再论洞穴石笋的沉积速率

通过对滇、黔、湘、桂洞穴石笋大型剖面的综合研究、，以代表性剖面和典型时（笋）段系统测年和沉积速率研究为例，初步认为，石笋沉积速率大小是气候演变、暖气候、冷气候的识别指标之一，沉积速率为10mm／100a以上是冰后（间冰）期温暖气候的沉积，趋于10mm／100a或以下者，是温暖期气候的冷转变，或冷期（阶）的沉积；1mm／100a左右是冰期寒冷气候的沉积，趋于1mm／100a或以上者是冰期寒冷气候的暖转变或间冰期的沉积；沉积速率极小，往往是冷气候显示，甚至是沉积间断，或是气候和地质、灾害事件的突变点。沉积速率具多变性，引用和识别时应避免以单一速率推算长时（笋）段年序和确定气候或地质事件的年代，不宜跨旋回计速，以避免遗漏沉积间断和气候、地质、灾害事件。石笋沉积间断很普遍，特别是寒冷的冰期气候间断更频繁，观测和测年表明，沉积间断时间累计占成笋期的28．92％～76．26％，全新世温暖气候的沉积间断时间累计，只占成笋期的13．80％以上。

Growth Rate of Cave Stalagmite

The growth rate of stalagmite is an index of distinguishing warm and cold climates as evidenced by a synthetic study of large stalagmite sections, synthetic dating of representative stalagmite sections in Yunnan, Guizhou, Hunan and Guangxi provinces. The growth rate is over 10 mm/100 a in warm humid climate in the interglacial or postglacial period, while that is 1 mm/100 a or less in the transition from warm humid to cold climate or cold stage. A growth rate of about 1 mm/100 a represents cold climate in the glacial period, and a growth rate close to 10 mm/100 a or much more indicates a transition from cold climate in the glacial period to warm humid climate period or interglacial period. The minimal growth rate is often indicative of cold climate and even depositional break and sudden change of climate and geology and hazardous events. The growth rate of stalagmite is not so reliable and should avoid using only the growth rate to calculate the age sequence of stalagmite in a long time span or ages of events. The growth rate should not be calculated across cycles to avoid missing some important information such as depositional break, climatic, geological and hazard events. Depositional breaks in stalagmite are very common and are especially more frequent in cold climate in the glacial period. The observation and dating age data suggest that the accumulative time of depositional break only accounts for 28. 92%-76. 26% of stalagmite formation and that of warm climate in the Holocene is only 13.80% of stalagmite formation.