The Lantian Formation is a 150-meter-thick sequence of rocks deposited in southern China during a 90-million-year epoch in the
Ediacaran period.
Its algal
macrofossil
Macrofossils, also known as megafossils, are preserved organic remains large enough to be visible without a microscope. The term ''macrofossil'' stands in opposition to the term microfossil. Microfossils, by contrast, require substantial magnifica ...
s (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 yet below
storm wave base,
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
The Marinoan glaciation, sometimes also known as the Varanger glaciation, was a period of worldwide glaciation that lasted from approximately 650 to 632.3 ± 5.9 Ma (million years ago) during the Cryogenian period. This glaciation possibly cover ...
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 from the
Cryogenian.
supplementary figure 4 of
Taphonomy
The fossils are preserved as carbonaceous films in a Burgess Shale type preservational fashion. '' Anhuiphyton lineatum'' 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
The Doushantuo Formation (formerly transcribed as Toushantuo or Toushantou, from ) is a geological formation in western Hubei, eastern Guizhou, southern Shaanxi, central Jiangxi, and other localities in China. It is known for the fossil Lagerst ...
, 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