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  本文關(guān)鍵詞：長江中下游地區(qū)第四紀(jì)紅土沉積特征與成因機(jī)制研究　出處：《華東師范大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 第四紀(jì)紅土 化學(xué)風(fēng)化作用 粉塵堆積 模型模擬

【摘要】：中國南方廣泛分布的第四紀(jì)紅土被認(rèn)為是重建第四紀(jì)古氣候演化歷史的重要載體,因此越來越受到學(xué)界重視。本文選擇中國南方長江中下游地區(qū)的安徽宣城剖面(XC)、江西九江剖面(JJ)、江西南昌剖面(NC)、江西新余剖面(XY)、湖南長沙剖面(CS)、浙江湯溪剖面(TX)等6個典型紅土剖面為研究對象,并基于電子自旋共振測年法(ESR)建立了時間標(biāo)尺。通過對紅土的粒度、石英顆粒表面形態(tài)等方面的分析,探討了剖面記錄的第四紀(jì)紅土沉積與物源特征,進(jìn)一步結(jié)合地球化學(xué)、環(huán)境磁學(xué)等分析,對研究區(qū)第四紀(jì)紅土的形成機(jī)制進(jìn)行了探討。本文的研究認(rèn)識有助于更好地理解中國東部晚第四紀(jì)古氣候、古環(huán)境演變歷史。論文取得的主要認(rèn)識如下:(1)長江中下游典型第四紀(jì)紅土的形成年代基于湖南長沙(CS)、江西南昌(NC)以及江西新余(XY)三個剖面的ESR測年,并結(jié)合前人研究成果,認(rèn)為長江中下游地區(qū)網(wǎng)紋紅土開始沉積的時間為～1.0-1.2Ma B.P.、結(jié)束于～0.4Ma B.P.,而后均質(zhì)紅土層以及黃棕色土層開始發(fā)育形成。(2)第四紀(jì)紅土的沉積動力特征利用新疆西風(fēng)區(qū)黃土、黃土高原黃土、江蘇下蜀黃土、長江河漫灘沉積物等典型的風(fēng)成沉積物與水成沉積物的粒度特征為訓(xùn)練樣本,建立了 Fisher線性判別函數(shù)。以此為基礎(chǔ),對研究剖面的第四紀(jì)紅土進(jìn)行了沉積動力判別分析。結(jié)果顯示,長江中下游地區(qū)第四紀(jì)紅土中均質(zhì)紅土層與黃棕色土層樣品全部被判定為風(fēng)成沉積;網(wǎng)紋紅土層上部樣品大多被判定為風(fēng)成沉積,網(wǎng)紋紅土層下部樣品有較大部分被判定為水成沉積,網(wǎng)紋紅土樣品被判定為水成沉積的比例隨著緯度的減小而增加。長江中下游地區(qū)第四紀(jì)紅土的粒度特征表明,無論樣品被判別為何中沉積,其平均粒徑都較黃土高原黃土以及下蜀黃土細(xì),而樣品中的石英顆粒粒度特征表明造成第四紀(jì)紅土粒度更細(xì)的原因不僅僅是風(fēng)化作用,其原始物質(zhì)來源本身也較黃土高原黃土與下蜀黃土細(xì)。樣品的C-M圖顯示第四紀(jì)紅土樣品的平均傳輸動能較黃土以及河漫灘沉積小,這表明了該區(qū)域內(nèi)第四紀(jì)紅土的主要搬運(yùn)動力仍然是風(fēng)力。被判定為水成沉積的網(wǎng)紋紅土樣品中含有較多的100 μm組分,其最大傳輸動能與河漫灘沉積相當(dāng),這將該類網(wǎng)紋紅土與典型的黃土高原黃土、下蜀黃土等風(fēng)塵沉積相區(qū)別。長江中下游地區(qū)網(wǎng)紋紅土中分離出來的石英顆粒的顯微照片表明,無論樣品被判別分析判定為何種沉積,石英顆粒樣品中往往都混合著磨圓度好與磨圓度差的石英顆粒。由此推測長江中下游地區(qū)的網(wǎng)紋紅土是一種近源風(fēng)塵與遠(yuǎn)源風(fēng)塵沉積的混合物,不同時期,不同位置遠(yuǎn)源于近源組分的比例不同。(3)第四紀(jì)紅土的地球化學(xué)特征利用X熒光光譜儀、ICP-MS等儀器對中國東部第四紀(jì)紅土的地球化學(xué)特征進(jìn)行了常、微量元素、稀土元素分析。第四紀(jì)紅土總體表現(xiàn)為高化學(xué)風(fēng)化指數(shù)(CIA)值和低鹽基淋溶系數(shù)(ba)值,表明其遭受了強(qiáng)烈的化學(xué)風(fēng)化作用。對于同一紅土剖面內(nèi)部,網(wǎng)紋紅土層的CIA值都較其上的均質(zhì)紅土或者黃棕色土高,而ba值則低,說明網(wǎng)紋紅土比均質(zhì)紅土層與黃棕色土層的風(fēng)化程度高。JJ、CS剖面表現(xiàn)出強(qiáng)風(fēng)化網(wǎng)紋紅土層的Si02/Al203值小于其上風(fēng)化相對較弱的黃棕色土以及均質(zhì)紅土,而Si02/Al203值的地球化學(xué)行為趨向于隨風(fēng)化程度的增加而增大。長江中下游第四紀(jì)紅土剖面的δCe表現(xiàn)為網(wǎng)紋紅土的輕微負(fù)異常,而均質(zhì)紅層與黃棕色土層為輕微正異常。強(qiáng)風(fēng)化的網(wǎng)紋紅土層輕稀土與重稀土的比值∑L/HREE小于相對弱風(fēng)化的均質(zhì)紅土層或者黃棕色土層,而稀土元素的地球化學(xué)特征表明,δCe與∑L/HREE值趨向于隨風(fēng)化程度的增加而增大。JJ、NC剖面稀土元素的聚類分析、Ti02/Al203與K20/A1203的散點(diǎn)圖都表明,網(wǎng)紋紅土層的下部、網(wǎng)紋紅土層上部以及均質(zhì)紅土或者黃棕色土層的地球化學(xué)組成差異較大。這些特征表明,第四紀(jì)紅土的物質(zhì)來源具有不穩(wěn)定性,不同時期,主要物質(zhì)來源不同。(4)第四紀(jì)紅土的環(huán)境磁學(xué)特征第四紀(jì)紅土剖面的磁學(xué)特征表明,網(wǎng)紋紅土層的磁化率相對于風(fēng)化較弱的黃棕色土層以及均質(zhì)紅土層顯著降低。相同氣候區(qū)內(nèi)的風(fēng)化殼紅土的磁學(xué)特征表明,網(wǎng)紋紅土中磁化率降低可能并不僅僅是風(fēng)化過程中強(qiáng)磁性礦物轉(zhuǎn)變?yōu)槿醮判缘某噼F礦等反鐵磁性礦物造成的。在JJ、NC兩個第四紀(jì)紅土剖面中,網(wǎng)紋紅土上部與其上的均質(zhì)紅土層以及黃棕色土層的主要磁性礦物類型、磁性礦物粒徑都沒有本質(zhì)的區(qū)別,但是磁化率卻顯著減小了,這說明了網(wǎng)紋紅土磁化率降低也不僅僅是網(wǎng)紋紅土層細(xì)粒磁性礦物減少造成的。第四紀(jì)紅土物質(zhì)來源差異很可能是造成網(wǎng)紋紅土層磁化率降低的主要原因。(5)第四紀(jì)紅土的成因機(jī)制綜合以上分析,在剝離風(fēng)化因素的影響后,本文認(rèn)為網(wǎng)紋紅土很可能是一種遠(yuǎn)源與近源的混合物。遠(yuǎn)源物質(zhì)由東亞冬季風(fēng)從亞洲內(nèi)陸地區(qū)搬運(yùn)來。