Lagu Fm

The type section is located along Yaze−Lagu, Baxoi County, Tibet. It was named by the No. 3 Regional Geological Survey Party of Sichuan Bureau of Geology in 1972.

Sandstone, Volcanics and Claystone. It is divided into three members: Lower member is composed of gray and gray-white moderately thick-bedded medium-grained and poorly sorted quartz sandstone and slate, intercalated with slaty siltstone and pebbly slate, and the Bottom, of dark-gray carbonaceous slate, calcareous sandstone and medium- to fine-grained feldspar-rich quartz sandstone, intercalated with sponge spicule-bearing slate and silty slate, 875 m thick. Middle member is purple-gray, gray-green and purple massive andesite basalt, andesite, dacite, amygdaloidal coarse-grained basalt and andesitic lava breccia, 417 m thick. Upper member is gray, gray-yellow and light yellow thin- to moderately thick-bedded slate, clayey-sandy slate, silty slate, siltstone and quartz sandstone intercalated with limestone lenses, gray-white thin-bedded crystalline limestone and dolomitic limestone, thickness >1451 m.

Sponge spicules in Lower member

It is interpreted as a clastic rock intercalated with eruptive volcanics and carbonates; locally metamorphosed.