Temporal constraints and pulsed Late Cenozoic deformation during the structural disruption of the active Kashi foreland, northwest China

Abstract

In response to the ongoing Indo‐Asian collision, structural deformation has encroached into the Tian Shan foreland in western China since the early Miocene. In order to reconstruct a detailed history of foreland deformation along the southern margin of the Tian Shan, we have synthesized extensive mapping, analysis of seismic sections, magnetostratigraphy of the foreland fill and associated growth strata, apatite fission track dating, changes in sediment accumulation rates, and geodetic surveys of deformed fluvial terraces. Across an area exceeding 6500 km2 that spans the Kashi foreland in the northwestern Tarim Basin, we use these data to place temporal constraints on individual structures that delineate at least 4 distinct stages of deformation. Stage 1 involved initial uplift of hinterland structures beginning at 20–25 Ma. Stage 2 began at ∼16.3 Ma when the basement‐involved deformation front stepped south to the Kashi Basin Thrust that bounds the foredeep strata. Stage 3 occurred from 13.5 to 4 Ma, as the deformation front migrated south in episodic steps above thin‐skinned detachment and ramp‐flat folding. Finally, stage 4 began after 4 Ma with growth of the Keketamu Anticline followed by rapid southward migration of the deformation front to the Atushi and then Kashi detachment anticlines. On the basis of the deformed Tertiary strata and available seismic data, calculations of the minimum magnitude of shortening yield totals ranging from 10 to 32 km since the early Miocene, of which 7–12 km occurred since ∼4 Ma. Although average shortening rates since 16.3 Ma were 0.8–1.3 mm/a, rates were faster from 16.3 to 13.5 Ma (1.1–3.2 mm/a), after which they decreased to 0.5 mm/a between 13.5 and 4 Ma before increasing to 2.2–2.7 mm/a after 4 Ma. Similarly, the rate of southward propagation of the deformation front was initially 3–7 mm/a for the first 10 Ma of basin development, slowed to 1.5 mm/a between 13.5 and 4 Ma, and increased to more than 10 mm/a since 4 Ma. These changes in shortening and structural migration rates over time suggest that the loci of orogenic deformation shifted in and out of the foreland during the Neogene. Surveyed stream terraces suggest that, although most current deformation is located along the southern front of the foreland, modest deformation and shortening continue in the hinterland. Structural style within the foreland has also changed over time from imbricate thrust faults with hanging wall folds along the northern margin, to ramp‐flat faults and detachment folds along the southern margin. Where the basement rocks are previously deformed, such as in the hinterland of the Kashi foreland, thick‐skinned fault ramps and related fault propagation folds dominate the structural style. As syntectonic sedimentation within the foreland produced thick, subhorizontal stratigraphy, the structural style evolved to detachment and fault bend folding above these footwall flats within the Neogene strata.

Cenozoic tectono-geomorphological growth of the SW Chinese Tian Shan: Insight from AFT and detrital zircon U–Pb data

“…By comparing with geodetic data, Sobel et al (2006a) suggested this region experienced a complex shortening history in late Cenozoic. Four stages of tectonic deformation in the Atushi Basin in front of the SW Chinese Tian Shan at 20 ~ 25 Ma, ca.16.3 Ma, 4 ~ 13.5 Ma and after 4 Ma were constrained by magnetostratigraphic study, which lead to a total north south shortening of 10 -32 km (Heermance et al, 2008). The kinematic mechanism of the Atushi and Kashi folds were well constrained by Scharer et al (2004) and Chen et al (2007).…”

Late Cenozoic continuous aridification in the western Qaidam Basin: evidence from sporopollen records

“…10e). The eastern part of the Qaidam Basin shows some evidence of tectonic activity at about ∼ 14.7 Ma events; the NW part after Zheng et al, 2000;Chen et al, 2002;Wang et al, 2003;Sun et al, 2004Sun et al, , 824 2005Sun et al, , 2007Sun et al, , 2009Charreau et al, 2005;2006;Huang et al, 2006;Heermance et al, 2007Heermance et al, , 2008825 Sun and Zhang, 2008;Tang et al, 2011 and; the NE part after Li et al, 1997;826 Song et al, 2001a, b;Zhao et al, 2001;Fang et al, 2003Fang et al, , 2005aZheng et al, 827 2006;Lin et al, 2010;Wang et al, 2010;and Wang et al, 2011a, b), and (g) the presumed 828 paleoaltimetry history after An et al (2006). 829 , tectonic uplift events in (e) the Qaidam Basin (rectangle showing the tectonic events; the western basin after Chang et al, 2012; the eastern basin after Fang et al, 2007, andXiong, 2009) and (f) the northern Tibetan Plateau (rectangles showing the tectonic events; the NW part after Zheng et al, 2000;Chen et al, 2002;Wang et al, 2003;Sun et al, 2004Sun et al, , 2007Sun et al, , 2009Charreau et al, 2005Charreau et al, , 2006Huang et al, 2006;Heermance et al, 2007Heermance et al, , 2008Tang et al, 2011, and; the NE part after ...…”

“…H. Song et al, 2001;Y. G. Song et al, 2001;Chen et al, 2002;Fang et al, 2003Fang et al, , 2005aWang et al, 2003;Sun et al, 2004Sun et al, , 2007Sun et al, , 2009Charreau et al, 2005Charreau et al, , 2006Huang et al, 2006;Heermance et al, 2007Heermance et al, , 2008Lin et al, 2010;Wang et al, 2010;W. T. Wang et al, 2011;Tang et al, 2011;Zhang and Sun, 2011;Nie et al, 2013) (Fig.…”

Cenozoic structural evolution of the Argentinean Andes at 34º40’S: A close relationship between thick and thin-skinned deformation

“…BaB.x-1 oil well registered the presence of several slices of the Choiyoi Group (Manceda et al, 1992). Comparable kinematic models, where superposition of basement-involved thrust sheets results in high elevations of basement rocks that produced deformation in the sedimentary cover, have been proposed in other fold and thrust belts in the Andes (e.g., Kley, 1996;McQuarrie et al, 2008) and elsewhere (e.g., Schönborn, 1999;Heermance et al, 2008).…”