【作者】 郑吉林；

【导师】 王训练； 张海军；

【作者基本信息】 中国地质大学(北京) ， 古生物学与地层学， 2012， 硕士

【摘要】 本文通过野外系统的1/1000大比例尺剖面实测和室内工作,研究东昆仑花石峡北部地区下大武组火山-沉积地层的年代、岩石学特征、以及该区大地构造意义,取得如下认识：(1)首次在下大武组地层中发现了菊石和双壳动物群化石,根据生物地层研究确定地层时代为早三叠世中期,提高了下大武组年代地层精度。(2)通过野外观察结合室内薄片分析,在下大武组识别出8种岩性,分别为熔结凝灰岩、凝灰岩、沉凝灰岩、凝灰质泥岩、凝灰质粉砂岩、凝灰质泥晶灰岩、长石砂岩和泥岩,在此基础上将下大武组火山碎屑岩共划分13个大的火山-沉积旋回,每个旋回内部又划分若干个亚旋回,体现了火山活动的频繁性。(3)通过对下大武组火山碎屑岩以及双壳、菊石类动物群化石的综合研究认为,花石峡北部地区下大武组火山碎屑岩可能形成于挤压背景下的岛弧环境,该区在早中三叠世时仍为深海沉积,是古特提斯巴颜喀拉残留洋洋壳继续向北发生B式俯冲的火山沉积记录,为巴颜喀拉残留洋的存在提供了新的证据。更多还原

【Abstract】 In this thesis,1/1000scale is used systematically for measuring sections in the field work and indoor work to study the age of Xiadawu Formation, petrological characteristics and tectonic significance in northern part of Huashixia area, eastern Kunlun. The conclusions are listed as follows:(1) Ammonite and bivalve fossils are firstly reported in Xiadawu Formation which are suggested to form in early Triassic medium-term by the analysis of their biostratigraphy. This work enhances the accuracy of the stratigraphy of Xiadawu Formation.(2) Combined with field observations and analysis of rock slice,8types of lithology of Xiadawu Formation are divided, including of ignimbrite, tuff, tuffite, tuffaceous mudstone, tuffaceous siltstone, tuffaceous limestone, arkosic sandstone and mudstone. On base of these analysis,13volcano-sedimentary cycles of volcaniclastic rocks of Xiadawu Formation are divided and each cycle is divided into several sub-cycles, which shows the frequent volcanic activity.(3) According to the synthetic study of volcaniclastic rocks, ammonite and bivalve fossils, the conclusion is that these volcaniclastic rocks maybe formed in the calc-alkaline island arc volcanic in the extrusion background. In the early and middle Triassic, this area was deep-sea sedimentary environment. There is a volcanic sedimentary record that the oceanic crust of Bayan Har remnant ocean in Paleo-Tethys was the northward occurrence of B-type subduction and it also provided a new evidence for the existence of the the Bayan Har remnant ocean.更多还原