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利用重庆芙蓉洞内各种新老沉积物的δ~(13)C、δ~(18)O以及对洞穴内的滴水、池水和洞外泉水的长期观测结果,发现芙蓉洞内的次生沉积物中氧同位素变化整体一致,处于稳定温度下(16℃)的平衡分馏状态。而且洞内滴水和池水的氧同位素也相当一致,反映了外界大气降水中氧同位素的年平均状态。芙蓉洞内各种沉积物中碳同位素变化范围很大,从0‰～-11‰均有分布。由于芙蓉洞内各种滴水以及池水中溶解无机碳(DIC)的δ~(13)C变化约在-8‰～-11‰,显著偏轻于部分洞穴沉积物中的δ~(13)C。通过研究从洞穴滴水到形成次生化学沉积物这个过程中的可能影响洞穴沉积物中碳同位素变化的因素,例如:洞穴温度、滴水高度和速率、CO_2脱气、生物作用、矿物同质异相转换等,同时参考芙蓉洞内连续生长达37 ka的FR5石笋的碳同位素记录,发现以上可能的影响因素都不能完全解释芙蓉洞内次生沉积物中碳同位素的异常偏重现象。虽然芙蓉洞内广泛存在文石与方解石共存的次生沉积物,但是综合分析表明这些沉积物的氧同位素处于平衡分馏状态,可以用来进行古气候研究。不过在利用石笋碳同位素解释古环境变化时需要慎重,特别是在讨论由文石或文石—方解石混合构成的次生沉积物时。
Based on the δ 13 C, δ 18 O of various old and new sediments in Furong Cave in Chongqing and the long-term observations of drip, water and springs outside the cave, it is found that secondary sedimentation in Furong Cave Oxygen isotopes in the overall change, at a stable temperature (16 ℃) equilibrium fractionation state. Moreover, the drip and water oxygen isotopes in the cave are also quite consistent, reflecting the annual average state of oxygen isotopes in the atmospheric precipitation. Furong cave sediments of various carbon isotopes vary widely, from 0 ‰ ~ -11 ‰ are distributed. The δ 13 C of dissolved inorganic carbon (DIC) in Furong Cave varies from -8 ‰ to -11 ‰, which is significantly lower than δ 13 C in some cave sediments. . By studying the factors that affect the carbon isotope variation in cave deposits during the process of drip from the cave to the formation of secondary chemical sediments, such as cave temperature, drip height and rate, CO 2 degassing, biological effects, mineral heterogeneity In the meantime, reference is made to the carbon isotope records of FR5 stalagmites that grew up to 37 ka in Furong Cave. It is found that the above possible influencing factors can not completely explain the abnormal carbon isotope imbalance in the secondary sediments in Furong Cave. Although the secondary sediments with aragonite and calcite exist widely in Furong Cave, the comprehensive analysis shows that the oxygen isotopes of these sediments are in a state of equilibrium fractionation and can be used for paleoclimate research. However, caution should be exercised when interpreting paleoenvironmental changes using stalagmite carbon isotopes, especially when discussing secondary sediments composed of aragonite or aragonitic-calcite mixes.