Holocene climatic fluctuations in the Gujarat Alluvial Plains based on a multiproxy study of the Pariyaj Lake archive, western India

Abstract

A sediment core from Pariyaj Lake, from the Vatrak River basin, located at the desert margin in the Gujarat Alluvial Plains of western India, was investigated in a multidisciplinary aspect. The goal was to reconstruct the palaeoclimate, palaeoenvironment and tectonic history and to understand the role these factors played in the geomorphological evolution of the area during the Holocene. Palaeoclimatic interpretations also shed light on the factors responsible for the rise and fall of the Harappan civilisation. The results obtained based on multiproxy studies show five climatic phases during the last 11,000 yr BP. Phase 1 (~ 11,000 cal yr BP) represents a very humid climate and high precipitation/discharge leading to high lake stand as attested by the high pollen concentration of semi-evergreen tree taxa, phytoliths belonging to cool and moist grasses, and large proportion of algae, marking the onset of Holocene. In phase 2 (~ 8000 to 9000 cal yr BP) a significantly reduced yield of pollen, phytoliths and aquatic algae indicates shrinkage of the lake. Phase 3 (~ 7630 cal yr BP) shows moderate yield of pollen and phytolith pointing towards fluctuating precipitation conditions. Phase 4 (~ 5864 to 4680 cal yr BP) shows very low pollen and phytolith counts, indicating a very dry spell. Finally, phase 5 (~ 4680 to 3500 cal yr BP) shows a good density and diversity of flora. The wet climate and high lake stand ~ 11,000 cal yr BP, 7630 cal yr BP and after ~ 4680 cal yr BP are synchronous with the lacustrine, marine and aeolian records of western India. The contribution of winter precipitation at 7630 cal yr BP and after ~ 4680 cal yr BP can be correlated with similar records from Rajasthan Lake. Decrease in the precipitation activity, the low lake stand and the onset of dry climatic condition between 8000 and 9000 cal yr BP corresponds to a near global anomaly of this period. Another dry event between ~ 5864 and 4680 cal yr BP documented in Pariyaj Lake record is synchronous with various proxy records of the mid–late Holocene Afro-Asiatic monsoonal belt.