Ma'ao Fm
Type Locality and Naming
It was named by the Petroleum Prospecting Party of Henan Province in 1959-1961. The naming section is located in the vicinity of Chengliu Village west of Ma’ao region, Jiyuan County, Henan Province.
Synonym: （马凹组）, Maao Fm
Lithology and Thickness
Lower member is composed of yellow-quartz sandstones, intercalated with violet and grey-green calcareous mudstones, yellow siltstones and fine-grained sandstones, with a thickness of about 118 m. Upper member is composed largely of brown-red, purple and grey-green calcareous mudstones, intercalated with variegated mudstones, marls and sandstones, with a thickness of about 100 m.
Relationships and Distribution
Lower contact
Its basal part overlies disconformably the Yima Fm, with no directly overlying strata having been found.
Upper contact
Regional extent
There are scattered exposures of the formation in the Qikeshu and Beiquan Temple areas of Queshan County, being composed largely of sandy shale intercalated with thin coal beds. According to the results of drilling wells, its thickness is of about 68 m, with its basal part overlying unconformably the lower Precambrian, and with its top part being overlain by the Triassic sandy conglomerates. The lower member of the present formation in the Yima area consists of grey-yellow, grey-green, purple and grey-white sandy claystones, intercalated with sandy conglomerates, with its basal part being composed of a layer of thick-bedded conglomerates, while its upper member represents brick-red sandy claystones, grey-green and grey-yellow sandy claystones and conglomerates, with a total thickness of 191 m, yielding spore-pollen fossils.
GeoJSON
Fossils
It yields bivalve fossils such as Psilunio ovalis, P. jiangyouensis, P. globitriangularis, P. chaoi, P. honanensis, P. lufengensis, Cuneopsis johannisboehmi, C. minatus, Lamprotula (Eolamprotula) jiyuanensis and “Unio” gigantus; spinicaudatan fossils as represented by “Euestheria” cf. changhangouensis, and “E.” cf. shiguaiziensis; and Ostracoda fossils as represented by Darwinula sarytirmenensis, D. cf. impudica and D. cf. changxinensis, as well as fish squama and turtle fossils.
Age
Depositional setting
The formation belongs to fluvial-lacustrine deposits, and is distributed in Chengliu and Ma’ao areas west of Jiyuan County Town, as well as in the Yima area of Xinan County.
Additional Information