近源物質(zhì)主要來自于附近水成沉積物釋放的粉塵,由夏季風(fēng)或者局地風(fēng)場搬運(yùn)而來。由于近源物質(zhì)被風(fēng)力搬運(yùn)的距離短,其被風(fēng)力改造也相對較弱,保留了大部分水動力沉積的特征。早期第四紀(jì)紅土的物質(zhì)來源以近源堆積為主。隨著冬季風(fēng)的逐漸加強(qiáng)以及河流的下切侵蝕,第四紀(jì)紅土中近源物質(zhì)的含量逐漸減少而遠(yuǎn)源物質(zhì)逐漸增加,直到0.4MaB.P.均質(zhì)紅土以及黃棕色土(下蜀黃土)開始出現(xiàn),第四紀(jì)紅土轉(zhuǎn)變?yōu)檫h(yuǎn)源堆積為主。不同時期其主要物質(zhì)來源不同,造成第四紀(jì)紅土剖面內(nèi)各層位粒度特征、地球化學(xué)與環(huán)境磁學(xué)差異。也由于近源物質(zhì)的影響,造成不同區(qū)域內(nèi)第四紀(jì)紅土粒度、地球化學(xué)環(huán)境磁學(xué)特征的差異。
[Abstract]:Quaternary red clay widely distributed in South China is considered as an important carrier of reconstruction of Quaternary paleoclimate evolution history, so more and more academic attention. In this paper Chinese Southern Yangtze River region of Anhui Xuancheng section (XC), Jiangxi Jiujiang section (JJ), Jiangxi Nanchang section (NC), Jiangxi Xinyu (section XY) Hunan, Changsha profile (CS), Zhejiang Tangxi section (TX) of 6 typical laterite profile as the research object, and based on the electron spin resonance (ESR) dating method is established. Through the time scale size of laterite, analysis of Shi Yingke particle morphology, discusses the sedimentary provenance and Quaternary red clay the characteristics of profile records, combining with geochemical analysis, environmental magnetism, formation mechanism of Quaternary red clay were discussed. The study contributes to a better understanding of the ancient climate in the east of the late Quaternary ancient Chinese. The environmental evolution history. The main ideas are as follows: (1) the formation of the Yangtze River in Hunan based on the typical Quaternary Red Changsha (CS), Jiangxi Nanchang (NC) and Jiangxi Xinyu (XY) the three section of the ESR dating, combined with the previous research, that the downstream areas of long river laterite deposition the time is 1.0-1.2Ma ~ B.P., B.P. ~ 0.4Ma in the end, then the homogeneous red and yellow brown layer which begins to develop. (2) dynamic sedimentary characteristics of Quaternary red clay loess in Xinjiang by the westerly wind area, the Loess Plateau, the Xiashu loess in Jiangsu, Yangtze River floodplain sediments and typical aeolian sediment granularity characteristic and water sediment the training samples to establish Fisher linear discriminant function. On this basis, the research of Quaternary red clay profile was used to analyze the sedimentary dynamics. The results showed that fourth of the Yangtze River Region Ji in laterite homogeneous laterite layer and yellow brown layer samples are judged as aeolian deposits; reticulate red clay upper layer samples are mostly judged as aeolian deposits, laterite sample has a lower layer is judged to be most sediments, reticulate red clay samples were determined as the proportion of sediments increases with decreasing latitude. The grain size characteristics of the Yangtze River area of Quaternary red clay, both samples were deposited in distinguishing why, the average particle size is