Yaopo Fm

It was named by Wang Zhuquan, Ji Rongsen in 1933. The naming section is located to the north of the Yuejiapo Village of the Mentougou District, Beijing City. Middle formation in Mentougou Gr.

Synonym: （窑坡组）

Lower member represents an alternating layer of grey-yellow and grey-green medium- and thick-bedded fine-grained sandstone in association with grey-white, yellow-green and grey-black thin-bedded to medium-bedded siltstones, intercalated with medium-, and coarse-grained sandstones, shales and coal beds, with a thickness commonly of 300-360 m, and with a maximum thickness being of 460 m; the member is possessed of many coal layers. Upper member is composed of grey-black, yellow-brown and grey siltstones, fine-grained sandstones, gritstones, pebble-bearing gritstones and coal beds, containing commonly siderite concretions, with a thickness of 140-195 m, its basal part with a 2-10 m thick layer of brown-yellow medium-, and coarse-grained arkosic sandstones, or of pebble-bearing gritstones and gritstones serves as a boundary marker in relation to the lower member. The formation represents important coal-bearing strata in western Beijing.

It yields plant fossils such as Equisetum lateral, E. giganteus, Neocalamites hoerensis, Annulariopsis simpsoni, Todites denticulata, Coniopteris hymenophylloides, C. tatungensis, Cladophlebis asiatica, Raphaelia aff. neuropteroides, Pterophyllum propinquum, Anomozamites thomasi, Nilssonia linearis, Tyrmia nathorsti, Ctenis kaneharai, Ginkgoites lepidus, Baiera gracilis, Czekanowskia rigida, Elatocladus manchurica and Podozamites lanceolatus, as well as bivalve fossils as represented by Naiadites? cf. krasnojarskiensis. N.? mentougouensis, Sibireconcha jenisejensis, Shaanxiconcha cf. clinovata, S. cf. obrutschevi, Pseudocarfinia? carinata, Ferganoconcha sibirica and F. elongata.

The formation is predominated by the coastal-lake facies and lacustrine-facies deposits, intercalated with swamp-facies deposits.