151 Chronology of Orogenesis: Unlocking the Timelines of Mountain Building (Posters)

The focus of this session is the use of geochronological methods (including but not limited to U-Pb, Ar/Ar, FT, (U/Th)-He) to establish the timing of key events in mountain building, including different orogenic phases, exhumation, and uplift rates.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Multi-Method Geo- and Thermochronologic Constraints on the Timing of Deformation and Exhumation in the Shyok Suture Zone, Ladakh, India, NW Himalayas.

Paper number: 151-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Understanding the structural and temporal evolution of suture zones is essential for reconstructing the closure of ocean basins, terrane accretion, continental collision, and ophiolite exhumation during orogenesis. In the northwestern Himalayas, it has been proposed that the Kohistan-Ladakh arc formed on the Eurasian margin and rifted southward in the Late Cretaceous, opening a back-arc basin between the arc and Eurasia. The Shyok suture zone in Ladakh, India, preserves a record of the northward subduction of this back-arc basin and the collision of the Kohistan-Ladakh island arc with the Eurasian margin. However, the sequence and timing of thrust faulting within the Shyok suture zone remains poorly constrained, along with the exhumation history of suture zone ophiolites. This study presents new multi-method U-Pb geochronology (zircon, titanite, apatite) and zircon (U-Th)/He (ZHe) thermochronologic results integrated with structural observations of major thrusts to analyze the timing of compressional deformation in the Shyok suture zone. We will focus on the thermal history of hanging wall exhumation to reveal how multiple phases of shortening have affected the structural architecture of the suture zone. U-Pb dating of titanite and apatite preserves the protolith crystallization ages despite penetrative ductile shear, suggesting that shearing took place at temperatures <450°C. The ZHe system, with a closure temperature of ~180°C, provides an opportunity to bracket episodes of brittle deformation in upper crustal thrust sheets. Comparison of ZHe ages from thrusts across the Shyok suture zone allows us to determine the timing of collision-related deformation and the influence of continuous shortening on the evolution of suture zone thrust systems. These constraints have implications for continental suturing processes, the exhumation of ophiolites in orogenic belts, and the tectonics of the India-Eurasia collisional system.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412706

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