Origin of Late Quaternary Gravel and Drainage Basin Expansion in the Northern Chinese Tian Shan: Insights From Sediment Provenance Analyses. Issue 5 (21st May 2022)

• Record Type: Journal Article
• Authors: Lu, Honghua; Jiang, Yutong; Li, Bingjing; Pang, Jianzhang; Wu, Dengyun; Pang, Lichen; Zheng, Xiangmin; Li, Youli
• Is Part Of: Journal of geophysical research. Volume 127:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-21
• Subjects: provenance analysis -- topographic evolution -- glacial erosion -- late Quaternary -- the Tian Shan; Geomorphology -- Periodicals; 551.3
• DOI: 10.1029/2021JF006472
• Languages: English
• ISSNs: 2169-9003

Abstract

Abstract: The source‐to‐sink relationship between a sedimentary basin and its adjacent mountain range is vital for understanding the genesis of piedmont coarse‐grained sediments and the evolution of mountain topography. By integrating zircon U‐Pb dating and heavy mineral assemblage analyses on 15 samples, this work focuses on the change of the provenance with time in the Urumqi River Neogene‐Pleistocene continental sequence in the northern Chinese Tian Shan foreland, which has been chronologically constrained to range from ∼6.8 to ∼0.55 Ma. The results of the integrated provenance analyses reveal two shifts in provenance during the periods of 4.6–2.5 and 0.9–0.55 Ma, yielding new zircon U‐Pb age signals from the glacier‐covered headwaters of the Urumqi River. These two identified provenance adjustments are causally related to enhanced glacial erosion in the high mountain. We propose that enhanced glacial erosion could have caused southward expansion of the Urumqi River drainage basin, increased production of coarse‐grained materials with new zircon U‐Pb age signals, and finally accumulation of piedmont alluvial gravel. The observed topographic and sedimentary responses to enhanced glaciation could have been common phenomena during the late Quaternary in alpine areas, where a large number of alluvial fans are widely distributed like aprons along the mountain front, as seen in the piedmonts of the Tian Shan in the arid interior of Asia. Plain Language Summary: Globally, a prominent geomorphic feature is that numerous late Quaternary alluvial fans are extensively distributed like aprons along the mountain front of active orogenic belts. The gravel of these alluvial fans and the underlying Neogene‐Early Pleistocene fluvio‐lacustrine sediments constitute an upward‐coarsening sedimentary succession. Open discussions persist about what mechanism has promoted origin of coarse‐grained sediments in this sequence. Understanding the change of the provenance with time in this sequence can bridge source and sink, and thus is helpful for deciphering this issue. Here we present a detailed provenance analysis on the Urumqi River Neogene‐Pleistocene sediments in the northern piedmont of the Chinese Tian Shan. Our results reveal that enhanced glacial erosion during the Quaternary could have caused expansion of the Urumqi River drainage basin, production of coarse‐grained materials with new source signals from the glacier‐covered headwaters of the river, and finally accumulation of piedmont alluvial gravel. Given the fact that numerous alluvial fans are widely distributed along the mountain front of active orogenic belts, as seen in the piedmonts of the Tian Shan, we propose that the observed topographic and sedimentary responses to enhanced glacial erosion could have been a common phenomenon during the Quaternary in alpine areas of the world. Key Points: Two shifts in sediment provenance in the Urumqi River drainage basin are identified by integrated provenance analyses Timing of the two source adjustments is determined during the periods of 4.6–2.5 and 0.9–0.55 Ma, respectively Causal linkages of source area expansion and origin of piedmont alluvial gravel with enhanced glacial erosion are proposed