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

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.