雅魯藏布江中游河谷沉積測年及階地測量
發(fā)布時(shí)間：2018-10-08 19:56
【摘要】：雅魯藏布江位于青藏高原南部,地處喜馬拉雅縫合帶,是世界上構(gòu)造作用最強(qiáng)烈的地區(qū)之一。同時(shí)其中下游地區(qū)也是世界上降雨強(qiáng)度最大的地區(qū)之一,氣候作用同樣明顯。探討氣候作用與構(gòu)造作用之間的耦合關(guān)系是目前學(xué)術(shù)界討論研究的熱點(diǎn)。雅魯藏布江獨(dú)特的地理環(huán)境是研究該問題的理想野外實(shí)驗(yàn)室。關(guān)于喜馬拉雅東構(gòu)造節(jié)加速隆升的時(shí)間和雅魯藏布江巨型裂點(diǎn)形成并長期保持穩(wěn)定的機(jī)制一直存在著巨大的爭議。過去對地殼隆升的研究主要通過低溫?zé)崮甏鷮W(xué)來完成。而目前正在實(shí)施的雅魯藏布江中下游鉆探勘測工作,為雅魯藏布江的研究工作帶來了新的契機(jī)。鉆孔資料揭示出雅魯藏布江中游寬谷段谷底沉積厚度超過700 m,其淤積歷史和內(nèi)容遠(yuǎn)遠(yuǎn)超過前人的想象。本文通過對河谷谷底沉積物的宇宙成因測年工作為南迦巴瓦地區(qū)地殼的隆升提供了全新的年代學(xué)證據(jù)。測年結(jié)果顯示,大約從2~2.5個(gè)百萬年以來,南迦巴瓦地區(qū)開始加速隆升,并導(dǎo)致了其上游河谷谷底的沉積和下游區(qū)域的強(qiáng)烈下切的開始。冰川堵江是另外一個(gè)保持裂點(diǎn)穩(wěn)定和導(dǎo)致下游河道加速侵蝕的重要因素,筆者使用差分GPS對雅魯藏布江中下游河段從加查開始直至加拉村的一系列階地進(jìn)行了實(shí)地測量和考察。對測量數(shù)據(jù)進(jìn)行差分處理后,得到了精度可達(dá)分米級的剖面連續(xù)高程數(shù)據(jù)。根據(jù)階地實(shí)測數(shù)據(jù),將中游河段分成三段,第一段加查至朗縣,發(fā)育河流相階地。第二段朗縣至大度卡段,發(fā)育湖積階地和河流階地。第三段大度卡至下游,發(fā)育河流相階地,頂部階地河拔高度較高,反映河流的強(qiáng)烈下切作用。結(jié)合對湖相沉積進(jìn)行的分析,推測出雅魯藏布江最高一期古堰塞湖的范圍。結(jié)果顯示,該期堰塞湖范圍為雅魯藏布江中下游段從朗縣到裂點(diǎn)處的大度卡附近。為末次盛冰期則隆弄冰川冰進(jìn)堵塞雅魯藏布江形成的堰塞湖。研究結(jié)果顯示地殼隆升的構(gòu)造作用和氣候因素導(dǎo)致冰川堵塞共同影響著雅魯藏布江的演化過程。
[Abstract]:Located in the southern part of Qinghai-Tibet Plateau and located in the Himalayan suture zone, the Brahmaputra River is one of the most tectonic regions in the world. At the same time, its middle and lower reaches are also one of the regions with the highest rainfall intensity in the world. It is a hot topic to discuss the coupling relationship between climate and tectonism. The unique geographical environment of the Brahmaputra River is an ideal field laboratory for studying this problem. There have been great controversies about the time of accelerating uplift of the eastern Himalayan structural joints and the mechanism of formation and long-term stability of the giant fracture point of the Brahmaputra River. In the past, the study of crustal uplift was mainly accomplished by low temperature thermochronology. The work of drilling and surveying in the middle and lower reaches of the Brahmaputra has brought a new opportunity for the research of the Brahmaputra. The borehole data reveal that the bottom of the valley in the middle reaches of the Yarlung Zangbo River is more than 700 m thick, and its siltation history and content far exceed the previous imagination. This paper provides a new chronological evidence for the uplift of the crust in the Nangabawa area by dating the cosmic origin of the sediments from the valley bottom. The dating results show that from about 2 to 2.5 million years ago, the Nangabawa area began to accelerate the uplift, which led to the deposition of the valley bottom in the upper valley and the beginning of the strong undercutting in the lower reaches of the valley. The glacial blocking is another important factor to maintain the stability of the fissure point and lead to the accelerated erosion of the lower reaches of the river. The authors use differential GPS to survey and investigate a series of terraces in the middle and lower reaches of the Brahmaputra River from the beginning of Gaja to the village of Gallas. After differential processing of the measured data, continuous elevation data with the accuracy of decimeter level can be obtained. According to the measured data of terrace, the middle reaches are divided into three sections, the first section is checked to Longxian, and the river facies terrace is developed. The second stage of Longxian to Daduka section, developed lake terrace and river terrace. In the third section, the river facies terrace is developed, and the top terrace is high, which reflects the strong down-cutting action of the river. Based on the analysis of lacustrine sediments, the range of the highest paleobarrier lake in Yalu Zangbo River is inferred. The results show that the range of the dammed lake in this period is near Duca from Longxian to the crack point in the middle and lower reaches of Yalu Zangbo River. It is a barrier lake formed by the last glacial period, Zelonong Glacier, blocking the Brahmaputra River. The results show that the tectonic action of crustal uplift and climatic factors which lead to glacial blockage affect the evolution of Yalu Zangbo River.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P512.2;P597.3
