The Lower Reaches Of The Yangtze River Stalagmite Records In Holocene East Asian Monsoon Precipitation In High-frequency Variability,

Based on 9 ²30Th dating ages and 1358 data of stable isotope compositions as well as annual layers of the stalagmites in Yi xing cave, Jiangsu province and Nan yang cave, Henan province, two high resolution climate records of East Asian monsoon during mid-Holocene (7 4 ka BP) are reconstructed. By comparing the stalagmite records with the data of ice core, ocean, lake and so on, the author analyzes the links between East Asian monsoon climate and the global changes during mid-Holocene and preliminarily investigates driven forces of the high frequency oscillation of East Asian monsoon climate.As our data indicated, there is markedly negative correlation between the changes of stalagmite δ¹8O and the precipitation fluctuation. The precipitation in Nan yang area, Henan province decreased during a period of 6155 4695 a BP and increased in Yi xing region, Jiangsu province during a period of 5.69 5.16 ka BP. Both two areas' precipitation present distinct oscillation on centennial- to decadal-scale, and the abrupt change of precipitation might have worked on the evolution of new stone civilization in the loci.The overall fluctuate trends of the carbon and oxygen isotope curves of the stalagmite in Yi xing, Jiangsu province is uniform but exists prominent discrepancy in detail: its carbon isotope curve presents three big apexes and two dales and its oxygen isotope curve characterized with high frequency oscillation. The change format of the carbon and oxygen isotope time series of the stalagmite in Nan yang, Henan province is similar, but its trends is reverse. The author suggests that the region ecologic discrepancies and the different productivity of soil CO₂ is the main cause of the variability of the stalagmite carbon isotope.The good corresponding between the two stalagmites δ¹8O time series and tree ring Δ¹4C_res curve during the counterpart periods of mid-Holocene suggests that the precipitation change of East Asian monsoon is markedly driven by the solar activity at the centennial- to decadal-scale. The cycles of 79a, 21a, 10a, 7.8a and so on shown by analysis of oxygen and carbon isotope power spectrum of the stalagmites corresponded to the Gleissberg period, the magnetic period and the sunspot period of the sun activities, and further demonstrated the driven mechanism.The grey level and carbon isotope series of the stalagmite ML(s) commendably corresponds to the seasonal rhythm of the stalagmite annual layers. Lower grey level and negative δ¹3C of the stalagmite are consistent with the compacter translucence laminas which were formed in the dry period when the precipitation markedly decreased. On the contrary, higher grey level and positive δ¹3C of the stalagmite are consistent with the thicker milky white layers deposited during the warm and humid period which occupies the most time of a year.The stalagmite ML(s) δ¹8O indicates the precipitation change in the locus. The periods of 7.1a and 2.8a shown by analysis of its δ¹8O power spectrum reveals that East Asian monsoon precipitation correlated to the ENSO events during the mid-Holocene.