Stalagmite multi-proxy evidence of wet and dry intervals in the middle Yangtze Valley during the last glacial period

Abstract

There continues to be debate on the wet and dry conditions in central China due to different geological archives and proxy interpretations. This study reconstructed multi-proxy sequences spanning intervals between 65 and 40 ka using high-precision Th-230 dates, which was carried out on a stalagmite from Yongxing cave in the middle Yangtze Valley located in the Meiyu belt, China. Merely according to the petrography of the sample, Heinrich (H) 5-H6, Dansgaard–Oeschger (DO) 9-DO18 (or even secondary changes including DO15a and DO15b; DO17a, DO17b, and DO17c) were directly identified alongside the oxygen isotope record. The δ 13 C, trace elements, mineralogical, and bio-geochemical proxies exhibited similar millennial changes to that of the δ 18 O. This provided an indication of responses to millennial-scale climatic events in the karst hydrological cycle, local environment, and soil vegetation; however, the sensitivities to these events differed. Petrographic analyses of the same stalagmite including scanning electrical microscope (SEM), X-ray diffraction (XRD), fluorescence intensity, the deposition rate, and the diameter index depicted a dry-cold climate during the H events, and a wet-warm climate during the DO cycles in the middle Yangtze Valley. These results are consistent with the peat records of Dajiuhu Lake in the same area. We suggest that a combination of Atlantic Meridional Overturning Circulation (AMOC) and El Niño-Southern Oscillation (ENSO) may exert a strong influence on the Meiyu region and the related precipitation. • Identification of H events and DO cycles through stalagmite's petrography. • The δ 13 C and trace elements have similar trend and different amplitude to that of δ 18 O. • Petrographic analysis (i.e. SEM, grey-level, etc.) show a humid climate in DO cycles. • Sedimentary features such as laminae morphology exhibit a dry climate in H events. • The coupling effect of AMOC and ENSO affect the climate in the Meiyu region.