mountain belt because its Quaternary history — derived from well-preserved and dated successions of landforms and sediments — is well established. Building on previous tectonic and geomorphic studies, terrestrial cosmogenic nuclide (TCN) ¹⁰Be surface exposure dating and apatite (U-Th)/He (AHe) thermochronology was applied along the Chandra Valley to quantify rates of fluvial incision and exhumation. TNC ages on successive strath treads at four locations along the Chandra River and one of its tributary rivers, between Batal and Khoksar, range from 0.56 to 5.36 ka, yielding post-glacial (after 10 ka) rates of fluvial incision of 1.5 to 13.5 mm/a. The highest rates are associated with straths along a narrow canyon-like stretch of the main drainage (Chandra River) and an associated tributary valley. These are an order of magnitude greater than those of gentler, broader alluviated reaches of the Chandra. The highest rates may suggest a change in uplift or landscape incision modulated by glacial fluctuation. AHe ages from leucogranite exposed near the Chandra River and at higher elevations in steep, deeply gorged, glaciated side valleys range between 1.46 and 2.51 Ma, marking a pulse of rapid cooling and denudation during the Late Pliocene-Quaternary. These TNC and AHe data suggest enhanced denudation of the region during the Quaternary and provide some of the first quantitative data for rates of landscape evolution in the Lahul Himalaya of northern India.
DE: 1105 Quaternary geochronology
DE: 1140 Thermochronology
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1825 Geomorphology: fluvial (1625)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting