Dengying Formation

Recent studies from some of the middle members of the formation have also yielded rare transitional fossiliferous rocks, namely between the Ediacaran biota and the Cambrian biota, providing insight as to where some Cambrian lineages may have started and diversified from, and filling in many empty gaps between the Ediacaran and Cambrian.

Geology

Due to the large area that the Dengying Formation covers, the geology and members within the formation differ from province to province. These members are listed below in ascending stratigraphic order (lowest to highest), under the respective provinces they are found in:

Members

Hubei Province Members

The formation within the Hubei Province primarily lies within the Yangtze Gorges area, overlaying the Doushantuo Formation, whilst it disconformably underlies the Cambrian aged Yanjiahe Formation.

• Hamajing Member: This member is characterized by light grey, medium- to thick-bedded dolomite, intercalated with thin layers of chert.
• Shibantan Member: This member is interpreted to represent a subtidal environment and is composed of dark grey, thin-bedded bituminous limestone. It is the most fossiliferous member of the Dengying Formation in Hubei and has yielded several trace fossils, such as Lamonte, as well as possible lobopodian trackways.
• Baimatuo Member: This member is primarily composed of light grey, thick-bedded dolomite.

Traditionally, the Tianzhushan Member was considered to be the uppermost unit of the Dengying Formation in Hubei. However, its small shelly fossils and Micrhystridium-like acritarchs are a shared characteristic with the Cambrian aged Yanjiahe Formation.

Yunnan Province Members

The formation can be found outcropping near the Fuxian Lake, and overlies the Lunasi Formation, whilst it underlies the Cambrian aged Zhujiaqing Formation.

• Donlongtan Member: This member is primarily composed of argilaceous dolomite rocks.
• Jiucheng Member: This member is dominated by various siltstone layers, with layers of sandstone throughout. This member is also fossiliferous in nature, containing the Jiangchuan Biota, with known forms such as Alienum and Lobodiscus being present with in member, as well as a number of yet to be described fossils which bear striking resemblances to many Cambrian animals.
• Baiyanshao Member: This member is predominately composed of dolomitic siltstone, which is argilaceous in nature.

Shaanxi Province Members

The formation in the Shaanxi Province is composed of three members, and is underlain by the Doushantuo Formation, whilst it is overlain by the Cambrain aged Kuanchuanpu and Huoshiwan Formations.

• Algal Dolomite: This member is predominately composed of light-gray peritidal dolostones, with paleo-karst structures being common throughout the member.
• Gaojiashan Member: This member is further sub-divided into three units. Unit 1 of the member is primarily composed of silstone, which it then inter-bedded with thin dolomite. This then transitions in Unit 2, which is predominately composed of dolomitic siltstones, with layers of calcareous mudstone and limestone found throughout. Then, at the top, Unit 3 differs greatly in being composed of conglomerate and sandstone, with layers of carbonate cement. This is also the fossiliferous member of the province, containing organisms such as Cloudina.
• Beiwan Member: This member is composed of grayish-white intra-clastic dolostone with occasional layers of chert near the base of the member, as well as locally occurring bitumen. It also contains an extensive microfossil assemblage.

Much like the Yanjiahe Formation in Hubei, the Kuanchuanpu Formation is also occasionally placed as a member of the Dengying Formation in Shaanxi, however it is likely separate for the same reasons.

Sichuan Province Members

The formation within the Sichuan Province is found outcropping in the Sichuan Basin in Southwestern China, as is primarily most well known for its gas reservoirs that can be found throughout the local area, such as the Weiyuan Gas Field. It is underlain once more by the Doushantou Formation, whilst it is overlain by the Cambrian aged Qiongzhusi Formation.

• First Member: This member is predominately composed of gray dolomite, which is micritic in nature. There are also occasional algal dolomites throughout, with gypsum and mudstone inter-bedded within.
• Second Member: The algal dolomite notably increases in this member, which is grayish-white in colour. There are also layers of clotted dolomite and algal mat-stromatolite dolostone.
• Third Member: The algal dolomite decreases in this member, which is primarily composed of argillaceous dolomite, inter-bedded with mudstones and shales.
• Fourth Member: The algal dolomite becomes a light gray to grayish-white algal dolostone, which is laminated in nature, alongside clotted dolomite and micritic dolostone, with siliceous nodules found throughout the member.

Jiangxi Province Outcrop

The Dengying Formation can also be found outcropping in the northern areas of the Jiangxi Province as a light-gray, thick-bedded stromatolite dolostone, and is underlain by the upper phosphorite and dolomicrosparite dominant layers of the Doushantuo Formation, whilst it is overlain by the black shales of the Cambrian aged Hetang Formation. Due to the limited exposed outcrops in Jiangxi, proper sequencing of the local stratigraphy has not been fully studied.