Paleoclimatic, paleovegetational and provenance change in the Ganga Plain during the late Quaternary

Abstract

Present study aims at reconstructing the paleomonsoonal rainfall, paleovegetation and provenance change during the late Quaternary. Towards this, Bhognipur core, collected from the southern Ganga Plain, have been sampled for soil carbonate (SC) and soil. The δ 18O values of SC (δ 18OSC) range from −7.6 to −4.9‰. The variations in δ 18OSC values suggest that during the late Quaternary, the monsoon intensified during MIS 3 and MIS 1 and the maximum lowering of rainfall intensity is observed during MIS 2. The δ 13C value of SC (δ 13CSC), organic matter dispersed in the soil (δ 13CSOM) and occluded in the carbonate nodules (δ 13CNOM) ranges from −4.1 to +1.4‰, −25.6 to −16.3‰, and −27.7 to −25.0‰, respectively, implies mixed C3–C4 vegetation over the Ganga Plain. Variations in δ 13CSOM and δ 13CNOM values at same depth imply preservation problem of pristine organic matter signature. Therefore, it is important to assess the preservation of residual organic matter before using it for paleovegetational reconstruction. The monsoon-vegetation relationship indicates that relative abundances of C3–C4 vegetation were mainly driven by variations in monsoonal rainfall intensity. Using 87Sr/86Sr in SC, we show that the Himalayan river was supplying sediments in the southern part of the Ganga Plain during MIS 3.