Stable (δ13C and δ15N) Isotopes and Magnetic Susceptibility Record of Late Holocene Climate Change from a Lake Profile of the Northeast Himalaya

Abstract

Abstract This study aims at reconstructing paleovegetation history in the northeast Himalaya during the past 2700 yrs using a 100 cm long sedimentary section selected near Anini village, Dibang valley, Arunachal Pradesh (India). Stable carbon and nitrogen isotopic composition (δ13C and δ15N); and total organic carbon (TOC) and total nitrogen (TN) content in organic matter as well as magnetic susceptibility were determined. Results obtained show a strong correlation between TOC-TN indicating similar source for organic matter. δ13C and TOC/TN ratio throughout the stratigraphic unit seems to be poorly correlated which suggests that the primary carbon isotope signatures are preserved in the sedimentary environment. Overall, δ13C values of the organic matter in the section vary in the range from −23.9 to −21.2 ‰ which is typical of mixed C3-C4 plants.. A distinguishable increasing trend in δ13C during 2700 to 1300 yrs indicates change in vegetation pattern from C3 to C4 plants due to significant climate change from wetter to drier conditions. After 1300 yrs δ13C values decrease rapidly by 1.3‰ and suggest increasing abundance of C3 plants in wetter climatic condition. The relatively small variation in δ13C values in the upper part of the section during 1200 yrs to present suggest a stable climatic condition.