Bulk organic carbon isotopic record of lacustrine sediments in Dahu Swamp, eastern Nanling Mountains in South China: Implication for catchment environmental and climatic changes in the last 16,000 years

Abstract

A combination of lithology, organic matter accumulation rate, bulk dry density, mass magnetic susceptibility, median grain size, carbon-to-nitrogen and trace element Rb/Sr ratio was utilized to characterize bulk organic carbon isotopic ratio (δ 13C org) of a lacustrine sediment core recovered at Dahu Swamp in the eastern Nanling Mountains as an indicator of past environmental and climatic changes. Chronological sequence of this core was established by twelve conventional radiocarbon dates and the bottom age was determined at ca. 16,000 cal year BP. Multiproxies demonstrate that terrestrial source organic matter may have played a more important role in contribution to accumulation of organic matter in Dahu Swamp than autochthonous source. Multiproxies support the interpretation that bulk δ 13C org record reflects carbon isotopic signal of allochthonous C3 plants on which atmospheric precipitation may exert a strong impact. Although changes in bulk δ 13C org of lacustrine sediments may be resulted from a mixing of materials with different δ 13C signature and with different fraction, and the cause and mechanism leading to the observed organic carbon isotope responses are presently not fully understood, however, this study demonstrates that bulk δ 13C org record of Dahu Swamp sediments has the potential to reflect variation of environmental and climatic changes of the lake catchment since the Last Deglaciation, the more negative the bulk δ 13C org values the stronger the summer monsoon precipitation and vice versa.