摘要
洞穴内部带沉积物是在同位素达到平衡的条件下缓慢结晶形成。桂林一些洞穴堆积物经同位素δ^(18)O测定,其值反映生成环境温度,最高32.07℃,最低0.42℃。其中温度在5℃以下的占23％。认为,当时洞穴沉积温度曾在0℃左右,洞外环境温度比这还低。
Karst-cave deposits at the inner part of cave are formed by slow crystallization under relatively confined condition and isotopic equilibrium. The δ18O values indicate the paleoclimate for the formation of the cave deposits. From the analyses of 26 samples, the δ18O values vary mostly within the range of 23—25‰, with the low value being 20.66‰ and the high value 27.98‰. According to the combined equation prosposed by Prof. Nobuyuki Nakai by using directly the δ18O value of stalactite and present water to calculate the paleoclimate during the formation of stalactite, the author substituted into the formula the mean δ18O value of dripping water of stalactites still growing in present caves and obtained the highest forming temperature of 32.07℃ and the lowest 0.41℃, with a difference of 30℃. Six samples are determined to form under a temperature less than 5℃, occupying 23% of the twenty-six. According to this analysis, it is considered that during the Quaternary some of the cave depo sits were formed under a low temperature of probably about 0℃. At that time, the yearly normal temperature in Guilin area is several degrees lower than that inside the cave.
出处
《中国岩溶》
CAS
CSCD
北大核心
1989年第3期222-225,共4页
Carsologica Sinica
