HR: 11:05h
AN: T12D-04    [Abstracts]
TI: Slip rates of active thrusts and rates of river incision in the Qilian Shan (NE-Tibet)
AU: * Hetzel, R
EM: rahetzel@uni-muenster.de
AF: Geologisch-Palaeontologisches Institut, Westfaelische Wilhelms-Universitaet Muenster Corrensstrasse 24, Muenster, 48149, Germany
AU: Palumbo, L
AF: Geologisch-Palaeontologisches Institut, Westfaelische Wilhelms-Universitaet Muenster Corrensstrasse 24, Muenster, 48149, Germany
AU: Tao, M
AF: College of Resources Sciences & Technology, Beijing Normal University, Beijing, 100875, China
AB: The Qilian Shan is the north-easternmost of several mountain chains, which constitute a several hundred kilometer wide intra-continental fold-and-thrust belt in NE-Tibet (1). Spectacular, up to 50-m-high fault scarps at the front of the Qilian Shan and well preserved geomorphic surfaces allow to quantify slip rates of active thrust faults using surface exposure dating. In order to constrain vertical uplift rates of dip-slip faults it is crucial to separate tectonically-controlled river incision from non-tectonic incision, which is ultimately related to climate change. This is best achieved at sites where fault scarps are transacted by small rivers and tectonic offsets determined from scarp profiles can be compared directly to the amount of river incision recorded by fluvial terraces. Detailed investigations of several thrust faults that offset alluvial fans and river terraces, or have tilted large pediments yielded Late Quaternary fault slip rates that are relatively low, i.e. 0.4 to 1.3 mm/yr (2-4). At each studied site, the amount of river incision is similar to the vertical fault displacement. In contrast, post-glacial incision of large rivers at the Qilian Shan mountain front is predominantly climate-related and resulted in steep valleys cut into Late Quaternary conglomerates. At the Shiyou He, for instance, climate-induced Holocene river incision proceeded at a rate of about 10 mm/yr, thus exceeding the Late Pleistocene incision rate - which may largely be controlled by tectonic forcing - by a factor of ten (5). References: (1) Meyer et al. (1998), GJI 135, 1-47; (2) Hetzel et al. (2002), Nature 417, 428-432; (3) Hetzel et al. (2004), Tectonics 23, TC6006, doi:10.1029/2004TC001653; (4) Hetzel et al. (2004), Terra Nova 16, 157-162; Hetzel et al. (2006), JGR Earth Surface 111, F03012, doi:10.1029/2005JF000352.
DE: 4918 Cosmogenic isotopes (1150)
DE: 8010 Fractures and faults
DE: 8107 Continental neotectonics (8002)
DE: 8175 Tectonics and landscape evolution
DE: 8177 Tectonics and climatic interactions
SC: Tectonophysics [T]
MN: 2007 Fall Meeting