青海循化盆地23.1～5.0Ma沉积地层中常量、微量元素组成特征及其古气候演变  

Major and Trace Element Characters of the Sediments and Paleoclimatic Evolvement during about 23.1-5.0 Ma in Xunhua Basin,Qinghai

作　　者：叶荷[1,2,3] 张克信[1,2,4] 季军良[1,2] 梁美艳[1,2] 张键钰[1,2] 徐亚东[1,2] 陈奋宁[5] 

机构地区：[1]中国地质大学生物地质与环境地质教育部重点实验室,湖北武汉430074 [2]中国地质大学地球科学学院,湖北武汉430074 [3]广东省地质局七五六地质大队,广东惠州516000 [4]中国地质大学地质调查研究院,湖北武汉430074 [5]西安地质矿产研究所,陕西西安710054

出　　处：《地球科学（中国地质大学学报）》2010年第5期811-820,共10页Earth Science-Journal of China University of Geosciences

基　　金：中国地质调查局项目(No.1212010610103);国家自然科学基金项目(Nos.40830212;40921062)

摘　　要：位于青藏高原东北缘循化盆地南缘的循化县积石镇羊圈贡拜-西沟上庄剖面,出露地层从老到新依次为他拉组、咸水河组和临夏组,总厚1047m.在野外地层剖面详细实测与沉积相研究基础上,系统采集地球化学样品进行常量和微量元素的测试和分析,结果表明:该剖面沉积物主要化学成分为SiO2、Al2O3、CaO和TFeO(Fe2O3+FeO),4者平均含量之和在80%以上.剖面沉积物中元素平均含量与上部陆壳(UCC)元素平均含量比揭示了研究区在23.1～5.0Ma期间总体较为干旱寒冷的气候环境特征.根据化学蚀变指数(chemicalindexofalteration,CIA)、Rb/Sr、Ti/Sr、CaO/Sr比值的变化划分为4个气候演变阶段:(Ⅰ)23.1～17.0Ma为冷干的气候阶段,分为Ⅰ1(23.1～21.8Ma)回暖的半干旱气候期和Ⅰ2(21.8～17.0Ma)变冷变干的气候期;(Ⅱ)17.0～13.0Ma为暖湿的气候阶段;(Ⅲ)13.0～8.5Ma为凉湿的气候阶段;(Ⅳ)8.5～5.0Ma为冷干的气候阶段,分为Ⅳ1(8.5～7.0Ma)波动的气候转型期和Ⅳ2(7.0～5.0Ma)转冷旱化的气候期.循化剖面常量、微量元素分布记录的循化盆地及周边地区的气候演化受青藏高原构造隆升和全球气候变化的共同影响.The measured Yangjuangongbai-Xigoushangzhuang Section, Xunhua Section, lies in the southern margin oi the Xun-hua basin, which is composed of three lithostratigraphic units named Tala Formation, Xianshuihe Formation and Linxia Formation from Oligocene to Pliocene with the thickness of 1 047 m. According to the detail research of the section and sedimentary facies, major and trace elements were analyzed to reveal paleoclimatic information from the deposits during 23. 1 - 5. 0 Ma. SiO2, A12 03, CaO and TFeO （Fe2O3 ＋ FeO） are the main chemical components with a sum of 80 % at the average level. The element ratios between the deposits and the upper continental crust （UCC） indicate that the paleoelimate of the studied area is characterized as cold and dry during 23. 1-- 5. 0 Ma. According to variations of CIA （chemical index of alteration）, Rb/Sr,TiO2/Sr and CaO/Sr, the paleoclimate can be divided into four stages. Stage Ⅰ： 23. 1--17. 0 Ma, it was characterized by mid-dry paleoclimate, including two substages： substage Ⅰ1 （23. 1- 21. 8 Ma） was half-dry and turned warm since Mil; substage Ie （21. 8- 17. 0 Ma） became cold and dry. Stage Ⅱ： 17. 0-1a. 0 Ma, it was warm and wet. Stage Ⅲ： 13. 0--8. 5 Ma, it was cooler than stage H but also wet. Stage IV： 8. 5--5. 0 Ma, it changed cold and dry again with two substages： substage Ⅳ1 （8. 5--7. 0 Ma） was fluctuant changeover and substage Ⅳ2 （7. 0--5. 0 Ma） became cold and dry. We conclude that both uplift of the Oinghai-Tibet plateau and global climatic changes had effect on the paleoclimatic evolvement during about 23. 1--5. 0 Ma in the Xunhua basin.

关 键 词：青藏高原 循化盆地 新近纪 常量和微量元素 气候演化 

分 类 号：P534[天文地球—古生物学与地层学]