Long-lived Cenozoic positive relief of the south-Eastern Tian Shan: Insights from provenance analyses of the northwestern Kuqa Depression sediments

Abstract

The Eastern Tian Shan, one of the most active intracontinental orogenic belts, should bear important information on the mechanisms of intracontinental mountain building. In this study, detrital zircon U-Pb geochronological analysis of the Cenozoic Tiereke section succession in the northern Tarim Basin-Eastern Tian Shan convergence zone, combined with stratigraphic results, reveals the provenance histories of the Cenozoic sediments in the northwestern Kuqa Depression of northern Tarim Basin. Nine Cenozoic samples obtained from the strata of the Kumugeliemu Group to the lowest Kangcun Formation of the Tiereke section exhibit high resemblance to provenances of the south-Eastern Tian Shan, indicating existence of a prolonged eroding relief within this mountain since the early Cenozoic (∼54 Ma). This prolonged state of eroding relief requires continuous intracontinental deformation of the Eastern Tian Shan to sustain a provenance region, implying immediate deformation responding to the initial Indian-Eurasian collision. Furthermore, the south-Eastern Tian Shan served as the only source region for the northwestern Kuqa Depression of northern Tarim Basin, demonstrating that the upper-crustal boundary between the south-Eastern Tian Shan and the northern Tarim Basin was possibly stationary during most of the Cenozoic Era (∼54 Ma to ∼9.7 Ma). Such a stationary basin-orogenic boundary would favor the predictions of the pure-shear-like thickening model for the intracontinental mountain building during this period. We suggest that the long-lived mountain building of the Eastern Tian Shan may be due to its small convergence rate.