Spatial pattern of erosion rates in the northern Chinese Tian Shan constrained by fluvial geomorphologic data

Authors: Dengyun Wu*, East China Normal University, Honghua Lu, East China Normal University
Topics: Geomorphology
Keywords: paleogeomorphology, fluvial terrace, erosion, Quaternary, the Tian Shan
Session Type: Paper
Day: 4/5/2019
Start / End Time: 1:10 PM / 2:50 PM
Room: Jackson, Marriott, Mezzanine Level
Presentation File: No File Uploaded

This work focuses on the spatial pattern of erosion rates of four typical rivers in the northern Chinese Tian Shan that have been constrained by river terraces. For each analyzed river, one of the defined terraces (terrace T5 of the Kuitun River, terrace T5 of the Jingou River, terrace T5 of the Manas River, and terrace T4 of the Urumqi River) is used as the reference surface for the reconstruction of the paleogeomorphology before the previous floodplain was abandoned as a terrace due to river incision. By comparing the reconstructed topography and the present-day one and after the porosity correction, the erosion volumes of the four rivers basin since formation of the reference terrace are estimated. When combined with the formation ages of the reference terraces, the erosion rates are estimated to 5.10 ± 1.85 mm/y (the Kuitun River), 3.53 ± 1.38 mm/y (the Jingou River), 3.38 ± 1.63 mm/y (the Manas River), and 0.91±0.60 mm/y (the Urumqi River), respectively. These rates display a noticeable trend of decreasing eastward from the Kuitun River to the Urumqi River. Our analyses indicate that the climate (precipitation) and the lithology cannot explain this observed spatial pattern of erosion rates. Instead, the observed pattern is in agreement with the changes of the slope, relief, and most importantly the N-S crustal shortening across the range. We thus propose that the tectonic factor is the first-order factor controlling the erosion and further the landscape evolution of the northern Chinese Tian Shan range.

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