The Lantian Formation is a 150-meter-thick sequence of rocks deposited in southern China during a 90-million-year epoch in the

Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and th ...

period. Its algal macrofossils (which have alternatively been interpreted as putative metazoans) are the oldest large and complex fossils known.

Sedimentology

The rocks were deposited in shallow seas, in the

photic zone The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...

yet below

storm wave base A storm is any disturbed state of the natural environment or the atmosphere of an astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstorm), ...

, yet were deposited in predominantly anoxic conditions. The fossils are located on the bedding planes, and are randomly oriented. The lowest part of the formation consists of a cap

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

, marking the end of the Marinoan glaciation and start of the Ediacaran. Above this is black shale containing the Lantian biota fossils. Above this are layers of dolomite, and shale followed by limestone. The highest part of the formation is black shale again. Above the formation is the Piyuancun formation consisting of silicious rock. The Lantian formation overlies

diamictite Diamictite (; from Ancient Greek ''δια'' (dia-): ''through'' and ''µεικτός'' (meiktós): ''mixed'') is a type of lithified sedimentary rock that consists of nonsorted to poorly sorted terrigenous sediment containing particles that ra ...

from the

Cryogenian The Cryogenian (from grc, κρύος, krýos, meaning "cold" and , romanized: , meaning "birth") is a geologic period that lasted from . It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by ...

.supplementary figure 4 of

Taphonomy

The fossils are preserved as carbonaceous films in a

Burgess Shale type preservation The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 69 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion. Additi ...

al fashion. ''

Anhuiphyton lineatum ''Anhuiphyton lineatum'' is an extinct species of Neoproterozoic algae, known from several fossils from the Lantian formation of China, first described in 1994. It lived probably more than 580 million years ago. The thalli Thallus (plural: th ...

'' is one example of a fossil located in the site.

Age

Originally presumed to be Cambrian in age, the formation is now correlated with the Doushantuo formation, with an overlying formation also falling in the Ediacaran period. The Lantian biota has a maximum Re-Os age of .

References

{{reflist Ediacaran Asia Ediacaran life Ediacaran geology Proterozoic Eonothem of Asia