Climate Induced Vegetational Evolution: Palynological and Thecamoebian Study from Coastal Archaeological Sites, Saurashtra

Abstract

Coastal archaeological sites serve as potential archive of past climate-culture and vegetation relationship responding to relative sea level changes. Most of the Harappan dwellers along the coastal region largely depended on perennial or monsoon-driven river systems for fresh water required for the agriculture based sustenance. The period since 4000 yrs, BP has witnessed climatic amelioration from warm and humid (high precipitation) to dry and arid (low precipitation). Consequences of climate change evolved the vegetation from evergreen/moist deciduous to dry deciduous as number of dry months per annum increased. The palynological results from Bet Dwarka, Bokhira (Porbander) reveal absence of vegetation, although fresh water thecamoebiins and few marine palynomorphs indicate the relative extent of fresh water and marine water incursion. Results from Kodinar (Kaj and Kanjetar) show significant abundance of evergreen and moist deciduous vegetation around 4000 yrs. BP which gradually declined and replaced by dry deciduous vegetation by around 2000 yrs. BP. The present day hinterland vegetation in these areas and adjacent north-east Gir Forest is largely represented by dry deciduous plant taxa except for mangrove in coastal areas. Overall results show that the dry and arid climate reached its climax in Bokhira and Porbander (22 degree-22 degree 30 minute Latitude) around 4000 yrs. BP while in Kodinar (21 degree - 21 degree 30 minute) it reached its climax around 2000 yrs. BP. Thus, the climatic climax of dry and arid conditions shifted from North to southern part of Saurashtra