Search

The western Kunlun thrust belt defines the boundary between the stable Tarim Basin in the north and the intensely deformed Cenozoic Tibetan Plateau in the south. Because of its important tectonic position, understanding its tectonic evolution should have important implications for propagation of deformation from Tibet to its neighboring cratonal regions during India-Eurasia convergence. We here present new structural analyses based on field investigations and seismic reflection profiles across the Hotan-Tiklik segment of the western Kunlun thrust belt. The results indicate that the structural section crosses two major thrust zones: the Tiklik zone in the hinterland to the south and the Hotan zone in the foreland to the north. Within these, the Hotan thrust zone is thin skinned, with its deformation characterized by fault-bend folding and fault slipping along detachment layers, whereas the Tiklik thrust zone involves basement, with its deformation driven by the currently steeply dipping Tiklik fault. Results from apatite fission track thermochronology in combination with growth strata and balanced cross section indicate that the Hotan-Tiklik segment underwent two-stage deformation: (1) development of the Tiklik thrust during the late Oligocene–early Miocene and again since the mid- to late Miocene and (2) activity of the Hotan thrust since the mid- to late Miocene as a result of basinward propagation of thrusting. The balanced cross section, combined with the apatite fission track results, suggests that the Hotan-Tiklik segment contributes a total shortening magnitude of more than ca. 34 ± 6 km. Within this, ca. 4 ± 2 and ca. 23 ± 1 km of the shortenings were absorbed by the Hotan anticline and the Hotan detachment fault, respectively, both of which were related to detachment layers. This suggests that detachment layers played an efficient role in propagating deformation from the western Tibetan Plateau into the Tarim Basin. [ABSTRACT FROM AUTHOR]

The amount of fault slip and timing of fault activation are two fundamental elements of quantitatively structural analysis. Currently, these two parameters are mainly determined by the geometry of fault-related folds and the growth strata over the fault ramp. In this study, we propose a new type of growth strata that directly constrain both the amount of fault slip and the timing of fault activity at the fault flat based on interpretations of seismic reflection profiles and related numerical modeling of the Manan Structure along the southern Tarim Basin. The seismic sections show a rootless synform beyond the north limb of the Manan Anticline with the hinge dipping toward north. Numerical modeling suggests that this synform is a result of northward migration of the growth strata along with the slip of the underlying detachment thrust with a bulge at the fault surface. We define this type of growth strata 'migrating growth strata (MGS)'. The dipping direction of the hinge of the synform marks the slip direction, the projecting distance of the hinge on the fault surface measures the slip amount, and the timing of the MGS represent the timing of the activity of the underlying detachment thrust. Analyses of the Manan MGS along the southern Tarim Basin suggest ∼13–22 km of northward fault slip passed by the Manan Structure along the basal Cenozoic detachment and was finally absorbed by the Mazatagh Belt, which confirms a ∼230-km-long detachment thrust along the southern Tarim Basin and provide key evidence to establish a kinematic linkage between the Hotan and Mazatagh Belts. Two-segment style of the hinge of the synform indicates that the Manan Structure has undergone two-stage evolution related to the lower Cambrian and the basal Cenozoic detachments, respectively. These results imply that detachments in difference depths and their sequential activities are key in transmitting strain from the Tibetan Plateau into the Eurasian continental interiors. • Seismic sections show a rootless synform in Manan Structure, southern Tarim Basin. • The synform was produced by growth strata migrating with the detachment thrust. • Such a structure was defined as 'migrating growth strata (MGS)'. • MGS provide a new tool for quantitatively analyzing the fold-thrust belts. • The results demonstrate a ∼230-km-long detachment thrust in southern Tarim Basin. [ABSTRACT FROM AUTHOR]

Paleo-uplift is one of the main controlling factors that influence the style of deformation in salt-bearing fold-and-thrust belt (FTB). Whereas, how paleo-uplift amplitude influences salt-related deformations in FTB remains unclear. Here we designed four series of experimental models that contain a basal brittle décollement and a shallow ductile décollement. Our studies show that the presence of paleo-uplift in the ductile décollement has a profound impact on deformation propagation in the supra-salt overburden during the contraction, which localizes shortening strain in the proximal and central parts of the models and deters rapid deformation propagation towards the distal part. As the amplitude of the paleo-uplift increases, its influence on deformation propagation becomes stronger, resulting in out-of-sequence deformation towards the hinterland. The increase of paleo-uplift amplitude also controls the distribution and migration of rock salt during the contraction. Particularly, when the paleo-uplift height equals or exceeds the thickness of salt layer, the position of salt pinch-out or welding point localizes shortening strain and thereby initiates folding and thrusting deformation over the salt-base high. This process leads to salt fed into the fold and fault belt over the paleo-high and the uplift of the supra-salt layers. Our modeling results are highly comparable with natural examples of Kuqa FTB and provide insights to the salt-influenced deformations in the Qiulitage structural belt. • The presence of paleo-uplift has a profound impact on deformation propagation in the supra-salt overburden. • The increase of paleo-uplift amplitude controls the distribution and migration of rock salt during the contraction. • Higher amplitude paleo-uplift results in localized deformation and salt thickening. [ABSTRACT FROM AUTHOR]

The Western Kunlun ranges and its foreland basin, the Tarim Basin, define the northwestmargin of the Tibetan Plateau, and provide important information on the Cenozoic expansionof the plateau after the India-Asia collision. In this study, we present a high-resolutionseismic reflection profile along the Hotan-Mazatagh transect of the Western Kunlun thrustsbelt in order to decipher the distribution of deformation and its propagation. Deformation inthis transect can be separated into three roughly east-west striking structures fromthe south to the north: the Hotan anticline, the Manan anticline, and the Mazataghthrust belt. The Hotan anticline is a fault-bend fold, mainly formed by the hangingwall sliding from the lower decóllement along the lower Cambrian units over apre-existing fault ramp into the upper decóllement that is located at the base ofthe Cenozoic strata. The Manan anticline, located ∼100 km north to the Hotananticline, is a reactivated low-amplitude fold with decreasing deformation upwards, theformation of which is mainly controlled by the lower decóllement. The Mazatagh thrustbelt, located ∼230 km north to the Hotan anticline, is controlled by both the upperdecóllement and the lower decóllement with the former ramping to the surface and thelatter building the Mazatagh anticline. The balanced cross-section reveals a totaldeformation of ∼28.93 km along this transect, with most deformation (∼25.0 km)transmitted by the upper decóllement among which at least 7.7 km of shortening hasbeen accommodated by the layer parallel compaction. The rest of shortening hasbeen absorbed by the Manan anticline (0.17 km) and the Mazatagh anticline (∼3.7km), respectively, transmitted along the lower decóllement. Our study highlightsthe effects of decóllement layer on transmitting deformation from the orogen intothe intracontinental region, the pre-existing structures on localizing distribution,and the penetrative strain on accommodating relatively homogeneous shortening. [ABSTRACT FROM AUTHOR]