Liangshuijing Fm

Named by the Compilation Team of the “Regional Geology of Sichuan Province” in 1991. The naming section is located at Liangshuijing (E103°28′29″, N39°36′06″ [maybe should be N29, not N39?), 1.5 km west of the seat of O’mei County, Sichuan. The section is measured by the Second Regional Survey Team of Sichuan Bureau of Geology in 1971.

A sequence of coarse- to fine-grained conglomerate, with gray to bluish gray silty clay bed and clay bed; the clay bed contains carbonized tree trunks, plant debris and sporopollen. The gravels are 3-30 cm in diameter, oriented and poorly sorted, and are filled by sandy mudstone and stained by limonite. The thickness is 104 m.

In the clay bed there occur large quantities of carbonized tree trunks and plant debris, suggesting a wet-hot climate. Identification by Chen Lirao of the Southwest Institute of Geology indicated that the sporopollen assemblage consists dominantly of pollen of angiosperms and spores of pteridophytes with minor pollen of gymnosperms, including Lycopodium sporites, Selaginellites, Gleicheniidites, Pinus pollenites etc.

This formation belongs to alluvial and diluvial deposits of fluvial facies and shows six rhythmic layers composed of the gravel layer to clay layer, suggesting that the piedmont rivers experienced several flood periods and normal water periods under the influence of the seasonal precipitation.