OSL Chronology Of Giant Landslides From Longyang Gorge To Liujia Gorge Along Upper Yellow River

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.