Matoushan Fm

The base of the formation an unconformity marked by dark purple thick-bedded sandstone and basal conglomerate is distinguished from purple red sandstone of the underlying Jurassic. In the Shuangbai area of Chuxiong, it lies unconformably on the Puchanghe Fm.

The Matoushan Formation is gradational with the overlying Jiangdihe Fm.

The formation occurs on both sides of the Yuanmo-Luzhijiang fault. It varies considerably in lithology. To the north of Yuanmo, the lower part of the formation is dominated by coarse gravel conglomerate and subordinated by sandstone, while to the south conglomerate decreases in gravel size, with multiple beds of siltstone, muddy shale and marl, locally cupreous. In the western part and in the Dayao area of the central Yunnan basin, it is dominated by siltstone with sandy mudstone, with small amounts of conglomerate at the base. It varies considerably in thickness, from 6 to 600 m and generally increases in thickness from north to south. It is 115 m in Dayao, 182 m in Yaoan, 550 m in Muding, 157 m in Yuanmo, 432-640 m in Lufeng, 41.5 m in Chuxiong and 248 m in Shuangbai. In the Shawan area of Lufeng it is called the Shimen series. In Liuju of Dayao, it is in disconformable contact with the overlying Jiangdihe Fm and also in disconformable contact with the Yaoandaju Fm in most areas. In the Shuangbai area of Chuxiong, it lies unconformably on the Puchanghe Fm and in the Yuanmo area it is in unconformable contact with the Jurassic.