As a trunk part of the Paleo-Tethyan archipelago ocean, the Changning-Menglian belt of western Yunnan, China, presents varied volcano-sedimentary records ranging in time from Early Devonian through Middle-Late Triassic. The typical pelagic sediments represented by radiolarites can not only signify a continuously evolved ocean but also constitute a complicated basin comprising different tectono-sedimentary units. It is likely that oceanic plateaus of diverse origins played a key role in constructing the pattern of eastern Tethys. The opening and closing of the Yunnan Tethys are discussed in the paper as well. 0 AcadCmie des sciences 1 Elsevier. Paris.