Changes in C<sub>3</sub>/C<sub>4</sub> vegetation in the continental interior of the Central Himalayas associated with monsoonal paleoclimatic changes during the last 600 kyr

Abstract

Abstract.A continuous lacustrine sediment core obtained from the Kathmandu Valley in the Central Himalayas revealed that cyclical changes in C 3 /C 4 vegetation corresponded to global glacial-interglacial cycles from marine isotope stages (MIS) 15 to MIS 4. The C 3 /C 4 vegetation shifts were reconstructed from significant changes in the δ 13 C values of bulk organic carbon. Glacial ages were characterized by significant 13 C enrichment, due to the expansion of C 4 plants, attributed to an intensification of aridity. Thus, the southwest (SW) summer monsoon, which brings the majority of rainfall to the Central Himalayan southern slopes, would have been weaker. Marine sediment cores from the Indian Ocean and Arabian Sea have demonstrated a weaker SW monsoon during glacial periods, and our results confirm that arid conditions and a weak SW monsoon prevailed in the continental interior of the Central Himalayas during glacial ages. This study provides the first continuous record for the continental interior of paleoenvironmental changes directly influenced by the Indian monsoon.

Two times lowering of lake water at around 48 and 38 ka, caused by possible earthquakes, recorded in the Paleo-Kathmandu lake, central Nepal Himalaya

“…As a result, changes of various kind of proxy during the last 600 kyr were reconstructed: history of vegetation and monsoon climate (Fujii et al 2004a;Maki et al 2004), ecological changes of diatom (Hayashi et al 2009), and changes in TOC, C/N, δ 13 C of organic matter (Mampuku et al 2008). Mineralogical study of lacustrine clay during the last glacial period revealed that amount of clay fraction, clay mineral assemblage, and crystallinity were strongly controlled by paleoclimate (Kuwahara et al 2010).…”