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Compressional salt tectonics and synkinematic strata of the western K uqa foreland basin, southern T ian S han, C hina
Author(s) -
Li Shiqin,
Wang Xin,
Suppe John
Publication year - 2012
Publication title -
basin research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.522
H-Index - 83
eISSN - 1365-2117
pISSN - 0950-091X
DOI - 10.1111/j.1365-2117.2011.00531.x
Subject(s) - diapir , geology , foreland basin , salt tectonics , structural basin , sedimentary depositional environment , geochemistry , tectonics , canada basin , anticline , paleontology , geomorphology
The synkinematic strata of the K uqa foreland basin record a rich history of C enozoic reactivation of the P alaeozoic T ian S han mountain belt. Here, we present new constraints on the history of deformation in the southern T ian S han, based on an analysis of interactions between tectonics and sedimentation in the western K uqa basin. We constructed six balanced cross‐sections of the basin, integrating surface geology, well data and a grid of seismic reflection profiles. These profiles show that the Q iulitage fold belt on the southern edge of the K uqa basin developed by thin‐skinned compression salt tectonics. The structural styles have been influenced by two major factors: the nature of early‐formed diapirs and the basinward depositional limit of the K umugeliemu salt. Several early diapirs developed in the western K uqa basin, soon after salt deposition, which acted to localize the subsequent shortening. Where diapirs had low relief and a thick overburden they tended to tighten into salt domes 3000–7000 m in height. Conversely, where the original diapirs had higher relief and a thinner overburden they tended to evolve into salt nappes, with the northern flanks of the diapirs thrusting over their southern flanks. Salt was expelled forward, up dip along the mother salt layer, tended to accumulate at the distal pinch‐out of K umugeliemu salt located at the Q iulitage fold belt. Furthermore, the synkinematic strata (6–8 km thick) of the K uqa basin indicate that during the C enozoic reactivation of the T ian S han, shortening of the western K uqa basin was mainly in the hinterland until the early M iocene. Then, compression spread simultaneously southwards to the D awanqi anticline, the Q iulitage fold belt and the southernmost blind detachment fold at the end of M iocene. The western K uqa basin has a shortening of ca . 23 km. We consider that ca . 9 km was consumed from the end of the M iocene (5.2/5.8 Ma) to the early P leistocene (2.58 Ma) and another ca . 14 km have been absorbed since then. Thus, we obtain a ca . 3.4/2.8 mm year −1 average shortening from 5.2/5.8 to 2.58 Ma, followed by a 60–90% increase in average shortening rate to ca . 5.4 mm year −1 since 2.58 Ma. This suggests that the reactivation of the modern T ian S han has been accelerating up to the present day.