Deep electrical resistivity imaging of crustal structures along the Satluj River valley, northwest Himalaya, India

Abstract

Magnetotelluric (MT) investigations along the Nahan- Kourick Chango transect in the Satluj river valley, northwest Himalayas, provide insight into the subsurface electrical properties. In the geoelectrical model, medium to highly metamorphosed crystalline rocks in the Lesser and the Higher Himalayas are observed as high resistive features. At a depth approximately 5–15 km, an intra-crustal low resistive layer is consistently present along the entire profile. The geometry of this dipping intra-crustal layer signifies the presence of the Main Himalayan Thrust, which represents the base of the accretionary wedge where all the major thrusts of the Himalayan tectonics sole down. The geometrical differences and distinct resistivity of this layer compared to the adjacent regions of Garhwal-Kumaon and Nepal Himalaya indicate the variability of tectonic processes in this part of the Himalaya. Another significant observation is the existence of a thin, highly conducting layer at a shallow depth (approximately 1–3 km). The spatial extent of this layer, along with the bending extent of the main central thrust toward the south, suggests its role in the southward translation of crystalline sheets during Himalayan tectonics.