Exploration of chronological development of coastal landscape: A review on geological and geomorphological history of Subarnarekha chenier delta region, West Bengal, India

Abstract

The physiography of the alluvium coast plays a very significant role to influence the coastal morphodynamics in response to outer environmental impacts with a significant change in boundary conditions of the local area. The present study deals with the chronological development of coastal landform units in different orders of formations, their surface morphometry, drainage features, hydro-geomorphology, nature of shoreline dynamics of the coastal plain topography. The chronology of the coastal evolution is explained in this study with the application of available Optically Stimulated Luminescence (OSL) and Radio Carbon dating records of different landform units. The existing works of literature, estimation of present-day wave hydro-dynamics and estimation of the energy level along with the sediment budget of the near shores are considered to predict and establish the geological and geomorphological evolution of Subarnarekha chenier delta. The present study reveals that the chenier plain is the product of the combination of sediment discharge into the coastal zones by fluvio marine deposition with the presence of strong longshore currents at the sea face, activities of repeated coastal storms, impacts of tectonics and past sea-level fluctuations. The modern shoreline beach ridge cheniers are segmented by older distributary channels and modified by present-day coastal processes. It is the specialized coastal plain topography of alluvium surface with beach ridge chenier and swales makeup the topographic diversity of the coastal belt. There are three bifurcated ridges in the form of narrow and low height ridges in the wide valley flat surface in between Ramnagar–Deuli beach ridge section and Digha–Junput beach ridge section. The three barriers are separated by linear depressions running parallel to the present ridgelines and represent as linear tidal basins of that time.