發(fā)布時(shí)間：2018-05-20 01:07

  本文選題：沱沱河盆地 + 磁性地層�。� 參考：《中國科學(xué)院研究生院(地球環(huán)境研究所)》2015年碩士論文

【摘要】：印度板塊與亞歐板塊的碰撞形成了面積超過250萬平方公里,平均海拔在5000m以上的青藏高原。由于青藏高原具有如此大的面積和海拔高度,它的隆升不僅對(duì)我國的氣候產(chǎn)生重大影響,而且造成全球氣候格局的改變。同時(shí)青藏高原是印度板塊與歐亞板塊碰撞的結(jié)果且這種碰撞作用仍然在繼續(xù),所以青藏高原也是研究碰撞造山帶、大陸變形以及地球動(dòng)力學(xué)的天然場(chǎng)所。到目前為止,對(duì)于印度板塊與歐亞板塊碰撞的時(shí)間、高原隆升的過程、機(jī)制都存在較大的爭(zhēng)議。沉積盆地是研究構(gòu)造隆升的重要場(chǎng)所,目前青藏高原周邊的盆地都得到了較高程度的研究,而高原中部的盆地研究相對(duì)滯后。沱沱河盆地屬于可可西里盆地的一部分,位于可可西里盆地的南邊,北邊是金沙江縫合帶,南邊是唐古拉山逆沖斷裂帶。沱沱河盆地包含有完整的一套從晚白堊到中新世的地層,即風(fēng)火山群、沱沱河組、雅西措組、五道梁組。這套地層有可能記錄了印度板塊俯沖以及與歐亞板塊碰撞所產(chǎn)生的構(gòu)造響應(yīng),對(duì)于理解青藏高原的隆升過程研究具有明顯的幫助,同時(shí)還有助于解決風(fēng)火山群的年代問題。本文通過巖石磁學(xué)、磁性地層學(xué)、沉積相、生物地層學(xué)以及磁化率各向異性等研究了沱沱河盆地的主要磁性礦物、高原隆升可能的時(shí)間節(jié)點(diǎn)、主要的古氣候變化事件等。本文得到以下結(jié)論:1.通過磁化率隨溫度變化曲線(K-T)、等溫剩磁(IRM)獲得曲線以及等溫剩磁的CLG模型分析,沱沱河盆地剖面的主要磁性礦物是赤鐵礦和磁鐵礦。同時(shí)在熱退磁的過程中,有些樣品在120℃左右磁化強(qiáng)度顯著的降低到原磁化強(qiáng)度的15%左右,說明存在一定量的針鐵礦。2.沱沱河盆地剖面自下而上(由老到新)可以劃分為沱沱河組、雅西措組。磁性地層及其生物地層研究表明沱沱河組的地質(zhì)年代為59.8-52.6Ma,雅西措的地質(zhì)年代為51.8-24.1Ma。如果風(fēng)火山群和沱沱河組是同一套地層,那么風(fēng)火山群的年齡至少要老于52.6Ma,如果沱沱河組不整合于風(fēng)火山群之上,那么風(fēng)火山群的年齡至少在59.8Ma之前。3.沉積相表明沱沱河盆地存在5次明顯的沉積相變化,分別是:第一次明顯變化開始的時(shí)間為52.6Ma,在此之前氣候干旱,從52.6Ma開始,氣候變得濕潤。通過孢粉、化石的分析以及與區(qū)域性的孢粉、化石對(duì)比,再結(jié)合全球溫度的變化,52.6Ma之前的干旱主要是受控于副熱帶高氣壓帶以及全球氣溫降低的雙重控制。之后氣候變得濕潤主要是受到早始新世氣候適宜期的影響。結(jié)合降水的變率以及這個(gè)時(shí)期氣候濕潤期的分布范圍,此時(shí)季風(fēng)有可能已經(jīng)發(fā)育。考慮到沱沱河盆地位于青藏高原的中部,不排除青藏高原的構(gòu)造隆升對(duì)盆地的氣候會(huì)產(chǎn)生影響。第二次明顯變化開始的時(shí)間為43.2Ma,地層中出現(xiàn)了白色的順層石膏。第三次開始的時(shí)間為41Ma,出現(xiàn)了厚層的石膏。這兩次時(shí)期的干旱化原因有可能是特提斯海的退卻、青藏高原的構(gòu)造隆升、全球氣候的變冷共同導(dǎo)致的。但是特提斯海的退卻很大程度上是受控于全球氣候變化,同時(shí),磁組構(gòu)和磁學(xué)相關(guān)指標(biāo)分析表明,在41Ma左右青藏高原發(fā)生了一次構(gòu)造運(yùn)動(dòng),而且磁學(xué)指標(biāo)表明高原的隆升對(duì)區(qū)域的干旱化作用開始變得明顯,因此青藏高原的隆升開始超過全球氣溫及特提斯海對(duì)區(qū)域的影響。第四次變化開始的時(shí)間為34.5Ma,地層中出現(xiàn)了厚層的石膏。這個(gè)時(shí)期的干旱同樣可以由特提斯海的退卻、青藏高原的隆升、全球氣候變冷導(dǎo)致形成,特提斯海的退卻還是受控于全球氣候變化,另外后面的磁學(xué)指標(biāo)從這個(gè)時(shí)候開始都整體下降,而全球的溫度變化幅度較大,磁學(xué)指標(biāo)與之變化的趨勢(shì)逐漸不一致,說明全球因素對(duì)沱沱河盆地的影響逐漸減小,而青藏高原的影響因素加大,占據(jù)主導(dǎo)。第五次變化也是出現(xiàn)了非常厚層的石膏,開始的時(shí)間為26.9Ma。磁學(xué)指標(biāo)暗示青藏高原對(duì)區(qū)域的干旱化作用更明顯。4.磁化率各向異性表明沱沱河盆地受到了構(gòu)造應(yīng)力的作用,從老到新可以劃分出四次構(gòu)造應(yīng)力期,分別是:T1段:地質(zhì)年代為59.8-52.6Ma,構(gòu)造應(yīng)力方向?yàn)槟衔?印度板塊與歐亞板塊在這個(gè)時(shí)間段之前已經(jīng)發(fā)生碰撞。T3段:地質(zhì)年代為46.8-44Ma,構(gòu)造應(yīng)力的方向?yàn)槟衔�。這段的構(gòu)造應(yīng)力作用比較明顯,具有區(qū)域性。根據(jù)沉積相的變化,C段以后出現(xiàn)了石膏,推測(cè)此時(shí)沱沱河盆地南部已經(jīng)存在可以阻擋水汽深入北進(jìn)的地貌,促進(jìn)了沱沱河盆地的干旱。T5段:地質(zhì)年代為41.1-34.3Ma,磁偏角的平均值,在41.1Ma發(fā)生了明顯的偏轉(zhuǎn),應(yīng)力的來源不僅來自南西,還來自南東。41.1Ma出現(xiàn)的南東方向構(gòu)造應(yīng)力,表明此時(shí)印度板塊在東部與歐亞板塊之間開始碰撞。此時(shí)青藏高原的平均海拔加大,對(duì)水汽的阻擋更加顯著。T7段:地質(zhì)年代為26.2-24.1Ma,應(yīng)力方向?yàn)槟衔鞣较蚝湍蠔|,通過磁學(xué)指標(biāo)分析,暗示著此時(shí)高原的構(gòu)造運(yùn)動(dòng)更加強(qiáng)烈。5.沱沱河盆地磁化率與頻率磁化率、百分比頻率磁化率之間的反位相關(guān)系表明超順磁顆粒組分對(duì)剖面的磁化率幾乎沒有貢獻(xiàn)。另外磁學(xué)指標(biāo)在51.8-41Ma與41-32Ma整體都趨于下降,與全球這個(gè)時(shí)間段溫度的下降以及沱沱河盆地逐漸變干的趨勢(shì)相符合,說明全球的氣候在51.8-41Ma與41-32Ma范圍內(nèi)對(duì)區(qū)域氣候有影響。但是在41-32Ma,各個(gè)指標(biāo)整體都高于51.8-41Ma、32-24.1Ma,分析表明約41Ma開始,青藏高原發(fā)生了一次構(gòu)造運(yùn)動(dòng)(磁化率各向異性結(jié)果也支持這個(gè)結(jié)論),此時(shí)青藏高原的構(gòu)造隆升對(duì)沱沱河盆地干旱的影響是疊加在全球的降溫趨勢(shì)上,但是高原對(duì)區(qū)域的影響開始占主導(dǎo)。在32-24.1Ma,指標(biāo)都整體下降,此時(shí)全球的溫度卻變化幅度較大,磁學(xué)指標(biāo)與之變化的趨勢(shì)逐漸不一致,說明全球因素對(duì)沱沱河盆地的影響逐漸減小,而青藏高原的影響因素加大,占據(jù)絕對(duì)主導(dǎo)地位。
