Crustal structure in the Siwalik Himalayas using magnetotelluric studies

Abstract

Tectonics in the Himalayan foothills is a result of the compressional forces active since the collision between Indian and Eurasian plates and is best understood as a combination of thin skin tectonics and the basement level faulting. In order to delineate the depth extent of various thrusts and faults, wide band Magnetotelluric (MT) studies were conducted at 17 stations over the Una-Mandi profile located in the Lesser Himalayas. These studies indicate that the Palampur thrust may be a composite of two thrust zones which merge together on the south of the MT profile and extends to depths of about 8 km. The Lambagraon syncline flanked by the Sarkaghat anticline on the NE and the Bahl anticline to the SW, is about 10 km deep. The crust is underlain by a conductive layer with a resistivity of about 100 − m at depth of about 50 km below the Palampur thrust and Sarkaghat anticline. This layer is delineated at shallower depths of about 35 km below the Lambagraon syncline and also on the NE towards the main boundary thrust.

Magnetotelluric Studies of Active Continent–Continent Collisions

“…Active convergence is accommodated on the Main Boundary Thrust (MBT) and Main Frontal Thrust (MFT) and the models of Israil et al (2008) and Patro and Harinarayana (2009) show northward dipping conductors that are probably due to underthrust sedimentary rocks units in the footwalls of these thrust faults. Similar structures were reported by Gokarn et al (2002b) in the Siwilak Himalaya. Higher resistivities are observed where higher grade metamorphic and igneous rocks are mapped to the North.…”

A review on out-of-sequence deformation in the Himalaya

“…Webb (2013) described the Bilaspur and Palampur Thrusts as a 'thrust system'. Gokarn et al (2002) reported through magnetotelluric studies that the Palampur Thrust could be two thrust zones and that they reached c. 8 km depth. Webb (2013) designated the Bilaspur Thrust as an out-of-sequence thrust.…”

Interpretation of Gravity Data using 3D Euler Deconvolution, Tilt Angle, Horizontal Tilt Angle and Source Edge Approximation of the North-West Himalaya

“…Reddy and Arora (1993) reported basement depth from 10.0 to 15.0 km below the Himalayan collision region with a high conductivity layer embedded in the crust at using geomagnetic deep sounding (GDS). Gokarn et al (2002) also observed the basement depth increases upto 15.0 km using magnetotelluric (MT) studies. Khattri et al (1989) also suggested the depth of detachment of 15.0-18.0 km underneath the Lesser Himalaya of Garhwal.…”

“…Various authors (Tripathi et al 2012, Chamoli et al 2011, Arora et al 2007, Gokarn et al 2002 had carried out the depth estimation and provided their views. However, the present study provides better results and detailed information of source depth locations and structural boundaries with dip information.…”