Influence of Overlapping décollements, Syntectonic Sedimentation, and Structural Inheritance in the Evolution of a Contractional System: The Central Kuqa Fold‐and‐Thrust Belt (Tian Shan Mountains, NW China)

Abstract

Contractional deformation in the Kuqa fold-and-thrust belt (southern foreland of the Tian Shan Mountains, NW China) is recorded by well-preserved syntectonic continental sequences. In addition, its structural evolution was strongly controlled by synorogenic salt (Eocene in age) and presalt décollements with varying spatial distribution. We present a balanced and sequentially restored cross section across the central part of this fold-and-thrust belt that provides a new interpretation of the structure beneath the evaporites, in which Paleozoic and Mesozoic strata are deformed by a thrust stack involving (i) a thin-skinned thrust system detached on Triassic-Jurassic coal units and (ii) an ensemble of south-directed basement thrusts. The latter formed from the inversion of Mesozoic extensional faults such as those preserved both in the Tarim foreland basin and beneath the frontal part of the Kuqa fold-and-thrust belt. The constructed section shows a total shortening of 35 km from the Late Cretaceous to the present. The restoration depicts a three-stage evolution for the Kuqa fold-and-thrust belt: (i) minor Mesozoic extension, (ii) an early compressional stage (Late Cretaceous to early Miocene) with low shortening and syntectonic sedimentary rates, and (iii) a later compressional stage (late Pliocene-Pleistocene) characterized by a greater and progressively increasing shortening rate and rapid deposition. Our results are discussed in light of previous analogue and numerical modeling studies and demonstrate the control exerted by the interplay between syntectonic sedimentation, the inversion of inherited basement structures, and the nature and extent of Triassic/Jurassic and Eocene décollements.

Structure and kinematics of the Central Sivas Basin (Turkey): salt deposition and tectonics in an evolving fold-and-thrust belt

“…Such deformation involving synorogenic salt has also been described in natural cases (Figure 15): in the Eastern Southern Pyrenees (e.g. Krzywiec and Vergés 2007), in the Eastern Carpathian fold-thrust belt (Stefanescu et al 2000), in the Dezful Embayment of the Zagros fold-thrust belt (Sherkati et al 2005;Najafi et al 2018) or in the Kuqa fold-thrust belt (Chen et al 2004;Hubert-Ferrari et al 2007;Zhao & Wang 2016;Izquierdo-Llavall et al 2018). However, none of these examples ever recorded the emplacement of a salt canopy, and thus of a supplementary décollement level, as in the Sivas Basin.…”

Preorogenic Folds and Syn‐Orogenic Basement Tilts in an Inverted Hyperextended Margin: The Northern Pyrenees Case Study

“…When fold-and-thrust systems involve evaporitic décollements, their geometry significantly differs from that of fold-and-thrust belts dominated by basement faults or detached over a frictional (shale-like) décollement (Callot et al, 2012;Costa & Vendeville, 2002;Coward, 1983;Davis & Engelder, 1985). In general terms, the presence of evaporitic levels enhances (i) out-of-sequence faulting (Letouzey et al, 1995;Santolaria et al, 2015), (ii) quick propagation of contractional deformation towards the foreland (Izquierdo-Llavall et al, 2018;Luján et al, 2003;Pla et al, 2019), and (iii) strong if not complete decoupling between supra-décollement structures and basement features developed underneath (Vendeville et al, 1995). In this scenario, the full understanding of fold-and-thrust systems that reactivate previous extensional basins and involve evaporites requires both (i) the proper distinction between early extensional and later contractional structures and (ii) the proper characterization of cover and basement features and their evolution through time.…”

Nature and origin of large-scale and intrasalt deformation within the Wieliczka salt mine, Poland

“…Not only are the Paleogene evaporites in volved in the fron tal de for ma tion, but they con tain interbedded siliciclastics and re worked/slumped evaporites (e.g., Carrillo et al, 2014). An other an a log is the Kuqa Ba sin of NW China, in the foot hills of the Tien Shan Moun tains, where the fron tal thrust is de tached in Palaeogene LES that have signif i cant lat eral and hin ter land-to-fore land vari a tions in the propor tions and fa cies of interbedded siliciclastics (e.g., Liu et al, 2008;Izquierdo-Llavall et al, 2018).…”