本文選題：龍門山 + 蓮花口組��； 參考：《成都理工大學》2015年碩士論文

【摘要】：青藏高原東緣龍門山中生代構造隆升是研究熱點。針對龍門山幕次構造運動多次疊加的特殊性,龍門山山前沖積扇一直被看做是盆山耦合的研究重點。前人大多數研究僅集中在早期(晚三疊世-早侏羅世)和晚期(白堊紀-新生代)的沖積扇研究,而對形成于區(qū)域氣候變化最顯著、沉積巖相突變階段的晚侏羅世蓮花口組的沖積扇的研究卻相對薄弱,究其主要原因可能是氣候、構造作用的同時疊加導致了對盆山耦合演化認識的局限。本論文針對受氣候和構造雙重控制的龍門山北段晚侏羅世蓮花口組沖積扇,對其進行細致的沉積相和沉積環(huán)境解析。首先在野外對剖面進行系統(tǒng)的巖相分析,然后識別礫石的不同成分,測量古水流方向,進而結合鏡下對砂巖碎屑組分的統(tǒng)計和陰極發(fā)光對碎屑組分的識別,綜合分析了蓮花口組沖積扇沉積特征及物源。本次研究取得了如下認識:(1)運用巖相分析方法和沉積巖相組合模式,首先在蓮花口組中識別出9種礫巖巖相:富砂質雜基礫巖Gmd,塊狀顆粒支撐礫巖Gcd,定向性粒序層理礫巖Gco,底沖刷正粒序礫巖Ghg,含砂質透鏡體礫巖Gmg,槽狀交錯層理礫巖Gt,夾層狀砂體礫巖Gst,斜層理礫巖Go,平行層理礫巖Ghi;5種砂巖巖相:槽狀交錯層理砂巖St,塊狀砂巖Sm,平行層理砂巖Sh,底沖刷沉積砂巖Ss,斜層理砂巖So;9種細粒沉積巖相:細紋層泥巖Fl,塊狀(板狀)泥巖-粉砂巖Fm,水平層理泥巖-粉砂巖Fh,細粒紋層泥巖-粉砂巖Fg,生物擾動泥巖-粉砂巖Fb,灰綠色泥巖Ms,含鈣化泥礫泥巖Cg,碳酸鹽巖Cm,古土壤P;7種主要沉積建造:沉積物重力流(SG),辮狀河道沉積(BF),河道沖刷充填沉積(CH),河漫灘-洪泛平原(OB),片流沉積(SF),天然堤(MF),淺湖泊相(LD)。在此基礎上共劃分出10類巖相組合:①-③復成分塊狀礫巖(PC):Ⅰ類、Ⅱ類、Ⅲ類;④礫巖和泥巖條帶CM;⑤礫巖和砂巖CS;⑥礫巖、砂巖和泥巖CSM;⑦泥巖和復成分礫巖MC;⑧砂巖和泥巖SM;⑨泥巖和砂巖透鏡體MS;⑩泥巖和泥灰?guī)rMCa。最終將研究區(qū)的蓮花口組的沉積環(huán)境劃分為4種:沖積扇沉積環(huán)境,辮狀河沉積環(huán)境,遠端河流沉積環(huán)境,淺湖沉積環(huán)境。(2)初步查明蓮花口組中礫石的古水流方向。對研究區(qū)的野外具古流向指示意義的沉積構造進行古水方向測定和統(tǒng)計,并對比了晚三疊世以來研究區(qū)的古流向特征,初步判斷蓮花口期古流向主要為SE向(140°~160°),并推斷龍門山北段自晚三疊世至早白堊世的古水流向具有明顯的整體繼承性,以SE向(130°~170°)為主。(3)限定了蓮花口組礫石與碎屑物質的成分及其物源區(qū)的巖性特征。利用系統(tǒng)的野外礫石成分統(tǒng)計、常規(guī)顯微鏡和陰極發(fā)光分析砂巖碎屑組分,礫石成分與砂巖碎屑組分具有一致性。礫石成分空間上存在明顯區(qū)域差異:①廣元金子山附近,礫石成分以石英巖和石英砂巖為主,石英質礫巖達67%~89%,灰?guī)r礫石成分最高不超過30%,白云巖礫石零星出現;②安縣附近,礫石成分以石英砂巖,灰?guī)r和白云巖為主,灰?guī)r礫石成分最高超過90%(平均52%),白云巖礫石成分比例明顯較其他地方高,最高可達23%。同時根據巖石學、生物化石的特征初步推斷了蓮花口組中礫石的物源:①灰?guī)r礫石主要來自龍門山地區(qū)的石炭系~二疊系(以二疊系為主);②石英砂巖礫石均為鈣質石英砂巖,陰極發(fā)光光色特征表明部分鈣質石英砂巖與泥盆系石英砂巖有較高的相似性。碎屑組分統(tǒng)計表明:①金子山剖面砂巖中石英含量一般30%(平均為20%~29%),長石含量為5.7%~16.3%,巖屑37.7%~74.4%,一般大于60%;②青林口地區(qū)砂巖中石英含量較穩(wěn)定為23%~25%,長石2.3%~9%,巖屑含量為65.6%~72.6%;③安縣地區(qū)砂巖中石英含量為26%~45%,長石含量為0.7%~2.8%,巖屑占53%~81.9%�；诘[巖成分、砂級碎屑組分、石英成因類型的差異性,以及古水流的繼承性,綜合表明沖積扇沉積物質展布受古河流水系控制,與源區(qū)為孤立式點狀物源對應關系。(4)晚侏羅世四川盆地從“黑層”轉變“紅層”后,從細粒的遂寧組到粗粒的蓮花口組,沉積物表現出相同氣候背景下的巖相和沉積環(huán)境的突變,應為龍門山地區(qū)強烈構造運動所驅使。對比“黑層”階段沉積的白田壩組沖積扇和“紅層”階段沉積的蓮花口組沖積扇的沉積序列,表明在相似活動構造背景下,蓮花口組的沉積序列旋回性明顯受區(qū)域氣候的控制。這表明在研究區(qū)陸相沉積體系研究中應重視構造和氣候的雙重因素,回避或忽略氣候因素是不可取的。(5)龍門山北段蓮花口期沖積扇的形成受構造-氣候-古河流水系三重因素聯合控制。蓮花口組沖積扇是龍門山構造活動背景下,構造隆升驅動源區(qū)和沉積空間、古河流水系控制沉積物空間展布、持續(xù)干旱和充沛雨水補給交替氣候變化影響沉積序列礫-泥旋回疊加,扇體礫石層重在垂向疊加,側向延展較弱的多期次復合型扇體。
[Abstract]:The Mesozoic tectonic uplift of the Longmen mountain in the eastern margin of the Qinghai Tibet Plateau is the focus of research. In view of the particularity of the repeated superposition of the subtectonic movement of the Longmen mountain episodes, the alluvial fan in the Longmen mountains has been regarded as the focus of the study of the basin mountain coupling. Most of the previous studies of the predecessors were concentrated only on the alluvium of the early (late three fold - Early Jurassic) and late (Cretaceous - Cenozoic). Fan studies, however, are relatively weak in the study of alluvial fans in the late Jurassic Lianhua Group formed by the most significant regional climate change and the sedimentary facies mutation stage. The main reason may be the climate, the superposition of the tectonics and the limitation of the understanding of the coupling evolution of the basin and mountain. This paper is aimed at the Dragon controlled by climate and structure. The sedimentary facies and sedimentary environment of the late Jurassic Lianhua mouth group in the northern part of mendan are analyzed. First, systematic lithofacies analysis is carried out in the field, and then the