Abstract
With the latest uplift episode of Tian Shan occurring since early Miocene, a series of thrust–fold belts were formed in front of Tian Shan. The Kashi foreland thrust–fold belt (KFTB) provided a unique case to understand the ongoing intracontinental deformation within the Pamir–Tian Shan convergence zone (PTCZ). Previous cosmogenic nuclide chronological studies on growth folds suggested that the young thrust–fold belt in front of Pamir formed during 6–1.07 Ma. However, the age constraints of late Cenozoic deformation in front of southwestern Tian Shan are still debated. In this study, we attempt to constrain the initial deformation time of the NEE-striking Atushi anticline (ATA) in the KFTB through the cosmogenic nuclide burial dating data of growth strata near the boundary between Pliocene–Pleistocene Atushi Formation and Xiyu Formation (Xiyu Conglomerate), which are exposed in the southern limb of ATA. Moreover, detailed geological interpretations of multiple remote sensing images and field investigations are also carried out to document the late Cenozoic structural deformation and geomorphologic features of ATA. The 26Al/10Be burial dating data of four fine-grained samples reveal that the syntectonic deposit of ATA initiated at 1.79 ± 0.16 Ma, and the deposit of Xiyu Conglomerate started since 1.67 ± 0.18 Ma. Thus, we suggest that the thrust–folding of ATA began at ca.1.79 Ma and is currently still active.
Highlights
The Pamir–Tian Shan convergence zone (PTCZ) in western Tarim (Figure 1A) has resulted from the northward indentation of the India plate into the Eurasia plate since ~55 Ma (Molnar and Tapponnier, 1975; Burtman and Molnar, 1993)
Our results show that the deformed late Cenozoic strata of Miocene Pakabulake Formation, Pliocene Atushi Formation, and Xiyu Conglomerate developed from the core to the southern limb of Atushi anticline (ATA) (Figure 2C)
The tectonic deformation of syntectonic growth strata related to a natural growth fold can provide a key to understand the coupling mechanisms of the sedimentary basin (KFTB) and adjacent southwestern Tian Shan orogenic belt
Summary
The Pamir–Tian Shan convergence zone (PTCZ) in western Tarim (Figure 1A) has resulted from the northward indentation of the India plate into the Eurasia plate since ~55 Ma (Molnar and Tapponnier, 1975; Burtman and Molnar, 1993). An accelerated uplift episode of Tian Shan and a rapid deformation of the Kashi foreland thrust–fold belt (KFTB) have generated 4 to 5 rows of thrust–fold belts in front of southwestern Tian Shan since Pliocene (Chen et al, 2002; Scharer et al, 2004; Heermance et al, 2008; Fu et al, 2010; Jia et al, 2015; Thompson-Jobe et al, 2018). The precisely constrained history of Deformation Time of Atushi Anticline tectonic deformation of thrust-related folds will provide a unique insight into the Cenozoic tectono-geomorphologic growth of PTCZ. Syntectonic growth strata in foreland basins recorded the kinematic process of tectonic deformation. Since the early pioneer study of unique angular unconformity in the south of Pyrenees, Spain (Riba, 1976), the growth strata have been widely used to explore the coupling mechanisms between sedimentary basin and adjacent orogenic belt (Suppe et al, 1992; Shaw and Suppe, 1994; Chen et al, 2002; Heermance et al, 2008; Sun et al, 2009; Hardy and Cardozo 2021). Various age dating methods have been applied to document the basal age of growth strata, which could chronologically constrain the initiation of a fold growth (Chen et al, 2002; Sobel et al, 2006; Chen et al, 2007a; Heermance et al, 2008; Kong et al, 2011; Li et al, 2013; Thompson-Jobe et al, 2015)
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