本文選題：沉積特征 + 粒度分析　； 參考：《南京大學(xué)》2017年碩士論文

【摘要】：作為對(duì)海陸交互作用敏感的負(fù)地形,擁有巨大容積的長(zhǎng)江下切河谷可將豐富的地質(zhì)和古環(huán)境信息記錄在其巨厚充填物中,因此,研究下切河谷充填物的沉積特征可獲得對(duì)地質(zhì)歷史時(shí)期海平面變化、海陸相互作用和沉積環(huán)境演化的認(rèn)識(shí)。本文以長(zhǎng)江下切河谷取心鉆孔為材料,通過沉積物粒度分析、有孔蟲鑒定、有機(jī)碳測(cè)定、AMS14C定年和靜力觸探等方法,對(duì)末次盛冰期以來長(zhǎng)江下切河谷充填物的沉積特征進(jìn)行了精細(xì)研究,總結(jié)其沉積相類型和特點(diǎn),探討沉積環(huán)境演化。從鎮(zhèn)江、揚(yáng)州一帶到長(zhǎng)江河口區(qū),末次盛冰期形成的長(zhǎng)江下切河谷侵蝕底界面整體上呈向東南方向傾斜的斜坡,局部地區(qū)底界面深度有所起伏。該河流侵蝕不整合面之下為晚第四紀(jì)中期地層,之上即為末次盛冰期以來的長(zhǎng)江下切河谷充填物,自下而上可劃分為河床、河漫灘、河口灣、淺海、三角洲和潮坪相等6種沉積相。河床相以砂礫沉積物為主、分選系數(shù)波動(dòng)大、跳躍搬運(yùn)為主、缺乏有孔蟲、炭屑豐富為特點(diǎn);河漫灘沉積物主要為黏土和粉砂,分選性差但穩(wěn)定,偶見貝殼,含少量有孔蟲;河口灣相在不同地區(qū)巖性差異較大,沉積物粗細(xì)分異明顯,潮汐成因構(gòu)造發(fā)育,底棲有孔蟲豐富但種屬及豐度垂向上波動(dòng)較大;淺海沉積物以深灰色淤泥質(zhì)黏土、粒度參數(shù)穩(wěn)定、懸浮搬運(yùn)方式、環(huán)境敏感粒級(jí)最細(xì)等顯著區(qū)別于其他沉積相,淤泥質(zhì)黏土富含有機(jī)質(zhì),具輕微臭味,底棲有孔蟲豐度較穩(wěn)定,以廣鹽性近岸生活的溫帶型屬種居多;三角洲相主要為粉砂質(zhì)細(xì)砂和黏土,分選較好,以跳躍搬運(yùn)為主,沉積構(gòu)造復(fù)雜,炭屑和貝殼豐富,有孔蟲豐度達(dá)到最高;潮坪相以粉砂質(zhì)黏土和黏土為主,見植物根系和鐵錳浸染斑。長(zhǎng)江下切河谷充填物基本上完整地記錄了末次盛冰期以來的環(huán)境變遷,沉積物具有由粗粒向上變?yōu)榧?xì)粒,再轉(zhuǎn)變?yōu)榇至５牧６刃蛄刑攸c(diǎn),反映出末次盛冰期以來長(zhǎng)江下切河谷沉積環(huán)境水動(dòng)力條件經(jīng)歷了"強(qiáng)—較弱—較強(qiáng)—弱—較強(qiáng)"的演化過程,切合該時(shí)期"低海面—海侵—高海面—海退"的周期性海平面升降歷史,整體上,沉積環(huán)境經(jīng)歷了由陸相漸變?yōu)楹ｊ戇^渡相再到海相,最后又轉(zhuǎn)變?yōu)楹ｊ戇^渡相的過程。同時(shí)由于越靠海方向河床下切時(shí)間越短,海相沉積時(shí)間越長(zhǎng),故存在由陸向海,河床相逐漸增厚,海相沉積記錄逐漸豐富的現(xiàn)象。靜力觸探技術(shù)能有效地反映長(zhǎng)江下切河谷末次盛冰期以來充填物的垂向變化特征,不同巖性層的靜力觸探數(shù)值指標(biāo)、曲線形態(tài)和相互位置關(guān)系具有顯著的差異,相同巖性層的靜力觸探曲線特征表現(xiàn)出相似性,并且整體上呈現(xiàn)出一定的規(guī)律性。
[Abstract]:As a negative terrain sensitive to the interaction of land and sea, the abundant geological and paleoenvironment information in the lower tangent valley of the Yangtze River can be recorded in its thick filling materials. Therefore, the study of the sedimentary characteristics of the backfill in the lower cut valley can obtain the understanding of the sea level change, the sea land interaction and the sedimentary environment evolution during the geological historical period. In this paper, taking the core boreholes in the lower valley of the Yangtze River as the material, through the sediment granularity analysis, the identification of foraminifera, the determination of organic carbon, the AMS14C dating and the static cone penetration, the sedimentary characteristics of the backfill in the lower Yangtze River Valley since the last glacial period are carefully studied, the types and characteristics of the sedimentary facies are summarized, and the evolution of the sedimentary environment is discussed. In the Yangtze River and the Yangzhou area to the Changjiang River Estuary, the erosion bottom interface of the lower tangent valley of the Yangtze River, which is formed in the last glacial period, is inclined to the southeastern slope, and the bottom interface depth fluctuates in some areas. The river erosion unconformable surface is the middle Late Quaternary strata, which is the backfill of the lower Yangtze River Valley since the last glacial period. From bottom to top, it can be divided into 6 