Daqing Fm

The formation rests conformably on the argillaceous limestone and sandy shale in the upper part of the Qiaojia Fm

It is conformably overlain by the calcareous mudstone and siltstone at the base of the Jiancaogou Fm [not yet in Lexicon]. Regionally, the next younger unit is the Guandi Fm of late Silurian.

The Daqing Fm, with a progressive rising horizon from south to north, is of characteristic unchanging lithology and considerably variable thickness. In Kunming, the equivalent strata, i.e. the previously defined Lower Qiaojia Fm and Upper Qiaojia Fm, are composed of dolomite intercalated with sandy shale, and recorded a total thickness of 220-330 m, and is thought to be roughly Arenig in age (Lai et al., 1982). This stratigraphic unit rests conformably on the Hongshiya Fm, and is disconformably overlain by the Devonian System. In Chenghai and Huaping, the equivalent strata, previously defined Beicaoping Fm (Yunnan Bureau of Geology and Mineral Resources, 1990), is represented by 20-250 m thick dolomite, and is Baotaian in age. In Zhaotong, the equivalent strata were previously divided into the Daqing Fm in the lower part and the Wangjiaheba Fm in the upper part (Yunnan Bureau of Geology and Mineral Resources, 1990). The lower part, 99-195 m thick, is characterized by massive dolomite intercalated with minor chert, and yields cephalopod Sinoceras chinense. The upper part is composed of dolomite intercalated with local chert bands and graptolite-bearing siltstone, and contains graptolites Dicellograptus ornatus, Orthograptus truncatus and trilobite Triarthrus cf. szechuanensis. Northward to Tiekfeik in Butuo County, Sichuan, the equivalent strata was previously named the Tiekfeik Gr (Mu et al., 1979), and is dominated by black dolomite, with a 4 m of limestone intercalated with siltstone at the top, and recorded a thickness of 80.3 m. From the limestone at the top, trilobite Dalmanitina and graptolite Climacograptus have been found. In Huatan, Ningnan, this strata was named Puge Fm (Mu et al., 1979), and is characterized by 600 m thick dolomitic limestone, and is conformably overlain by the Silurian System. From its lower part cephalopod Discoceras and coral Calostylis were found.