本文選題：晚中新世 + 古生物化石��； 參考：《中國(guó)地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：西寧盆地位于青藏高原東北緣,處于我國(guó)東部濕潤(rùn)季風(fēng)區(qū)、西北內(nèi)陸干旱區(qū)和青藏高原高寒區(qū)三大自然地理區(qū)的交界處。盆地內(nèi)沉積一套記錄始新世-晚中新世青藏高原隆升和環(huán)境變化的連續(xù)的河湖相地層,是研究青藏高原隆升和氣候變化的理想之地。本文采用古地磁學(xué)手段建立了班彥剖面和紅崖子剖面剖面晚中新世的年代格架,通過(guò)分析沉積物粒度、磁化率、碳酸鹽含量、(C、O)同位素古氣候代用指標(biāo),研究探討了晚中新世西寧盆地沉積演化及環(huán)境變化。初步的得到以下認(rèn)識(shí):1.磁性地層學(xué)研究結(jié)果顯示,古地磁年齡范圍為8.22 Ma~6.98Ma,化石年齡為8.1 Ma;紅崖子剖面古地磁年齡范圍為12.15 Ma~6.92Ma。這在前人咸水河組地層年齡研究基礎(chǔ)之上,擴(kuò)展了西寧盆地晚中新世地層咸水河組的頂部年齡。2.西寧盆地在8.25Ma左右其沉積時(shí)速率突然增加到147.03 m/Ma,其粒度、磁化率、(C、O)同位素發(fā)生明顯變化,古生物化石顯示在這一時(shí)期氣候?yàn)闇嘏膩啛釒О敫珊怠；瘜?duì)比表明拉脊山在8.1 Ma左右快速隆升。3.紅崖子剖面沉積物速率在7.33Ma達(dá)到整個(gè)剖面的最大值320m/Ma,沉積物為一套礫石;磁化率、碳酸鹽含量及C、O同位素發(fā)生顯著改變。西寧盆地7.33Ma干冷氣候很可能是全球變冷和青藏高原加速隆升雙重驅(qū)動(dòng)使得沉積環(huán)境發(fā)生了變化。4.根據(jù)沉積環(huán)境的指標(biāo)顯示,西寧盆地晚中新世氣候環(huán)境呈現(xiàn)階段性變化趨勢(shì):四個(gè)主要時(shí)期共6個(gè)沉積階段。1)晚中新世早期(12.16~8.25Ma):包括Ⅰ階段(12.16~11.1Ma)、Ⅱ階段(11.1~9.46Ma)和Ⅲ階段(9.46~8.25Ma),沉積物速率較為穩(wěn)定,西寧盆地氣候條件相對(duì)溫暖半濕潤(rùn)—潮濕。2)晚中新世中—中晚期(8.25~7.91Ma):即Ⅳ階段(8.25~7.91Ma),該時(shí)期沉積物粒度、磁化率強(qiáng)烈波動(dòng),沉積物速率突然升高到147.03 m/Ma,沉積物為濱湖相的礫石層。構(gòu)造活動(dòng)強(qiáng)烈,氣候以半干旱為主。3)晚中新世中晚期(7.91~7.16Ma):即Ⅴ階段(7.91~7.16Ma),其湖泊水位波動(dòng)較大,總體呈現(xiàn)出間歇式變淺趨勢(shì)。西寧盆地干冷氣候很可能是全球變冷和青藏高原加速隆升雙重驅(qū)動(dòng)引起的。4)晚中新世晚期(7.16~6.92Ma):即Ⅵ階段(7.16~6.92Ma):該時(shí)期沉積物粒度呈現(xiàn)出劇烈的波動(dòng),C同位素迅速降低,O同位素快速增大,該時(shí)期氣候溫度比晚中新世中晚期高。
[Abstract]:Xining basin is located in the northeast margin of Qinghai-Xizang Plateau, at the junction of three natural geographical regions: the humid monsoon region in the eastern part of China, the inland arid region in the northwest and the high and cold region of the Qinghai-Xizang Plateau. A set of continuous fluvial facies strata recording the uplift and environmental change of the Qinghai-Tibet Plateau during the Eocene to the late Miocene is an ideal place to study the uplift and climate change of the Qinghai-Xizang Plateau. The late Miocene dating framework of Banyan and Hongyazi sections has been established by paleomagnetic means. The paleoclimate substitution indices of sediments, magnetic susceptibility, carbonate content and paleoclimate have been analyzed. The sedimentary evolution and environmental change of Xining basin in the late Miocene were studied. A preliminary understanding of the following: 1. The results of magnetic stratigraphic study show that the paleomagnetic age range is 8.22 Ma ~ 6.98 Ma and the fossil age is 8.1 Ma, and the paleomagnetic age range of Hongyazi section is 12.15 Ma ~ 6.92 Ma. This extends the upper age of Xianshuihe formation of late Miocene in Xining Basin on the basis of the previous study on the stratigraphic age of Xianshuihe formation. The deposition rate of Xining basin suddenly increased to 147.03 m / Ma. the grain size and magnetic susceptibility of Xining basin suddenly increased to 147.03 m / Ma.The paleontological fossils showed a warm subtropical semi-arid climate during this period. The fossil correlation indicates that the Lachi Mountain rapidly uplifted at about 8.1 Ma. The sediment velocity of Hongyazi section reaches the maximum value of 320m / Ma. in 7.33Ma, the sediment is a set of gravel, and the magnetic susceptibility, carbonate content and Con O isotopes are significantly changed. The 7.33Ma dry cold climate in Xining basin is probably driven by global cooling and accelerated uplift of the Qinghai-Xizang Plateau. According to indicators of the sedimentary environment, The late Miocene climatic environment in Xining basin shows a phase change trend: 6 sedimentary stages in four major periods. 1) early late Miocene stage 12. 16 + 8. 25 MaA: including stage I (12. 16 + 11. 1 Ma), stage II (11. 1 + 9. 46 Maa) and stage III (9. 46 ~ 8. 25 Ma-1), and the sediment rate is relatively stable. The climatic conditions of Xining basin are relatively warm, semi-humid and humid. 2) the late Miocene middle to late Miocene is 8.257.91MaA: stage 鈪，

本文編號(hào)：1955869