Late Quaternary active faulting on the inherited Baoertu basement fault
within the eastern Tian Shan: Implications for regional tectonic
deformation and slip partitioning, NW China
Abstract
The deformation pattern and slip partitioning related to oblique
underthrusting of the Tarim Basin in the eastern Tian Shan are not well
understood because of the lack of interior deformation images. The
Baoertu fault (BF) is an E-W-striking, ~350 km-long
reactivated basement structure within the eastern Tian Shan. In this
study, we quantify its late Quaternary activity based on detailed
high-resolution remote sensing image interpretations and field
investigations. Three field observation sites along an
~80 km-long fault segment indicate that the BF is
characterized by sinistral thrust faulting. Based on surveying of the
displaced geomorphic surfaces with an unmanned drone and dating of the
late Quaternary sediments using radiocarbon and optically stimulated
luminescence (OSL) methods, we estimate a late Quaternary left-lateral
strike-slip rate of 1.87 ± 0.29 mm/yr and a N-S shortening rate of 0.26
± 0.04 mm/yr for this fault. The lithospheric BF acts as a decoupling
zone and accommodates the left-lateral shearing caused by the oblique
underthrusting of the Tarim block. In the eastern Tian Shan, the oblique
convergence is partitioned into thrust faulting across the entire range
and sinistral slip faulting on the high-dip basement structure within
the orogen. This active faulting pattern in the eastern Tian Shan of
sinistral shearing in the center and thrust faulting at both sides can
be viewed as giant positive flower structures.