TY - JOUR A1 - Bufe, Aaron A1 - Burbank, Douglas W. A1 - Liu, Langtao A1 - Bookhagen, Bodo A1 - Qin, Jintang A1 - Chen, Jie A1 - Li, Tao A1 - Jobe, Jessica Ann Thompson A1 - Yang, Huili T1 - Variations of Lateral Bedrock Erosion Rates Control Planation of Uplifting Folds in the Foreland of the Tian Shan, NW China JF - Journal of geophysical research : Earth surface N2 - Fluvial planation surfaces, such as straths, commonly serve as recorders of climatic and tectonic changes and are formed by the lateral erosion of rivers, a process that remains poorly understood. Here we present a study of kilometer-wide, fluvially eroded, low-relief surfaces on rapidly uplifting folds in the foreland of the southwestern Tian Shan. A combination of field work, digital elevation model analysis, and dating of fluvial deposits reveals that despite an arid climate and rapid average rock-uplift rates of 1-3mm/yr, rivers cut extensive (>1-2km wide) surfaces with typical height variations of <6m over periods of >2-6kyr. The extent of this beveling varies in space and time, such that different beveling episodes affect individual structures. Between times of planation, beveled surfaces are abandoned, incised, and deformed across the folds. In a challenge to models that link strath cutting and abandonment primarily to changes in river incision rates, we demonstrate that lateral erosion rates of antecedent streams crossing the folds have to vary by more than 1 order of magnitude to explain the creation of beveled platforms in the past and their incision at the present day. These variations do not appear to covary with climate variability and might be caused by relatively small (much less than an order of magnitude) changes in sediment or water fluxes. It remains uncertain in which settings variations in lateral bedrock erosion rates predominate over changes in vertical erosion rates. Therefore, when studying fluvial planation and strath terraces, variability of both lateral and vertical erosion rates should be considered. KW - strath terraces KW - lateral erosion KW - detachment folds KW - Quaternary geochronology Y1 - 2017 U6 - https://doi.org/10.1002/2016JF004099 SN - 2169-9003 SN - 2169-9011 VL - 122 SP - 2431 EP - 2467 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Bufe, Aaron A1 - Bekaert, David P. S. A1 - Hussain, Ekbal A1 - Bookhagen, Bodo A1 - Burbank, Douglas W. A1 - Jobe, Jessica Ann Thompson A1 - Chen, Jie A1 - Li, Tao A1 - Liu, Langtao A1 - Gan, Weijun T1 - Temporal changes in rock uplift rates of folds in the foreland of the Tian Shan and the Pamir from geodetic and geologic data JF - Geophysical research letters N2 - Understanding the evolution of continental deformation zones relies on quantifying spatial and temporal changes in deformation rates of tectonic structures. Along the eastern boundary of the Pamir-Tian Shan collision zone, we constrain secular variations of rock uplift rates for a series of five Quaternary detachment- and fault-related folds from their initiation to the modern day. When combined with GPS data, decomposition of interferometric synthetic aperture radar time series constrains the spatial pattern of surface and rock uplift on the folds deforming at decadal rates of 1-5mm/yr. These data confirm the previously proposed basinward propagation of structures during the Quaternary. By fitting our geodetic rates and previously published geologic uplift rates with piecewise linear functions, we find that gradual rate changes over >100kyr can explain the interferometric synthetic aperture radar observations where changes in average uplift rates are greater than similar to 1 mm/yr among different time intervals (similar to 10(1), 10(4-5), and 10(5-6) years). KW - InSAR KW - Tian Shan KW - folds KW - uplift rate changes KW - geologic versus geodetic rates KW - continental neotectonics Y1 - 2017 U6 - https://doi.org/10.1002/2017GL073627 SN - 0094-8276 SN - 1944-8007 VL - 44 SP - 10977 EP - 10987 PB - American Geophysical Union CY - Washington ER -