Complicated responses of stalagmite δ~（13）C to climate change during the last glaciation from Hulu Cave, Nanjing, China

摘要

We present a record on carbon stable isotopic composition (δ~(13)C), covering 75 through 10 thousands years ago (ka B.P.), from Hulu Cave, Nanjing. The overlapping δ~(13)C profiles are very similar in pattern and range, indicating that they mainly record climatic signal. During the last glacial-interglacial transition, the >6 per thousand change of δ~(13)C values implies different contributions of C3 vs. C4 type plants in soils. On millennial scale, however, the increased calcite δ~(13)C during the warm Dansgaard-Oeschger (DO) events suggests a decrease of dissolved bio-genic CO_2 when water flux rate through soil is large. This correlation between heavier δ~(13)C and higher precipitation is consistent with our previous report on the samples' stable oxygen isotope records (Wang et al., 2001). Comparison of coeval δ~(13)C and δ~(18)O of stalagmites indicates that kinetic fractionation of carbon isotope is closely related to growth rate of stalagmites. This study also shows that local vegetation changes may lag behind precipitation changes by ～700 years during the deglaciation.