大渡河流域古滑坡堰塞湖光释光测年研究
发布时间：2018-10-16 14:19
【摘要】：由于青藏高原东缘独特的地理位置及构造地貌环境,发育了众多堰塞湖。大渡河流域的古滑坡堰塞湖便是其中之一。堰塞湖是重要的极端地表过程之一,往往会造成灾难性的后果,对古堰塞湖的研究有助于对区域堵江风险的认识。本文以大渡河上游的石广东和中游的加郡两个古滑坡堰塞湖为研究对象,选取共选取7个剖面,采集了22个OSL样品,采用单片再生法(single aliquot regeneration,SAR)与标准生长曲线法(Standard Growth Curve,SGC)相结合的方法,测定了22个样品的光释光(Optically Stimulated Luminescence,OSL)年龄,在进行OSL测年实验前,我们进行了条件实验,选择了合适的测试条件进行年代测定,所以OSL方法及测试条件对本文大渡河流域湖相沉积物测年具有可行性及可靠性。首先揭示大渡河流域古堰塞湖形成的主要原因,在此基础上探讨了古滑坡堰塞湖与地震和气候之间的关系以及古滑坡堰塞湖形成的主要诱因。然后根据两处古滑坡堰塞湖的地质证据,分析了堰塞坝对河流地貌的控制作用。本文研究的主要结论如下:(1)本文石广东和加郡两处古滑坡堰塞湖的湖相沉积物主要以粉砂质粘土和粉细砂为主,实验室内提取的石英为中颗粒组分(粒径为38~63μm)。(2)在进行OSL年代测定前,进行了预热坪及剂量恢复实验,来判断并选择了合适的实验条件,得到石广东和加郡两处湖相沉积OSL样品的适宜预热温度分别为260℃和220℃。剂量恢复实验结果表明本文的OSL年代数据结果具有可靠性。(3)根据OSL数据结果并结合前人的研究,结果显示:石广东古滑坡堰塞湖形成于距今约3.0ka,结束于1.6ka;加郡古滑坡堰塞湖至少在距今9ka左右的全新世早期就已经形成。结合前人对青藏高原东缘古堰塞湖的年代研究,结果表明,古堰塞湖发生的年代集中在晚更新,全新世以来较少。(4)通过分析研究区的地震和气候条件,探讨了研究区古滑坡堰塞湖的形成原因,得出研究区域具备诱发古滑坡的地震条件,古滑坡堰塞湖可能由于地震触发。(5)通过分析研究区石广东和加郡古滑坡堰塞坝的特征,讨论了堰塞坝对河道的改造作用及堰塞湖对河流纵剖面的影响。
[Abstract]:Due to the unique geographical location and tectonic geomorphological environment of the eastern margin of the Qinghai-Tibet Plateau, many barrier lakes have been developed. The ancient landslide barrier lake in the Dadu River Basin is one of them. Barrier lake is one of the most important extreme surface processes, which often results in disastrous consequences. The study of ancient barrier lake is helpful to understand the risk of blocking the river in the region. In this paper, two ancient landslide dammed lakes in the upper reaches of the Dadu River and two ancient landslide lakes in the middle reaches of the Dadu River are selected as the research objects. Seven sections are selected and 22 OSL samples are collected. Using monolithic regeneration method (single aliquot regeneration,SAR) and standard growth curve method (Standard Growth Curve,SGC), the (Optically Stimulated Luminescence,OSL ages of 22 samples were determined. Prior to the OSL dating experiment, the conditional experiments were carried out. Therefore, OSL method and test conditions are feasible and reliable for lacustrine sediment dating in Dadu River Basin. The main reasons for the formation of ancient barrier lake in Dadu River basin are revealed, and the relationship between ancient landslide barrier lake and earthquake and climate, and the main cause of formation of ancient landslide barrier lake are discussed. Then, based on the geological evidence of two ancient landslide dammed lakes, the controlling effect of Weir dam on river geomorphology is analyzed. The main conclusions of this paper are as follows: (1) the lacustrine sediments of two ancient landslide dammed lakes are mainly silty clay and silty sand. The quartz extracted in the laboratory is a medium particle component (the particle size is 38 ~ 63 渭 m). (_ 2). The preheating plateau and dose recovery experiments were carried out before the OSL dating, and the appropriate experimental conditions were determined and selected. The optimum preheating temperatures of OSL samples deposited in ShiGuangdong and Jiajun are 260 鈩，
本文编号：2274633
[Abstract]:Due to the unique geographical location and tectonic geomorphological environment of the eastern margin of the Qinghai-Tibet Plateau, many barrier lakes have been developed. The ancient landslide barrier lake in the Dadu River Basin is one of them. Barrier lake is one of the most important extreme surface processes, which often results in disastrous consequences. The study of ancient barrier lake is helpful to understand the risk of blocking the river in the region. In this paper, two ancient landslide dammed lakes in the upper reaches of the Dadu River and two ancient landslide lakes in the middle reaches of the Dadu River are selected as the research objects. Seven sections are selected and 22 OSL samples are collected. Using monolithic regeneration method (single aliquot regeneration,SAR) and standard growth curve method (Standard Growth Curve,SGC), the (Optically Stimulated Luminescence,OSL ages of 22 samples were determined. Prior to the OSL dating experiment, the conditional experiments were carried out. Therefore, OSL method and test conditions are feasible and reliable for lacustrine sediment dating in Dadu River Basin. The main reasons for the formation of ancient barrier lake in Dadu River basin are revealed, and the relationship between ancient landslide barrier lake and earthquake and climate, and the main cause of formation of ancient landslide barrier lake are discussed. Then, based on the geological evidence of two ancient landslide dammed lakes, the controlling effect of Weir dam on river geomorphology is analyzed. The main conclusions of this paper are as follows: (1) the lacustrine sediments of two ancient landslide dammed lakes are mainly silty clay and silty sand. The quartz extracted in the laboratory is a medium particle component (the particle size is 38 ~ 63 渭 m). (_ 2). The preheating plateau and dose recovery experiments were carried out before the OSL dating, and the appropriate experimental conditions were determined and selected. The optimum preheating temperatures of OSL samples deposited in ShiGuangdong and Jiajun are 260 鈩，
本文编号：2274633
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