Longli Fm

Central easternmost Guizhou. The Longli Fm was named by the Guizhou Party of Regional Geological Survey in 1962 and formally published in 1965 (Guidebook of 1:200 000 Scale of Geological Map of Zhenyuan Sheet). The typical section is situated in Longli of Jinping County, Guizhou Province. Upper formation in the Banxi Gr and in the Xianjiang Gr.

Synonym:

The Longli Fm is subdivided into two members. First member is composed of light gray to gray blasto-siltstone intercalated with sandy slate, silty slate and sericite-slate, occasionally bearing tuffaceous slate. The blasto-sandstone and blasto-siltstone contain sometimes pebbles or lenses of conglomerate (see figure). From northwest to the southeast, the thickness of sandstone decreases. Around Tianzhu to Congjiang, the first member generally is 600 to 800 m thick, the thinnest is 250 m, and in Rongjiang, Sandu and Danzhai it is thicker, most of them are more than 1000 m, and the thickest is 2200 m. Second member consists of greenish gray sericite slate, silty slate intercalated with minor blasto-psammitic rock, occasionally bearing red-purple sericite slate, with spots of chlorite, locally slump convolute beddings and brecciation. The second member is 450 to 900 m thick and it thickens from southeast to northwest.

[Figure: The Stratigraphic column of the Xiajiang Gr. in Guizhou Province. A-Volcanic ash beds in the Jialu Fm and zircons from the ash bed.]

[Figure: The blasto-sandstone and blasto-siltstone contain scattered pebbles or lenses of conglomerate in the Longli Formation in Jinping County, Guizhou Province (photo by Chen Jianshu)]

The Longli Fm yields abundant microplants including Leiopsophosphaera, Kildinella, Pseudozonosphaera, Trachysphaeridium, etc.

According to the sedimentary features, the Longli Formation is dominated by neritic terrigenous detrital deposit, probably bearing debris-flow deposits.