[Abstract]:The collision between the India plate and the Eurasian plate has formed the Qinghai Tibet Plateau with an area of more than 2 million 500 thousand square kilometers and above 5000m above sea level. Because of such a large area and altitude of the Qinghai Tibet Plateau, its uplift not only has a significant impact on the climate of our country, but also causes a change in the global climate pattern. At the same time, the Qinghai Tibet Plateau is a India plateau. The collision between the plate and the Eurasian plate and the collision are still continuing, so the Qinghai Tibet Plateau is also a natural place to study the collision orogenic belt, continental deformation and geodynamics. So far, there are considerable disputes over the time of the collision between the India plate and the Eurasian plate, the process of Plateau uplift, and the sedimentary basin. It is an important place to study the tectonic uplift. At present, the basins around the Qinghai Tibet Plateau have been studied in a high degree, while the basin research in the middle of the plateau is relatively lagging. The Tuo Tuo basin belongs to a part of the cocoa Xili basin, located on the southern side of the cocoa West Basin, the northern side of the Jinsha River suture zone and the Tanggula Mountain Thrust Belt on the south. The Tuotuo basin contains a complete set of strata from the late Cretaceous to the Miocene, that is, the wind volcano group, the Tuotuo River formation, the Iasi measure and the five road formation. This set of strata may record the subduction of the India plate and the tectonic response to the collision with the Eurasian plate, which is of great help to the understanding of the uplift process of the Qinghai Tibet Plateau. In this paper, the main magnetic minerals of the Tuotuo basin, the possible time nodes of the uplift of the plateau and the major paleoclimate change events are studied through rock magnetism, magnetic stratigraphy, sedimentary facies, biostratigraphy and the anisotropy of magnetic susceptibility. The following conclusions are obtained: 1. the following conclusions are obtained by magnetization With the temperature change curve (K-T), the isothermal remanence (IRM) obtained curve and the CLG model of isothermal remanence, the main magnetic minerals in the Tuo Tuo basin section are hematite and magnetite. In the process of thermal demagnetization, the magnetization of some samples is significantly reduced to about 15% of the original magnetization at about 120 degrees C, indicating that there is a certain degree of magnetization. The.2. Tuo Tuo basin section from the Tuo Tuo River Basin (from the old to the new) can be divided into Tuo Tuo formation and Iasi measures. The study of magnetic strata and its biostratigraphy shows that the geological age of the Tuo Tuo formation is 59.8-52.6Ma, and the geological age of the Tuo Tuo group is 