Climate, vegetation and ecology during Harappan period: excavations at Kanjetar and Kaj, mid-Saurashtra coast, Gujarat

Abstract

A multi-proxy study was carried out to address climate–culture relationship from two trenches one each from Kaj and Kanjetar (mid-Saurashtra coast) deposited in a lacustrine setting, since ∼1960 Cal BC and ∼2230 Cal BC, respectively. The salinity of aqueous soil solution (0.1 ppt) and fresh water thecamoebians in both the sites indicate fresh water depositional environment. But, an increase in salinity (0.2 ppt) in the top clayey sediment in Kanjetar is attributed to water evaporation through upward capillary action from moisture deficit exposed land. The fragments of ancient potteries and other artefacts recovered from the bottom sediment provide evidences of Sorath-Harappan colonization in the vicinity which was not an urban site. The abundant cyanobacterium remains, low terrigenous organic matter, aquatic pollen and low thecamoebians in bottom sediment indicates low precipitation and arid climatic conditions ∼2000 BC. During this period the dominance of evergreen and moist deciduous arboreals from both the sites do not show equilibrium with the prevailing dry/arid climate and therefore, the pollen assemblage here represents the remnants of wetter middle Holocene vegetation in the region. Phytoliths of drought-tolerant summer season crops also reflects here changes made in the agricultural strategy by Harappans in response to climate. The increase in deciduous arboreal pollen since the last ∼2000 years represents equilibrium with the dry/arid climate. But, enhanced limnic conditions recorded with the help of thecamoebians during this period is attributed to changes in wetland configuration induced by hydrostatic changes in the river mouth that was largely defined by the dynamics of sediment deposition through rain-fed rivers/streams in the region.