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

Key words: 
• Hunan province /
• Late Katian-Hirnantian Age of Late Ordovician /
• sedimentary facies /
• lithofacies palaeogeography /

Abstract: 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.