The original Xinyang Group should be disintegrated into two parts, i. e., theGuishan tectono--stratigraphic terrane and the Nanwan Formation. The former,consisting of an Early Paleozoic calc--alkaline volcanosedimentary sequence, includesa series of thrust--imbrication sheets tectonically emplaced in the major sutureduring the Caledonian subduction and collision orogeny. The latter is composed ofthe sediments deposited in the foreland basin of the Caledonian collisional oroge-nic belt, in which many Middle to Late Devonian microfossils, such as spores,scol-ecodents, chitinozoans and acritarchs, have been found.Thus this formation maybe correlated to the Liuling Group in the eastern Qinling orogenic belt. The aboveresults sufficiently prove that the Dabieshan--Tongboshan area is part of the Qi-nling orogenic belt and that the major suture of the belt is located along theTianshui-Danfeng-Xinyang-Shucheng line.