Substrate control of C4 plant abundance in the Himalayan foreland: A study based on inter-basinal records from Plio-Pleistocene Siwalik Group sediments

Abstract

Data from different parts of the globe including the Himalayan foreland suggest that the expansion of C4 plants was not synchronous and hence invoke influences of regional factors on C4 plants evolution. The disparity in the abundance of C4 plants across different regions of the Kangra sub-basin, NW Himalaya, has been attributed to variation in grain size of the substrate and its moisture content. In the absence of vegetation and climate data from the Upper Siwaliks of the Kangra sub-basin, the present study considers the adjacent Subathu sub-basin. The δ13C values of soil carbonate nodule (SC) from the Ghaggar and Moginanda regions and fossil tooth enamel from the Haripur Khol region of the Subathu sub-basin have been measured and compared to data from the other Siwalik regions to assess the spatio-temporal distribution of C4 plants. Additionally, the δ18OSC values have been evaluated to reconstruct local climatic conditions. Stable carbon and oxygen isotope data from SC across the Siwaliks indicate that climate was not the only driver influencing the C4 plant abundance.Comparison of the sedimentary architecture among the different Siwalik regions indicates that the abundance of overbank fine sediments is higher in the western Siwaliks than the central and eastern Siwaliks. The δ13C values and abundance of overbank fine sediments across different Siwaliks suggest a significant influence of substrate on the abundance of C4 plant in the Himalayan foreland.