Xuman Fm

The named section is located in Xuman Village, about 30 km to the northwest of Wangmo County, Guizhou. It was named by Guizhou Bureau of Geology and Mineral Resources in 1987.

Synonym:

The Xuman Formation is mainly composed of flysch sandy shale and limestone. It may be subdivided into two major cyclothems and four lithologic members based on the petrographic characteristics. First member (81 to 153 m thick) and the Third member (170 to 452 m thick) are mainly the interbeds of thin to medium-thick gray micritic limestone and calcareous claystone, in different thickness, which are interbedded with siltstone. Second member (142 to 1117 m thick) and the Fourth member (485 to 863 m thick) are mainly composed of grey, gray-green calcareous siltstone, sandy claystone and calcareous claystone, interbedded with limestone occasionally. There are generally size graded layer and Bouma sequence in this formation, especially the turbidite in the second member, with Ta-e and Tc series. And the bottom structure of load cast, groove cast, flute cast and erosional basal surface is well developed. The limestone beds of the third section are very stable in the area and can be used as a marker bed.

Two bivalves zone can be established from bottom to top: (1) Daonella guizhoensis zone; (2) Daonella ignobilis - D. obtusa assemblage zone; the ammonoid Leiophyllites-Hollandites assemblage zone can be established in the first to the third sections.

It is interpreted as a turbidity (flysch) sediment environment.