A set of darkgray， grayishblack or black calcareous shale(bearing shell sometimes)occurred at the Upper Triassic Carnian—Norian Maantang Formation in the Longmen Mountains region， Sichuan Province. Numerous bivalves， primary divalent metal sulfides(pyrite)， thinintermediate layers and horizontal bedding observed in the shale indicated an anoxic lowenergy environment. The Late Carnian sediments mainly mudstone，shale  or silty slate， calcareous slate which are timeequvalent to this black shale，can be found in the east Paleotethys including Songpan—Ganzi Area， Changdu Area，and Hoh Xil Area. We considered that they reflected a black shale event which strongly influenced the marine sediments in the eastern Paleotethys of west China. The global correlation indicated that the dark color mudstone（shale）were widely distributed in western China， Indian Himalayas， Eastern Alps， and overlied on the Early Carnian carbonate rocks. Thus we proposed a Tethyswide black shale event， which caused the late Early Carnian global carbonate production crisis occurred， while the dark color mudstone(shale)developed in the middle part of the Maantang Formation is a reflection of this event along the western margin of the Yangtze Platform. Based on investigation and studies of the Upper Triassic sections in Hanwang， Jushui， and Maantang areas in northwestern Sichuan， it is concluded that the Carnian limestone(ie. oolid limestone， sponge reef limestone in the middlelower Maantang Formation)was deposited before the anoxic event， and the Norian gray siltstone and fine sandstone was laid down after the event. The black mudstone(shale)triggered by the event not only indicated the significant lithological change， but also was the turning point of sudden paleontological and paleoecological changes. Marine fossils such as hexactinellida， crinoid， bryozoa，and coral were abundant in the limestones of the lower Maantang Formation， but they suddenly disappeared in the black shales in the Maantang Formation. Shell fauna fossils such as rich bivalves， ammonoids，and brachiopods occurred in the middleupper Maantang Formation.