静水沉积地层中Ti含量变化对干湿环境的响应——以重庆中坝遗址为例  

Ti CONTENTS IN STILL-WATER DEPOSITS AND ITS RESPONSE TO DRY-WET ENVIRONMENTAL CHANGES:A CASE STUDY AT ZHONGBA,CHONGQING

作　　者：李中轩[1] 朱诚[2] 闫慧[1] 吴国玺[1] 

机构地区：[1]许昌学院城市与环境学院,许昌461000 [2]南京大学地理与海洋科学学院,南京210093

出　　处：《海洋地质与第四纪地质》2010年第5期137-143,共7页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目(90411015;40701190);南京大学现代分析中心测试基金

摘　　要：用XRF和ICP-AES方法,分别测出中坝遗址地层中Rb、Sr和Ti含量,结果显示Ti元素在地层中含量的变化与对应地层中指示环境干湿的Rb/Sr值变化呈显著的正相关。对比泔井河流域含Ti矿物物源和化学蚀变指数(CIA),发现地层中Ti变化与流域元素迁移集聚无本质关联;而对应地层中的TOC含量与Ti含量有对应关系,同时有机物产生的有机酸可使含Ti矿物(如钛铁矿)发生离解过程,中坝遗址地层中Ti含量变化取决于沉积环境的Eh值和有机质的分解产物。通过与其他环境指标对比后,认为在准静水沉积地层中Ti元素对干湿环境变化具有普遍指示意义。Rb/Sr ratios as an important proxy to reveal dry-wet climatic variation have been applied in many fields, and the method is comparatively mature. However, some literatures documented that it seemed not too precise enough for the records in a short time scale, lka for instance. Therefore, we require a new proxy for short time studies. The Zhongba Site in Chongqing has remained a continuous sequence since 5 kaBP. From the stratigraphical sequences it is expected to extract more information to reveal the local palaeo-environment evolution. Ti is an inactive element which exists in oxides in nature, the authors measured Ti contents of each layer by Inductively Coupled Plasma Atomic Elelectronic Spectrometer. For comparison, Rb and Sr contents in relevant layers were also measured with X-ray fluorescent. Results show that it is correlative between Ti values and Rb/Sr ratios. It suggests that Ti may become an environmental proxy. Ti is usually endowed with hornblende, biotite, sphene, and ilmenite etc. When weathered, Ti and its oxides is hard to be transported, and little will be leached, although Nesbitt W H（1984） suggested that Ti would be hydrolyzed when index of chemical alteration（CIA） exceeding 90. However, CIA of each layer in this study is less than 85.69, consequently, it excludes the possibility of chemical weathering which will influence Ti variations. Through measuring the contents of TOC in layers, it is found that a Ti-enriched layer is consistent with low organic materials, and vice versa. In contrast with Rb/Sr ratios, Ti variation has relatively larger ranges and higher frequency that can be used to delineate climatic changes distinctly and precisely. In addition, the Ti content variation at the Zhongba Site suggests more climatic cycles than Rb/Sr ratios do, especially during the interval from 2.5ka-2.6kaB. P.

关 键 词：TI含量 Rb/Sr值 准静水沉积 中坝遗址 

分 类 号：P595[天文地球—地球化学]