Neoproterozoic

Neoproterozoic
1000 – 538.8 ± 0.2 Ma Pha. Proterozoic Archean Had'n
Clockwise, from top left: Otavia, a multicellular organism from Tonian period, Snowball Earth glaciations from Cryogenian period, Ediacaran biota from Ediacaran period
Chronology
−1000 — – −950 — – −900 — – −850 — – −800 — – −750 — – −700 — – −650 — – −600 — – −550 — – P r o t e r o z o i c P Mesoproterozoic N e o p r o t e r o z o i c Paleozoic Tonian Cryogenian Ediacaran   An approximate timescale of key Neoproterozoic events. Axis scale: millions of years ago.
Proposed redefinition(s)	850–541 Ma Gradstein et al., 2012
Proposed subdivisions	Cryogenian Period, 850–630 Ma Gradstein et al., 2012 Ediacaran Period, 630–541.0 Ma Gradstein et al., 2012
Etymology
Name formality	Formal
Usage information
Celestial body	Newfoundland, Canada 47°04′34″N 55°49′52″W / 47.0762°N 55.8310°W / 47.0762; -55.8310
Upper GSSP ratified	1992[citation needed]

The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago.^[2]

It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is preceded by the Mesoproterozoic Era and succeeded by the Paleozoic Era of the Phanerozoic Eon.

The most severe

According to Rino and co-workers, the sum of the continental crust formed in the Pan-African orogeny and the Grenville orogeny makes the Neoproterozoic the period of Earth's history that has produced most continental crust.^[3]

Geology

At the onset of the Neoproterozoic the supercontinent Rodinia, which had assembled during the late Mesoproterozoic, straddled the equator. During the Tonian, rifting commenced which broke Rodinia into a number of individual land masses.

Possibly as a consequence of the low-latitude position of most continents, several large-scale glacial events occurred during the Neoproterozoic Era including the

These glaciations are believed to have been so severe that there were ice sheets at the equator—a state known as the "Snowball Earth".

Subdivisions

Neoproterozoic time is subdivided into the Tonian (1000–720 Ma), Cryogenian (720–635 Ma) and Ediacaran (635–538.8 Ma) periods.^[2]

Russian regional timescale

In the regional timescale of Russia, the Tonian and Cryogenian correspond to the Late Riphean; the Ediacaran corresponds to the Early to middle Vendian.^[4] Russian geologists divide the Neoproterozoic of Siberia into the Mayanian (from 1000 to 850 Ma) followed by the Baikalian (from 850 to 650 Ma).^[5]

• 

  Russian timescale for Proterozoic. Neoproterozoic is equivalent to the time span from Late Riphean to Late Vendian.

Paleobiology

The idea of the Neoproterozoic Era was introduced in the 1960s. Nineteenth-century paleontologists set the start of

In addition to Ediacaran biota, two other types of biota were discovered in China. The Doushantuo Formation preserves fossils of microscopic marine organisms in great detail.^[7] The Hainan biota consists of small worm-shaped organisms.^[8]

The nomenclature for the terminal period of the Neoproterozoic Era has been unstable. Russian and Nordic geologists referred to the last period of the Neoproterozoic as the

However, in 2004, the International Union of Geological Sciences ratified the Ediacaran Period to be a geological age of the Neoproterozoic, ranging from 635 to 538.8 (at the time to 542) million years ago.^[10][11] The Ediacaran Period boundaries are the only Precambrian boundaries defined by biologic Global Boundary Stratotype Section and Points, rather than the absolute Global Standard Stratigraphic Ages.

See also

• Boring Billion – Earth history, 1.8 to 0.8 billion years ago

References

External links

• Neoproterozoic (chronostratigraphy scale)

Wikimedia Commons has media related to Neoproterozoic.