Macaoyuan Fm
Type Locality and Naming
Southwest-central Hubei. The Macaoyuan Fm was named by the Hubei Party of Regional Geological Survey in 1974 (Guidebook of 1: 200 000 Scale of Geological Map of Shennongjia Sheet). The typical section is situated in Macaoyuan of Gufu in Shennongjia Forest District in Hubei Province. Formerly, was a formation within the Shennongjia Gr.
Synonym: （马槽园组）
Lithology and Thickness
The Macaoyuan Fm is a suite of molasse formation dominated by dolomitic conglomerate bearing pyroclastics. Lower part is dominantly composed of dolomitic conglomerate, with pyroclastic matter. Upper part is pyroclastic-bearing dolomitic conglomerate (cobbles, pebbles and granules), gray pyroclastic dolomitic sandstone and siltstone. Uppermost part is yellowish gray to gray white massive dolomite bearing stromatolites, intercalated with lenses of marly sandstone. The total thickness is 2153 m.
Relationships and Distribution
Lower contact
The Macaoyuan Fm rests unconformably on the underlying Shennongjia Gr (Mesoproterozoic) of which Wagangxi Fm is the uppermost unit.
Upper contact
It is disconformably or unconformably overlain by the Liantuo Fn
Regional extent
Southwest-central Hubei. With a limited distribution, it is only exposed in Macaoyuan area in the boundary of the Shennongjia forest and Xingshan County, Hubei Province.
GeoJSON
Fossils
It yields microplants Trematosphaeridium minutum, T. holtedahlii, Polyporata obsoleta etc.
Age
Depositional setting
Molasse. It belongs to the neritic environment with volcanic activity, which represents the initial stage of Yangtze Platform formation after the Dinning movement.
Additional Information
The Macaoyuan Formation is very important for defining the Qingbaikouan System in the Yangtze stratigraphic region, although it is very limitedly distributed.