in the Loess Plateau and Xiashu loess and fine granularity characteristics of quartz grains in the sample showed that the cause of Quaternary red clay fine granularity is not only the weathering, the original source material itself is the Loess Plateau loess and Xiashu loess samples. The fine C-M figure shows that the average kinetic energy of Quaternary red clay samples of loess and floodplain sediment transmission is small, which shows in the region The main handling power is still the wind. The Quaternary red clay was judged to be 100 m group containing more water deposited in a sample of Plinthitic red earth, the maximum transmission of kinetic energy and floodplain sediment, this will be the typical laterite and loess of the Loess Plateau, distinguish Xiashu loess. The wind dust deposition. Micrographs the quartz particles separated from the lower reaches of the Yangtze River in the laterite showed that both samples were discriminant analysis to determine what kind of deposit, quartz particles in the sample are often mixed with good roundness and rounded quartz grains. Thus the poor area of the lower reaches of the river long Plinthitic red earth is a near and far away from the source of the dust source aeolian sediment mixture, different period, different position comes from near source component ratio. (3) the geochemical characteristics of Quaternary red clay by X fluorescence spectrometry, ICP-MS and other instruments on the eastern fourth China Ji The geochemical characteristics of laterite are often, trace elements, rare earth elements analysis. The overall performance of the Quaternary red clay high chemical weathering index (CIA) value and low base leaching coefficient (BA) value, that it has suffered strong chemical weathering. The same clay profile, the reticulate red clay layer CIA value is the homogeneous red or yellow brown soil is high, and the Ba value is lower than that of homogeneous laterite, clay layer and yellow brown soil weathering degree of high.JJ, CS profile showed strong weathering Plinthitic red earth layer of the Si02/Al203 value is less than the weathered relatively weak yellow brown soil and homogeneous laterite geochemical behaviors. The Si02/Al203 value increases with increasing trend in weathering degree. The lower reaches of the Yangtze River Delta Ce quaternary laterite profile showed slight negative anomalies and homogeneous laterite, red and yellow brown soil layer for the slight positive anomalies of strong weathering. The reticulate red clay layer LREE and hree ratio of sigma L/HREE lower than that of the homogeneous clay layer is relatively weakly weathered or yellow brown soil, and the geochemical characteristics of rare earth elements Ce and L/HREE show that the delta sigma value tends to increase with the increasing of the weathering degree of.JJ cluster analysis of NC profile of rare earth elements, plot Ti02/Al203 and K20/A1203 have shown that lower reticulate red clay