HR: 0830h
AN: T21D-0481    [PDF]
TI: Displacement Gradients on the Eastern Kunlun Fault: Implications for the Kinematics of Deformation in Tibet
AU: Harkins, N
EM: nharkins@geosc.psu.edu
AF: Dept. of Geosciences, Penn State University, University Park, PA 16802 United States
AU: * Kirby, E
EM: ekirby@geosc.psu.edu
AF: Dept. of Geosciences, Penn State University, University Park, PA 16802 United States
AU: Burbank, D
EM: burbank@geosc.psu.edu
AF: Institute for Crustal Studies, Univ.of CA, Santa Barbara, Santa Barbara, CA 93106 United States
AU: Wang, E
EM: erchie-wang@mail.igcas.ac.cn
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China
AB: The question of whether large strike-slip fault systems in Asia accommodate eastward extrusion of quasi-rigid Tibetan lithosphere or whether these faults accommodate internal variations in strain between deforming regions of thickened Tibetan crust is central to a more fundamental question - do the rules of plate tectonics govern intracontinental deformation? The Kunlun fault, in north-central Tibet presents a key opportunity to evaluate competing models for the kinematics of Asian deformation. Although initial remote sensing interpretations of the eastward extent of the fault system suggested that the fault terminated within the Tibetan Plateau, recent regional maps interpret the fault to be linked with structures transecting the plateau margin. Coupled with rapid and uniform slip rate ($\sim$1 cm/yr) along $\sim$600km of the fault (Van der Woerd, 2002), the fault is argued to accommodate eastward extrusion of much of central Tibet, Here we evaluate this hypothesis with new geomorphic mapping and observations of Holocene fluvial terraces and fault scarps along the easternmost $\sim$100km of the Kunlun fault. Our mapping suggests that significant displacement is not transmitted beyond the eastern margin of the Tibetan Plateau. Moreover, we exploit the preservation of flights of fluvial terraces as precise markers of displacement along this segment of the fault; coupled with radiocarbon ages of detrital charcoal, offsets of terrace risers at two localities yield preliminary slip rates ranging from $\sim$6 mm/yr to $\sim$2 mm/yr. Viewed in concert with previous rate determinations, slip rates appear to decrease toward the eastern end of the fault. We are currently working to assess the degree to which this displacement gradient is absorbed by shortening and crustal thickening within the Anyemaqen Shan and/or reflects distributed shear and rotation of the fault. Regardless, our preliminary results indicate that the Kunlun fault does not control extrusion of Tibetan lithosphere, but rather suggest that fault displacement is intimately tied to regional deformation gradients.
DE: 8102 Continental contractional orogenic belts
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting