重庆地区石笋沉积速率与古气候意义初探

选取了重庆南川市梁天湾洞、丰都县水鸣洞相对沉积较快的两根石笋,通过TIM S- U测年数据进行平均生长速率计算,再结合其氧、碳稳定同位素数据进行分析,发现重庆地区末次冰期晚期以来石笋沉积速率与沉积特征、稳定同位素存在一定联系: 氧同位素偏轻,降水较多,石笋沉积颜色较浅,沉积速率较快;反之亦反。但石笋生长速率最快的时期并非总是氧同位素最偏轻、气候最为湿润的时期,可能因为除了温度、降水、植被的影响外,还受到其它因素的干扰,如洞穴岩层滴水管道条件的变化等。因此,石笋生长速率与稳定同位素的关系极为复杂,不能简单地一一对应,且以石笋生长速率作为古气候研究的替代指标还需谨慎。 

Growth rate and the paleoclimatic significance of stalagmites in Chongqing

Two stalagmites collected from Liangtianwan cave and Shuiming cave in Chongqing have been precisely dated by thermal ionization mass spectrometric uranium-series dating.Based on the comparison between the high resolution stable isotopic records and the average growth rate in each depositional phase,it is found that the more fast the growth rate is,the lighter the depositional color is,and the oxygen isotope decreased during the late last glaciation.However,the fast growth rate has not always related with warm-wet periods,just because the factors that affecting the growth rate of stalagmite are not only temperature and rainfall but also any other unknown controlling processes,such as the change in the routing of the cave water.The authors consider that there is a very complicated correlation between growth rate and oxygen isotope of stalagmite.So the growth rate used as an indictor of external paleoclimate should be prudent.