Abstract

Author:
Saurodeep Chatterjee, Shelcy Deori, Budi Ampi, Manab Jyoti Phukan, Lobsang Tashi Sunickjee

Doi: 10.26480/gsrj.01.2024.41.50

This is an open access article distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

The present study aims towards the study of the different mesoscopic and microscopic structures present in the lesser Himalayan rocks of the Rupa area of the West Kameng district of Arunachal Pradesh (India) and discuss their tectonic implications. Also, strain markers were demarcated in conglomerates (the deformed elliptical pebbles) and the strain values were calculated using fry method. The structures that were observed were classified into compressional, extensional structures and some shear structures (both in mesoscopic and microscopic scale). Compressional structures include folds of multiple generation and the extensional structures include joints and faults. The compressional structures were used to determine the direction of compression which is found to be varying from NNE-SSW (older) to NW-SE (younger). The extensional structures (mainly the joints) provided the direction of extension which also changed from NNW-SSE (older) to ENE-WSW (younger). The shear structures depicted that the major orientation of shearing is sinistral (NNE-SSW to NE-SW) with some rare exceptions of dextral shear (ESE-WNW). The microstructures observed within the schists and phyllites also depict sinistral shear with an orientation of NE-SW. The deformed pebbles in the conglomerates showed that the strain is highly variable in the lesser Himalayan rocks of this geo-transect (within 0.58 to 0.11), with the highest values observed where the Himalayan thrusts are located. The study enhances the basic geological knowledge of the lesser Himalayan rocks of the Rupa area, which is lacking in the area despite sporadic specific studies are made in the area.