丹江上游全新世早期古洪水滞流沉积物粒度特征研究  

Grain-size characteristics of the early Holocene flood Slackwater deposits in the upper reaches of Danjiang River

作　　者：李晓刚[1,2] 黄春长[1] 庞奖励[1] 

机构地区：[1]陕西师范大学旅游与环境学院,陕西西安710062 [2]商洛学院城乡发展与管理工程系,陕西商洛726000

出　　处：《干旱区地理》2014年第4期646-655,共10页Arid Land Geography

基　　金：国家自然基金重点项目(41030637);陕西省软科学研究计划项目(2012KRM119);陕西省教育厅科学研究项目(12JK0486)

摘　　要：通过对丹江流域广泛的野外考察,在丹江上游竹林关峡谷段右岸发现典型的全新世古洪水滞流沉积层剖面。根据野外宏观特征及沉积环境,鉴别出该剖面夹有四层古洪水滞流沉积物,均匀致密,分选良好,各层界面自然开裂,具有波状-水平状平行层理。室内粒度成分分析表明,沉积物以粉沙为主,粘粒含量次之,细沙含量很少,沉积学分类属粉沙和粘土质粉沙。粒度自然分布频率曲线为正偏,主峰高且尖锐,分选良好。粒度概率累积分布曲线为典型的两段式,沉积物投影在CM图的Ⅶ区(SWD1和SWD3)和Ⅷ区(SWD2和SWD4)。将四层古洪水SWD与2010年洪水SWD进行对比分析,粒度组成成分、粒度参数、自然分布频率曲线都呈现相似形态。综合分析说明四层古洪水SWD是丹江洪水悬移质泥沙在高水位滞流环境下的沉积物,为丹江上游开展古洪水水文学研究奠定了基础,对于丹江洪水水文泥沙特性、水资源开发利用具有重要意义。The Danjiang River, a major tributary of the Hanjiang to-North Water Diversion project. Recent flood disasters and flood River, is noted for the current national South- damages have attracted media and public atten- tions from the world. The data generated from palaeoflood hydrology will facilitate an appropriate assessment of these flood events and the regional response of the hydrological system to global climatic change at a long time scale. Pal- aeoflood slackwater deposit （SWD） is a major evidence used for inference about hydrological parameters of the past flood events. This fine-grained sediment is deposited at high flood stage from suspended load in overbank floodwa- ter. It could be buried and preserved by various surface processes in the Holocene pedo-stratigraphy in the river- banks. Field investigations were carried out along the upper reaches gorge of the Danjiang River that drains from thesouth piedmont of the Qinling Mountains. A set of 4 palaeoflood slackwater deposit beds （SWDs） of the Holocene age were found in the depth range of 10-40 cm by using the sedimentological criteria at the LZT sites, which is situ- ated at the riverbank terrace land. The front of the terrace land is ca. 16 m above the normal river water level. It formed an outstanding threshold （censoring level） for registration of extraordinary overbank floods through deposi- tion of the suspended sediment load. It was further checked by comparison with the modern flood events and their SWDs deposited on the channel sides in the same reaches. They were identified by sedimentary criteria during field- work initially, sampled and invested in detail. Particle-size distribution of the samples was determined using a Mas- tersizer-S laser analyzer. Analysis of the grain-size distribution indicates that these SWD consist of sandy silt, sourced from the suspended sediment load of the floodwater. Therefore they were well sorted during the deposition. The shape of particle-size distribution curves of the SWD is high and thin. The c

关 键 词：古洪水 滞流沉积物 全新世 丹江 

分 类 号：P534.632[天文地球—第四纪地质学] P512.2[天文地球—古生物学与地层学]