Vegetation, climate and culture in Central Ganga plain, India: A multi-proxy record for Last Glacial Maximum

Abstract

Multi-proxy study of a 240 cm deep Lashoda Tal (lake) sediment profile, located adjacent to an archaeological mound in Central Ganga Plain, highlights the climate induced changes in the vegetation, ecology and culture since ∼25500 cal BP. Between ∼25500 and 22200 cal BP, the region shows grassland, incipient drainage and small ponds formed seasonally with moisture loving terrestrial thecamoeba suggesting supply of moisture in short spells under the winter monsoon regime. The sediment became sandy and invaded by trees during ∼22200 to 14300 cal BP indicating an increase in lake levels with more aquatic pollen and algal forms portraying the strengthened monsoon and high energy fluvial system. This observation is further supported by low percentage of thecamoeba. Subsequently, the climate became increasingly supportive showing low seasonality and formation of meandering channels, which favoured aquatic weeds and meadew-cutoffs with marshy areas and dense vegetation in the vicinity during ∼14300 to 7100 cal BP. High arboreal and non-arboreals pollen and thecamoebian diversity with, change in nature of sediment (increasing clay content) suggest the expansion of Lashoda lake ecosystem ∼7100 cal BP. Since the last 2 millennium and until ∼1550 AD the studied site was under immense human pressure of Kushana, Gupta and Mughal cultures, which is evident by the artifacts recovered from the mound situated near the study site. The palynological study revealed reduced monsoon, fragmentation or desiccation of lake ecosystem ∼1550 AD, which is attributed to geomorphological changes caused by the ameliorating climate. The records of Cerealia pollen ∼1300 cal BP indicate expansion of agricultural activities that might have affected the lake ecosystem.