本文編號：2258070
[Abstract]:Located in the southern part of Qinghai-Tibet Plateau and located in the Himalayan suture zone, the Brahmaputra River is one of the most tectonic regions in the world. At the same time, its middle and lower reaches are also one of the regions with the highest rainfall intensity in the world. It is a hot topic to discuss the coupling relationship between climate and tectonism. The unique geographical environment of the Brahmaputra River is an ideal field laboratory for studying this problem. There have been great controversies about the time of accelerating uplift of the eastern Himalayan structural joints and the mechanism of formation and long-term stability of the giant fracture point of the Brahmaputra River. In the past, the study of crustal uplift was mainly accomplished by low temperature thermochronology. The work of drilling and surveying in the middle and lower reaches of the Brahmaputra has brought a new opportunity for the research of the Brahmaputra. The borehole data reveal that the bottom of the valley in the middle reaches of the Yarlung Zangbo River is more than 700 m thick, and its siltation history and content far exceed the previous imagination. This paper provides a new chronological evidence for the uplift of the crust in the Nangabawa area by dating the cosmic origin of the sediments from the valley bottom. The dating results show that from about 2 to 2.5 million years ago, the Nangabawa area began to accelerate the uplift, which led to the deposition of the valley bottom in the upper valley and the beginning of the strong undercutting in the lower reaches of the valley. The glacial blocking is another important factor to maintain the stability of the fissure point and lead to the accelerated erosion of the lower reaches of the river. The authors use differential GPS to survey and investigate a series of terraces in the middle and lower reaches of the Brahmaputra River from the beginning of Gaja to the village of Gallas. After differential processing of the measured data, continuous elevation data with the accuracy of decimeter level can be obtained. According to the measured data of terrace, the middle reaches are divided into three sections, the first section is checked to Longxian, and the river facies terrace is developed. The second stage of Longxian to Daduka section, developed lake terrace and river terrace. In the third section, the river facies terrace is developed, and the top terrace is high, which reflects the strong down-cutting action of the river. Based on the analysis of lacustrine sediments, the range of the highest paleobarrier lake in Yalu Zangbo River is inferred. The results show that the range of the dammed lake in this period is near Duca from Longxian to the crack point in the middle and lower reaches of Yalu Zangbo River. It is a barrier lake formed by the last glacial period, Zelonong Glacier, blocking the Brahmaputra River. The results show that the tectonic action of crustal uplift and climatic factors which lead to glacial blockage affect the evolution of Yalu Zangbo River.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P512.2;P597.3
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