本文選題：沉積相 + 沉積環(huán)境演化��； 參考：《南京大學(xué)》2014年碩士論文

【摘要】：南黃海江蘇岸外海底,分布著巨大的輻射沙脊群,是中國大陸架淺海所特有的大型沙體組合,內(nèi)部儲存著豐富的海岸演變、河口環(huán)境、海面變化、氣候變化以及海洋環(huán)境的各種環(huán)境信息,是研究陸海相互作用及全球環(huán)境變化的最理想載體。苦水洋內(nèi)水下沙脊是南黃海輻射沙脊群東北部潮流堆積沙脊,屬于開闊陸架潮流沙脊范疇,研究其全新世以來的沉積環(huán)境演變、成因機制,對了解整個輻射沙脊群的動態(tài)變化具有深遠(yuǎn)意義。 2011年11月,在南黃海輻射沙脊群苦水洋海域鉆探了6根20-60m長柱樣,4根1-1.5m長的短柱樣,其中4孔在沙脊上,6孔在潮流通道中。本文選取位于苦水洋南部的柱狀樣11DT05孔(33°04.475'N,121°48.298'E)作為材料,該孔進(jìn)尺深度36.97m,實際芯長22.20m,取芯率為60.05%,兼以淺柱樣11DT(sc)02柱、11DT(sc)04柱、11DT(sc)05柱、11DT(sc)06柱為輔助,通過室內(nèi)鉆孔描述和巖性編錄工作,對樣品進(jìn)行了粒度、210Pb、XRF巖芯掃描的測試和分析,結(jié)合14C測年、光釋光測年,對苦水洋內(nèi)水下沙脊的沉積相和長周期演變進(jìn)行了綜合分析,為港口建設(shè)提供重要參考資料。 根據(jù)沉積物巖性、粒度、沉積結(jié)構(gòu)和構(gòu)造,以及所含生物化石進(jìn)行沉積相分析,在11DT05孔共識別出4種沉積相類型： (1)潮流沙脊相：位于鉆孔最頂部0-5.69m。主要由橄欖灰棕灰色細(xì)砂、青灰色粉砂質(zhì)細(xì)砂、橄欖綠色粉砂質(zhì)細(xì)砂以及粉砂組成,夾有棕灰色粉砂質(zhì)黏土和青灰色黏土質(zhì)粉砂。常見塊狀層理、壓扁層理(或稱脈狀層理),以及波狀層理,局部發(fā)育變形構(gòu)造。含較多貝殼碎片、云母片,局部有炭屑富集。 (2)陸相硬黏土：該沉積相出現(xiàn)在11DT05孔的中偏上部5.69-6.49m,以雜斑狀、花斑狀黃棕色黏土、粉砂質(zhì)黏土為主(質(zhì)地細(xì)膩、致密、粘手)。發(fā)育極細(xì)的水平—微波狀紋層(厚度lmm)�？梢姶罅胯F銹斑(大小1-5mmm)、細(xì)小植物根莖、以及分散狀有機質(zhì)條斑、鐵質(zhì)、鈣質(zhì)結(jié)核。 (3)高潮灘相：該沉積相出現(xiàn)在11DT05孔6.49-13.51m處,平均粒徑6.21φ,砂平均含量為7.3%,粉砂平均含量約為75%,黏土平均含量為17.7%。由橄欖灰色深灰色黏土質(zhì)粉砂、含黏土粉砂或黏土組成,夾薄層粉砂或透鏡體狀、斑狀粉砂體,發(fā)育水平紋層(紋層厚度1mm)。 (4)中低潮灘相：該沉積相出現(xiàn)在11DT05孔下部13.51-22.20m,由青灰色粉砂、橄欖灰色粉砂質(zhì)粗砂、暗黃棕色黏土質(zhì)粉砂和少量細(xì)砂組成。普遍發(fā)育透鏡狀層理、脈狀層理(或稱壓扁層理)和波狀層理(砂/泥互層)構(gòu)成的潮汐韻律層理。按照沉積特征,又可進(jìn)一步分為中潮灘和低潮灘亞相。 11DT05鉆孔沉積物主要由黏土、粉砂質(zhì)黏土、黏土質(zhì)粉砂、細(xì)砂質(zhì)粉砂和少量細(xì)砂組成。粒度組成上,粉砂的含量最大,占76.13%；其次是砂,含量占19.82%；黏土含量最少,占3.6%。整個鉆孔平均粒徑在1.78～8.6φ之間波動,平均值為5.68φ；分選系數(shù)介于0.51～3.72之間,平均值為1.75,分選較差；偏態(tài)范圍在-0.46～0.89之間,平均值為0.58；峰態(tài)在0.56～5.2之間波動,平均值1.21。4個淺柱樣的沉積物全部為極細(xì)砂。平均粒徑的平均值分布在3.22～3.56φ之間,顆粒較細(xì)；分選系數(shù)的平均值在0.57～1.41之間,分選較好；偏態(tài)平均值在0.02～0.06,近對稱；峰態(tài)平均值在0.95～1.06,為中等峰態(tài)類型。11DT(sc)04柱和11DT(sc)06柱的粒度分布呈現(xiàn)一個上粗下細(xì)的沉積序列,反映出近期沖刷作用加劇。柱狀樣的210pb測試結(jié)果表明,潮灘上部的沉積速率介于0.47～3.42cm/a,中部沉積速率為0.16cm/a,下部無法獲得沉積速率,反映了近30a來潮灘侵蝕加劇。 苦水洋內(nèi)水下沙脊鉆孔長周期演化顯示,從晚更新世以來從老到新依次經(jīng)歷了中低潮灘相→高潮灘相→陸相暴露(硬黏土)→潮流沙脊相。在約60-25KaBP晚更新世時期(氧同位素3.0期),進(jìn)入玉木冰期,全球氣候變冷,研究區(qū)經(jīng)歷了一個海平面下降過程,發(fā)育潮灘環(huán)境。在約25-2KaBP晚更新世晚期(氧同位素2.0期),進(jìn)入晚玉木冰期,此時全球氣候再次變冷,海平面又經(jīng)歷了一個下降過程,研究區(qū)完全暴露形成標(biāo)志性的“硬黏土”層。全新世初期經(jīng)歷海侵,研究區(qū)復(fù)又開始潮灘沉積,隨后被海水完全淹沒,潮流作用漸強,改造下伏潮灘和“硬黏土”,塑造潮流沙脊地形。沙脊的形成年代可能在距今1-2KaBP左右。14C測年數(shù)據(jù)、光釋光測年數(shù)據(jù)、210pb、XRF巖芯掃描測試和分析、粒度分析以及與淺柱樣的分析對比為上述沉積環(huán)境的判別提供了證據(jù)。
