THE STALAGMITE RECORDS OF CLIMATE AND ENVIRONMENT CHANGE ON THE WESTERN SHANDONG PENINSULA DURING THE PAST 1000 YEARS: ¹⁸O AND ¹³C VALUES(Ⅰ)

The Stalagmite Ky1, a 75 mm long stalagmite, was collected from the Kaiyuan Cave on western Shandong Peninsula. Upon the basis of high precision U-²³⁰Th dating, further dated with annual lamination counting and interpolation/extrapolation of the average deposition rate, the stalagmite is about 1 000 years in age from 892AD to 1894AD. 583 samples are collected along the growth axis of the Ky1 stalagmite, and the δ¹⁸O and δ¹³C values for 303 samples are measured. The average temporal resolution is about 3 years. The δ¹⁸O values of the stalagmite Ky1 are obviously phased in the recent 1000 years. There are a series of centennial to multicentennial climatic fluctuations in the Little Ice Age (LIA) and Medieval Warm Period (MWP). The δ¹⁸O records also indicates a climate mutation occurred at about 1482AD on Shandong Peninsula corresponding to the MWP/LIA transformation, relatively wet and strong summer monsoon climate was prevailing over the Medieval Warm Period before 1482AD, and relatively dry and weak summer monsoon climates dominated the Little Ice Age after 1482AD. The weakest summer monsoon occurs in 1609AD. The δ¹³C curve of the stalagmite Ky1 is also composed of the two stages corresponding to MWP and LIA respectively with a mutation in between. Relatively, the curve of δ¹³C is smoother than the curve of δ¹⁸O and the variation in δ¹³C values and δ¹⁸O values are obvious out of sync in late LIA.
The climate mutation corresponding to the MWP/LIA transformation was happened roughly in the middle Ming Dynasty in China. The climate variation tendency is different in different dynasties. The changing stages of different dynasties are usually corresponding to the secondary climate period within MWP and LIA. So the impact of the fluctuation of the secondary climate variation on human society development in MWP and in LIA looked more prominent than the most violent climate transition between MWP and LIA in a millennium scale. On the other hand, the degree of the land use showed unceasing enhancement in the study area together with the climate change that affected vegetation-soil-groundwater environment system in the mountain land above the cave, and the δ¹³C values of stalagmite. The impact level of the land use by human on the mountain vegetation composition, soil characteristics and their variation trend has not reached the level of the climate change from 892AD to 1318AD, but reached or exceeded the slight climate changes from 1318AD to 1479AD, and reached or exceeded the sharply climate change from 1483AD to 1779AD, the impact of the human land use and the environment seemed to be stabilized from 1779AD to 1894AD, and the impact of the climate change on the environment was intensified relatively.