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Late Pleistocene/Holocene slip rate of the Zhangye thrust (Qilian Shan, China) and implications for the active growth of the northeastern Tibetan Plateau
Author(s) -
Hetzel Ralf,
Tao Mingxin,
Stokes Stephen,
Niedermann Samuel,
IvyOchs Susan,
Gao Bo,
Strecker Manfred R.,
Kubik Peter W.
Publication year - 2004
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2004tc001653
Subject(s) - geology , fault scarp , thrust fault , alluvial fan , fault (geology) , quaternary , slip (aerodynamics) , seismology , holocene , pleistocene , geomorphology , alluvium , paleontology , sedimentary rock , physics , thermodynamics
We derive a slip rate for a thrust at the central Qilian Shan mountain front by combining structural investigations, satellite imagery, topographic profiling, luminescence dating, and 10 Be exposure dating. The seismically active Zhangye thrust transects late Pleistocene alluvial fan deposits and forms a prominent north facing scarp. The fault consists of two segments that differ in orientation, scarp height, and age. A series of loess‐covered terraces records the uplift history of the western thrust segment. Loess accumulation on all terraces started at 8.5 ± 1.5 kyr and postdates terrace formation. Gravels from the highest terrace yielded a 10 Be exposure age of 90 ± 11 kyr, which dates the onset of faulting. With a displacement of 55–60 m derived from fault scarp profiles, this yields a vertical slip rate of 0.64 ± 0.08 mm yr −1 . Along the eastern thrust segment, three 10 Be ages from the uplifted alluvial fan constrain that faulting started at ∼31 ± 5 kyr. Together with a displacement of 25–30 m this leads to a vertical faulting rate of 0.88 ± 0.16 mm yr −1 . A dip estimate of 40° to 60° for the fault plane combined with lower and upper limits of ∼0.6 and ∼0.9 mm yr −1 for the vertical slip rate gives minimum and maximum horizontal shortening rates of 0.4 and 1.1 mm yr −1 across the Zhangye thrust. Our results are consistent with geologic and GPS constraints, which suggest that NNE directed shortening across the northeastern Tibetan Plateau is distributed on several active faults with a total shortening rate of 4 to 10 mm yr −1 .