洞庭盆地古沅江砾石层的沉积特征及沉积环境  

Sedimentary Characteristics and Sedimentary Environment of the Gravel Bed within Paleo-Yuanjiang River from Dongting Basin

作　　者：赵举兴 李长安[1,2] 许应石[1] 

机构地区：[1]中国地质大学地球科学学院,武汉430074 [2]中国地质大学生物地质与环境地质国家重点实验室,武汉430074

出　　处：《地质科技情报》2014年第1期85-89,共5页Geological Science and Technology Information

基　　金：中国地质调查局地质调查项目(1212011121142)

摘　　要：以野外调查中发现的2处出露较好的古沅江沉积砾石层剖面，即河袱山剖面和黄土山剖面为研究对象，分析了所出露沉积物的沉积特征和沉积环境并建立了沉积序列。结果表明，古沅江砾石层在地貌上表现为古，十积扇，但该古）十积扇并不是一期冲积扇。依据2个剖面的岩性特征与沉积特征，以岩性层作为对比标志层，将剖面划分为3期，十积扇。河袱山剖面第2层与黄土山剖面第2层构成第1期冲积扇，表现为扇顶一扇中相；河袱山剖面第3、4层与黄土山剖面第3～6层构成第Ⅱ期冲积扇，该期，十积扇较完整，表现为完整的扇顶一扇中相以及部分扇缘相；河袱山剖面第5层与黄土山剖面第7～9层构成第Ⅲ期冲积扇，表现为以扇顶相为主的扇顶一扇中相。该古冲积扇的成因类型表明）十积扇形成时的气候较为湿润；以砾质为主的沉积物则说明当时洞庭盆地周缘的地形较现在陡峻，古沅江也具有更强的搬运能力。The research targets are the Hefushan profile and the Huangtushan profile, two well cropped gravel beds profiles within paleoYuanjiang River. By analyzing the sedimentary characteristics and sedi mentary environment of the outcropped sediments, combined with the established sedimentary sequence, it shows that the gravel beds of paleoYuanjiang River has the characteristics of paleoalluvial fan from the perspective of geomorphology, however, the paleoalluvial fan was not formed within one phase. Combi ning with the lithology and sedimentary characteristics of these two profiles, the paleoalluvial fan is divid ed into three stages by lithological layer as the contrast marker bed. The @ layer of both profile make up the first phase of alluvial fan which shows relatively intact feature of the fanhead to fanmiddle~ The （~ @ layers of Hefushan profile and the （~）@ layers of Huangtushan profile compose the second phase of alluvial fan which shows relatively intact feature of the fanhead to fanmiddle and a small part of the fan edge; The @ layers of the Hefushan profile and the （~@ layers of the Huangtushan profile are the third phase of alluvial fan which demonstrates the fanhead to fanmiddle, yet dominated by fanhead. Genetic types of the paleoalluvial fan indicate that the climate was relatively humid when the alluvial fan formed. The deposits that mainly composed by gravel reveal that the terrain of peripheral Dongting Basin was steepper than it＇s now, meanwhile, the paleoYuanjiang River had stronger ability of transporting.

关 键 词：古沅江 古冲积扇 沉积特征 沉积环境 

分 类 号：P53[天文地球—古生物学与地层学]