High-resolution δ18O and δ13C records during the past 65 ka from Fengyu Cave in Guilin: Variation of monsoonal climates in south China

The δ¹⁸O and δ¹³C records of a ²³⁰Th/U dated, 2.2-m long stalagmite from Fengyu Cave in south China provide a continuous decadal-resolution (with 3698 measurements) proxy for regional climatic and environmental conditions during 4–65 ka. This single stalagmite reveals all Heinrich cold events, most Dansgaard-Oeschger warm events, deglaciation and Holocene Optimum, generally supporting the Hulu and Dongge records. On 5000–10000 year time-scales, the δ¹⁸O and δ¹³C variations show strongly positive correlations (R = 0.7), reflecting that a common climatic factor controls both δ¹⁸O and δ¹³C of F-1. The comparison of the speleothem, ice core, insolation and marine records reveals strong linkages between N. Atlantic temperature and the Asian summer monsoon over most of the study period. However, there are some regional discrepancies between the stalagmite δ¹⁸O records following the deglaciation. Although the NH summer insolation provides the major forcing on Asian monsoon variability over orbital time-scales, the weakest summer monsoon intensity during the last glacial occurred ca. 16 ka corresponding to the Heinrich event 1; a 5–6 ky lag from the minimum insolation during the Last Glacial Maximum. Variations in the monsoonal climate of the study area over the past 700 years have been reconstructed from the δ¹⁸O and δ¹³C records of a 14.6-cm long stalagmite F4 in Fengyu cave, showing wet conditions between AD 1550 and AD 1850 (the Little Ice Age) and relatively dry conditions before and after this interval. Human impacts on local vegetation since AD 1700 were recorded by the δ¹³C record of stalagmite F4.