Field documentation and genesis of the back-structures from the Garhwal Lesser Himalaya, Uttarakhand, India
Published:September 25, 2019
Narayan Bose, Soumyajit Mukherjee, 2019. "Field documentation and genesis of the back-structures from the Garhwal Lesser Himalaya, Uttarakhand, India", Crustal Architecture and Evolution of the Himalaya–Karakoram–Tibet Orogen, Rajesh Sharma, Igor M. Villa, Santosh Kumar
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Collisional fold-and-thrust belts are characterized by foreland-verging thrusts. Conversely, structures with hinterland-ward vergence, known as the back-thrusts, also exist. Strain intensification, critical taper deformation and the presence of thrust ramps generate back-thrusts. This study focuses on the exposure-scale brittle and ductile structures showing hinterland-ward vergence (back-structures) from a part of the Garhwal Lesser Himalaya, NW India, mainly along the Bhagirathi river section. In our field-traverse, back-structures were found at 31 locations. Towards the north, in the Outer Lesser Himalaya, the back-structures are located on the inverted limb of the Mussoorie Syncline (Group 1). The Tons Thrust is a south-dipping thrust (i.e. back-thrust). Hence, the Tons Thrust and nearby areas show intense back-structures (Group 2). In the Inner Lesser Himalaya, back-structures have been generated by shearing related to the folded Berinag Thrust (Group 3). The back-structures at and near the Main Central Thrust Zone (MCTZ) (Group 4) can be correlated with the presence of the Delhi–Haridwar Ridge. In this way, this study establishes the back-structures to be an integral part of the Garhwal Lesser Himalaya and provides the genesis of those structures by correlating them with the (local) tectonic settings.
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Crustal Architecture and Evolution of the Himalaya–Karakoram–Tibet Orogen
CONTAINS OPEN ACCESS
This volume comprises 17 contributions that address the architecture and geodynamic evolution of the Himalaya–Karakoram–Tibet (HKT) system, covering wide aspects, from the active seismicity of the present day to the remnants of the Proterozoic orogen. The articles investigate the HKT system at different scales, blending field research with laboratory studies. The role of various lithospheric components and their inheritance in the geodynamic and magmatic evolution of the HKT system through time, and their links to global geological events, are studied in the field. The laboratory research focuses on the (sub-)micrometre scale, detailing micro-structural geology, crystal chemistry, geochronology, and the study of circulating fluids, their preservation (trapped in fluid inclusions) and their evolution, distribution, migration and interaction with the solid host. An orogen over 2000 km long can be understood only if the processes at the nanometre and micrometre scales are taken into account. The contributions in this volume successfully combine these scales to enhance our understanding of the HKT system.