構(gòu)造與氣候?qū)χ袊胁课己优璧爻练e動力學(xué)的影響
發(fā)布時間：2018-09-01 18:45
【摘要】：新生代地球巖石圈發(fā)生強(qiáng)烈構(gòu)造變動,導(dǎo)致全球海陸格局、地貌形態(tài)、大氣環(huán)流和氣候系統(tǒng)發(fā)生了劇烈變化。亞洲最為顯著的構(gòu)造事件是印度板塊向歐亞板塊的俯沖,導(dǎo)致了青藏高原的隆升。青藏高原隆升過程中,印度板塊擠壓的應(yīng)力不斷向NE方向傳遞,導(dǎo)致?lián)P子地塊向東南推出,在秦嶺山前形成大型左旋走滑斷層。同時太平洋板塊自東而西向亞洲板塊下俯沖,華北板塊受到NW-SE向拉張作用,也加劇了渭河盆地的拉張斷陷。斷陷盆地內(nèi)堆積了較為連續(xù)的湖相-河流相-粉塵堆積,這些堆積記錄了青藏高原隆升遠(yuǎn)程的構(gòu)造效應(yīng)、東亞季風(fēng)系統(tǒng)演化過程、黃河及其支流的形成及演化過程。本論文通過分析汾渭盆地東北部鹵陽湖鉆孔LYH-1上部221m (約1Ma)沉積地層,結(jié)合臨近洛河下游的地貌及沉積學(xué)分析,重建1Ma以來鹵陽湖的演化過程及其對區(qū)域構(gòu)造、水系演變及氣候變化的響應(yīng)。論文第一章結(jié)合區(qū)域地質(zhì)、水文與氣候背景,介紹了研究選題、思路及技術(shù)路線。第二章詳細(xì)介紹了研究方法。第三章首先建立了年代框架,結(jié)合巖性及沉積特征、古生物學(xué)及其它沉積學(xué)指標(biāo)如粒度分布等手段描述了鹵陽湖地區(qū)的沉積環(huán)境演變過程。第四章通過使用地球化學(xué)和礦物學(xué)手段進(jìn)一步分析了鹵陽湖地區(qū)沉積環(huán)境演變特征。第五章結(jié)合洛河下游地貌及沉積學(xué)分析,研究洛河演化對鹵陽湖地區(qū)沉積歷史的貢獻(xiàn)和影響。第六章中通過對比鉆孔沉積物的沉積特征與黃土高原黃土-古土壤序列,進(jìn)一步精確第三章中建立的年齡框架。最終,利用頻譜分析提取沉積物中的頻譜數(shù)據(jù)并探討其可能指示的氣候信息。研究主要結(jié)論如下:(1)鹵陽湖沉積巖相變化較大,主要沉積環(huán)境為沖積扇、淺水湖泊、干鹽湖以及風(fēng)塵堆積,部分沉積相上部曾經(jīng)歷微弱的成壤過程。重建的沉積環(huán)境及構(gòu)造特征表明,鹵陽湖位于斷陷洼地內(nèi)河流沖積扇末端,其北部的河流源自疏松易蝕的黃土高原,其搬運(yùn)攜帶的大量碎屑物不僅堆積了出山口的沖積扇,也為鹵陽湖的沉積發(fā)育提供了物源。(2)沖積扇的生長發(fā)生于氣候較冷時期,該時期黃土高原缺乏足夠的植被保護(hù)。相反,沖積扇的后退則發(fā)生于氣候溫暖時期,該時期土壤的發(fā)育使得流域侵蝕減弱。當(dāng)流域降雨和蒸發(fā)加強(qiáng)時,淺水湖泊及干鹽湖發(fā)育。(3)巖心沉積物磁化率、碳酸鹽以及粒度組分的頻譜分析顯示,沉積序列中存在著米蘭科維奇旋回。這表明,氣候?qū)ξ己优璧乇辈砍练e具有驅(qū)動作用。然而,沉積物中的旋回并不連續(xù)并且依賴于鉆孔點(diǎn)位置的構(gòu)造沉降速率。當(dāng)鉆孔位置沒有足夠空間容納沉積物時,氣候信息將難以保留。除了米蘭科維奇旋回外,同時存在著由沖積扇自旋回產(chǎn)生的更高頻率的旋回。通過對沉積物地球化學(xué)分析得到區(qū)域長尺度的氣候變化信息:0.7-0.6Ma前,盆地中粘土含量開始增高。這與夏季風(fēng)開始增加的時間相吻合,夏季風(fēng)的加強(qiáng)也有利于黃土高原土壤發(fā)育及自生粘土的形成。(4)根據(jù)巖相分布特征,將研究部分鉆孔分為3段:1-0.69Ma; 0.69-0.33 Ma;0.33-0 Ma。首尾兩個階段湖面擴(kuò)大,而中間階段湖面萎縮。末期湖面擴(kuò)大可能是盆地逐漸減弱的沉降速率導(dǎo)致。對洛河流域的地貌及沉積學(xué)分析也證實(shí)了這一觀點(diǎn),現(xiàn)今洛河沿鉆孔附近河谷流動,但早期洛河卻通過自身沖積扇向鹵陽湖區(qū)提供沉積物。在200-240 ka左右,斷層活動加強(qiáng),洛河下切改道并停止對鉆孔位置沉積物的物質(zhì)輸送,此后鹵陽湖沉積物主要源自其北部的河流。由于斷層引發(fā)的褶皺作用,鹵陽湖區(qū)相對沉降速率增加,導(dǎo)致洪水沉積增多,淺水湖面擴(kuò)大,同時伴隨水生生物多樣性的增加。(5)本次研究揭示了構(gòu)造活動、水系演變及氣候變化對渭河盆地北部沉積作用的復(fù)雜影響,研究并未發(fā)現(xiàn)1Ma來該地區(qū)有大湖存在的證據(jù),表明三門古湖僅存在于1Ma前。
[Abstract]:Strong tectonic changes in the Cenozoic lithosphere led to drastic changes in the global land-sea pattern, geomorphology, atmospheric circulation and climate system. The most notable tectonic event in Asia was the subduction of the Indian plate to the Eurasian plate, which led to the uplift of the Qinghai-Tibet Plateau. The NE-trending faulting resulted in the southeastward extension of the Yangtze block and the formation of large-scale sinistral strike-slip faults in the piedmont of the Qinling Mountains. At the same time, the Pacific plate subducted from the east to the West under the Asian plate, and the North China plate was extensionally affected by NW-SE trending, which aggravated the extensional fault depression of the Weihe basin. Dust accumulation, which records the long-range tectonic effect of the uplift of the Qinghai-Tibet Plateau, the evolution of the East Asian monsoon system, the formation and evolution of the Yellow River and its tributaries. The evolution process of the lake and its response to regional tectonics, river system evolution and climate change since the beginning of the year are introduced in the first chapter of this paper. Combining regional geology, hydrology and climate background, the research topics, ideas and technical routes are introduced. The second chapter introduces the research methods in detail. Physical and other sedimentological indices such as grain size distribution are used to describe the evolution of sedimentary environment in the area. Chapter 4 further analyzes the evolution characteristics of sedimentary environment in the area by using geochemical and mineralogical methods. In Chapter 6, by comparing the sedimentary characteristics of borehole sediments with the loess-paleosol