Wayaobao Fm

It was named in 1934 by Pan Zhongxiang. The named section is located in Zichang County, Shaanxi Province (Wayaopu); the reference section is located in Qishuihe, Tongchuan, Shaanxi Province. Uppermost formation of the Yanchang Gr.

Synonym: Wayaopu Fm. The name “Wayaopuo Coal-bearing” refers to the strata integrated above the Yanchang bed. Most of the strata are grey sandstone, shale and black shale, the lower part contains several layers of coal, coal line, age is defined as early Jurassic. Wang Shangwen (1950) discovered an erosional surface in the Wayaopu coal-bearing, and thus classified the strata above the erosional surface as Jurassic. The Northwest Mesozoic and Cenozoic stratigraphic conference (1976) renamed the Wayaopu Formation and dated to the Late Triassic. The Institute of Geology of the Chinese Academy of Geological Sciences (1980) classified it as the top of the Yanchang Fm, corresponding to the fifth member of the original Yanchang Fm. Regional Stratigraphic Table of Shaanxi Province (1983) and Regional geological records of Shaanxi Province (1989), The study of multiple division and correlation of strata in Shaanxi Province (1994) is classified as the Wayaopu Formation of Yanchang Group. [Tong et al., 2019, and other English-language entries in the Triassic portion of the Lexicon use a spelling of Wayaoboa, so this is adopted here.]

Characterized with the interbeds of yellow green, gray black and gray yellow mudstone with sandstones and siltstones, and interbedded with multi-layer coal seams or black shales, with thickness of 224 m.

Rich in animal and plant fossils. Plants: Danaeopsis fecunda, Bernoullia zeilleri, Cladophlebis gigantea, Cl. raciborskii, Todites shensiensis, Nilsssonia pterophyllloides, Thinnfeldia nordenskioldi, etc.; Ostracoda: Darwinula, Tungchuania, etc.; Bivalves: Shaanxiconcha.

The Wayaopu Fm (Wayaobao Fm) is swamp-lacustrine facies.

In 1959, Gan Kewen and others renamed the "Yanchang Series", and divided 5 lithological members and included the lower strata of the "Wayaobao Coal System" built by Pan Zhongxiang. In 1980, the Institute of Geology of the Chinese Academy of Geological Sciences named the first and second members of the Yanchang Series as the Tongchuan Fm, and the age was Middle Triassic; The third, fourth, and fifth members are named "Yanchang Fm", and their ages are the Late Triassic. Regional Geology of Shaanxi Province combined Tongchuan Fm, Hujiacun Fm, Yongping Fm and Wayaopu Fm as Yanchang Gr, in which, Tongchuan Formation equal to the first and the second member of Yanchang Gr; Hujiacun Fm, Yongping Fm and Wayaopu Fm (Wayoaboa Fm) equal to the third, fourth and the fifth member correspondingly.