Shennongjia Stalagmite Record Late Holocene East Asian Monsoon Evolution And Mutation

The Holocene is the interglacial period of the latest glacial-interglacial cycle. Characterized by several abrupt climate events, Holocene climate change is suggested to be closely related to human-civilization development. Thus study of the Mid-Late Holocene paleoclimate fluctuation and its mechanism is significant.In the present research, three stalagmites were collected from Yongxing Cave of Shennongjia, Hubei Province. Based on19230Th dates and1683oxygen isotope data, valuable and high-resolution δ18O profiles have been established for the Middle and Late Holocene. In these profiles, the largest amplitude of the δ18O (3.5%o) is much bigger than the DA δ18O record from Dongge Cave, implying that the Yongxing stalagmites have recorded local paleoclimate variation sensitively. By comparing with other climate records, the Yongxing δ18O record is generally concordant with the Northern Hemisphere summer isolation at65°N. Importantly, four positive excursion, around1200yr BP,3000yr BP,4200yr BP and5800yr BP respectively, were found in the record, corresponding to four ice-rafting events in ice rafted debris record of North Atlantic. It should be the evidence for the correlation between North Atlantic climate change and East Asian Monsoon change at millennium scale. Periodicities of200yr,80yr, pene-70yr and53yr were shown by Power Spectrum, suggesting that the East Asian Monsoon variation should be deeply influenced by solar activity at decadal-centennial time scales.Among the four weak monsoon events in Yongxing δ18O record, the3000yr BP event is the most notable one. Based on the δ18O records of two U/Th-dated stalagmites (YX37a and Yx37b) and an annual-layers-counted one (YX57), this event started abruptly at3005yr BP and ended slowly, the duration is179±7yr. This3000yr BP weak monsoon event may be related to both solar activity and positive feedback of Ocean. And it is probably the most severe climate change event in China during the past5000yr. As the monsoon became weaken, rain belt moved southward, and disasters of aridity/flood should have happened frequently. Thus correlation should exist between climate change and the Chinese dynastic change; climate should have played an important role in human civilization development.