Variation in lithospheric structure in the vicinity of Palghat Cauvery Shear Zone, southern Indian shield: Inference from magnetotelluric data

Published magnetotelluric apparent resistivity data indicate a heterogeneous nature of the lithosphere in the vicinity of the Palghat-Cauvery Shear Zone (PSCZ). Data from two locations, one in the vicinity of PCSZ and the other further south near Palani, are inverted to decipher this contrast. Results reveal the presence of a highly resistive crust underlain by a thick conducting layer and a relatively uniform average sub-crustal structure near Palani that seems to extend up to PCSZ. The sub-crustal structure in the vicinity of PCSZ is highly heterogeneous at a depth greater than 60 km and possibly represents the presence of a dipping fault at this depth. The sub-crustal structure north of PCSZ is drastically different and has high conductivity. A qualitative analysis of TE and TM mode data along Kolattur-Palani profile indicates that the conducting lithosphere laterally extends up to 60 km north of PCSZ and correlates well with the Bouguer gravity high anomaly which was earlier explained in terms of mid-crustal high-density body.