發(fā)布時(shí)間：2018-05-27 11:32

  本文選題：黃土高原 + 侵蝕環(huán)境��； 參考：《中國(guó)科學(xué)院研究生院(教育部水土保持與生態(tài)環(huán)境研究中心)》2016年博士論文

【摘要】：黃土高原土壤侵蝕是關(guān)系黃河中下游安全以及黃土高原區(qū)可持續(xù)發(fā)展的重要生態(tài)問(wèn)題。過(guò)去學(xué)者們?cè)邳S土高原降雨侵蝕產(chǎn)沙過(guò)程、植被水土保持效應(yīng)、土壤侵蝕時(shí)空分布特征等方面的研究都取得了豐碩的成果,對(duì)現(xiàn)代黃土高原土壤侵蝕問(wèn)題的防治起到了積極關(guān)鍵的作用。但學(xué)術(shù)界對(duì)黃土高原土壤侵蝕問(wèn)題的由來(lái)、地質(zhì)歷史時(shí)期的發(fā)展規(guī)律以及土壤侵蝕的驅(qū)動(dòng)機(jī)制和影響因素,還存在許多爭(zhēng)議,主要原因在于缺乏下游的地質(zhì)沉積記錄證據(jù)。本文通過(guò)科學(xué)鉆探對(duì)黃土高原南部關(guān)中盆地鹵陽(yáng)湖區(qū)進(jìn)行了巖芯采樣分析,通過(guò)古地磁、光釋光等定年手段,對(duì)鹵陽(yáng)湖1號(hào)鉆巖芯400 m以上的沉積速率,2號(hào)鉆50 m巖芯沉積速率,鹵陽(yáng)湖東灘的天驕湖人工剖面2.8 m沉積速率進(jìn)行了計(jì)算,并通過(guò)碳酸鹽、粒度、磁化率等氣候環(huán)境代用指標(biāo)對(duì)2號(hào)鉆和天驕湖人工剖面進(jìn)行了詳細(xì)的氣候環(huán)境變化分析,主要得出以下幾項(xiàng)重要結(jié)果:(1)鹵陽(yáng)湖1號(hào)鉆巖芯400 m(5.23 Ma)沉積速率計(jì)算結(jié)果表明,湖區(qū)沉積速率在2.58 Ma后有明顯上升,與黃土古土壤剖面底界年齡一致。鹵陽(yáng)湖區(qū)5.23 Ma以來(lái)的沉積速率在4.18-3.58 Ma、2.5-1.7 Ma、1.07-0.78 Ma、0.78-0.12 Ma、0.12-0.09Ma、67-63 ka、13-9.8 ka,這7個(gè)時(shí)期有明顯加快,其中后6個(gè)時(shí)期與青藏高原自青藏運(yùn)動(dòng)(2.58 Ma開(kāi)始)以來(lái)的抬升活動(dòng)具有明顯的對(duì)應(yīng)關(guān)系,說(shuō)明黃土高原土壤侵蝕周期在長(zhǎng)時(shí)間尺度上受控于青藏高原的構(gòu)造隆升作用。第四紀(jì)以來(lái)鹵陽(yáng)湖區(qū)沉積速率以0.12 Ma為界可劃分為前后兩個(gè)階段,2.58-0.12 Ma期間,鹵陽(yáng)湖沉積速率變化微弱增加,變化范圍在3-10 cm/ka,0.12 Ma后,沉積速率明顯加大,0.12-0.09Ma間的平均沉積速率是前段時(shí)間的近10倍,說(shuō)明0.12 Ma左右是黃土高原土壤侵蝕環(huán)境演變的重要轉(zhuǎn)折期。(2)鹵陽(yáng)湖2號(hào)鉆50 m巖芯將近15萬(wàn)年的沉積序列表明,12萬(wàn)年前后構(gòu)造強(qiáng)烈抬升的同時(shí),也恰好對(duì)應(yīng)黃土-古土壤S1階段,屬溫濕氣候期,該階段在鹵陽(yáng)湖上游地區(qū)侵蝕面分布廣泛,在下游三門峽地區(qū)則發(fā)生了黃河徹底貫通的重大環(huán)境事件。這些證據(jù)說(shuō)明鹵陽(yáng)湖區(qū)在12萬(wàn)年前后的高沉積速率是構(gòu)造強(qiáng)烈抬升、溫濕氣候環(huán)境以及三門峽的徹底貫通三種因素共同作用的結(jié)果。(3)鹵陽(yáng)湖東灘2.8 m的人工剖面研究結(jié)果表明近三萬(wàn)年來(lái),鹵陽(yáng)湖區(qū)湖泊水位經(jīng)歷了低-高-低的變化過(guò)程,與該區(qū)末次冰盛期以來(lái)的干-濕-干的氣候變化序列一致,表明鹵陽(yáng)湖區(qū)水位變化主要受控于東亞夏季風(fēng)影響。全新世后期4.6 ka后的干旱氣候造成了鹵陽(yáng)湖的大面積萎縮,為鹵陽(yáng)湖的快速消亡創(chuàng)造了條件。在此基礎(chǔ)上,2 ka后圍湖造田,撈硝曬鹽等湖區(qū)周邊人為活動(dòng)的快速增加,是導(dǎo)致鹵陽(yáng)湖沉積速率快速上升,退化為鹽堿灘,并逐漸消亡的原因。
[Abstract]:Soil erosion in the Loess Plateau is an important ecological problem related to the safety of the middle and lower reaches of the Yellow River and the sustainable development of the Loess Plateau. In the past, scholars have achieved fruitful results in the process of rainfall erosion and sediment yield, the effect of vegetation soil and water conservation, and the space-time distribution characteristics of soil erosion on the Loess Plateau. It plays an active and key role in the prevention and control of soil erosion in the Loess Plateau. However, there are still many controversies about the origin of soil erosion in the Loess Plateau, the law of development in geological history, the driving mechanism and influencing factors of soil erosion, mainly due to the lack of evidence of geological deposition records in the lower reaches of the Loess Plateau. In this paper, the core sampling and analysis of Hanyang Lake region of Guanzhong Basin in the southern Loess Plateau are carried out through scientific drilling, and the dating methods such as paleomagnetism and photoluminescence are used. The sedimentation rates of the cores above 400 m in Hanyang Lake 1, 50 m in drill 2 and 2.8 m in the artificial section of Tianjiao Lake on the Dongtan of Hanyang Lake are calculated, and the carbonate, granularity, granularity are