different components of the gravel are identified and the direction of the paleo flow is measured. Then, the statistics of the debris components in the sandstone and the identification of the debris components by the cathodic luminescence under the mirror are combined. The characteristics and source of the alluvial fan in Lianhua mouth formation are analyzed. (1) 9 kinds of conglomerate facies are identified in Lianhua Kou formation by lithofacies analysis and sedimentary facies combination model: Gmd, massive granular conglomerate Gcd, directional granular bedding conglomerate Gco, and bottom scour Rock Ghg, sandy lenticular conglomerate Gmg, grooved staggered conglomerate Gt, sandwich conglomerate Gst, diagonal conglomerate Go, parallel bedding conglomerate Ghi; 5 sandstone facies: trough staggered bedding sandstone St, massive sandstone Sm, parallel bedding sandstone Sh, bottom scour sedimentary sandstone Ss, diagonal bedding sandstone So; 9 fine grain sedimentary facies: fine striate Fl, block like (fine grain mudstone Fl, massive (")" Mudstone siltstone Fm, horizontal bedding mudstone - siltstone Fh, fine grain layer mudstone - siltstone Fg, bioturbate mudstone, siltstone Fb, gray green mudstone Ms, calcified mudstone Cg, carbonate Cm, paleosol P, 7 main sedimentary formations: sediment gravity flow (SG), braided channel deposition (BF), river scour filling deposition (CH), river flood Flood flood. Plain plain (OB), SF, natural dike (MF) and shallow lacustrine facies (LD). On this basis, 10 types of lithofacies assemblages are divided: (1) (3) complex block conglomerate (PC): class I, class II, class III; (4) conglomerate and mudstone strip CM; (5) conglomerate and sandstone CS; conglomerate and CS; conglomerate, sandstone and mudstone CSM; (7) mudstone and complex conglomerate MC; sandstone and mudstone SM; mudstone The sedimentary environment of Lianhua Group in the study area is divided into 4 types: alluvial fan sedimentary environment, braided river sedimentary environment, distal river sedimentary environment and shallow lake sedimentary environment. (2) preliminary identification of the direction of the paleo flow of gravel in Lianhua mouth group is preliminarily identified by the sedimentary environment of the Lianhua group in the study area. (2) the direction of the paleo direction of the study area is indicative of the direction of the paleo direction in the study area. The sedimentary structure carries out the measurement and statistics of the direction of the paleo water, and compares the characteristics of the paleo direction of the study area since the late three fold. It is preliminarily judged that the paleo flow of the lotus estuary was mainly SE (140 ~160), and that the paleo water flow from the late three to the early Cretaceous in the northern section of the Longmen mountain had obvious overall inheritance and was dominated by (130 [degree ~170]). (3). The composition of gravel and debris in Lianhua mouth group and the lithologic characteristics of its source area are determined. Using the statistics of the field gravel composition of the system, conventional and cathodoluminescence analysis of sandstone debris components, the conglomerate composition is consistent with the sandstone fragments. There are obvious regional differences in the space of the gravel composition: (1) near the gold mountain in Guangyuan, gravel. Quartzite and quartzite