Soft-Sediment Deformation Structures in Gujarat Alluvium: Evidence for Palaeo-Seismicity, around Patan, Cambay Basin, Western India

ABSTRACT Patan District of Gujarat, known for its medieval history, UNESCO heritage monuments, is located along the banks of the Saraswati River and lies in the central part of the NW-SE to N-S trending elongated intra-cratonic Cambay basin of western India. The Patan area is covered by thick Quaternary Gujarat alluvium and exposes Pleistocene to Holocene, fluvial, marine, and aeolian sediments. The East Cambay Fault (ECF) and its associated transverse faults pass through the study area, and the Soft Sediment Deformation Structures (SSDSs) are recorded in its vicinity within the Holocene Younger alluvium made up of sand-silt-clay, exposed along the T1 terraces of the Saraswati River in Patan. The present study is aimed at the identification and characterisation of these SSDSs within the Gujarat Alluvium with special emphasis on the interpretation of deformation mechanisms and reporting palaeo-seismicity at Patan through field evidence correlation and OSL dating. The morphology of SSDSs noted in the central part of the Cambay basin, in the Patan area, indicates that the trigger mechanism of deformations is essentially related to gravitational instability, dewatering, liquefaction-fluidisation, and brittle deformation, caused by regional seismicity. The present study provides imprints of two historic catastrophic seismic events through the SSDSs preserved within the fluvial archives of the Saraswati River, around Patan city of Gujarat.