sequence of the Loess Plateau, the age framework established in Chapter 3 is further refined. The following: (1) The sedimentary facies of the lake changed greatly. The main sedimentary environments were alluvial fans, shallow lakes, dry salt lakes and aeolian dust deposits. The upper part of some sedimentary facies had undergone a weak process of soil formation. In the Loess Plateau, a large amount of debris not only accumulated in the alluvial fans at the entrance of the mountain, but also provided a source of material for the sedimentary development of the lake. As rainfall and evaporation intensify, shallow lakes and dry salt lakes develop. (3) Spectral analysis of magnetic susceptibility, carbonate and grain size components of core sediments shows that Milankovitch cycles exist in sedimentary sequences. This indicates that climate drives sedimentation in the northern Weihe basin. The cycles in the sediments are discontinuous and depend on the rate of tectonic subsidence at the point of the borehole. Climate information is difficult to retain when the borehole location does not have enough space to accommodate sediments. In addition to the Milankovitch cycle, there are also cycles of higher frequency generated by the alluvial fan spin. Sediment geochemical analyses have yielded results. Regional long-scale climate change information: before 0.7-0.6 Ma, the clay content in the basin began to increase. This coincides with the time when the summer monsoon began to increase. The strengthening of the summer monsoon is also conducive to the development of soil and the formation of authigenic clay in the Loess Plateau. (4) According to the lithofacies distribution characteristics, some boreholes were divided into three sections: 1-0.69 Ma; 0.69-0.33 Ma; 0.33-0. Ma. The lake surface enlarged in the first and last two stages and shrank in the middle stage. The lake surface enlarged in the last stage may be caused by the subsidence rate of the basin gradually weakening. Geomorphological and sedimentological analysis of the Luohe River Valley confirms this view. Today the Luohe River flows along the valley near the borehole, but in the early stage the Luohe River provides subsidence to the Hanyang Lake area through its own alluvial fan. The deposits were mainly from the rivers in the north of the lake. Due to the folding caused by faults, the relative subsidence rate of the lake area increased, resulting in the increase of flood deposits and the enlargement of the shallow lake surface accompanied by water. (5) This study reveals the complex effects of tectonic activities, river system evolution and climate change on sedimentation in the northern Weihe Basin. No evidence of the existence of a large lake in this area has been found in the past 1 Ma, indicating that Sanmen ancient lake existed only 1 Ma ago.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P512.2
本文編號：2218033
[Abstract]:Strong tectonic changes in the Cenozoic lithosphere led to drastic changes in the global land-sea pattern, geomorphology, atmospheric circulation and climate system. The most notable tectonic event in Asia was the subduction of the Indian plate to the Eurasian plate, which led to the uplift of the Qinghai-Tibet Plateau. The NE-trending faulting resulted in the southeastward extension of the Yangtze block and the formation of large-scale sinistral strike-slip faults in the piedmont of the Qinling Mountains. At the same time, the Pacific plate subducted from the east to the West under the Asian plate, and the North China plate was extensionally affected by NW-SE trending, which aggravated the extensional fault depression of the Weihe basin. Dust accumulation, which records the long-range tectonic effect of the uplift of the Qinghai-Tibet Plateau, the evolution of the East Asian monsoon system, the