Abstract: Hunan area is located between the Yangtze and Cathaysia Blocks.According to its petrologic characteristics，archeological features and other depositional features，this area can be divided into open carbonate platform，shallow marine shelf，deep-water basin and shelf-margin-slope facies in the Sandbian-Katian Ages of Late Ordovician. The open carbonate platform facies was characterized by the deposition of“chap-cracked”limestones and nodular limestones，while the shallow marine shelf deposited mainly sandy slate，slate with siltstone and marl interbeds.The deep-water basin was composed of black carbonaceous shale and radiolarian-bearing silicolites with thin thickness，which reflected a withlead，anoxic and uncompensated deep water environment.The shelf-margin-slope facies deposited lithic quartz silt-fine sandstone，feldspar quartz silt-fine sandstone with slate interbeds，which showed typical features of turbidite deposits with more than kilometers sedimentary thickness. The water was increasing gradually in the central Hunan area(from northwestern to southeastern)during the Sandbian-Early Katian Ages of Late Ordovician，and the southern-central Hunan area was the deepest area.

Key words: Hunan area, Sandbian-Early Katian Ages of Late Ordovician, sedimentary facies, depositional model

摘要： 湖南地区地处扬子陆块和华夏陆块之间，根据沉积地层的岩石学特征、古生物特征及其他沉积特征变化，将湖南地区晚奥陶世桑比期—凯迪期早期的沉积相，划分为开阔台地相、浅海陆棚相、深水盆地相和陆架边缘—斜坡相。开阔台地相以沉积“龟裂纹”灰岩和瘤状灰岩为特征，浅海陆棚相转为沉积砂质板岩，板岩并夹有粉砂岩及泥灰岩透镜体。深水滞流盆地发育黑色碳质页岩及含放射虫硅质页岩，沉积厚度很小，代表了一个相对缺氧还原的欠补偿深水环境；陆架边缘—斜坡相则为岩屑石英粉—细砂岩，长石石英粉—细砂岩及砂质板岩、板岩的韵律互层，沉积厚度超过1000m，具浊流沉积特征。晚奥陶世桑比期—凯迪期早期，湖南地区总体表现为由西北和东南方向往中部逐渐变深，湘中南一带为水体最深地区。

关键词: 湖南地区, 晚奥陶世桑比期—凯迪期早期, 沉积相, 沉积模式

CLC Number: 

• P512.2