TY - JOUR
T1 - Evaluating young fluvial terrace riser degradation using a nonlinear transport model
T2 - Application to the Kongur Normal Fault in the Pamir, northwest China
AU - Xu, Jianhong
AU - Arrowsmith, J. Ramón
AU - Chen, Jie
AU - Schoenbohm, Lindsay M.
AU - Li, Tao
AU - Yuan, Zhaode
AU - Owen, Lewis A.
N1 - Funding Information:
This research was supported by the National Natural Science Foundation of China (Grant Numbers: 41802229 and 41772221) and the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (2019QZKK0901). We thank Zhanyu Wei and Peng Su for the meaningful discussions. We also thank Wenqiao Li and Edward R. Sobel for their help in the field work. We are greatly thankful for constructive and thoughtful comments of anonymous reviewers and editors
Publisher Copyright:
© 2020 John Wiley & Sons, Ltd.
PY - 2021/1
Y1 - 2021/1
N2 - Selecting an appropriate hillslope transport model and calibrating model parameters are essential for morphological dating of fault and fluvial scarps. In this paper, we refine the method of profile-based morphologic dating by updating the representation of nonlinearity in sediment flux dependence on the hillslope gradient. We apply this revised method to fluvial scarps bounding fluvial terraces offset along the Kongur Normal Fault in the semi-arid high-altitude Pamir mountains, northwestern China. One of these terraces, the T3 surface, is dated to 7.0+1.9/−1.6 kyr using 10Be cosmogenic depth profile analysis. Well-preserved, dated terraces make this an ideal site to test the utility of morphological modelling in constraining ages of the young terrace risers. To do this, 35 topographic swath profiles across the terrace risers are extracted from a 0.2 m-resolution digital elevation model produced using structure from motion from photos collected by an unmanned aerial vehicle. The best estimates of morphological age are 13.9 ± 1.3 m2 for the riser T3/T4 and 11.9 ± 1.3 m2 for T2/T3 using a linear diffusion approach. These two morphological ages overlap within uncertainty and fail to distinguish between two young terrace risers. Alternatively, we employed a nonlinear diffusion model, calibrated with transport constant k = 1 m2 kyr−1, nonlinearity n = 2, and critical gradient Sc = tan(33°). This nonlinear model produces ages of 7.3 ± 0.5 kyr for T3/T4 and 4.0 ± 0.2 kyr for T2/T3; these ages are consistent with terrace surface ages deduced by using vertical offset divided by independently determining average throw rate. This comparison shows the advantage of a nonlinear model in defining ages of young scarps. Furthermore, we explored the minor effect of heterogeneous degradation along steep sections of the scarp profiles. The nonlinear scarp modelling scheme we develop in this paper is suitable for studying scarp degradation in other regions.
AB - Selecting an appropriate hillslope transport model and calibrating model parameters are essential for morphological dating of fault and fluvial scarps. In this paper, we refine the method of profile-based morphologic dating by updating the representation of nonlinearity in sediment flux dependence on the hillslope gradient. We apply this revised method to fluvial scarps bounding fluvial terraces offset along the Kongur Normal Fault in the semi-arid high-altitude Pamir mountains, northwestern China. One of these terraces, the T3 surface, is dated to 7.0+1.9/−1.6 kyr using 10Be cosmogenic depth profile analysis. Well-preserved, dated terraces make this an ideal site to test the utility of morphological modelling in constraining ages of the young terrace risers. To do this, 35 topographic swath profiles across the terrace risers are extracted from a 0.2 m-resolution digital elevation model produced using structure from motion from photos collected by an unmanned aerial vehicle. The best estimates of morphological age are 13.9 ± 1.3 m2 for the riser T3/T4 and 11.9 ± 1.3 m2 for T2/T3 using a linear diffusion approach. These two morphological ages overlap within uncertainty and fail to distinguish between two young terrace risers. Alternatively, we employed a nonlinear diffusion model, calibrated with transport constant k = 1 m2 kyr−1, nonlinearity n = 2, and critical gradient Sc = tan(33°). This nonlinear model produces ages of 7.3 ± 0.5 kyr for T3/T4 and 4.0 ± 0.2 kyr for T2/T3; these ages are consistent with terrace surface ages deduced by using vertical offset divided by independently determining average throw rate. This comparison shows the advantage of a nonlinear model in defining ages of young scarps. Furthermore, we explored the minor effect of heterogeneous degradation along steep sections of the scarp profiles. The nonlinear scarp modelling scheme we develop in this paper is suitable for studying scarp degradation in other regions.
KW - Kongur Normal Fault
KW - Pamir
KW - fluvial terrace riser
KW - nonlinear transport model
KW - structure from motion (SfM)
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U2 - 10.1002/esp.5022
DO - 10.1002/esp.5022
M3 - Article
AN - SCOPUS:85096754715
SN - 0197-9337
VL - 46
SP - 280
EP - 295
JO - Earth Surface Processes and Landforms
JF - Earth Surface Processes and Landforms
IS - 1
ER -