TY - JOUR A1 - Sobel, Edward A1 - Schoenbohm, Lindsay M. A1 - Chen, Jie A1 - Thiede, Rasmus Christoph A1 - Stockli, Daniel F. A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Late Miocene-Pliocene deceleration of dextral slip between Pamir and Tarim: Implications for Pamir orogenesis JF - EARTH AND PLANETARY SCIENCE LETTERS N2 - The timing of the late Cenozoic collision between the Pamir salient and the Tien Shan as well as changes in the relative motion between the Pamir and Tarim are poorly constrained. The northern margin of the Pamir salient indented northward by similar to 300 km during the late Cenozoic, accommodated by south-dipping intracontinental subduction along the Main Pamir Thrust (MPT) coupled to strike-slip faults on the eastern flank of the orogen and both strike-slip and thrust faults on the western margin. The Kashgar-Yecheng transfer system (KYTS) is the main dextral slip shear zone separating Tarim from the Eastern Pamir, with an estimated cumulative offset of similar to 280 km at an average late Cenozoic dextral slip rate of 11-15 mm/a (Cowgill, 2010). In order to better constrain the slip history of the KYTS, we collected thermochronologic samples along the eastward-flowing, deeply incised, antecedent Tashkorgan-Yarkand River, which crosses the fault system on the eastern flank of the orogen. We present 29 new biotite (40)Ar/(39)Ar ages, apatite and zircon (U-Th-Sm)/He ages, and apatite fission track (AFT) analysis, combined with published muscovite and biotite (40)Ar/(39)Ar and AFT data, to create a unique thermochronologic dataset in this poorly studied and remote region. We constrain the timing of four major N-trending faults: the latter three are strands of the KYTS. The westernmost, the Kuke fault, experienced significant dip-slip, west-side-up displacement between > 12 and 6 Ma. To the east, within the KYTS, our new thermochronologic data and geomorphic observations suggest that the Kumtag and Kusilaf dextral slip faults have been inactive since at least 3-5 Ma. Long-term incision rates across the Aertashi dextral slip fault, the easternmost strand of the KYTS, are compatible with slow horizontal slip rates of 1.7-5.3 mm/a over the past 3 to 5 Ma. In summary, these data show that the slip rate of the KYTS decreased substantially during the late Miocene or Pliocene. Furthermore, Miocene-present regional kinematic reconstructions suggest that this deceleration reflects the substantial increase of northward motion of Tarim rather than a significant decrease of the northward velocity of the Pamir. (C) 2011 Elsevier B.V. All rights reserved. KW - thermochronology KW - neotectonics KW - Pamir KW - Tien Shan KW - strike-slip fault KW - intracontinental subduction Y1 - 2011 U6 - https://doi.org/10.1016/j.epsl.2011.02.012 SN - 0012-821X VL - 304 IS - 3-4 SP - 369 EP - 378 PB - ELSEVIER SCIENCE BV CY - AMSTERDAM ER - TY - JOUR A1 - Deeken, Anke A1 - Thiede, Rasmus Christoph A1 - Sobel, Edward A1 - Hourigan, J. K. A1 - Strecker, Manfred T1 - Exhumational variability within the Himalaya of northwest India JF - Earth & planetary science letters N2 - In the Himalaya of Chamba, NW India, a major orographic barrier in front of the Greater Himalayan Range extracts a high proportion of the monsoonal rainfall along its southern slopes and effectively shields the orogen interior from moisture-bearing winds. Along a similar to 100-km-long orogen perpendicular transect, 28 new apatite fission track (AFT) and 30 new zircon (U-Th)/He (ZHe) cooling ages reveal marked variations in age distributions and long-term exhumation rates between the humid frontal range and the semi-arid orogen interior. On the southern topographic front, very young, elevation-invariant AFT ages of <4 Ma have been obtained that are concentrated in a similar to 30-km-wide zone; 1-D-thermal modeling suggests a Plio-Pleistocene mean erosion rate of 0.8-1.9 mm yr(-1). In contrast, AFT and ZHe ages within the orogen interior are older (4-9 and 7-18 Ma, respectively), are positively correlated with sample elevation, and yield lower mean erosion rates (0.3-0.9 mm yr(-1)). Protracted low exhumation rates within the orogen interior over the last similar to 15 Myr prevailed contemporaneously with overall humid conditions and an effective erosional regime within the southern Himalaya. This suggests that the frontal Dhauladar Range was sufficiently high during this time to form an orographic barrier, focusing climatically enhanced erosional processes and tectonic deformation there. Thrusting along the two frontal range-bounding thrust, the Main Central Thrust and the Main Boundary Thrusts, was initiated at least similar to 15 Ma ago and has remained localized since then. The lack of evidence for localized uplift farther north indicates either a rather flat decollement with no ramp or the absence of active duplex systems beneath the interior of Chamba. Exhumational variability within Chamba is best explained as the result of continuous thrusting along a major basal decollement, with a flat beneath the slowly exhuming internal compartments and a steep frontal ramp at the rapidly exhuming frontal range. The pattern in Chamba contrasts with what is observed elsewhere along the Himalaya, where exhumation is focused in a zone similar to 150 km north of the orogenic front. In the NW Himalaya, preserved High Himalayan Crystalline nappes and Lesser Himalayan windows alternate on a relatively small scale of <100 km; these alternations are closely correlated with the pattern of exhumation. Although the spatial distribution of high-exhumation zones varies considerably between individual Himalayan sectors, all of these zones are closely correlated with locally higher rock-uplift rates, sharp topographic discontinuities, and focused orographic precipitation, suggesting strong feedbacks between tectonically driven rock uplift, orographically enhanced precipitation, and erosional processes. KW - apatite fission-track KW - zircon uranium-thorium-helium KW - thermochronology KW - exhumation KW - Himalaya KW - Haimantas Y1 - 2011 U6 - https://doi.org/10.1016/j.epsl.2011.02.045 SN - 0012-821X VL - 305 IS - 1-2 SP - 103 EP - 114 PB - Elsevier CY - Amsterdam ER -