Ediacaran
The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last ...
(551-541 Ma) fossiliferous geologic formation found in
South China
South China ( zh, s=, p=Huá'nán, j=jyut6 naam4) is a geographical and cultural region that covers the southernmost part of China. Its precise meaning varies with context. A notable feature of South China in comparison to the rest of China is ...
. It was deposited on a shallow marine
carbonate
A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...
platform.
Members
Listed by ascending age:
* The Hamajing Member is characterized by light grey, medium- to thick-bedded dolomite, intercalated with thin layers of
chert
Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
.
* The Shibantan Member is interpreted to represent a subtidal environment and is composed of dark grey, thin-bedded
bituminous
Bitumen ( , ) is an immensely viscous constituent of petroleum. Depending on its exact composition, it can be a sticky, black liquid or an apparently solid mass that behaves as a liquid over very large time scales. In American English, the m ...
limestone
Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
. It is the most fossiliferous of the Dengying Formation members and has yielded several
trace fossils
A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...
, such as ''
Lamonte
LaMonte, Lamonte or La Monte may refer to the following people:
Surname
* Bob LaMonte, American sports agent
* Collene Lamonte, American politician from Michigan
* Francesca LaMonte (1895–1982), American ichthyologist
* Karen LaMonte (born 1967 ...
'', as well as possible lobopodian trackways.
* The Baimatuo Member consists of light grey, thick-bedded dolomite.
Traditionally, the Tianzhushan Member was considered to be the uppermost unit of the Dengying Formation. However, its
small shelly fossils
The small shelly fauna, small shelly fossils (SSF), or early skeletal fossils (ESF) are mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambri ...
acritarchs
Acritarchs () are organic microfossils, known from the Precambrian to the present. The classification is a catch all term used to refer to any organic microfossils that cannot be assigned to other groups. Their diversity reflects major ecologi ...
are a shared characteristic with the
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...
Yanjiahe Formation
The Yanjiahe Formation is an Ediacaran to Cambrian fossiliferous geologic formation found in South China.Dong et al., 2009 The Kuanchuanpu Formation also is occasionally placed as a member of the Dengying Formation, however it is likely separate for the same reasons.
Paleobiota
The Dengying formation is unique from other Ediacaran formations in that its top is almost right up against the Ediacaran - Cambrian boundary, with more recent organisms being described that have striking similarities with Cambrian fauna, like
Alienum
''Alienum'' is an extinct animal of uncertain affinities from the late Ediacaran. Estimated to be about 541 million years old, the type species, ''A. velamenus'' demonstrates some anatomical characters reminiscent of vetulicolians, predating th ...
. There are also a lot of ichnogenera in the form of burrows, something that is common in younger Ediacaran rocks the closer to the Cambrian boundary they are.
Ediacaran biota
The Ediacaran (; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were enigmatic tubular and frond-shaped, mostly sessile, organis ...