A 2500 years deglacial record of paleo-vegetation over a cave of southern India as inferred from carbon isotopes of stalagmite

Carbon isotopes of stalagmites are influenced by various factors operating in a cave, like evaporation, vegetation, drip rate and changes in partial pressure of carbon-di-oxide (pCO2) inside and around a cave system. Consequently, interpretation of δ13C record becomes a bit complicated. However, the vegetation changes at a given cave location are generally considered as the dominating factor influencing δ13C values of a stalagmite. The δ13C records can provide useful information regarding changes in the class of vegetation over a cave due to dissimilar pathways of photosynthesis linking C3 and C4 vegetation. Here we present a high-resolution δ13C record from a 180 mm long VSPM1 stalagmite collected from the Valmiki cave in Kurnool district of southern India. This study is mainly based on high-resolution δ13C measurements of 263 subsamples. The data has been used to infer vegetation and climatic variations for the last deglacial period starting from 15,607 to 13,161 years BP. The StalAge modelling was employed on eight U–Th dates to reconstruct the age model of the stalagmite sample. The stalagmite grew at the rate of 0.07 mm per year with varying growth rate from around 0.03 to 0.8 mm per year. X-ray diffraction analysis reveals absolute aragonite mineralogy of the sample. The record exhibits a weak positive relationship between δ13C and δ18O values. The main factors influencing δ13C values were associated with local hydroclimate. The δ13C record suggests vital evidence of rapid alterations in vegetation changes from ~15,607 to 13,161 yr BP. A major shift in vegetation activity occurred from 15,607 to 15,105 yr BP with an episode of highly poor vegetation cover around 15,460 yr BP, followed by a gradual decline in vegetation conditions between 15,105 and 14,722 yr BP.