Soft Sediment Deformation Structures in Quaternary Sediments from Dadra and Nagar Haveli, Western India

Quaternary sediments are preserved in disconnected patches along the middle and lower reaches of major river valleys like Damanganga, Par, Ratakhadi and Dongarkhadi in the Dadra and Nagar Haveli region of Konkan coastal belt, Western India. These deposits mainly consist of stratified sand, silt, clay and gravel beds. The study area has been earlier affected by moderate earthquakes. The identified soft-sediment deformation structures (SSDS) are mainly developed in the sand silt, sand gravel and clay beds; and includes intrusive sedimentary bodies (dykes and sills), slump structures, suspended clast blocks and convolute structures. The nature, shape and dimension of SSDS suggest that the trigger mechanism and driving forces for the origin of these structures were seismic shock waves. Sediment loading and storm events as a trigger for the SSDS are less likely the reason and the proximity of these structures to the faults support the inference that it may be of seismic origin. Deformation in the Quaternary sediments of Dadra and Nagar Haveli imply the presence of neotectonic activity and points to an earthquake of magnitude >5.5 that struck the study area after sediment deposition.