TY - JOUR

T1 - A constant slip rate for the western Qilian Shan frontal thrust during the last 200 ka consistent with GPS-derived and geological shortening rates

AU - Hetzel, Ralf

AU - Hampel, Andrea

AU - Gebeken, Pia

AU - Xu, Qiang

AU - Gold, Ryan

N1 - This paper benefited from thoughtful comments by Marie-Luce Chevalier and an anonymous reviewer that led to significant improvements of the final manuscript. We are grateful to Jessica Thompson Jobe for insightful comments on an early version of this manuscript. We thank A. Niehus for her help during preparation of the 10Be samples, A. Reschka for ICP-OES analysis of the quartz samples, and R. Wolff for his contribution to data analysis. We gratefully acknowledge funding for fieldwork and AMS.

PY - 2019/3/1

Y1 - 2019/3/1

N2 - Active thrust faulting at the front of the Qilian Shan accommodates the northeastward growth of the Tibetan Plateau, however, the lifespan of individual faults and their slip history on different timescales remain largely unknown. Here, we show that the main range-bounding thrust fault of the western Qilian Shan has accrued tectonic slip at an almost constant rate during the last ∼200 ka, and possibly since fault initiation in the mid-Miocene. Our finding is based on 10 Be ages from a flight of five deformed fluvial terraces along the Hongshuiba river, which constrain the vertical slip rate of the Qilian Shan frontal thrust to be 1.2±0.1 m/ka during the last 200 ka. With a fault dip of 30±5° constrained by seismic reflection data, we obtain a horizontal shortening rate of 2.0±0.3 m/ka. This value is consistent with both the short-term shortening rate of 1.7±0.3 mm/a derived from GPS data and the long-term shortening rate of 2.1±0.4 m/ka, which is based on a balanced geological cross-section. The latter provides a total shortening estimate of 25±3 km since the thrust fault initiated 12±2 Ma ago. The agreement between the shortening rates on the range of timescales between 10 0 and 10 7 years suggests that the western Qilian Shan frontal thrust has slipped at a steady rate since its initiation and implies that this fault is the main structure responsible for the growth of the western Qilian Shan.

AB - Active thrust faulting at the front of the Qilian Shan accommodates the northeastward growth of the Tibetan Plateau, however, the lifespan of individual faults and their slip history on different timescales remain largely unknown. Here, we show that the main range-bounding thrust fault of the western Qilian Shan has accrued tectonic slip at an almost constant rate during the last ∼200 ka, and possibly since fault initiation in the mid-Miocene. Our finding is based on 10 Be ages from a flight of five deformed fluvial terraces along the Hongshuiba river, which constrain the vertical slip rate of the Qilian Shan frontal thrust to be 1.2±0.1 m/ka during the last 200 ka. With a fault dip of 30±5° constrained by seismic reflection data, we obtain a horizontal shortening rate of 2.0±0.3 m/ka. This value is consistent with both the short-term shortening rate of 1.7±0.3 mm/a derived from GPS data and the long-term shortening rate of 2.1±0.4 m/ka, which is based on a balanced geological cross-section. The latter provides a total shortening estimate of 25±3 km since the thrust fault initiated 12±2 Ma ago. The agreement between the shortening rates on the range of timescales between 10 0 and 10 7 years suggests that the western Qilian Shan frontal thrust has slipped at a steady rate since its initiation and implies that this fault is the main structure responsible for the growth of the western Qilian Shan.

KW - Qilian Shan

KW - active faulting

KW - cosmogenic Be

KW - fault scarp

KW - fluvial terrace

KW - slip rate

UR - http://www.scopus.com/inward/record.url?scp=85059812051&partnerID=8YFLogxK

U2 - 10.1016/j.epsl.2018.12.032

DO - 10.1016/j.epsl.2018.12.032

M3 - Article

VL - 509

SP - 100

EP - 113

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

SN - 0012-821X

ER -