本文選題：南京地區(qū) + 中新世��； 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：南京及鄰區(qū)的古礫石層是組成該地區(qū)新生代地層的重要地質(zhì)類型之一。它與該地區(qū)的玄武巖是研究古長江下游演化的重要地貌和時(shí)代材料。為此對(duì)該地區(qū)沉積地層的劃分、沉積物成因和沉積物相分析展開研究,借助于玄武巖K-Ar和Ar-Ar測(cè)年、沉積物ESR測(cè)年、動(dòng)植物化石時(shí)代分析、沉積剖面勘察及測(cè)量等研究手段,反映南京地區(qū)新近紀(jì)以來的地貌演化過程。南京及鄰區(qū)的沉積地層多為河流相。通過玄武巖和砂礫層測(cè)年、野外地貌觀察及剖面測(cè)量等手段對(duì)河流階地橫剖面、級(jí)序、年代學(xué)及沉積物與玄武巖的接觸關(guān)系進(jìn)行研究,南京地區(qū)的沉積物可分為6套并與現(xiàn)代長江沉積物一起構(gòu)成長江的7級(jí)階地。本文重點(diǎn)研究的橫山古礫石層剖面由底至頂經(jīng)歷了由河床相-河漫灘相的變化,頂部被玄武巖覆蓋。前人測(cè)得上覆玄武巖K-Ar年齡為12.42Ma,本研究測(cè)得橫山沉積砂層ESR年齡為16.7±1.6Ma,并依據(jù)與其相當(dāng)?shù)亩葱^組含中新世早中期的安琪馬Anchitherium aureilianense等哺乳動(dòng)物化石,得出其沉積時(shí)代為早中新世晚期至中新世早期的結(jié)論。橫山古礫石層內(nèi)礫石扁平面傾向南南西方向,沉積層頂面向北北東方向傾斜。通過分析其沉積相、沉積規(guī)模以及沉積物所處地理位置,得出橫山砂礫石層位于一條由南向北或北北東方向扇形展開的大河在出山口外所形成沉積層的中上部,后期或由于河流改道轉(zhuǎn)變?yōu)闇\水河漫灘相且該沉積物為古長江產(chǎn)物。南京地區(qū)玄武巖覆蓋的礫石層已經(jīng)構(gòu)成了長江水系(長江及其支流滁河的各級(jí)支流)與洪澤湖或高郵湖水系的分水嶺或局部已越過分水嶺;礫石層成分非常復(fù)雜,磨圓良好,非當(dāng)?shù)鼗蚪串a(chǎn)物,進(jìn)一步證明形成南京地區(qū)古礫石層的主要?jiǎng)恿楣砰L江。在中更新世早期長江的流向?yàn)楸被虮北睎|向,根據(jù)南京地區(qū)砂礫層的分布特征以及玄武巖噴發(fā)時(shí)代,北或北北東向的古長江在后期由于火山噴發(fā)以及西部地區(qū)的隆升和東部地區(qū)的強(qiáng)烈下降而流向逐漸轉(zhuǎn)為向東。
[Abstract]:The paleo-gravel layer in Nanjing and its adjacent area is one of the important geological types of Cenozoic strata in this area. It and the basalt in this area are important geomorphology and age materials for studying the evolution of the lower reaches of the ancient Yangtze River. For this reason, the division of sedimentary strata, the origin of sediments and the analysis of sedimentary facies in this area are studied. By means of K-Ar and Ar-Ar dating of basalts, ESR dating of sediments, age analysis of flora and fauna and fossils, investigation and survey of sedimentary profiles, etc. It reflects the geomorphological evolution process of Nanjing area since Neogene. The sedimentary strata in Nanjing and adjacent areas are mostly fluvial facies. By means of basalt and sandy gravel dating, field geomorphological observation and profile survey, the river terrace cross section, sequence, chronology and the contact relationship between sediment and basalt are studied. The sediments in Nanjing can be divided into 6 sets and, together with modern Yangtze River sediments, form the seventh terrace of the Yangtze River. The section of Hengshan paleo-gravel layer studied in this paper has undergone changes from the bottom to the top from the bed facies to the floodplain facies with the top covered by basalt. The K-Ar age of overlying basalt is 12.42 Ma.The present study shows that the ESR age of sedimentary sand bed in Hengshan is 16.7 鹵1.6 Ma. it contains mammal fossils such as An Qi horse Anchitherium aureilianense and so on in the early and middle Miocene, according to its equivalent Dongxuan formation. It is concluded that the sedimentary age is from the late Miocene to the early Miocene. The flat surface of the gravel in Hengshan paleo-gravel layer is inclined to the west of South-South and the top of the sedimentary layer to the north-east direction. By analyzing the sedimentary facies, scale and geographical location of the sediments, it is concluded that the sand and gravel beds in Hengshan are located in the middle and upper part of the sedimentary layer formed outside the outpass of a large river fan-shaped from the south to the north or north to the north. In the later stage, the river changed to shallow water floodplain facies and the sediment was a paleoYangtze river product. The gravel layer covered by basalt in Nanjing area has formed a watershed or part of the Yangtze River system (the tributaries of the Yangtze River and its tributaries Chuhe) and those of Hongze Lake or Gaoyou Lake. It is further proved that the main driving force of the formation of paleogravels in Nanjing area is the ancient Yangtze River. In the early Middle Pleistocene, the direction of the Yangtze River was NNE or NNE, according to the distribution characteristics of sand and gravel in Nanjing area and the basalt eruption time, In the later period, the ancient Yangtze River trending eastward due to volcanic eruption, uplift in the west and strong decline in the eastern region.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P588.212.5

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