Structural framework of a major intracontinental orogenic termination zone: the easternmost Tien Shan, China

Abstract

The Barkol Tagh and Karlik Tagh ranges of the easternmost Tien Shan are a natural laboratory for studying the fault architecture of an active termination zone of a major intracontinental mountain range. Barkol and Karlik Tagh and lesser ranges to the north are bounded by active thrust faults that locally deform Quaternary sediments. Major thrusts in Karlik Tagh connect along strike to the east with the left-lateral GobiTien Shan Fault System in SW Mongolia. From a Mongolian perspective, Karlik Tagh represents a large restraining bend for this regional strike-slip fault system, and the entire system of thrusts and strike-slip faults in the Karlik Tagh region defines a horsetail splay fault geometry. Regionally, there appears to be a kinematic transition from thrust-dominated deformation in the central Tien Shan to left-lateral transpressional deformation in the easternmost Tien Shan. This transition correlates with a general eastward decrease in mountain belt width and average elevation and a change in the angular relationship between the NNE-directed maximum horizontal stress in the region and the pre-existing basement structural grain, which is northwesterly in the central Tien Shan (orthogonal to SH max ) but more east-west in the eastern Tien Shan (acute angular relationship with SH max ). Ar-Ar ages indicate that major range-bounding thrusts in Barkol and Karlik Tagh are latest Permian-Triassic ductile thrust zones that underwent brittle reactivation in the Late Cenozoic. It is estimated that the modern mountain ranges of the extreme easternmost Tien Shan could have been constructed by only 10-15 km of Late Cenozoic horizontal shortening.

Late Early Permian (266 Ma) N–S compressional deformation of the Turfan basin, NW China: the cause of the change in basin pattern

“…Progressive shortening and thrusting likely led to uplift of the basement to form the Bogda Mountains that divided the unified basin into two isolated parts. This suggestion is supported by structural observations in the Barkol Tagh and Karlik Tagh ranges (Cunningham et al 2003) and by 40 Ar/ 39 Ar dating of sericite (223 ± 12 and 224 ± 14 Ma; Zhu et al 2007) in Aubearing quartz veins from the Bindaban area. It is reasonable to suggest that the northward subduction of PalaeoTethyan oceanic crust under the Kunlun to the far south was the driving force for the Permian N-S contractional deformation of the unified Junger-Turfan basin (Allen and Vincent 1997).…”

“…Obviously this transition implies variations in tectonic setting, the cause of which is still open (Wartes et al 2002). Valuable constraints come from structural studies in the Tianshan Range (e.g., Windley et al 1990;Allen et al 1992;LaurentCharvet et al 2003;Xu et al 2003;Cunningham et al 2003;Yang et al 2007), but the temporal and spatial relations between the basin evolution and the tectonics of adjacent ranges have not been explained satisfactorily (Allen et al 1991), the reasons for which include: (1) an absence of high quality geochronological data and detailed basin analysis has obscured correct definition of the basins and their extent; multi-stage strong deformation has worsened the situation. For example, some incorrect age estimates of associated strata (Bureau of Geology and Mineral Resource of Xinjiang 1983) were used to synthesis a basin evolution model (Allen et al 1991).…”

“…(3) The Tianshan has had a multi-stage (e.g., Windley et al 1990;Cunningham et al 2003) and complicated (e.g., Yang et al 2007) deformation history; structures of different age have not been clearly defined. With such a situation, it is not possible to suggest a reasonable dynamic relation between basin evolution and regional tectonics.…”

Late Quaternary glacial history of the Karlik Range, easternmost Tian Shan, derived from 10Be surface exposure and optically stimulated luminescence datings

“…Glacial landforms and moraines were delineated based on field investigation and Google Earth images. The thrust fault in front of the Karlik Range was delineated based onCunningham et al (2003). All ages are in ka.…”

Folded Basinal Compartments of the Southern Mongolian Borderland: A Structural Archive of the Final Consolidation of the Central Asian Orogenic Belt

“…This event is recorded by apatite fission-track data that reveal a pulse of mid-Jurassic erosion and cooling [32], regional-scale folding and thrusting along the Mongolia-Chinese border and in the eastern Beishan region [29], and deposition of thick siliciclastic sedimentary successions (up to 2500 m-thick) in the Gobi Altai region as far north as the southern Hangay Dome margin [33][34][35]. In addition, the Beishan and eastern Tien Shan regions also record a major Jurassic cooling/exhumation event [30,[36][37][38]. The surface expression of this event in Mongolia is obscured in many areas by subsequent tectonic events that have either overprinted Jurassic structures, or by younger sedimentary rocks that unconformably overlie and conceal rocks affected by Jurassic contraction.…”