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根据遗迹相和沉积特征，将龙洞水组、大河口组和屯上组划分为８个层序，其中包括２个Ⅰ型、６个Ⅱ型层序，在此基础上，对缺失标准化石依据的中、下泥盆统界线提出了讨论。黔南独山地区的龙洞水组和大河口组为海平面逐渐下降、富氧环境的沉积，屯上组为海平面迅速上升、缺氧或贫氧环境的沉积，大河口组和屯上组之间存在一古风化壳层，是海平面下降至最低点的产物，并有地层缺失，为一较明显的自然界线，下、中泥盆统界线置于此界面更近于实际。产于舒家坪组的Ｅｕｒｙｓｐｉｒｉｆｅｒｐａｒａ－ｄｏｘｕｓｓｈｕｊｉａｐｉｎｇｅｎｓｉｓ腕足化石群不能作为下泥盆统的顶界。
According to the facies facies and sedimentary characteristics, the Longdongshui Formation, the Dahekou Formation and the Tuen Shang Formation are divided into 8 sequences, including 2 type Ⅰ and 6 type Ⅱ sequences. On this basis, the criteria for missing standard fossils The middle and lower Devonian boundaries proposed a discussion. The Longdongshui Formation and the Dahekou Formation in Dushan area, southern Guizhou, are characterized by the gradual decline of sea level and the deposition of oxygen-rich environment. The Tuen-Shang Formation is characterized by the rapid increase of sea level and the deposition of anoxic or oxygen-poor environment. The Dahekou Formation and Tunshang Formation There is an ancient weathering crust, which is the product of the sea level descending to the lowest point, and there is a lack of strata. As a more obvious natural boundary, the boundary between the Middle Devonian and the Middle Devonian is closer to reality. The Euryspiriferpara-doxusshujiapingensis brachiopods, produced in the Shujiaping Formation, can not serve as the top boundary of the Lower Devonian.