河北阳原盆地井儿洼钻孔岩心氧化铁变化的古环境记录

Paleoenvironmental records of iron oxides variations in drill core from Jing'erwa ,Yangyuan basin,Hebei Province

系统分析了阳原盆地西部井儿洼钻孔剖面的Fe2O3、FeO、TFe(全铁)、Fe3+/Fe2+的变化特点,探讨了阳原古湖氧化铁地球化学特征及其所记录的气候变迁规律。结果表明,阳原盆地的沉积环境相对富集铁,气候总体较温和,垂向上的变化记录了气候的变化过程分为7个明显的阶段。0.2Ma以前以还原环境为主,以后以氧化环境为主。井儿洼岩心沉积物中全铁谱分析表明,0.78Ma之后,具有显著的21.7ka岁差周期,证明了天文因素对气候的影响,而100ka的周期不明显,这与黄土、深海沉积物的记录存在差别。另外还存在390ka、156ka、52ka、33.9ka及14.4ka等周期,表现了湖泊记录的古气候周期的复杂性。

This paper systematically analyzes the characteristics of variations of Fe 2 O 3 ,FeO,TFe(total iron oxides)contents and Fe 3+ /Fe 2+ ratio in sediments of cores from Jingerwa drill hole in the Yangyuan basin,and on that basis the paper discusses the geochemical characteristics of iron oxides in the Yangyuan paleo-lake and the paleoclimatic changes recorded in the iron oxides.The research results show that the sedimen-tary environment in the Yangyuan basin is relatively enriched in iron and that the climate was generally relatively warm in the region.The climatic changes recorded in the iron oxides occurred in seven stages.The reducing environment predominated in the lake before200ka,and the oxidizing environment was dominant after200ka.The TFe spectrum analysis of the core sediments clearly shows the presence of a precessional period of 21.7ka after780ka,which proves that the climatic change was influenced by the astronomic factor.However,the100ka period after780ka is not pronounced,which is different from the records of loess and deep-sea sediments.In addition,the periods of 390,156,52,33.9and14.4ka are also involved in the climatic change,indicating the complexity of the palaeoclimatic periods recorded by lacustrine deposits.