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对最近250 ka大荔地区两个剖面全岩碳酸盐的碳同位素组成进行了分析,初步探讨了影响黄土.古土壤序列δ13Csc值的因素及其古环境意义.大荔黄土-古土壤序列δ13Csc值与磁化率的变化基本同步,δ13Csc曲线的负峰分别对应着不同的古土壤发育期.研究认为,植物成因Co2的介入会导致δ13Csc值降低,降低的幅度主要与古植被发育程度和古湿度有关,植被中C4植物的相对含量可能仅影响其次一级的变化.低δ13Csc值大体上指示了植被相对丰富、气候湿润的环境状况.倒数第2次间冰期以来,大荔地区植被发育最差、最干旱的时期是L2的黄土堆积期;而植被最为丰富、气候最湿润的则是末次间冰期.发生在MIS(深海氧同位素)第3阶段晚期即40～30 kaBP的青藏高原“高温大降水事件”的水文效应已波及气候相对湿润的关中地区,对当地植被和湿度均产生了明显影响.
The carbon isotopic compositions of the whole carbonate rocks in the two sections of the Dali area in the recent 250 ka were analyzed, and the factors influencing the δ13Csc value of the loess-paleosol sequence and their palaeoenvironmental implications were discussed. The sequence of δ13Csc The values of δ13Csc and the negative peaks of δ13Csc curve correspond to different paleo-soil development periods respectively. It is concluded that the involvement of plant genesis Co2 leads to the decrease of δ13Csc value, which is mainly attributed to the relationship between paleo-vegetation development and paleo-humidity , The relative content of C4 plants in vegetation may only affect the next level of change.The low δ13Csc value generally indicates the relatively rich vegetation and humid climate conditions.The vegetation in Dali area has the poorest development since the penultimate interglacial period , The driest period is the loess accumulation period of L2, while the most abundant vegetation and the most humid climate are the last inter-glacial period occurred in the late stage 3 of MIS (deep sea oxygen isotope), that is, the high temperature of 40 ~ 30 kaBP The hydrological effects of the “precipitation event” have spread to the relatively humid climate of the Guanzhong region, which has a significant impact on the local vegetation and humidity.