洞穴石笋地质事件的定年及意义

Ages and Significance of Geological Events from Stalagmites in Caves, Southern China

本文以贵州荔波董歌洞3号石笋第6、1次和4号石笋第2次主要沉积间断为例,说明依序发生于89.96kaBP、128.65kaBP、113.40kaBP,结束于0.32kaBP、128.21kaBP、65.50kaBP,延续时间89.65ka、0.44ka、47.90ka的沉积间断,具多级次的地质、气候演变属性,沉积间断时间长,显示度明显,气候事件复杂,间断频发,必有更丰富的气候、环境、地质内涵。贵州都匀凯酉七星洞2号石笋Q2F1、Q2F2,5号石笋Q5F3是碰断面,依序发生于74.24kaBP、60.72kaBP、36.80kaBP,彼此相间隔13.52ka、23.92ka,断面及其上、下石笋段的沉积特征,属突变(灾害)性事件,也有其古气候环境意义。系列事件的测年,须在系统测年基础上,于间断、碰断面上下加密测试,及石笋沉积特征的综合观测,以提高事件测年和定性的可信度,增加古气候环境信息量。

This paper took the main deposition interruption of the sixth, third and first order from D3 stalagmite and the second order from D4 stalagmite in the Dongge cave as the examples to show that interruptions occurred in 89964 a, 119658 a, 128650 a and 113399 a and ended in 316 a, 11960 a, 128211 a and 65500 a respectively according to the forming order. The age of the duration of 89684 a, 58 a, 439 a and 47899 a respectively indicated that the deposition interruptions and sedimentary cycles from the stalagmites have the property of the multiple orders and climate events, and also that the time of the deposition interruption is very long, and the property of climate events is complex. If there is interrupted sedimentation, it certainly adds more complicated connotation of climate, environment and geology, for instance, the second deposition interruption from D4 stalagmite is an integrated indication of climate, environment and geological events. The three collision events from Q2 stalagmite occurred in 74253 a, 60738 a, and 36800- 40000 a respectively and the interval time is 13515 a and 22639 a. These data and sedimentary characteristics of the interruption interface from the upper part and lower part of stalagmite represented the calamitous property of the collision interface and contained information of paleoclimate environment. Dating of serial events must be carried out on the upper part and lower part of sedimentary interruption and collision interface together with observation of synthetic sedimentary characteristics of stalagmite parts on the basis of systematic dating, to enhance the dating and qualitative reliability and information of paleoclimatic environment.