Based on study of the features of distribution

lithofacies and palaeontology of the Upper Triassic Maantang Fm.and its bioherm as well as their provenience

this paper suggests that the distribution area and extinction of the bioherms in the Maantang Fm.be controlled by the Late Triassic transition from marine carbonates to marine clastics.The clastics of the marine strata in western Sichuan Basin were mainly sourced from the northern Qinlin area.The clastic input beginning in the Carnian increased in amount progressively and spread from north to south.It is indicated that the formation and uplifting of Longmen Mountain is a progressive process from north to south and is controlled by the formation and evolution of Qinling orogenic zone.The transition is critical to the structural evolution of the superimposed Sichuan Basin and constrained the development of marine source rocks in the Maantang Fm and the development sequence of the bioherms.The Maantang Fm is worthy of further exploration as high energy reefs might have developed in areas near the central Sichuan Basin.