Mark Coakley

This project presents new microtectonic kinematic data on the rocks of the Lesser Himalayan Sequence (LHS), Greater Himalayan Sequence (GHS), and Chekha Formation in the vicinity of Tashigang, Kingdom of Bhutan. The shear sense of 13 samples is determined and interpreted in terms of the displacement vectors. The shearing of these rocks is caused by movement along the South Tibetan Detachment to the north and structurally above and along the Main Central Thrust, to the south and structurally below the study area. These rocks are 13.5 to 23 Ma. The shears senses of these rocks are determined using the techniques of optical microscopy. The shear senses of the rocks from the study area suggest that they underwent a complex pattern of shearing and a complex history of deformation, in which contrasting shear fabrics were overprinted. These rocks have undergone both a down dip component and a strike slip component of simple shear. They have also been affected by a component of pure shear. They have undergone flattening. From early to mid Miocene the MCT experienced top-to-the-south shearing and at mid Miocene top-to-the-north shearing along the STD began to dominate, overprinting many of the top-to-the-south metamorphic fabrics of the MCT movement. The implication of this data is that the shear pattern and history of the rocks is much more

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Supervisor: Djordje Grujic