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Aeonothem Arathem system Age
( mya )
later later later


Duration: 300 Ma

Duration: 400 Ma

Duration: 400 Ma

Duration: 400 Ma

formerly: Hadaikum

The Neo-Archean is a geological age . It represents the last of four eras (Neoarchean = new Archean ) within the geological eon of the Archean . It begins about 2800 million years ago with the end of the Mesoarchean and ends about 2500 million years ago with the beginning of the Paleoproterozoic .

Redefinition of the Neo-Archean

In the course of moving away from period boundaries determined purely by radiometry, the GSSP principle should now be applied as far as possible in the Precambrian, according to Gradstein et al. (2012) . The periods are thus defined on the basis of significant geological events and no longer on arbitrary radiometric ages.

For the Neo-Archaic, Gradstein propose the following new classification:

“The Neo-Archean is divided into the two periods Methanium and Siderium . Methanium begins at 2,780 million years BP with the first appearance of continental flood basalts and a positive d 13 C value in hydrocarbons for the first time . It is followed by the siderium around 2630 million years BP with the first appearance of ribbon ores , which ends around 2420 million years BP with the first paleoproterozoic, glacial deposits . The GSSP for the methanium is at the base of the Mount Roe Basalt of the Fortescue Group ( Mount Bruce Supergroup ) in Western Australia , that of the siderium at the base of the Marra Mamba Iron Formation of the Hamersley Group (also Mount Bruce Supergroup, Western Australia) "

The newly defined Neo-Archean lasts 360 million years; the Mesoarchean-Neoarchean boundary tapers by 20 million years and the Archean-Proterozoan boundary by 80 million years.


Ribbon ore in the Dales Gorge, Hamersley Range

Recent research suggests that the prerequisites for the formation of higher mountains were given for the first time in the Neo-Archean . In the ages before that, the continental lithosphere was not yet sufficiently stable for topographical elevations of more than 2,500 meters due to its lower viscosity (high temperature and insufficient thickness) .

A pulse of magmatic activity , the so-called late archaic super event, is unique in the history of the earth . In the period from 2700 to 2500 million years BP it led to enormous crustal growth and probably to the formation of one or more supercontinents ( Kenorland or Superia and Sclavia ). Maxima in the zircon age and in the frequency distribution of greenstone belts and associated orogenic gold deposits underline the importance of this event.

The last period of the Neo-Archean, the Siderium, is characterized by the worldwide formation of ribbon ores . A large part of the iron dissolved in the oceans was thereby precipitated, so that from the Paleoproterozoic the oxygen concentration in the sea ​​water and finally also in the earth's atmosphere could increase (see also Great Oxygen Disaster ).



Significant sedimentary basins and geological formations



See also

Individual evidence

  1. ^ Felix M. Gradstein et al .: On the Geologic Time Scale . In: Newsletters on Stratigraphy . tape 45/2 , 2012, p. 171-188 .
  2. P. Rey, N. Coltitce: Neoarchean lithospheric strengthening and the coupling of Earth's geochemical reservoirs. ( Memento of the original from June 9, 2013 in the Internet Archive ) Info: The @1@ 2Template: Webachiv / IABot / archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Geology. Volume 36, 2008, pp. 635-638.
  3. RW Ojakangas et al: The Talya Conglomerate: an Archean (~ 2.7 Ga) Glaciomarine Formation, Western Dharwar Craton, Southern India . In: Current Science . tape 106 , N ° 3, 2014, p. 387-396 .
  4. ^ NJ Page: The Precambrian diamictite below the base of the Stillwater Complex, Montana . In: MJ Hambrey, NB Harland (Ed.): Earth's Pre-Pleistocene Glacial Record . Cambridge University Press, Cambridge 1981, pp. 821-823 .
  5. LM Heaman: 2.45 Ga global mafic magmatism: Earth's oldest superplume? In: Eighth International Conference on Geochronology, Cosmochronology & Isotope Geology, Program with Abstracts, US Geol. Surv. Circular 1107 . Berkeley, California 1994, pp. 132 .