BalunhalagenBed Fm

The type section is located at Dahongshan (big red hill) (E113°53′, N43°20′), about 60 km southeast of Sonid Zuoqi County, Xilinhot City, central Nei Mongol. It was named by Wang et al. (2009).

The Balunhalagen Bed consists of basal gravels and orange red sandstones and siltstones. This bed is usually well marked by visible bedding planes and forms a resistant bench that protects the softer mudstones of top of the Aoerban Fm. It contains abundant mammalian fossils. Its thickness is less than 8 m.

Mammals: Mioechinus? cf. M. gobiensis, Proscapanus sp., Quyania sp., Yanshuella sp., Heterosoricinae indet., Soricinae indet., Ayakozomys mandaltensis, Ansomys Borealis, A. lophodens, Tamias ertemtensis, Spermophilinus mongolicus, Tamiops minor, Atlantoxerus orientalis, A. exilis, A. major, Sinotamias primitivus, Prospermophilus orientalis, Pliopetaurista cf. P. rugosa, P. cf. P. speciosa, Hylopetes bellus, Orientiglis wuae, Miodyromys asiamediae, Keramidomys fahlbuschi, K. magnus, Leptodontomys gansus, L. lii, Pentabuneomys feijfari, Eozapus major, Sicista ertemteensis, Heterosminthus orientalis, Lophocricetus xianensis, Zapodidae indet. 1, Zapodidae indet. 2, Protalactaga grabaui, P. lantianensis, P. lophodens, Paralactaga anderssoni, Brachyscirtetes wimani, Dipus fraudator, Metaeucricetodon mengicus, Democricetodon lindsayi, D. tongi, Megacricetdodon sinensis, Cricetodon fengi, Plesiodipus leei, P. progressus, P. robustus, Gobicricetodon aff. G. flynni, G. robustus, Khanomys baii, Colloides xiaomingi, Sinocricetus zdanskyi, Nannocricetus primitivus, N. mongolicus, Kowalskia similis, Microtoscoptes fahlbuschi, Abudhabia wangi, Pseudomeriones abbreviatus, Prosiphneus qiui, Hansdebruijnia pusilla, Desmatolagus? sp., Alloptox sp, Bellatona sp., Ochotona sp., Ligeromeryx/Lagomeryx sp.. (Wang et al., 2009; Qiu and Li, 2016).

It is interpreted as a river environment.