新疆吐鲁番盆地古近纪气候事件的研究  

Study on the Paleogene climatic events in Turpan Basin,Xinjiang

作　　者：昝立宏[1] 程捷[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《古地理学报》2008年第6期647-656,共10页Journal of Palaeogeography：Chinese Edition

基　　金：中国核工业总公司地质局资助项目(编号:2-8-01-04)

摘　　要：吐鲁番盆地是天山山脉中的一个山间盆地,古近系保存完好,是研究中国西北地区古近纪气候变迁的良好地区。通过对吐鲁番盆地连木沁剖面古近系多种气候代用指标(Fe2O3、FeO、CaCO3、有机碳、有机碳同位素)的研究,探讨了吐鲁番盆地古近纪的气候变迁和重要气候事件。利用Fe3+/Fe2+值,恢复了吐鲁番盆地古近纪的气温:古新世的年均气温为22.35℃,始新世为21.82℃,渐新世为15.69℃,并且在渐新世的早期和晚期发生较大幅度的降温事件。对地层中CaCO3(碳酸钙)含量的研究表明,古新统和始新统碳酸钙平均含量分别为4.68%和6.66%,指示该沉积时期气候相对比较湿润,而渐新统达15.01%,指示渐新世气候明显干旱化,并且渐新世的早期和晚期气候更为干旱。有机碳同位素(δ13Corg)值分布于C3植物的范围内,表明其受C3植物的影响。对地层中的δ13Corg值研究显示,该值与地层中碳酸钙含量呈负相关,与气温呈正相关,即该值偏负时,地层中碳酸钙含量增加,气温降低。各种气候指标指示吐鲁番盆地古新世和始新世气候比较温暖湿润,而渐新世气候干旱温凉。The Turpan Basin is an intermountain basin in the Tianshan Mountains. A good preservation of the Paleogene in this basin provides abundant information for studying of the Paleogene climate in Northwest China. Based on various climatic proxies from a section at Lamjin in the Turpan Basin, such as Fe2O3, FeO, CaCO3, organic carbon and organic carbon stable isotopes, this paper focuses on climatic changes and key climatic events during the Paleogene. Temperatures of the Paleogene in the Turpan Basin are estimated by the ratios of Fe37Fe^2＋ Annual mean temperatures were 22.35℃ in the Paleocene, 21.82℃ in the Eocene and 15.69℃ in the Oligocene respectively. A key temperature-falling event took place during the transitional period from the Late Eocene to the Early Oligocene. Researches on CaCO3 content of the Paleogene indicate that the mean content of CaCO3 was 4.68% in the Paleocene and 6.66% in the Eocene respectively, while the mean content of CaCO3 reached 15.01% in the Oligoeene. These data show that the climates in the Paleocene and Eocene were relatively humid, while arid in the Oligocene. Values of organic carbon stable isotopes （δ^13Corg） from the Paleogene sediments concentrate in the scope of the C3 plants, which indicates C3 plants were developed in the Turpan Basin at that time, and δ^13Corg values have a negative relationship with CaCO3 content but a positive relationship with temperatures. Namely, a decrease of the δ^13Corg value corresponds to an increase of the CaCO3 content and a fall of the temperature. The various climatic proxies indicate that the climate was relatively warm and humid in the Paleocene and Eocene, while arid and cool in the Oligocene.

关 键 词：吐鲁番盆地 古近纪 气候事件 地球化学 有机碳同位素 

分 类 号：P532[天文地球—古生物学与地层学]