layer, the upper layer and the reticulate red clay homogeneous red soil or yellow brown soil geochemical composition differences. These characteristics suggest that the material source of Quaternary red earth is unstable, different period, different source material. (4) showed that the magnetic characteristics of environmental magnetic characteristics of Quaternary quaternary laterite profile laterite, magnetization reticulated red soil layer rate compared to weathering weak yellow brown soil and red soil layer decreased significantly. The homogeneous laterite in the same climate zone Show that the magnetic characteristics, may not be the transformation process of strong magnetic minerals weathering weak magnetic hematite, anti ferromagnetic minerals caused the reduction of vermicular red earth in magnetic susceptibility. In JJ NC, the two section of Quaternary Red Earth in laterite layer and the upper part of the homogeneous red soil and yellow brown soil is the main type of magnetic minerals the particle size, magnetic minerals are not essentially different, but the magnetization rate decreased significantly, indicating that the reticulate red clay is not only reduce the susceptibility of the reticulate red clay layer of fine magnetic mineral decrease. The Quaternary red clay material source of difference might be mainly caused by the reticulate red clay layer magnetic susceptibility (5) causes reduced. The mechanism of Quaternary red earth based on the above analysis, the influence factors of the weathering peeling, the laterite is likely to be a mixture of a distant source and near source. The source material from far east Asia winter monsoon from the inland areas of Asia. Handling the near source material from dust emission in the vicinity of hydatogen sediment, by summer monsoon or local wind field due to transport. Because the near source material is carried by wind short distance, the wind transformation is relatively weak, retains the characteristics of most of the water power source material deposition. The source of early Quaternary red clay accumulation. With the gradual strengthening of the winter monsoon and the river erosion, the content of near source material in Quaternary red clay decreases gradually and far source material gradually increased, until the 0.4MaB.P. in yellow brown soil and red soil homogeneous (Xiashu loess) began to appear, into a distant source of Quaternary red clay deposits the main source of material. In different periods of different grain size characteristics of each layer of Quaternary laterite profile by, geochemistry and environmental magnetism differences. Also due to the influence of near source material, cause The difference between the granularity of the Quaternary Red Soil in the same region and the geochemical characteristics of the geochemical environment.

【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P534.63;P512.2

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