The Late Neogene distribution of C 3 -C 4 plants in the Himalayan foreland basin: Insight from the δ 13 C values and sedimentological architecture of the Siwaliks

Abstract

Recent studies emphasize that in addition to climate-driven forces, sediment grain size and depositional setting with respect to mountain front significantly influenced the abundance of late Neogene C 3 -C 4 plants in the Himalayan Foreland Basin (HFB). The contrasting depositional settings of the Siwalik Group exposed across the western, central and eastern HFB therefore provide an ideal opportunity to understand the influence of sedimentary architecture on the distribution of C 3 -C 4 plants in paleolandscapes. Towards this end, we generate new δ 13 C soil carbonate data from Siwaliks of the Katilukhad region (12 Ma to 6 Ma) of Kangra sub-basin and synthesize these data with compiled sedimentological data and δ 13 C values of organic matter, soil carbonate and n -alkane data from western to eastern HFB Siwalik Group. Our comparison suggests that the rate and magnitude of positive shift in the 13 C/ 12 C ratios were higher in the floodplain-dominated Siwaliks. Despite an existing conducive climate in the late Neogene for the growth of C 4 plants, the channel-fill-dominated Siwaliks favored C 3 over C 4 plants in the eastern HFB. Supplementary material at https://doi.org/10.6084/m9.figshare.c.7168691