Magnetotellurics Study to Identify Subsurface Resistivity Structure in the Eastern Part of Kachchh (Little Rann Area) of Gujarat, India

Abstract

A magnetotelluric (MT) survey has been conducted in the eastern part of the Kachchh region of Gujarat State (crossing Little Rann) starting from Adesar village in the north to Enjar village in the south, where limited geophysical data is available. The profile has been acquired in the N–S direction having a total length of 52 km with the interstation spacing of 3–4 km. From two-dimensional (2D) inversion of the MT data, four conductive zones are identified. The analysis reveals that the depth of the basement varies from 1.2 km (in the south) to 1.8 km (in the north). The first conductive zone is found at a distance of ~ 3 km in the south of Adesar and is identified at the location of the Kanmer fault [KF; the eastern extension of South Wagad fault (SWF)] and might be the KF. The second conductive zone is found at a distance of ~ 42 km in the south of Adesar and ~ 13 km north of Enjar village and is located at the contact zone of Kachchh and Saurashtra peninsula at the location of the North Kathiawar fault (NKF). It is inferred as the NKF. The third conductive zone (at a distance of ~ 27 km in the south of Adesar) is found between the first and second conductor. This is interpreted as a step fault, formed during the rifting process of Kachchh. The lower crust (below 20 km) is found conductive (~ 120 Ω m) and might indicate the presence of fluid-filled mafic/ultramafic rocks in the lower crust.