Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: Timing of Basin Inversion and Associated Deformation-Field Evolution

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The Tajik basin and southwestern Tian Shan constitute the North-western tip of the India-Asia collision zone. Likely Oligocene-Neogene basin inversion formed the top-to-WNW, thin-skinned Tajik thrust-fold belt, outlined by westward convex fold trains, and underlain by a décollement in Jurassic evaporites. The southwestern Tian Shan constitutes the thick-skinned foreland buttress. The Tajik thrust-fold belt forms an asymmetric (rotational) extruding-gliding-spreading nappe, connecting Pamir-plateau crustal collapse with shortening in the Tajik-basin depression. Building on studies by my group, firstly we will develop a full understanding of the evolution of deformation during the inversion of the Tajik basin via a regional "paleostress" study. The outcome will be the establishment of a detailed relative deformation-field evolution, from early, rotated structural fabrics to late, un- or little-rotated ones; the latter should approximate/match today’s deformation field. Second, we will complement the existing thermochronologic database by dating additional samples using the apatite fission-track and (U-Th)/He methods. With this data, we will get a full, regional coverage of ages to interpret the time evolution of the inversion of the Tajik basin. Third, we aim to date the deformation history of the Tajik thrust-fold belt using U-Pb calcite geochronology, placing constraints on fault movements and tension-gash formation. Importantly, we will make use of the detailed analysis of the pre-, syn-, and post-folding stages of deformation and date faults and gashes related to this relative evolution. In addition, we will also select calcite from faults that indicate early and late stages in vertical axis rotation of fault-sets. The expected outcome is a basin-wide establishment of the onset of inversion and an understanding of the subsequent out-of-sequence reactivation in various parts of the basin.