| Wanxiang Cave is located in the transition zone between the eastern edge of Qinghai-Tibet Plateau and southwestern edge of the Loess Plateau. This zone,closed to the northern boundary of the summer monsoon,is a typical monsoon systems interaction area, is sensitive to changes in the Asian monsoon,and is a ideal location to study the Asian monsoon.There are many climate proxy indicators in stalagmite,including: carbon and oxygen isotopes, gray, micro-level, trace elements, growth rate, the molecular fossils, density and so on. In the past ten years,the climate research on Wanxiang cave was focus on the carbon and oxygen isotope records.In this paper,we use stalagmite WXB07-4 and WXB07-3 collected from Wanxiang Cave as the research materials. We extract the reflected light gray curve of the stalagmite WXB07-4, combined with its 18 230Th age and 311 oxygen isotope records,to research the gray features of Asian monsoon changes between 8.9 ka BP to 5 ka BP. And through comparing with other records,we discuss the driving mechanism of gray change.then we research the micro-level characteristics of the stalagmite WXB07-3,and discuss possible factors of the stalagmite formation. And we obtained the following conclusions:1,The change of the growth rate of WXB07-4 is great. The minimum is in 5.6-5.lka BP and the maximum is near 6.4ka BP.On the whole,during 8.9-6.7 ka BP, the growth rate is relatively low. During 6.7-6.2 ka BP, although there have been two growth rate fluctuations, but the overall growth rate is higher. From the beginning of 6.2ka BP, the growth rate gradually declined to the lowest value.2, The gray characteristics of the stalagmite WXB07-4 can be divided into four stages:(1) During 8.9-8.5ka BP, the gray level increase from a low value; (2) During 8.5-6.4ka BP, although the gray value is ups and downs, but overall has a little change; (3) During 6.4-5.6ka BP, the gray value has a sudden increase and then gradually decreased; (4) During 5.6-5ka BP, the gray value is lower.3,The correlation coefficient of the gray and d18O of WXB07-4 is-0.35. This proves that there is a strong correlation between the gray and d18O. When d18O value is great, this is representative of the relatively weak monsoon, low temperatures,little precipitation,and small gray value,vice versa. This proves that the gray change in stalagmite can provide an effective supplement for paleoclimate and paleoenvironment reconstruction.4, WXB07-4 gray, d18O, Dongge DA d18O and Aman Q5 d18O consistent record four monsoon weakened events occur in 8.2ka BP,7.25ka BP,6.25ka BP and 5.6-5.2ka BP.5, There is a good correlation between WXB07-4 gray and total solar irradiance. It indicate that Asian monsoon closely related to solar activity.Between WXB07-4 gray and GISP2 ice core oxygen isotope also have a good correlation,indicating that Asian monsoon synchronously change with northern hemisphere high latitude temperature.6, The micro-layer microscopic characteristics of stalagmite WXB07-3 is classified in typical North-type stalagmite micro-layer characteristics.Contrast with Shihua Cave stalagmite,combined with the modern climate change discipline in these two places,we find that the thickness of dark tripes in micro-layer may be related closely to changes of the annual precipitation and average temperature.
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