A high-resolution stalagmite record of the Holocene East Asian monsoon from Mt Shennongjia, central China

摘要

High-resolution oxygen isotope (δ~(18)O) profiles of six stalagmites from Sanbao Cave in Hubei province, central China, established with 1413 oxygen isotope data and 65 ~(230)Th ages, provide a continuous history of East Asian Summer Monsoon (EASM) intensity for the period from 13-0.2 thousand years before present (ky BP, relative to AD 1950). The δ~(18)O record includes four distinct stages in the evolution of the EASM: (1) an abrupt transition (～11.5 ky BP) into the Holocene; (2) a period of gradual increase in monsoon intensity (11.5-9.5 ky BP); (3) the maximum humid period (9.5-6.5 ky BP); and (4) a period of gradual decline in monsoon intensity (6.5-0.2 ky BP). Comparison of Sanbao with regional records of comparable resolution reveals that the timing of the beginning and end of the Holocene Optimum (as defined by the minimum in δ~(18)O) was similar in the Indian and East Asian monsoon systems. This supports the idea that shifts in the monsoon tied to shifts in the mean position of the Inter-Tropical Convergence Zone (ITCZ) may control monsoon intensity throughout the entire low-latitude region of Asia on orbital timescales. This observation also supports the idea that the fluctuations in δ~(18)O recorded across southern Asia reflect broad changes in the monsoon, as opposed to local meteoric precipitation. The EASM records from Sanbao largely follow orbital-scale insolation changes, yet exhibit similar variability to Greenland ice core δ~(18)O on millennial to centennial scales during the early to middle Holocene (r = 0.94).