formation and evolution of the Yellow River and its tributaries. The evolution process of the lake and its response to regional tectonics, river system evolution and climate change since the beginning of the year are introduced in the first chapter of this paper. Combining regional geology, hydrology and climate background, the research topics, ideas and technical routes are introduced. The second chapter introduces the research methods in detail. Physical and other sedimentological indices such as grain size distribution are used to describe the evolution of sedimentary environment in the area. Chapter 4 further analyzes the evolution characteristics of sedimentary environment in the area by using geochemical and mineralogical methods. In Chapter 6, by comparing the sedimentary characteristics of borehole sediments with the loess-paleosol sequence of the Loess Plateau, the age framework established in Chapter 3 is further refined. The following: (1) The sedimentary facies of the lake changed greatly. The main sedimentary environments were alluvial fans, shallow lakes, dry salt lakes and aeolian dust deposits. The upper part of some sedimentary facies had undergone a weak process of soil formation. In the Loess Plateau, a large amount of debris not only accumulated in the alluvial fans at the entrance of the mountain, but also provided a source of material for the sedimentary development of the lake. As rainfall and evaporation intensify, shallow lakes and dry salt lakes develop. (3) Spectral analysis of magnetic susceptibility, carbonate and grain size components of core sediments shows that Milankovitch cycles exist in sedimentary sequences. This indicates that climate drives sedimentation in the northern Weihe basin. The cycles in the sediments are discontinuous and depend on the rate of tectonic subsidence at the point of the borehole. Climate information is difficult to retain when the borehole location does not have enough space to accommodate sediments. In addition to the Milankovitch cycle, there are also cycles of higher frequency generated by the alluvial fan spin. Sediment geochemical analyses have yielded results. Regional long-scale climate change information: before 0.7-0.6 Ma, the clay content in the basin began to increase. This coincides with the time when the summer monsoon began to increase. The strengthening of the summer monsoon is also conducive to the development of soil and the formation of authigenic clay in the Loess Plateau. (4) According to the lithofacies distribution characteristics, some boreholes were divided into three sections: 1-0.69 Ma; 0.69-0.33 Ma; 0.33-0. Ma. The lake surface enlarged in the first and last two stages and shrank in the middle stage. The lake surface enlarged in the last stage may be caused by the subsidence rate of the basin gradually weakening. Geomorphological and sedimentological analysis of the Luohe River Valley confirms this view. Today the Luohe River flows along the valley near the borehole, but in the early stage the Luohe River provides subsidence to the Hanyang Lake area through its own alluvial fan. The deposits were mainly from the rivers in the north of the lake. Due to the folding caused by faults, the relative subsidence rate of the lake area increased, resulting in the increase of flood deposits and the enlargement of the shallow lake surface accompanied by water. (5) This study reveals the complex effects of tectonic activities, river system evolution and climate change on sedimentation in the northern Weihe Basin. No evidence of the existence of a large lake in this area has been found in the past 1 Ma, indicating that Sanmen ancient lake existed only 1 Ma ago.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P512.2
【參考文獻(xiàn)】
相關(guān)期刊論文 前9條
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