12-1 Evaluating the role of terrane accretion on the evolution of indenter corner fault systems, an example from the eastern Himalaya

Session: The Geodynamic Evolution of the Himalaya: From Mountain Building to Modern Seismicity and Climate Change

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Orogenic syntaxes are regions of high crustal strain that accommodate the transition from convergence to strike-slip motion at the margins of an indenting plate collision. For several decades, tectonics research has focused on strain partitioning within the indented plate, with a focus on the role of surface processes in localizing strain. While surface processes remain an important factor, this focus has overlooked the influence of strain partitioning within the indenting plate, and in particular, the role of sliver terrane accretion on the evolution of indenter corner fault intersections. Recent observations from the eastern Himalayan orogen suggests that the accretion of the Burma sliver terrane along the Sagaing transform fault flanking the collision led to a ‘double collision’ where an India–Eurasia thrust-transform fault intersection changes into a triple junction between India–Eurasia–Burma fault systems of the Himalayan wedge, Indo-Burman Ranges, and northern terminus of the Sagaing transform, altering the kinematics of the indenter corner and the patterns of upper plate deformation. To evaluate the broader influence of terrane accretion on indenter corner dynamics, we focus on the kinematic history of the Noa Dihing Fault (NDF), a key structure that juxtaposes the India-Eurasia collision zone with the subduction zone between Indian and the Burma Sliver Terrane (BST), as well as the BST-Eurasia transform zone. We present new field mapping, structural modeling, detrital ¹⁰Be analyses to demonstrate active uplift of the Manabhum anticline, a fault-propagation fold that is forming in the Brahmaputra valley above the eastern tip of the NDF. Erosion rates of ~1 km/Myr in the hanging wall of the NDF suggest uplift rates comparable to those elsewhere in the eastern Himalaya and indicate contemporaneous slip along the Himalayan, Indo-Burman, and Noa Dihing thrust systems which all intersect at the triple junction. Overall, we show evidence that oblique-convergent strain between the India-Eurasia-Burma plates: a) propagates 50 km into the foreland basin, b) is partitioned along discrete, nearly orthogonal active thrust faults, and c) the intersection of these active faults forms a triple-thrust junction reflective of the broader tectonic configuration. Our results highlight how sliver terrane accretion along the flanks of collisional orogens can modify the dynamics of indenting plate collisions.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8032

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