长江中游阳逻砾石层沉积环境分析  

SEDIMENTARY ENVIRONMENT OF GRAVEL BED IN YANGLUO TOWN IN THE MIDDLE REACHES OF YANGTZE RIVER

作　　者：梅惠[1] 李长安[2,3] 杨勇[3] 齐国凡[1] 康春国[2] 

机构地区：[1]湖北大学资源环境学院,武汉430062 [2]中国地质大学生物地质与环境地质教育部重点实验室,武汉430074 [3]中国地质大学地球科学学院,武汉430074

出　　处：《第四纪研究》2009年第2期370-379,共10页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40771213);湖北省自然科学基金项目(批准号:2008CDB054400-092469);中国地质大学生物地质与环境地质教育部重点实验室开放基金项目(批准号:BGEG0806)资助

摘　　要：本文在野外调查的基础上,选择典型剖面,通过剖面沉积学、岩相划分和粒度分析研究,对长江中游"阳逻砾石层"沉积环境进行了讨论。研究表明,阳逻砾石层的岩性主要砾石层夹砂层,由Gm,Sh和Sp沉积相类型组成;大多数频率曲线图形态为双峰,且以不对称曲线为主;概率累积曲线大都为上三段式,以滚动总体为主,约占50%～60%,斜率较大,在35°～45°;悬浮总体约占20%～30%,斜率在40°以上;跳跃总体约占20%～30%,斜率较小,多在10°～20°。跳跃总体和滚动总体之间均存在有混合带,分选性较差。综合分析认为,阳逻砾石层沉积环境为具有辫状河特点的河流沉积。根据电子自旋共振测年(ESR)得到阳逻砾石层的形成年龄为1.12～1.56MaB.P.,表明阳逻砾石层形成于第四纪早更新世。Gravel beds from Yangluo, Jiujiang, and Anqing as well as from Yuhuatai in Nanjing are the earliest deposits after the Cretaceous-Tertiary redbed deposition in the hilly areas of two banks of the lower-middle reaches of Yangtze River, representing the highest river terrace of this part of the river. Through field investigation and lithoface and granularity analysis of sediments from two typical sections,we discussed the sedimentary environment of the gravel bed in Yangluo Town. The result shows that the bed is mainly composed of gravels and sands. Three sedimentary facies, Gin, Sh,and Sp can be recognized. Most frequency curves are of two peaks and are asymmetry. Most probability cumulative curves are of up three segments type and the main ones are the rolling collectivities which are of about 50% to 60%. Their slope angle is between 35°and 45°The suspending collectivities take the second place ,which are of about 20% to 30% ,with their slopes angle exceeding 40° The proportion of the jumping collectivities is about 20% to 30%,with slope angle between 10° and 20°. There exists mixed zone between the jumping and the rolling collectivities,in which it is difficult to distinguish collectivities. Comprehensive analysis suggests that the sedimentary environment of the gravel bed in Yangluo Town is a braided river. The result of ESR shows the age of gravel bed in Yangluo Town is between 1.12MaB. P. and 1.56MaB. P. This shows that gravel bed in Yangluo Town were formed in Early-Pleistocene of Quaternary.

关 键 词：阳逻砾石层 沉积环境 沉积相 长江中游 

分 类 号：P343.5[天文地球—水文科学] P535[天文地球—地球物理学]