calculated. In this paper, the climatic and environmental changes of the artificial sections of No. 2 drill and Tianjiao Lake are analyzed by using the climatic and environmental proxy indexes such as magnetic susceptibility. The main results are as follows: 1) the calculation results of the sedimentation rate of the core of Hanyang Lake 1 are as follows: the core of Huiyang Lake 1 is 400 m / m ~ (5.23) Ma), and the results are as follows: The sedimentary rate of the lake area increased obviously after 2.58 Ma, which is consistent with the age of the bottom boundary of the loess paleosol profile. The sedimentation rate since 5.23 Ma in Hanyang Lake area is 4.18-3.58 Ma ~ 2.5-1.7 Ma ~ 1.07-0.78 Ma ~ (0.7) -0.12 Ma ~ 0.12 Ma ~ 0.12-0.09 Ma ~ (67) ~ (63) ka ~ (- 9.8) ka, and the latter six periods are obviously related to the uplift activity of Qinghai-Xizang Plateau since the Qinghai-Xizang Plateau started at 2.58 Ma, and there is a significant correlation between the latter six periods and the uplift activity of Qinghai-Tibet Plateau since the Qinghai-Tibet Plateau started at 2.58 Ma. The results show that the soil erosion period in the Loess Plateau is controlled by the tectonic uplift of the Qinghai-Xizang Plateau on a long time scale. Since the Quaternary period, the sedimentary rate of the Hanyang Lake area has been divided into two stages (0.12 Ma, 2.58-0.12 Ma), and the variation of the deposition rate of the lake has increased slightly, ranging from 3-10 cm / kg to 0.12 Ma. The average deposition rate of 0.12-0.09 Ma is 10 times higher than that of the previous period. It shows that 0.12 Ma is an important turning point of soil erosion environment evolution on the Loess Plateau. It also corresponds to the loess paleosol S1 stage, which belongs to the climate period of temperature and humidity. It is widely distributed in the upper reaches of Hanyang Lake, and a major environmental event of the Yellow River is completely connected in the lower Sanmenxia area. These evidences indicate that the high deposition rate of the lake area around 120,000 years is a strong tectonic uplift. The result of the combined action of three factors, namely, temperature and wet climate environment and the thorough penetration of Sanmenxia, shows that the lake water level in Hanyang Lake area has undergone a process of low to high to low variation in the past 30, 000 years, according to the artificial section of 2. 8 m on the east beach of Hanyang Lake. It is consistent with the dry-wet-dry climate change sequence since the last ice peak in this area, which indicates that the water level change in the Hanyang Lake region is mainly controlled by the East Asian Summer Monsoon (East Asian Summer Monsoon). The arid climate after 4.6 ka in the late Holocene resulted in a large area shrinkage of Hanyang Lake, which created conditions for the rapid extinction of Hanyang Lake. On this basis, the rapid increase of anthropogenic activities around the lake area after 2 ka, such as reclaiming the lake and recovering salt, is the reason why the deposition rate of Hanyang Lake increases rapidly, which degenerates into saline-alkali beach and gradually dies away.
【學(xué)位授予單位】：中國(guó)科學(xué)院研究生院(教育部水土保持與生態(tài)環(huán)境研究中心)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：S157.1

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