51.8-24.1Ma. if the wind volcano group and Tuo Tuo River group are the same set of strata, then the wind volcano group. The age of the Tuo Tuo River group is at least 52.6Ma. If the Tuo Tuo formation is not integrated with the wind volcano, the.3. sedimentary facies of the Tuo Fire Mountain Group at least before 59.8Ma indicates that there are 5 obvious sedimentary facies changes in the Tuo Tuo basin, respectively: the first obvious change began to be 52.6Ma. Before this, the climate was drought, from 52.6Ma to the climate. It becomes humid. Through the analysis of sporopollen, fossils, and regional sporopollen, fossils, and global temperature changes, the drought before 52.6Ma is mainly controlled by the double control of the subtropical high pressure zone and the global temperature reduction. Then the climate becomes wetted mainly by the early Eocene climatic suitability period. When the Tuotuo basin is located in the middle of the Qinghai Xizang Plateau, the tectonic uplift of the Qinghai Xizang Plateau affects the climate of the basin. The second obvious change begins at 43.2Ma, and the white Paris stone appears in the formation. The third time began with a thick layer of gypsum. The reasons for the two periods of droughts may be the retreat of the Tethys Sea, the tectonic uplift of the Qinghai Tibet Plateau, and the cooling of the global climate. But the retreat of the Tethys Sea is largely controlled by global climate change, at the same time, magnetic fabric and magnetism are related. The index analysis showed that a tectonic movement occurred on the Qinghai Tibet Plateau around 41Ma, and the magnetic indexes indicated that the uplift of the plateau began to become obvious to the region. Therefore, the uplift of the Qinghai Tibet Plateau began to exceed the global temperature and the effect of the Tethys on the region. The fourth change began as 34.5Ma. The droughts of this period can also be retreated by the Tethys Sea, the uplift of the Qinghai Tibet Plateau, the cooling of the global climate and the global climate change in the Tethys Sea. In addition, the following magnetic indicators have fallen from this time, and the global temperature changes are larger, magnetic indexes are larger. The trend of the change is gradually disagreement, indicating that the influence of the global factors on the Tuo Tuo basin is gradually decreasing, while the influence factors of the Qinghai Tibet Plateau are increasing and dominant. The fifth change is also a very thick layer of gypsum. The beginning time of the 26.9Ma. magnetic index suggests that the Qinghai Tibet Plateau has more obvious.4. magnetization to the region. The rate anisotropy indicates that the Tuo Tuo basin has been subjected to tectonic stress, and four tectonic stress periods can be divided from the old to the new. The T1 section is: the geological age is 59.8-52.6Ma, the tectonic stress is South West, the India plate and the Eurasian plate have collided.T3 segments before this time period: the geological age is 46.8-44Ma and the structure should be constructed. The direction of the force is Nancy. The tectonic