are the main stones, the quartzite conglomerate is 67%~89%, the composition of the limestone is not more than 30%, and the dolomite gravel occurs sporadically. In the vicinity of Anxian, the conglomerate is mainly composed of quartz sandstone, limestone and dolomite, and the highest composition of limestone is over 90% (average 52%), and the proportion of the dolomite gravel is obviously higher than that of other places. According to the characteristics of petrology and biological fossils, the source of the 23%. is preliminarily deduced from the characteristics of petrology and biological fossils: (1) the limestone gravel mainly comes from the Carboniferous Permian in the Longmen mountain area (mainly Permian), and the quartz sandstone gravel is calcareous quartz sandstone, and the glowing color characteristics of the Yin pole show that some calcareous quartz sandstone and mud are found. The quartz sandstone of the basin system has high similarity. The statistics of debris composition show that the quartz content in the sandstone of the Jin Zi Shan section is generally 30% (average 20%~29%), the feldspar content is 5.7%~16.3%, and the debris 37.7%~74.4% is more than 60%, and the quartz content in the sandstone of the Qinghai Province is more stable than that of 23%~25%, the feldspar 2.3%~9%, and the content of the cuttings is 65.6%~72.6%; 3. The quartz content in the sandstone in the county area is 26%~45%, the feldspar content is 0.7%~2.8%, the cuttings account for the 53%~81.9%. based on the conglomerate composition, the sand grade debris component, the quartz origin type difference and the inheritance of the paleo flow, which shows that the alluvial fan sedimentary material distribution is controlled by the ancient river water system and corresponds to the source area as the isolated point source. (4) late The Jurassic Sichuan basin has changed from the "black layer" to the "red layer" from the fine grain Suining group to the coarse-grained lotus flower mouth group. The sediment shows the abrupt change of the lithofacies and sedimentary environments in the same climate background. It should be driven by the strong tectonic movement of the Longmen mountain area. The depositional sequence of the alluvial fan in the Lianhua mouth group, which is deposited in the section, indicates that the cyclicity of the sedimentary sequence of the Lianhua mouth group is obviously controlled by the regional climate under the similar active tectonic setting. This indicates that the dual factors of structure and climate should be paid attention to in the study of the continental sedimentary system in the study area. It is not advisable to avoid or ignore the climatic factors. (5) the north of Longmen. The formation of the alluvial fan in the lotus flower mouth period is controlled jointly by three factors. The alluvial fan of Lianhua mouth formation is the source area and sedimentary space of the tectonic uplift in Longmen mountain. The ancient river flow system controls the spatial distribution of the sediment, and the continuous drought and the abundant rainwater supply alternate climate change influence the sedimentary sequence. The gravel layer is superimposed, and the fan gravel layer is vertically superimposed and the lateral extension is weak.
【學位授予單位】：成都理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P534.52;P512.2

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