The Relationship Between Gray Scale,Layer Counting And Trace Elements Of A Stalagmite From Wanxiang Cave,Wudu,Gansu

The serious climate problem is now gotten more and more attention,and the climate has a direct impact on people's production and life.Most parts of China are affected by the Asian monsoon and sometimes heavy rains or severe dry weather caused by monsoon often bring a series of negative effects on the local people.Therefore,it is very important to reconstruct the past climate and predict the future weather.Wanxiang Cave which located in the Intersection zone of Chinese Loess Plateau and Tibetan Plateau influences by Asian monsoon and records climate change information in a timely manner as well.Here we take a stalagmite WXB081 as our object,analyzing and discussing the climate indexes such as gray scale,layer and trace elements.By comparing the relationship between stalagmite gray scale and trace elements,we can get the variation of Asian monsoon during stalagmite deposition.By analyzing the layer of a particular period of stalagmite,the relationship between the stalagmite layer and the gray scale of the stalagmite is discussed,and the following conclusions are obtained:1.Changing in the gray curve of stalagmite WXB081 can response the Asian Monsoon at the time:(1)the stalagmite gray increases in 0-38 mm,75-130 mm,170-258 mm,280-325 mm,which reflect a strong Asian monsoon,adequate precipitation and high temperature at that time in Wudu area;(2)the dramatic decline of the stalagmite gray in 38-75 mm,130-170 mm,258-280 mm,325-350 mm indicates weakening stages of Asian monsoon with few precipitation and low temperature;(3)the rising trend with small range of stalagmite in 350-560 mm indicates a strengthened stage with a small range of Asian monsoon.2.By comparison layer counting with gray scale in a special period,we consider that gray scale data can better identify fuzzy region layer numbers and characteristics,which provide a basis for further establishment of layer and gray chronology.3.Comparing the common trace elements ratios of stalagmite WXB081(K/Ca,Sr/Ca,Ba/Ca)and less common trace elements ratios(Mn/Ca,Al/Ca,Pb/Ca)with the stalagmite gray scale,we can obtain the following conclusions: the trace elements ratios have a consistent change with gray scale in the deposition period of stalagmite WXB081,which indicates that the trace elements and stalagmite gray scale have the same control factors during the deposition period affected by Asian monsoon.However the magnitude of the ratios of K/Ca,Sr/Ca and Ba/Ca can directly reflect the climate information such as soil,vegetation,microbial activity and local dust at the time of stalagmite deposition.The reduction of the ratios corresponds to the increase of the gray degree,indicating that the monsoon was an enhancement phase,and vice versa.As for the ratios of Mn/Ca,Pb/Ca and Al/Ca,because of its special presence of trace elements in water bodies,the ratios of the curve is smaller.But the size of the ratios is still a direct response to the strength of the Asian monsoons at the time.The larger the ratios are,the weaker the monsoon is,and vice versa.