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通过对黄河中游河口镇-龙门段峡谷进行详细的野外考察,在多个地点发现了含有古洪水滞流沉积物的全新世地层剖面。对山西省临汾市吉县段冯家集剖面的古洪水滞流沉积物系统采样,进行了沉积学及年代学分析研究。野外观测和粒度成分分析表明冯家集剖面夹有5层典型的古洪水滞流沉积物,其性质为细沙质粉沙,具有水平层理,层与层之间被坡积石渣土分隔。该层系的顶界高出黄河平水位达18m。它们是特大洪水在高水位滞流情况之下的悬移质沉积物,客观地记录了全新世时期黄河中游一期5次特大古洪水事件。通过分离出125—2251~m石英颗粒,应用单片再生剂量法(sAR)测得其光释光年龄值,结合地层对比及各种气候替代性指标的分析,确定这些古洪水事件发生在3200~3000a B.P.之间,处于全新世中期大暖期向全新世晚期相对干旱期转折的阶段。这对应我国历史上的商末一西周初期,季风气候状态不稳定,黄河流域既有严重地干旱,又有特大洪水事件发生。本文的研究成果为深入揭示河流水文系统对于全球变化的响应规律提供了新的可靠证据。
Through a detailed field investigation of the Hekouzhen-Longmen Gorge in the middle reaches of the Yellow River, Holocene stratigraphic sections with pale flood stagnant sediments have been found in various places. The sedimentology and chronology analysis of the ancient flood stagnant sediment system sampled at Fengji-Ji section of Jixian section in Linfen City, Shanxi Province was conducted. Field observations and grain-size analysis show that there are 5 layers of typical flood flood sediment in the section of Fengjiatu, which is characterized by fine sandy silt with horizontal bedding and separated by slop gravel . The top of this layer is above the level of the Yellow River water level up to 18m. They are suspended sediments under the condition of stagnant high water level in the extremely large floods and objectively recorded the first 5 flood events in the middle reaches of the Yellow River during the Holocene. By separating 125-2251 ~ m quartz particles, the light-released age value was measured by single-cell regeneration dose method (sAR). Based on the stratigraphic correlation and the analysis of various climate alternatives, it was determined that these ancient flood events occurred at 3200 ~ 3000a BP, in the mid-Holocene mantle to the late Holocene relative dry period turning point. This corresponds to the late Shang Dynasty and the early Western Zhou Dynasty in China’s history. The monsoon climate was unstable. Both the serious drought and the extraordinary flood occurred in the Yellow River basin. The research results in this paper provide new and reliable evidence for revealing the response of river hydrological systems to global changes.