YunshanCret Fm

E. Heilongjiang – Wandashan. Upper-Middle formation of Longwangzhang Gr. Named after Yunshan in Hulin County, Heilongjiang Province, by Heilongjiang Research Team of Mesozoic Coal-bearing Strata, 1986, Research on the Longzhaogou Group and Its Correlation with the Jixi Group of Eastern Heilongjiang Province, Harbin: Heilongjiang Science and Technology Press.

NOTE: There is also a "Yunshan" Formation of sandstone in middle Devonian of Jiangxi Province. Therefore, "Cret" appended to this one in Lexicon.

"The marine and nonmarine strata are composed of black mudstone, siltstone, fine- to medium-grained sandstone, coal, tuff, volcaniclastics and lava. Total thickness of the formation is about 2100 m." (Futakami, M., et al., 1995). "The lower member is dominated by non-marine coal-bearing deposits containing two to four coal beds, tuffs, andesites, and lava, with three intercalations of marine deposits. In the upper member, in contrast, the marine and non-marine conditions alternate, containing at least nine marine intercalations and four to eleven coal beds. Locally, the rocks are associated with thin-bedded tuff layers." [from Kosenko et al, 2021]

Plant, brachiopod, foraminifer, gastropod, bivalve and ostracod fossils have been found. The formation yields some plant megafossils in the coal-bearing strata and numerous marine fossils in the marine beds. They include various bivalves such as the Aucellina caucasica - A. aptiensis - Filosina subovalis - Thracia rotundata and A. cf. caucasica - A. cf. aptiensis assemblages (reported from the upper member), some gastropods, such as Mathilda asiatica, Uchauxia aff. peregrinorsa, U. yunshanensis, and Trochactaeon sp., the Odontochitina operculata - Vesperopsis didaoensis dinoflagellate cyst assemblage, rare brachiopods, and ostracods. The flora assemblage from the Yunshan Formation is very rich and is dominated by ferns and conifers. It is similar to the late subassemblage of the Late Assikaevka Fm flora assemblage. Common taxa are represented by Birisia onychioides, Anemia dicksoniana [=Acanthopteris szei], Osmunda (Todites) denticulata, Sequoia reichenbachi, Taxites brevifolius [=Elatocladus (Cephalotaxopsis) anguistifolius] and others. Genera Osmunda, Gleichenites, Birisia, Elatides, Athrotaxites, Sequoia, Taxites are common in both assemblages. The difference is that the Yunshan Formation does not contain angiosperms.