湖南晚奥陶世凯迪晚期-赫南特期沉积相及岩相古地理

湖南晚奥陶世凯迪晚期-赫南特期沉积的地层在湘西北区为五峰组、观音桥组；湘中区为五峰组；湘南区为天马山组和苏水冲组。根据其岩性特征、沉积构造及古生物特征，将湖南地区晚奥陶世凯迪晚期-赫南特期沉积相划分为局限浅海相、潮坪相、深水盆地相、陆棚边缘-斜坡相等类型。凯迪期晚期，由于华夏陆块向扬子陆块不断挤压碰撞，黔中隆起、川中隆起等边缘古隆起面积不断增大，此时海平面相对上升，湘西北区变为被各古隆起围限的沉积了黑色碳、硅质页岩及泥灰岩的局限浅海环境，湘中地区主要为黑色碳、硅质页岩、粉砂质页岩的深水盆地环境，而湘南地区由于两陆块挤压隆升而沉积了陆棚边缘-斜坡相的砂板韵律；赫南特期随着全球冰川事件的发生，整个南方地区发生大规模海退，湘西北永顺-张家界-慈利一线以北抬升成湘鄂隆起，该线以南的湘西北区水体继续变浅，主要沉积了厚度仅十几厘米的观音桥组泥灰岩，湘中湘南地区沉积格局基本未变。

Sedimentary Facies and Lithofacies Palaeogeography in the Late Katian-Hirnantian of Late Ordovician in Hunan Province

During the Late Katian-Hirnantian Age of Late Ordovician, it were deposited Wufeng and Guanyinqiao Formations in the Northwestern Hunan, Wufeng Formation in the central Hunan, Tianmashan and Sushuichong formations in the southern Hunan. According to the lithological characters, sedimentary structures and paleontological features, Hunan can be divided into restricted shallow marine facies, tidal-flat facies, deep-water basin facies and shelf-margin-slope facies. In the Late-Katian, As a result of the continuous extrusion and collision between Yangtze and Cathaysia blocks, the area of the central Sichuan and central Guizhou uplifts gradually increased and the sea level relatively rise, the northwestern Hunan were changed into restricted shallow marine with black carbonaceous, siliceous shales and marlstones surrounded by ancient uplifts, the central Hunan was a deep-water basin with black carbonaceous, siliceous and sility shales, whereas the southern Hunan deposited the interbeds of sandstones and shales in the shelf-margin-slope facies. In the Hirnantian age of Late Ordovician, as the global glacier event occurred, large scale of retrogression had begun in the south area, the north area of the Yongshun-Zhangjiajie-Cili line were lifted to be Hunan-Hubei uplift, and the south of the front line deposited marlstones with more than 10 centimeters in thickness, but the depositional pattern of southern and central Hunan did not change.