HR: 1340h
AN: T23D-1641    [Abstracts]
TI: Investigating the Tectonic Aneurysm Model: Measuring Slip Rates Along the Kongur Detachment Fault in the Chinese Pamir
AU: * Kirby, B T
EM: kirby.106@osu.edu
AF: School of Earth Sciences The Ohio State University, 275 Mendenhall Laboratory, 125 S. Oval Mall, Columbus, OH 43210, United States
AU: Schoenbohm, L M
EM: schoenbohm.1@osu.edu
AF: School of Earth Sciences The Ohio State University, 275 Mendenhall Laboratory, 125 S. Oval Mall, Columbus, OH 43210, United States
AU: Chen, J
EM: chenjie@ies.ac.cn
AF: Institute of Geology, China Earthquake Administration, Box 9803, Beijing, 100029, China
AU: Lei, S
EM: chenjie@ies.ac.cn
AF: Institute of Geology, China Earthquake Administration, Box 9803, Beijing, 100029, China
AB: The Kongur Shan and Muztagh Ata massifs in the Chinese Pamir have experienced recent exhumation at a rate not readily explained by the crustal shortening associated with the Indo-Asian collision. Given the extensive glaciation of the peaks and the deep exhumation compared to the surrounding region, it has been proposed that Kongur Shan and Muztagh Ata are undergoing a ‘tectonic aneurysm', a process in which the positive feedback between focused erosion and exhumation of the upper crust results in lower crustal flow into the area and increased relief. The exhumation of these peaks is primarily accommodated by the Kongur detachment fault, in addition to several lesser normal faults trending sub-parallel to the main detachment. Previous studies have used thermochronology to determine the long-term exhumation history of the footwall, and have identified a possible increase in cooling rate at ~2 Ma near the peaks which has not been experienced by the rest of the range. If a tectonic aneurysm is taking place, recent fault slip rates should be higher close to the massifs and should increase through time. By mapping regional stream terraces displaced by this fault system with the aid of a handheld GPS receiver/recorder, this study aims to quantify the total recent vertical displacement at several points along the detachment. To establish slip rates, age control must be applied to offset surfaces, thereby yielding a maximum age for the tectonic event offsetting the surface and a minimum slip rate. A previously established age of 39+/-5 ka to 58+/-15 ka for the uppermost terrace surfaces near Kongur Shan, obtained in a previous study using Cosmogenic Radionuclide surface exposure dating, is used here. The fault system was mapped at three locations NW of Kongur Shan (at various distances from the peak): Zouba Valley (80km), Wulu Valley (65km), and Kalagile (40km). Near the north end of the Kongur detachment, displacement across the Wulu and Zouba faults sums to 0.53-1.14 m/kyr. The slip rate at Kalagile, nearer the massif, is 0.82-1.76 m/kyr. This increase in slip rate near Kongur Shan is consistent with the occurrence of a tectonic aneurysm.
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 4918 Cosmogenic isotopes (1150)
DE: 8107 Continental neotectonics (8002)
DE: 8177 Tectonics and climatic interactions
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2007 Fall Meeting