摘要
通过对黄河中游晋陕峡谷段的深入调查研究,在山西省大宁县平渡关基岩峡谷河段左岸沟口岩棚内发现了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,鉴别出平渡关(PDG)剖面夹有4层古洪水滞流沉积物。结合粒度成分、磁化率、烧失量、CaCO3含量等室内分析测定结果,确定为河流悬移质和跃移质在高水位滞流环境当中的沉积物,是典型的古洪水滞流沉积物。不同层次沉积物是不同古洪水事件的客观记录,既有细沙质粉沙,也有细沙或者中沙,反映出其物质来源的不同或者水动力大小的差异。粒度自然分布频率曲线为正偏和极正偏,主峰高且尖锐,表明其分选良好,其粒度概率累积分布曲线为典型的两段式。沉积物磁化率和烧失量均低于全新世风成黄土和古土壤,CaCO3含量介于古土壤和黄土之间,说明在黄河晋陕峡谷段,洪水所携带的悬移质泥沙是流域内黄土区和风沙区水土流失物质的混合物。
Field investigation was carried out along the Shaanxi--Shanxi Gorges in the middle reaches of the Yellow River. Typical palaeoilood slackwater deposits of the Holocene age were found at the Pingduguan sites. They were identified by sedimentary criteria during fieldwork initially, sampled and invested in detail. Analysis of the grain-size distribution, loss-on-ignition and CaC03 content indicated that these slackwater deposits consisted of sandy silt, silt fine sand and sand. They were classified as sandy silt, silt fine sand and sand in contrast to loess and paleosoil which were classified as clayey silt on the loess tableland in the middle reaches of the Yellow River. The magnetic susceptibility of the slackwater deposits was very low hecause they were newly deposited and unaffected by weathering and pedogenesis. The CaCO3 content of the slackwater deposits was between paleosoil and loess indicated that the suspended sediment load is mixture of aeolian loess and sand, which came from the windy and sandy areas. They were well sorted because of long distance transportation in floodwater. The shape of particle-size distribution curves of the slackwater deposits was high and thin. It represented a low turbulence deposit.
出处
《水土保持通报》
CSCD
北大核心
2013年第6期216-221,共6页
Bulletin of Soil and Water Conservation
基金
国家自然科学基金重点项目"汉江上游(南水北调水源区)万年尺度古洪水水文学研究"(41030637)
教育部博士点基金优先发展领域项目(20110202130002)
关键词
黄河中游
古洪水
滞流沉积物
全新世
middle reach of the Yellow River
palaeoflood
slackwater deposits
holocene
