71-2 Structure and Kinematic Evolution of the Naga Fold-Thrust Belt, Northeast India

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

Poster Booth No.: 254

Presenting Author:

Jackson Swartz

Authors:

Swartz, Jackson Perry¹, Betka, Paul M.², Rakshit, Raghupratim³, Lang, Karl⁴, Howes, Cecilia Mai Chen⁵, Zeien, Hannah⁶, Nayak, Suvam Somyadarshi⁷, Patel, Rabindra Kumar⁸

(1) Geology Department, Western Washington University, Bellingham, Washington, USA, (2) Geology Department, Western Washington University, Bellingham, WA, USA, (3) Department of Geology, Jagannath Barooah College, Jorhat, Assam, India, (4) School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA, (5) Geology Department, Western Washington University, Bellingham, WA, USA, (6) School of Earth & Environmental Sciences, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA, (7) Wadia Institute of Himalayan Geology, Dehradun, Uttarakhand, India, (8) Wadia Institute of Himalayan Geology, Dehradun, Uttarakhand, India,

Abstract:

The easternmost terminus of the Himalayan orogen is defined by a continental triple junction between the Indian, Eurasian, and Burman plates. The Naga fold-thrust belt (NFTB) represents the SW arm of this triple junction and accommodates convergence between the Burma plate and the trailing edge of the Indian plate. Previous studies disagree on the kinematic evolution of the NFTB, interpreting it as either a dextral shear zone or a strain-partitioned orogenic wedge. This study attempts to resolve these discrepancies through field-based structural analyses and construction of balanced cross-sections to constrain the structural evolution of the FTB and test competing hypotheses for the kinematic evolution of the triple junction. We collected structural data along three ~40 km transects mapped perpendicular to the strike of the fault-cored anticlines in the NFTB.  The stratigraphy of the NFTB includes the Mio-Pliocene syn-orogenic Namsang Formation, the Miocene-Pliocene fluvial Tipam Group, the Miocene shallow marine Surma Group, the Eocene-Miocene shallow marine and deltaic Barail Group, and the Eocene shallow marine Disang Group. Preliminary results identify the frontal thrust (Naga thrust) as a blind thrust that folds the Tipam Formation. A second thrust splay places the Barail Group above the Tipam Group ~20 km southeast of the Naga thrust. A third thrust splay, ~15 km southeast, imbricates the Barail–Tipam section again. The southern transect contains an additional duplex-related thrust that is not present in the central or northern transects.  The frontal thrusts are cross-cut by an out-of-sequence thrust (Disang Thrust) that juxtaposes the Disang Group above the Barail Group in the internal part of the wedge. In the hanging wall of the Disang thrust, the Disang-Barail contact is folded into regional anticlines and synclines and thickened by imbricated intraformational thrusts. The central and northern transects contain outcrop-scale folds and faults within the shale of the Disang Group. Preliminary results reveal a series of thrusts and fault-cored anticlines that propagated northwestward to accommodate margin-normal convergence, no evidence for significant strike-slip faulting was observed in the study area. Our results provide evidence for strain partitioning in the NFTB and constrain the kinematic evolution of the India–Burma–Eurasia triple junction.

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

doi: 10.1130/abs/2025AM-8065

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