As to the Lunmachian paleogeography in the Llandovery, the Taojiang—Baimashan—Yuechengling is the boundary between the Cathaysia Oceanic Crust Block to the southeast and the the Yangtze Continental Crust Block to the northwest. The Cathaysia Oceanic Crust Block was characterized by a deep- water turbidite basin consisting of the Llandovery Rhuddanian (i.e., the Zhoujiaxi Formation), of which clastic sediments would have fed by the central Hunan fold mountains further southeast. The Yangtze Continental Crust Block was a sedimentory oceanic basin composed of the Longmaxi Formation. The distant edge to the southeast was in an upper continental shelf environment and the margin to the northwest was the lower continental shelf ones. The fold mountains in south—central Hunan would have supplied most of detrital materials to basins. The Siaohopan lithofacies and paleogeography were obviously different from the past. The subduction—collision of the Cathaysia Block with the Yangtze Block took place at the end of the D. triangulates graplite zone time,ca. 440.8±1.2 Ma. The orogenesis of the Zhoujiaxi Formation (in the Cathaysia Block) itself created the Cathaysia fold mountains, resulting in the closure of the Cathaysia Ocean Basin. At the same time the Cathaysia Block wedged beneath the Yangtze Block by the A- type subduction, leading to the uplift of the Caledonian Xuefeng Orogenic Belt along the southeast margin of the Yangtz Block on a large scale. The Xuefeng Mountain, as a tectonic load, resulted in the formation of a retroarc foreland basin of the Cathaysia Ocean Crust Block in the new southeast margin of the Yangtze Block. The Siaohopan Formation was the cover of the retroarc foreland basin. Its terrigenous material supply would have derived from the Xuefeng Orogenic Belt. The Siaohopa Formation was comprised mainly of delta- facies deposits in southeast distant edge and littoral- facies deposits in northwest margin. The Siaohopan Formation graded into a platform facies stratigraphic unit of the Shiniulan Formation to the northeast- , northwest- and southwest, towards the north- east and north- west and towards the south-west the Xiaohepa Formation grades into the Shiniulan Formation(platform facies).Further to the north- west the Shiniulan Formation changes to the Banjiuguan Formation(basin facies)in Ziyang,Southern Shaanxi Province. glaucophane, a typomorphic mineral of glaucophane- schist, was obtained two times from the panned concentrate samples of the Siaohopa Formation. The discovery of glaucophan is the discriminative mark for the Cathaysia—Yangtze collision and Xuefeng’s rise in the Caledonian period.