sedimentary facies, river bed, river beach, estuarine, shallow sea, Delta and tidal flat. The river bed facies is mainly sandy gravel, the separation coefficient fluctuates greatly, the jump transport is large, the foraminifers are short of foraminifera and the carbon chips are rich. The river beach sediments are mainly clay and silt, and the separation is poor but stable. Foraminifera, the lithologic difference between the estuary and the estuarine facies is larger in different areas, the thickness of sediment is distinct, the formation of tidal formation is developed, the benthic foraminifera is rich but the species and abundance fluctuate greatly, and the shallow sea sediments are with deep gray silt clay, the grain size parameters are stable, the suspension transport mode and the finest environmental sensitive grain grade are distincently different from the others. Sedimentary facies, the silt clay is rich in machine quality, a slight odor, the abundance of benthic foraminifera is more stable, most of the temperate genus in the wide salt near shore life; the delta facies mainly is silty sand and clay, the separation is good, the main sediment is hopping, the sedimentary structure is complex, the charcoal and shell are rich, the abundance of foraminifera is the highest; tidal flat is the highest. Silty clay and clay are dominant, and plant roots and ferromanganese stains are found. The backfilling of the lower Yangtze River Valley in the Yangtze River basically records the environmental changes since the last glacial period. The sediment has the characteristics of grain sequence from coarse grain to fine grain and then to coarse grain, reflecting the sedimentary environment of the lower Yangtze River Valley since the last glacial period. The hydrodynamic conditions have gone through the evolution process of "strong - weak - strong - weak - strong", and the period of the periodic sea level rise and fall of "low sea level - transgression - high sea level - regressive" in this period. On the whole, the sedimentary environment has undergone a gradual change from land facies to sea and land transition phase to marine facies, and finally the process of transition to sea land transitional phase. The shorter the cutting time of Yu Yue by the river bed is shorter and the longer the sedimentary time of the marine facies, the gradually thickening of the Lu Xianghai, the riverbed phase and the gradual enrichment of the marine sedimentary records. The static cone penetration technique can effectively reflect the vertical change characteristics of the filling material since the last glacial period in the lower cut River Valley of the Yangtze River. There are significant differences in the relationship between the curve shape and the position of each other. The characteristics of the static sounding curves in the same lithologic layer show the similarity, and a certain regularity is presented on the whole.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P512.2;P534.6

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本文編號(hào)：1969728