Late Paleozoic faunal, climatic, and geographic changes in the Baoshan block as a Gondwana-derived continental fragment in southwest China

The Carboniferous and Permian of the Baoshan block consist of three major d epositional sequences: a Lower Carboniferous carbonate sequence, a Lower Pe rmian siliciclastic sequence, and a Middle Permian carbonate sequence. Thes e three sequences were interrupted by two major regressive events: first, t he Namurian Uplift ranging in age from Serpukovian to Gzhelian, and second, the Post-Sakmarian Regression occurring probably at Artinskian time in the Baoshan block, although the precise time interval of the latter event is s till unclear. The Baoshan block is characterized by warm-water, highly dive rse and abundant faunas during the Early Carboniferous, by cold-water and l ow diversity faunas during the Early Permian, and by possibly warmwater but low diversity faunas during the Middle Permian. The Sweetognathus bucarama ngus conodont fauna constrains the upper boundary of the diamictite-bearing siliciclastic deposits (Dingjiazhai Formation) to the Sakmarian to early A rtinskian, as well as the eruption of the rifting basalts (Woniusi Formatio n) to, at least, the post-early Artinskian. Paleozoogeographically, affilia tion of the faunas in the Baoshan block changed from Eurasian in the Early Carboniferous, to Peri-Gondwanan in the Early Permian, and to Marginal Cath aysian/Cimmerian in the Middle Permian. Cimmerian blocks have more or less comparable geohistory to one another in the Carboniferous and Permian. Duri ng the Middle Permian, the eastern Cimmerian blocks such as Sibumasu (s.s), Baoshan, and Tengchong are not far from the palaeoequator, but apparently more distant than the western Cimmerian blocks based on the presence or abs ence of some index taxa such as the fusulinaceans Eopolydiexodina and Neosc hwagerina, and the corals Thomasiphyllum and Wentzellophyllum persicum. (C) 2001 Elsevier Science B.V. All rights reserved.