TY - JOUR A1 - Thompson, Jessica A. A1 - Chen, Jie A1 - Yang, Huili A1 - Li, Tao A1 - Bookhagen, Bodo A1 - Burbank, Douglas T1 - Coarse- versus fine-grain quartz OSL and cosmogenic Be-10 dating of deformed fluvial terraces on the northeast Pamir margin, northwest China JF - Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques N2 - Along the NE Pamir margin, flights of late Quaternary fluvial terraces span actively deforming fault-related folds. We present detailed results on two terraces dated using optically stimulated luminescence (OSL) and cosmogenic radionuclide Be-10 (CRN) techniques. Quartz OSL dating of two different grain sizes (4-11 mu m and 90-180 mu m) revealed the fine-grain quartz fraction may overestimate the terrace ages by up to a factor of ten. Two-mm, small-aliquot, coarse-grain quartz OSL ages, calculated using the minimum age model, yielded stratigraphically consistent ages within error and dated times of terrace deposition to similar to 9 and similar to 16 ka. We speculate that, in this arid environment, fine-grain samples can be transported and deposited in single, turbid, and (sometimes) night-time floods that prevent thorough bleaching and, thereby, can lead to relatively large residual OSL signals. In contrast, sand in the fluvial system is likely to have a much longer residence time during transport, thereby providing greater opportunities for thorough bleaching. CRN Be-10 depth profiles date the timing of terrace abandonment to similar to 8 and similar to 14 ka: ages that generally agree with the coarse-grain quartz OSL ages. Our new terrace age of similar to 13-14 ka is broadly consistent with other terraces in the region that indicate terrace deposition and subsequent abandonment occurred primarily during glacial-interglacial transitions, thereby suggesting a climatic control on the formation of these terraces on the margins of the Tarim Basin. Furthermore, tectonic shortening rates calculated from these deformed terraces range from similar to 1.2 to similar to 4.6 mm/a and, when combined with shortening rates from other structures in the region, illuminate the late Quaternary basinward migration of deformation to faults and folds along the Pamir-Tian Shan collisional interface. KW - Tectonic geomorphology KW - Deformation KW - Quaternary terraces KW - Pamir KW - Tian shan Y1 - 2018 U6 - https://doi.org/10.1016/j.quageo.2018.01.002 SN - 1871-1014 SN - 1878-0350 VL - 46 SP - 1 EP - 15 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kirby, Eric A1 - Whipple, Kelin X. T1 - Expression of active tectonics in erosional landscapes JF - Journal of structural geology N2 - Understanding the manner and degree to which topography in active mountain ranges reflects deformation of the Earth's surface remains a first order goal of tectonic geomorphology. A substantial body of research in the past decade demonstrates that incising channel systems play a central role in setting relationships among topographic relief, differential rock uplift rate, and climatically modulated erosional efficiency. This review provides an introduction to the analysis and interpretation of channel profiles in erosional mountain ranges. We show that existing data support theoretical expectations of positive, monotonic relationships between channel steepness index, a measure of channel gradient normalized for downstream increases in drainage area, and erosion rate at equilibrium, and that the transient response to perturbations away from equilibrium engenders specific spatial patterns in channel profiles that can be used to infer aspects of the forcing. These aspects of channel behavior lay the foundation for a series of case studies that we use to illustrate how focused, quantitative analysis of channel morphology can provide insight into the spatial and temporal dynamics of active deformation. Although the complexities of river response to climate, lithology, and uplift patterns mean that multiple interpretations of topographic data alone will always possible, we show that application of stream profile analysis can be a powerful reconnaissance tool with which to interrogate the rates and patterns of deformation in active mountain belts. KW - Tectonic geomorphology KW - Active tectonics KW - River profiles KW - Neotectonics Y1 - 2012 U6 - https://doi.org/10.1016/j.jsg.2012.07.009 SN - 0191-8141 VL - 44 SP - 54 EP - 75 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Gao, Mingxing A1 - Zeilinger, Gerold A1 - Xu, Xiwei A1 - Wang, Qingliang A1 - Hao, Ming T1 - DEM and GIS analysis of geomorphic indices for evaluating recent uplift of the northeastern margin of the Tibetan Plateau, China JF - Geomorphology : an international journal on pure and applied geomorphology N2 - The northeastern margin of the Tibetan Plateau is a tectonically active region consisting of a series of faults with bounded intermountain basins and is located in the transition zone between the Tibetan Plateau and the Loess Plateau. Active deformation that may affect the topography in this region can be quantified using geomorphic indices. Therefore, we applied geomorphic indices such as the hypsometric integral and the stream length gradient index to infer neo-tectonics in the northeastern margin of the Tibetan Plateau. Different time-scaled geodetic leveling data and river incision rates were also integrated into the investigation. The results show that the hypsometric integrals are not significantly affected by lithology but spatially correspond to the hanging walls of thrust faults. The hypsometric integrals are also positively correlated with the leveling data. Although the stream length gradient index is influenced by lithology, its most pronounced anomalies of the stream length gradient are associated with the thrust faults. Consequently, the uplift in the northeast margin of the Tibetan Plateau appeared to be concentrated along the hanging walls of the thrust faults. KW - Tectonic geomorphology KW - Hypsometry analysis KW - Stream length gradient KW - Active tectonics KW - Leveling data KW - Tibetan Plateau Y1 - 2013 U6 - https://doi.org/10.1016/j.geomorph.2013.02.008 SN - 0169-555X VL - 190 IS - 20 SP - 61 EP - 72 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kirby, Eric A1 - Harkins, Nathan T1 - Distributed deformation around the eastern tip of the Kunlun fault JF - INTERNATIONAL JOURNAL OF EARTH SCIENCES N2 - Whether active strain within the Indo-Asian collision zone is primarily localized along major strike-slip fault systems or is distributed throughout the intervening crust between faults remains uncertain. Despite refined estimates of slip rates along many of the major fault zones, relatively little is known about how displacement along these structures is accommodated at fault terminations. Here, we show that a systematic decrease in left-lateral slip rates along the eastern similar to 200 km of the Kunlun fault, from > 10 mm/year to < 1 mm/year, is coincident with high topography in the Anyemaqen Shan and with a broad zone of distributed shear and clockwise vorticity within the Tibetan Plateau. Geomorphic analysis of river longitudinal profiles, coupled with inventories of cosmogenic radionuclides in fluvial sediment, reveal correlated variations in fluvial relief and erosion rate across the Anyemaqen Shan that reflect ongoing differential rock uplift across the range. Our results imply that the termination of the Kunlun fault system is accommodated by a combination of distributed crustal thickening and by clockwise rotation of the eastern fault segments. KW - Tibetan plateau KW - Active tectonics KW - Tectonic geomorphology KW - Strike-slip faults Y1 - 2013 U6 - https://doi.org/10.1007/s00531-013-0872-x SN - 1437-3254 SN - 1437-3262 VL - 102 IS - 7 SP - 1759 EP - 1772 PB - SPRINGER CY - NEW YORK ER -