Dengying Formation

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, • Hamajing Member: This member is characterized by light grey, medium- to thick-bedded dolomite, intercalated with thin layers of chert. as well as possible lobopodian trackways. • Baimatuo Member: This member is primarily composed of light grey, thick-bedded dolomite. • 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. • 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. 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, It is underlain once more by the Doushantou Formation, whilst it is overlain by the Cambrian aged Qiongzhusi Formation. • 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. == Dating ==

The Dengying Formation goes right up to the boundary of the Ediacaran and Cambrian periods, currently dated to , whilst the age of the base of the formation varies depending on the province. The middle Gaojiashan Member from the Shaanxi Province has had U-Pb dating done on several detrital zircon crystals, which recovered a maximum deposition date of . Meanwhile, the middle of the Third Member has been dated to . The base of the Dengying Formation in the Yangtze Gorges Hubei Province has been firmly dated to . == Taphonomy ==

The Dengying Formation is home to at least three different styles of preservation, which includes the classic Ediacaran-type preservation seen in the Shibantan Biota where only a negative or positive print "death mask" of the organism is made, Pyritization as seen in the Gaojiashan Biota where any organic parts of the organisms are replaced with pyrite, and the rare Burgess Shale-type preservation seen in the Tongshan and Jiangchuan Biotas, where the bodies are preserved as carbonaceous films, including some examples of Phosphatization throughout the Jiangchuan Biota. as such making it difficult to find and Cambrian-like biotas in the Ediacaran. == Paleobiota ==

The Dengying Formation is unique from most other Ediacaran formations, in that the top of the formation goes right up to the Ediacaran - Cambrian boundary, resulting in not only a wide array of Ediacaran organisms such as Paracharnia and Dickinsonia, but also rare examples of Cambrian-like organisms, such as Alienum. The formation is also well known for its abundant algal organisms, from Longfengshania to the enigmatic Vendotaenia. Recent studies have also found rare examples of Burgess Shale-type Preservation, in what is known as the Tongshan Lagerstätte and the Jiangchuan Biota from the Jiucheng Member. These preserves a wide range of fossil forms, from the first rangeomorph fronds with Burgess Shale-type preservation in the Tongshan, to the first reports of more recognizable Cambrian-like organisms, bolstering evidence that bilaterian animals where diversifying around this time, back up by the increase in the well known various burrows, movement traces, etc. Proarticulata Petalonamae Trilobozoa Porifera incertae sedis Flora Microorganisms Ichnogenera Undescribed ==See also==