Geomorphological Characterization of Shallow Sub-surface Deformation Structures along the Densely Populated Regions of Mahanadi Delta: East Coast of India

Abstract

We discuss two near-surface faults (Jajpur fault and Gop fault) identified along the coastal plains of Odisha on the Indian east coast. The sub-surface nature of these faults has been characterized using tectono-geomorphological signatures and Ground Penetrating Radar (GPR). GPR profiles indicate listric nature of the sub-surface deformation structures, striking parallel to the basement faults. Due to geomorphic modification, negligible relief, and high sedimentation, direct expression of fault scarps are not available. These faults are marked as broad zones showing various fluvial anomalies. Topographic profiles across the inferred fault plain show slope break up to 10 m. The river longitudinal profiles of Shalandi and Kharsuan Rivers show the development of knickpoints across the Jajpur fault. Borehole logs across the inferred faults show lithological discontinuity. The basement at the upthrown side of Jajpur fault is close to the surface, whereas it is at a deeper level on the downthrown side. Stratal discontinuities in fluvial sediments are also observed across the Gop fault. Optically stimulated Luminescence (OSL) age (~7 ka B.P.) of Kushabhadra River paleochannel crossing the Gop fault suggests that gradient change across the Gop fault provided space for the mid-Holocene channel avulsion.