Evolution of Iskapalli lagoon in Penner delta region, east coast of India—A sedimentological and palynological approach

Abstract

The Holocene evolution of the Iskapalli lagoon has been reconstructed through landform mapping, vibracore lithology and foraminiferal analysis, supplemented by radiocarbon dating. The characteristics: texture, boundary surfaces and the palynological assemblages of the lagoon sediments obtained from two cores indicate three distinct sediment units. The lower part of the core (Unit I) consisting of highly (>85%) oxidized coarse sand mixed with shells, moderate bioturbation, high concentration of <i style="">Spiniferites, Casuarina</i>, fungal spores and algal cysts together with terrestrial herbaceous taxa and sub-parallel laminations suggests deposition in a sandy river mouth bar environment under strong wave influence. The middle part of the core (Unit II) comprising high silty to sandy mud, and parallel laminations together with <i style="">Protoperidinium</i> sp., <i style="">Rhizophora</i> and <i style="">Avicennia </i>indicated low energy lagoonal environment analogous to the modern lagoonal conditions. The upper part of the cores (Unit III) consisting of well sorted fine sands with abundant terrestrial taxa are considered to be wind blown sands. The oxidized condition of the distributary mouth bar sediments of Unit I and the occurrence of fine sediments of Unit II suggest the lagoon had witnessed at least one cycle of sea level fall and rise during the Late Holocene between 2000 yr BP and 1500 yr BP. <b style=""></b>