[Abstract]:The outer seabed of the South Huangjiang river is a large group of radiant sand ridges, which is a large combination of large sand bodies in the shallow sea of China's continental shelf. It is the most ideal carrier for studying the interaction of land, sea and the global environment with abundant coastal evolution, estuarine environment, sea surface change, climate change and various environmental information of the marine environment. The sediment ridge in the bitter water ocean is a tidal sediment ridge in the northeast of the South Yellow Sea, which belongs to the category of tidal sand ridges in the open shelf. It is of profound significance to study the sedimentary environment evolution and the genetic mechanism since the Holocene, and to understand the dynamic changes of the whole radiation sand ridges.
In November 2011, 6 20-60m long columns and 4 1-1.5m long short columns were drilled in the sands of the Southern Yellow Sea, with 4 holes on the sand ridges and 6 holes in the tidal channel. This paper selects a column like 11DT05 hole (33 04.475'N, 121 48.298'E) located in the southern bitterwater ocean as a material. The depth of the hole is 36.97m, the actual core 22.20m, 22.20m, 22.20m core, 22.20m, actual core 22.20m, taken from the actual core 22.20m, taken from the actual core. The core rate is 60.05%, with a shallow column like 11DT (SC) 02 column, 11DT (SC) 04 column, 11DT (SC) 05 column and 11DT (SC) 06 column as auxiliary. Through the indoor borehole description and lithologic cataloging work, the samples are tested and analyzed for the grain size, 210Pb, XRF core scanning and the sedimentary facies and long period evolution of the underwater sand ridges in the bitter water ocean. A comprehensive analysis is made to provide important reference materials for port construction.
