Soft Sediment Deformation Structures in the Sediment Deposits of Ganga River and Its Oxbow Lakes in Parts of Indo-Gangetic Plain: Implications for Quake Proxies and Paleoseismicity Tracking

Abstract

The Late Quaternary thick sedimentary fills of the Ganga basin predominantly consist of unconsolidated fluvial sandy deposits which are often intercalated with mud. These deposits at various places record the evidence of earthquakes, which occurred in the recent geological past. The evidence is contained and manifested in the form of Soft Sediment Deformation Structures (SSDSs). Saturated sediments/muds/soils are liquefied by earthquake tremors which either generate SSDS or produce structural discordance in the pre-existing sedimentary structures. The present study reports the occurrence of SSDS, e.g. load and associated flame structures, clastic dikes and sill structures, slump structures and sedimentary breccias, etc. from the Ganga River and adjacent oxbow lake sediment deposits. An attempt has been made to establish the origin of soft sediment structures of this region in accordance with its neotectonic history and in turn, identification of seismic structural proxies to delineate paleoseismic events in this region with futuristic implications. The preservation of soft sediment deformation structures in large numbers with multiple geomorphology and scale, in the river and adjoining lake sediments, is indicative of frequent earthquakes of high magnitude consequent to tectonic activism in the Himalayan region.