Abstract
AbstractInvestigation on the kinematics and deformation rates about active fault interior of the Tian Shan can provide significant information for strengthening our understanding on the present tectonic evolution of this range. The Baoertu Fault (BETF) is a major E-W striking active structure within the eastern Tian Shan and separates the south and central Tian Shan. But its kinematics and slip rates in the late Quaternary have never been systematically reported before. Based on interpretations of remote sensing images, drone photography, and detailed field investigations, we propose that the BETF is characterized by left-lateral strike-slip faulting with a thrust component and provides the first late Pleistocene slip rate for this fault. At the northern margin of the Kumishi Basin, combining offset reconstructions of displaced alluvial fan surfaces with the terrestrial cosmogenic nuclide (TCN) exposure age dating, we calculate an average sinistral slip rate of 0.65±0.16 mm/yr and average vertical slip rate of 0.07±0.01 mm/yr for the BETF since 95-106 ka. The differential movement eastward between the central Tian Shan block and Yanqi-Kumishi Basin block is likely the dominant driver of the left-lateral slip of the BETF. Synthesizing other quantitative data in eastern Tian Shan, we suggest that the hinterland active faults or folds, including the BEFT, roughly accommodate ~28-45% of the total N-S convergence across the eastern Tian Shan.
Highlights
The Tian Shan is one of the most intensely deformed and seismically active intracontinental mountain belts in the world, which extends for nearly 2500 km from Uzbekistan in the west to NW China in the east (Figure 1(b))
Due to the semiarid climate in the eastern Tian Shan, a sequence of late Quaternary alluvial fans are well preserved on the piedmont along the northwestern margin of the Kumishi Basin
At the northern margin of the Kumishi Basin, numerous left-laterally displaced channels on late Quaternary alluvial fans are observed at the BET01, BET02, and BET03 sites, and the disproportionate ratios of horizontal to vertical displacement suggest that BEFT is a left-lateral strike-slip fault with a reverse component
Summary
The Tian Shan is one of the most intensely deformed and seismically active intracontinental mountain belts in the world, which extends for nearly 2500 km from Uzbekistan in the west to NW China in the east (Figure 1(b)). This intracontinental range was reactivated due to the ongoing collision between the India and Eurasia plates during the Cenozoic [1,2,3,4]. Global Positioning System (GPS) measurements indicate that the western Tian Shan has accommodated ~20 mm/yr northsouth crustal shortening [7,8,9], nearly half amount of the northward indentation of the India Plate.
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