Based on sedimentary lithology, grain size, sedimentary structure and structure, and sedimentary facies analysis of the biologic fossils, 4 sedimentary facies types were identified in 11DT05 hole.
(1) tidal sand ridge facies: at the top of the borehole, 0-5.69m. is mainly composed of olive grey brown gray fine sand, green grey silty fine sand, olive green powder sand and silty sand, with brown grey silty clay and green grey clay silt. The structure consists of more shell fragments, mica sheets, and locally enriched with carbon dust.
(2) terrestrial hard clay: the sedimentary facies appeared in the upper middle partial 5.69-6.49m of the 11DT05 hole, with variegated porphyry, variegated yellow brown clay and silty clay (fine texture, dense, sticky). A very thin level of microwave like layer (thickness LMM). A large number of iron rust spots (size 1-5mmm), fine plant rhizomes, and dispersed organic strips were found. Spot, iron, calcareous tuberculosis.
(3) high tidal flat facies: the sedimentary facies appeared at 11DT05 hole 6.49-13.51m, with an average particle size of 6.21 phi, the average content of sand was 7.3%, the average content of silt was about 75%. The average content of clay was 17.7%. from olive gray dark grey clay silt, clay silt or clay, and thin layer silt or lens, porphyritic sandbody, and developed horizontal layer. Lamellar thickness 1mm).
(4) middle and low tidal flat facies: the sedimentary facies appeared in the lower part of the 11DT05 hole 13.51-22.20m, composed of green gray silt, olive grey powder sand, dark yellow brown clay silt and a small amount of fine sand. It can be further divided into middle tidal flat and low tide subfacies.
11DT05 drilling sediments are mainly composed of clay, silty clay, clay silt, fine sand silt and a small amount of fine sand. On the size composition, the content of silt is the largest, which is 76.13%, followed by sand, the content is 19.82%, the clay content is least, and the average diameter of the whole drill hole is between 1.78 and 8.6 phi, the average value is 5.68 phi, and the separation coefficient is 5.68. The average value is between 0.51 and 3.72, the average value is 1.75, the separation is poor, the partial range is between -0.46 and 0.89, the average value is 0.58, the peak state fluctuates between 0.56 and 5.2, and the average value of the 1.21.4 shallow column samples is all fine sand. The average particle size distribution is between 3.22 and 3.56 phi, the particle is fine, the average value of the separation coefficient is 0.57 The separation between 1.41 and 1.41 is better; the mean values are 0.02 ~ 0.06, near symmetry, the average of the peak state is 0.95 ~ 1.06, and the size distribution of the medium peak type.11DT (SC) 04 column and the 11DT (SC) 06 column shows a thick and thin sedimentary sequence, reflecting the recent scour effect plus the play. The 210Pb test results of the columnar sample show that the upper part of the tidal flat is deposited. The rate is between 0.47 and 3.42cm/a, the middle deposition rate is 0.16cm/a, and the lower part is unable to get the deposition rate, which reflects the erosion of the 30A tidal flat.
The long period evolution of the drilling hole length of the sand ridges in the bitter water ocean shows that from the late Pleistocene to the new period, the middle and low tidal flat, the high tide beach phase, the terrestrial exposure (hard clay) and the tidal sand ridge facies were experienced from the late Pleistocene to the late Pleistocene (3 phase of oxygen isotope), and the global climate became cold, and the study area experienced a sea level. In the late Pleistocene (2 phase of oxygen isotopes) in the late Pleistocene (2 stage of oxygen isotope), the global climate was again cooled, and the sea level experienced a decline process, and the study area was completely exposed to a marked "hard clay" layer. The early Holocene experienced transgression in the early Holocene, and the research area began to sink into the tidal flat again. The formation age of the tidal tidal flats and the "hard clay" and shaping the tidal sand ridge are likely to be formed at the date of 1-2KaBP.14C dating from the date, the 210Pb, the XRF core scanning and analysis, the grain size analysis and the analysis of the shallow column samples for the above deposition. The discrimination of the environment provides evidence.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P736.2

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