华北平原中部晚上新世以来沉积物碳氧同位素特征及其古环境意义

利用华北平原中部衡水水文地质科研深孔的岩芯,对平原区古土壤钙结核层碳氧同位素组分的古气候环境意义及相关气候指标的定量转换进行探讨,发现碳氧同位素对古气候变化具有较好的响应关系:3.5MaB.P.以来华北平原古气候逐渐由湿润转向干旱,早更新世由多个干湿冷暖旋回组成,晚期气候由暖迅速转凉;中更新世气候略温和,由3个冷干-暖湿旋回组成;晚更新世气候变化趋势为湿润-干燥-湿润,总体上呈现增温趋势。进入全新世后,δ13C平均值(-5)较低,属于相对湿润期;δ18 O平均值(-9.5)较低,属于相对寒冷期。应用相关公式可以定量恢复古温度变化,但平原区古土壤层受后期地下水作用的影响较大,如何消除这一影响还需更多数据支持。

Carbon and Oxygen Isotopic Characteristics of Sediments and Their Paleoenvironmental Significance on the Central North China Plain since Pliocene

By using the core of the hydrogeological research hole in Hengshui on the central North China Plain,this paper discussed the climatic and environmental significance of carbon and oxygen isotope in the calcareous concretion layer and their quantitative conversion among the related climatic indexes.The carbon and oxygen isotopes has better response to ancient climate change had been found:1) For the North China Plain,since 3.5 MaB.P.,the ancient climate gradually changed into arid from humid;in early Pleistocene,there were many cycles of wet-dry and cooling-heating;and in later Pleistocene,the climate rapidly changed into cool from warm;2) In middle Pleistocene,the climate was milder,and there were three cycles of cold-dry and warm-wet;3) Late Pleistocene,the climate change trend was moist-dry-moist,the overall trend appeared rising temperatures.Since the Holocene,the lower average value of δ13C and δ18O reflected a relatively moist-cold period.The paleo-temperature change can be quantitatively recovered by using correlation formula.But it was great that the late groundwater influenced on the paleosoil layer after being soiled and covered at plain area,how to eliminate this influence still requires more data to support.