【作者】 高雪莲；

【导师】 苏春乾； 杨志华；

【作者基本信息】 长安大学 ， 矿物学、岩石学、矿床学， 2008， 硕士

【摘要】 宜昌市位于湖北省的西部,地处长江上游和中游的交汇处,鄂西山区向江汉平原的过渡地带。湖北省内以青峰-襄广断裂为界,分为南部扬子地层区和北部南秦岭-大别山地层区,宜昌位于扬子地层区的上扬子地层分区,地质变动较少,距今18亿年前的元古界到距今百万年前的新生界之间的各个地质时代的地层均有分布,且发育完整,出露齐全。本研究区宜昌黄花场位于黄陵背斜的东翼,在奥陶纪时期处于扬子碳酸盐台地的中北部。黄花场奥陶系剖面不仅结构简单,地层发育完整,各门类化石也非常丰富,研究程度较高,该剖面既是我国奥陶系划分与对比的典型层型剖面,也是大湾阶的界线层型剖面,同时还是全球最完美的中-下奥陶统界线剖面。通过野外调查和室内对研究区内奥陶纪地层划分并描述其岩性特征,特别是对沉积相标志的研究和对比,结合前人的研究成果,建立了湖北宜昌黄花场奥陶纪时期的沉积相模式,恢复了当时的沉积环境,明确了当时的古地理演化及海平面升降变化。湖北宜昌黄花场地区在奥陶纪时期沉积属陆表海性质,它以分布广阔、海水较浅、海底坡度平缓为特征,显示了一种稳定的构造环境,沉积了一套以清水碳酸盐岩为主的岩性。沉积模式主要属滨浅海碳酸盐沉积组合,可划分出浅海陆棚相(含陆棚内盆地相)、盆地边缘相、台地边缘生物礁相、台地边缘浅滩相、开阔海台地相和局限海台地相六种类型。从西陵峡组至五峰组,是一个海侵范围不断扩大和海水不断加深的过程。同时整个奥陶纪海水进退存在着多旋回现象,主要为四次Ⅲ级旋回,反映了四次海水进退规程。盆地边缘黄花场地区在奥陶纪时期,大致经历了一个从碳酸盐台地相-台地边缘礁滩相-浅海陆棚相-碳酸盐台地-浅海陆棚相的过程。更多还原

【Abstract】 Yichang city is located in western Hubei Province, is situated at intersection point of upstream Yangtze River and the middle reaches, the transition zone from mountain area to the plain area. Taking Qingfeng-Xiangguang fracture as demarcation line, it can divide into southern Yangzi strata area and northern South Qinling-Dabie Mountain strata area, Yichang is located on the Yangzi strata district, the geological change are few, the strata distribution is extensive, from the Proterozoic groups 1800Ma ago to Cenozoic groups 1Ma ago, also the growth integrity, appearing is complete.This research area of Yichang Huanghuachang is located the east limb of the Huangling anticline, is in the middle-north of the Yangzi carbonate platform in Ordovician. Not only the Huanghuachang Ordovician system section plane the structure is simple, the strata growth is integrity, each class of fossil is also extremely rich, the research degree is high, is also the typical profile of Ordovician system division and the contrast, but also is the boundary stratotype section of Dawan stage, simultaneously the global most perfect boundary stratotype section of middle-lower Ordovician.Through the geology survey in the open air and studying and contrasting Ordovician system strata division, the lothological characteristics, specially the sedimentary facies symbol research, connecting with predecessor’s research results, it has established the Yichang Huanghuachang deposition facies model of Ordovician period, restored the environment of deposition then, has made clear the evolution of paleogeography and the fluctuation change of sea level then.Ordovician period, epicontinental sea spread out the Huanghuachang area in Yichang, Hubei province, it is characteristics of broad distribution, shallow sea water and gentle seabed slope, indicates that is stable surroundings, forming the suit stratum that is mainly carbonatite. The sediment mode is belongs to shore epicontinental sea`s carbonatite assemble principally, including basin facies, wide continental shelf facies, basin marginal facies, mesa marginal biohermal facies, mesa marginal riffle facies, wide-sea mesa facies and limited-sea mesa facies. The transgression continuous expanding and sea water constant deeping from Xilinxia Formation to Wufeng Formation, and have multi-gyre phenomenon in sea water advance and retreat. The aggradation is divided into two high level gyre of the sea level, that stands for sea water advance and retreat process respectively, and many basic gyre overprinted on the each high level gyre. The low high level gyre include three basic gyre, the sediment facies mainly focus to limited-sea mesa facies, wide-sea mesa facies and mesa marginal riffle facies; The top high level gyre include two basic gyre, the sediment facies mainly focus to wide continental shelf facies and basin marginal facies. The transgression scale that responsed to the the top high level gyre more lager than the low high level gyre, that is to say, the largest transgression taken place in Ordovician period, and the Wufeng Formation record the most high tide of the transgression.更多还原