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

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 delta O-18 values of SC (delta O-18(SC)) range from -7.6 to -4.9aEuro degrees. The variations in delta O-18(SC) 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 delta C-13 value of SC (delta C-13(SC)), organic matter dispersed in the soil (delta C-13(SOM)) and occluded in the carbonate nodules (delta C-13(NOM)) ranges from -4.1 to +1.4aEuro degrees, -25.6 to -16.3aEuro degrees, and -27.7 to -25.0aEuro degrees, respectively, implies mixed C-3-C-4 vegetation over the Ganga Plain. Variations in delta C-13(SOM) and delta C-13(NOM) 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 C-3-C-4 vegetation were mainly driven by variations in monsoonal rainfall intensity. Using Sr-87/Sr-86 in SC, we show that the Himalayan river was supplying sediments in the southern part of the Ganga Plain during MIS 3.