【作者】 郭小花；

【导师】 杨太保；

【作者基本信息】 兰州大学 ， 地球化学， 2012， 硕士

【摘要】 黄河上游龙羊峡-刘家峡段黄河谷地中形成了众多残留体积大于1×108m3的巨型滑坡,最大体积达近30×108m3,且曾引发堵塞黄河事件。因此确定黄河上游龙羊峡至刘家峡段巨型滑坡的形成年代对黄河上游龙羊峡至刘家峡段巨型滑坡形成机理研究具有重要的研究意义。但该河段巨型滑坡的年代一直存在争议,其原因可能是由于缺乏适合滑坡测年的物质。最近,光释光(optical stimulated luminescence)测年技术被成功地运用到滑坡测年中。滑坡光释光测年的关键是滑坡堆积物或滑坡形成后残留体表部物质在沉积之前经历过最后一次曝光事件或者受热事件使得滑坡堆积物的石英光释光信号回归到零。本文运用光释光测年技术对研究区4个滑坡,共30个样品探讨光释光测年在研究区滑坡测年的适用性,并结合研究区地质构造背景以及区域环境对滑坡的发生原因进行探讨。(1)两种直接确定滑坡年代的采样法：①堰塞湖湖相底部沉积物；②滑坡剪切带温度高于400。C的界面物质。以及一种间接确定滑坡年代的采样法：①通过采集滑坡体上覆黄土底部确定滑坡发生年代的下界；滑坡体覆盖阶地堆积物顶部来确定滑坡发生年代的上界。(2)光释光测年方法在黄河上游龙羊峡至刘家峡段的巨型滑坡堆积物和堰塞湖和滑坡后缘滑坡湖的湖相沉积地层中具有良好的适用性。几乎所有30个样品的De值都分布比较集中,呈正太分布。黄河上游龙羊峡至刘家峡段巨型滑坡形成后的沉积物都存在一条标准生长曲线(SGC)。所有样品运用SGC方法获得的年代与SAR法获得的年代具有较好的一致性。部分较老样品(De大于400Gy)的再生剂量达到800Gy时生长曲线依然在增长,且生长曲线都很集中,这为光释光技术运用到更老的测年样品提供了可能性。释光陷阱在400。C被排空然后重新接受辐射,因此高速滑坡剪切带摩擦温度达到400。C的样品可用来滑坡测年。(3)德恒隆滑坡、锁子滑坡、堰塞湖湖相年代以及德恒隆断层最后一次活动年代具有很好的一致性,德恒隆滑坡和锁子滑坡的发生与研究区的8-9万年构造活动有密切关联。夏藏滩滑坡发生于80±9ka,康杨滑坡发生于33.2±2.5ka和堰塞湖湖相年代之间,两者发生原因可能是堰塞湖库岸再造。更多还原

【Abstract】 Giant landslides (1×108m3) are common in the upper Yellow River from Longyang Gorge to Liujia Gorge, the largest one of30×108m3, which even blocked and dammed the Yellow River. To research the mechanism for giant landslides in the study area, it is inevitable to date the giant landslides. However, there are controversies existing in the chronology of giant landslides from Longyang Gorge to Liujia Gorge along Upper Yellow River due to lack of a appropriate chronology methods, although chronology plays a significant role in the landslide research. Recently, OSL (optical stimulated luminescence) has been successfully applied in the landslide dating. It is critical to make sure that the clock of a mineral grain’s luminescence has been completely rest. In this thesis,30OSL samples were collected from4giant landslides to explore the applicability of OSL dating in landslide mass, and to discuss the trigger mechanism of giant landslides combining with tectonic movement and geomorphology in the study area, we conclude that(1)Two ideas about directly sampling landslides mass have been concluded, firstly, sampling at the bottom of lacustrine sediments from dammed lake; secondly, sampling at the shear surface where clashing renders temperature above400°C. And one indirectly sampling landslides mass has been summarized, minimal age obtained from the losses above landslide mass and maximum age from terrace sediments covered by landslide mass.(2)Most of the30samples were well-bleached with regard to the De distribution. The OSL method is appropriate for being applied in the landslide mass and lacustrine sediments. There is an OSL SGC (standardized growth curve) for De determination on quartz from Longyang Gorge to Liujia Gorge along upper Yellow River, and the Des determined by SGC are in agreement with the Des by the SAR protocol, what’s more, the SGC doesn’t show saturation up to a dose of800Gy, which potentially allows OSL method to date those much older samples.(4)Chronology of Dehenglong landslide is in agreement with those of Suozi landslide, dammed lake and dehenglong fault. Dehenglong landslide and Suozi landslide might be triggered by earthquake related to the80～90ka tectonic movement. And then the dammed lake caused by Dehenglong landslide and Suozi landslide might triggered Xiazangtan landslide and Kangyang landslide.更多还原