ECOLOGICAL RESPONSE OF δ¹³C TO HOLOCENE CLIMATE CHANGES FROM STALAGMITE RECORD IN NUANHE CAVE, LIAONING

A speleothem δ¹³C time series was reconstructed based on 962 stable isotope measurements and 7 ²³⁰Th dates. The sequence covers a time range from 10.6 to 3.5 ka BP, suggesting the evolution of ecological conditions and associated climate changes. The long-term trend of the δ¹³C profile bears a high similarity to SST changes in North Atlantic. Three phases are evident in the stalagmite δ¹³C record:(1) a transition to humid climate in 10.6~8.8 kaBP, during which δ¹³C value displays negative excursions from-9.4‰ to -10.3‰; (2) a humid stage between 8.8 and 6.7 kaBP, in which the δ¹³C value shows negative excursions to the minimum with an average δ¹³C value of -11.3‰. Temporally, this period is in line with the Holocene Optimum; (3) a gradually drying period from 6.7 to 3.5 kaBP, during which δ¹³C value displays positive excursions from -11.3‰ to -8.3‰. Constrained by annual layer counting, the duration of the Holocene Optimum in our record is about 1945 years. Both δ¹³C and δ¹⁸O records show a rapid positive excursion around 6.7 kaBP, indicating an abrupt climate transformation. Annual layer counting suggests that the duration of transformation is about 40 years. It reveals that the interaction of vegetation atmosphere system and lower SST in North Atlantic may amplify the influence of reduced solar insolation via feedback processes.