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Dissertation
Exhumation and Structural Evolution of the Northwestern Indian Himalaya: Insights from the Tso Morari Nappe and the Tethyan Himalayan Fold-Thrust Belt
Doctor of Philosophy (PhD), Washington State University
2025
Abstract
The northwestern Indian Himalaya preserves a remarkable record of crustal-scale processes, from deep burial to exhumation within the Himalayan orogenic wedge. This dissertation investigates the structural, thermal, and exhumation history of the Tso Morari nappe and the Tethyan Himalaya in northwestern India using a multi-disciplinary approach, integrating field-based structural mapping, petrographic thermometry, and multi-technique thermochronometry.Chapter 1 focuses on the structural architecture of the Tso Morari nappe, demonstrating that it was emplaced as a large-scale, coherent sheet, with strain localized along discrete ductile shear zones and minor internal deformation. Thermometric data reveal peak metamorphic conditions ranging from amphibolite- to granulite-facies, providing a quantitative framework for reconstructing the nappe’s burial depth.
Chapter 2 reconstructs the post-extrusion exhumation history from mid-crustal depths during the Middle Eocene to Oligocene. Cooling histories derived from zircon and apatite fission track and 40Ar/39Ar thermochronology indicate rapid exhumation rates initially, followed by a period of slower, distributed cooling. These results suggest that underthrusting of the Greater Himalayan sequence, rather than localized faulting or surface erosion, controlled the late-stage exhumation of the nappe.
Chapter 3 concentrates on the Tethyan Himalayan fold-thrust belt further south and places it within a broader Himalayan orogenic context, comparing its structural and thermal evolution with coeval units across the orogen. This synthesis highlights the role of regional tectonic processes in shaping the metamorphic and exhumation patterns of rocks.
Collectively, this work provides new constraints on the burial and exhumation mechanisms of the northwestern Indian Himalaya, offering insights into the dynamic evolution of the Himalayan orogenic wedge and contributing to a more comprehensive understanding of continental collision processes.
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Details
- Title
- Exhumation and Structural Evolution of the Northwestern Indian Himalaya: Insights from the Tso Morari Nappe and the Tethyan Himalayan Fold-Thrust Belt
- Creators
- Adelie Ionescu
- Contributors
- Sean P. Long (Advisor)Johannes Haemmerli (Committee Member)Scott Jess (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of the Environment (CAHNRS)
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 239
- Identifiers
- 99901357689701842
- Language
- English
- Resource Type
- Dissertation