【摘要】：由于青藏高原東緣獨(dú)特的地理位置及構(gòu)造地貌環(huán)境,發(fā)育了眾多堰塞湖。大渡河流域的古滑坡堰塞湖便是其中之一。堰塞湖是重要的極端地表過程之一,往往會造成災(zāi)難性的后果,對古堰塞湖的研究有助于對區(qū)域堵江風(fēng)險的認(rèn)識。本文以大渡河上游的石廣東和中游的加郡兩個古滑坡堰塞湖為研究對象,選取共選取7個剖面,采集了22個OSL樣品,采用單片再生法(single aliquot regeneration,SAR)與標(biāo)準(zhǔn)生長曲線法(Standard Growth Curve,SGC)相結(jié)合的方法,測定了22個樣品的光釋光(Optically Stimulated Luminescence,OSL)年齡,在進(jìn)行OSL測年實(shí)驗(yàn)前,我們進(jìn)行了條件實(shí)驗(yàn),選擇了合適的測試條件進(jìn)行年代測定,所以O(shè)SL方法及測試條件對本文大渡河流域湖相沉積物測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,在此基礎(chǔ)上探討了古滑坡堰塞湖與地震和氣候之間的關(guān)系以及古滑坡堰塞湖形成的主要誘因。然后根據(jù)兩處古滑坡堰塞湖的地質(zhì)證據(jù),分析了堰塞壩對河流地貌的控制作用。本文研究的主要結(jié)論如下:(1)本文石廣東和加郡兩處古滑坡堰塞湖的湖相沉積物主要以粉砂質(zhì)粘土和粉細(xì)砂為主,實(shí)驗(yàn)室內(nèi)提取的石英為中顆粒組分(粒徑為38~63μm)。(2)在進(jìn)行OSL年代測定前,進(jìn)行了預(yù)熱坪及劑量恢復(fù)實(shí)驗(yàn),來判斷并選擇了合適的實(shí)驗(yàn)條件,得到石廣東和加郡兩處湖相沉積OSL樣品的適宜預(yù)熱溫度分別為260℃和220℃。劑量恢復(fù)實(shí)驗(yàn)結(jié)果表明本文的OSL年代數(shù)據(jù)結(jié)果具有可靠性。(3)根據(jù)OSL數(shù)據(jù)結(jié)果并結(jié)合前人的研究,結(jié)果顯示:石廣東古滑坡堰塞湖形成于距今約3.0ka,結(jié)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經(jīng)形成。結(jié)合前人對青藏高原東緣古堰塞湖的年代研究,結(jié)果表明,古堰塞湖發(fā)生的年代集中在晚更新,全新世以來較少。(4)通過分析研究區(qū)的地震和氣候條件,探討了研究區(qū)古滑坡堰塞湖的形成原因,得出研究區(qū)域具備誘發(fā)古滑坡的地震條件,古滑坡堰塞湖可能由于地震觸發(fā)。(5)通過分析研究區(qū)石廣東和加郡古滑坡堰塞壩的特征,討論了堰塞壩對河道的改造作用及堰塞湖對河流縱剖面的影響。
[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，

本文編號：2274633