本文關(guān)鍵詞： 信江盆地 晚白堊世 物源分析 古大氣CO_2濃度　出處：《東華理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：信江盆地位于贛杭構(gòu)造帶中部,是中國東南部地殼拉張背景下形成的陸相斷陷盆地之一。白堊系陸相紅層發(fā)育,是區(qū)內(nèi)丹霞地貌發(fā)育的物質(zhì)基礎(chǔ)。本次通過野外露頭測量和描述、礫石統(tǒng)計(jì)、砂巖薄片鑒定及碎屑顆粒統(tǒng)計(jì)、古土壤碳-氧同位素分析,對(duì)晚白堊世塘邊組沉積特征、物源和古氣候進(jìn)行了詳細(xì)的研究,取得了以下研究成果:信江盆地塘邊組為河流-湖泊-風(fēng)成沉積。塘邊組早期發(fā)育辮狀河沉積的河床亞相和泛濫平原亞相,中期發(fā)育湖泊沉積的濱湖和淺湖亞相,晚期氣候干旱化,轉(zhuǎn)變?yōu)轱L(fēng)成相。早期沉積的礫巖層礫石成分復(fù)雜,分選磨圓差,成分和結(jié)構(gòu)成熟度低。古流向玫瑰花圖指示物源來自盆地的北、北東、東部和南部。砂巖碎屑顆粒統(tǒng)計(jì)表明,石英含量高,巖屑次之,長石最少。C_m=3.72,指示成分成熟度為中等,分選、磨圓為中等偏好,指示中等結(jié)構(gòu)成熟度。通過Dickinson投圖可知,砂巖碎屑沉積物主要來自再旋回造山帶物源區(qū),消減雜巖帶提供了大量的物源,同時(shí)具有弧造山帶物源的成分。盆地兩側(cè)隆起地區(qū)的中-新元古界低級(jí)變質(zhì)巖系地層、燕山期中酸性火山-侵入雜巖和塘邊組沉積時(shí)期遭受剝蝕的前晚白堊世地層可能也提供了碎屑物源。對(duì)采自江西信江盆地晚白堊世塘邊組的成壤碳酸鹽樣品碳、氧同位素測試表明,δ~(13)C值在-4.30‰~-2.10‰之間,平均值為-2.84‰。δ18O值在-6.62‰~-1.14‰之間,平均值為-3.62‰。由Cerling經(jīng)驗(yàn)公式估算出晚白堊世Campanian期75Ma的大氣CO_2濃度在782~1420 ppmv之間,平均值為1181ppmv,是當(dāng)今大氣CO_2濃度的2~4倍左右。因此,基于信江盆地塘邊組成壤碳酸鹽的大氣CO_2濃度估算結(jié)果,可能指示了晚白堊世Campanian晚期存在一個(gè)大氣CO_2濃度高值,反映了晚白堊世大氣CO_2濃度的波動(dòng)性。
[Abstract]:The Xinjiang basin, located in the middle of the Ganhang tectonic belt, is one of the continental faulted basins formed in the crustal extensional background of southeastern China. It is the material foundation of Danxia geomorphology development in this area. Through field outcrop survey and description, gravel statistics, sandstone sheet identification and clastic particle statistics, paleosol carbon-oxygen isotope analysis, the sedimentary characteristics of the late Cretaceous Tangbian formation were studied. The provenance and paleoclimate were studied in detail, and the following results were obtained: the Tangbian formation in Xinjiang Basin was fluvial, lacustrine and aeolian sediments, and the fluvial bed subfacies and flood plain subfacies were developed in the early stage of the Tangbian formation. The lacustrine and shallow lacustrine subfacies were developed in the middle period, and the late climate was arid and changed into eolian facies. The trace indicator of the paleoflow rose map comes from the north, north, east, east and south of the basin. According to the statistics of sandstone clastic grains, quartz content is high, lithic debris is the second, feldspar is the least. Sorting, grinding circle is medium preference, indicating medium structural maturity. According to the Dickinson chart, sandstone-clastic sediments mainly come from the source area of the re-cycle orogenic belt, and the subtractive complex belt provides a large number of provenances. The lower metamorphic strata of the Mesoproterozoic in the uplift areas on both sides of the basin, The acid volcanic-intrusive complex in Yanshanian period and the denuded strata of Tangbian formation in the sedimentary period may also provide a source of clastic material. The carbonates collected from the late Cretaceous Tangbian formation in Xinjiang Basin, Jiangxi Province, were studied. The oxygen isotope test shows that the 未 ~ (13) C value is -4.30 鈥，

本文編號(hào)：1549938