【摘要】 1972年的1/20万《溆浦幅》区域地质调查报告说,从南沱组底到板溪群顶,只有江口组一个地层单位,岩性简单。经过考察,发现那里的"江口组"包含了现在江口群的长安组、富禄组的两界河段和古城段,以及间冰期的大塘坡组。其中古城段只见于区内的部分地区,而在其他一些地方则缺失;这里的大塘坡组与湘黔桂及相邻地区不同,它几乎全部为灰绿色板岩,完全不见黑色或炭质的板岩,底部也没有含锰层位,说明这里大塘坡组的沉积环境十分特殊。更多还原

【Abstract】 The report of the regional geological reconnaissance in 1972 described the strta between the Nantuo Formation and the Banxi Group as a single unit,the "Jiangkou Formation" a stratigrphic term that has been fallen into disuse.Our recent field investigation has shown that the "Jiangkou Formation" includes the redefined Jiangkou Group and the interglacial Datangpo Formation.The Jiangkou Group in turn includes the Chang’an Formation and Fulu formations,the latter consisting of the Liangjiehe and Gucheng members.However,the Nanhuan stratigraphy of this area is characterized by several interesting features.First,contrary to the general belief that the Gucheng Member is widely distributed,this unit is missing in many places.Second,unlike elsewhere in South China where the Datangpo Formation consists mostly of black or carbonaceous shale and manganese-rich deposits(e.g.,in Hunan,Guizhou,and Northern Guangxi provinces),this unit in the study area is composed of grey-green slate,with little carbonaceous or manganese-bearing shale,highlighting the unusual sedimentary environment of the study area.更多还原