stress of this section is obvious and regional. According to the change of the sedimentary facies, the gypsum has appeared after the C section. It is presumed that in the south of the Tuo Tuo basin there is a geomorphology that can block the deep water vapor entering into the North of the Tuo Tuo basin, which promotes the arid.T5 segment of the Tuo Tuo basin: the geological age is 41.1-34.3Ma, the average magnetic deflection angle is the average. There is a significant deflection in 41.1Ma. The source of the stress is not only from the South West, but also from the South East.41.1Ma tectonic stress, which indicates that the India plate began to collide between the East and the Eurasian plate at this time. The average elevation of the Qinghai Tibet Plateau increased, and the water vapor was blocked more.T7 segment: the geological age was 26.2-24.1Ma, The direction of stress is South West and South East. Through the analysis of magnetic index, it is suggested that the tectonic movement of the plateau is more intense at this time, and the magnetic susceptibility and frequency susceptibility of.5. Tuo Tuo basin and the reverse phase relation between the percentage frequency magnetization of the Tuo Tuo basin show that the superparamagnetic particle composition has little contribution to the magnetic susceptibility of the section. In addition, the magnetic index is in the 51.8-41. Both the Ma and the 41-32Ma tend to decline, in accordance with the global temperature decline and the trend of the Tuo Tuo basin gradually drying up, indicating that the global climate has an impact on the regional climate in the range of 51.8-41Ma and 41-32Ma. But in 41-32Ma, each index is higher than 51.8-41Ma, 32-24.1Ma. Analysis shows that 41Ma began, Qinghai Xizang There is a tectonic movement in the plateau (the results of the anisotropy of magnetic susceptibility also support this conclusion). At this time, the influence of the tectonic uplift of the Qinghai Tibet Plateau on the Tuo Tuo basin drought is superimposed on the global cooling trend, but the influence of the plateau on the region begins to dominate. In 32-24.1Ma, the indices are all decreased, and the global temperature changes at this time. The amplitude of the magnetic index is not consistent with the change trend, which indicates that the influence of the global factors on the Tuo Tuo basin is gradually reduced, while the influence factors of the Qinghai Tibet Plateau are increasing, which occupies an absolute dominant position.
【學(xué)位授予單位】：中國科學(xué)院研究生院(地球環(huán)境研究所)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P318.4;P534.6

【參考文獻(xiàn)】

相關(guān)期刊論文 前5條

1 李云通;;西寧—民和盆地晚自堊世和晚古新世淡水腹足類化石的發(fā)現(xiàn)[J];地層古生物論文集;1988年03期

2 金振民;高山;;底侵作用(underplating)及其殼—幔演化動(dòng)力學(xué)意義[J];地質(zhì)科技情報(bào);1996年02期

3 吳珍漢,江萬,周繼榮,李冀湘;青藏高原腹地典型巖體熱歷史與構(gòu)造-地貌演化過程的熱年代學(xué)分析[J];地質(zhì)學(xué)報(bào);2001年04期

4 吳乃琴;;江西清江盆地臨江組非海相腹足類化石及時(shí)代討論[J];古生物學(xué)報(bào);1989年06期

5 吳珍漢,孟憲剛,胡道功,江萬,葉培盛,朱大崗,劉琦勝,楊欣德,邵兆剛,吳中海;當(dāng)雄縣幅地質(zhì)調(diào)查新成果及主要進(jìn)展[J];地質(zhì)通報(bào);2004年Z1期

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