Stenium

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Aeonothem Arathem system Age
( mya )
later later later
P
r
o
t
e
r
o
z
o
i
k
u
m

Duration:

1959
Ma 		Neoproterozoic
Jungproterozoikum
Duration: 459 Ma 		Ediacarium 541
⬍
635
Cryogenium 635
⬍
720
Tonium 720
⬍
1000
Mesoproterozoic
Mittelproterozoikum
Duration: 600 Ma 		Stenium 1000
⬍
1200
Ectasium 1200
⬍
1400
Calymmium 1400
⬍
1600
Paleoproterozoic
Altproterozoikum
Duration: 900 Ma 		Statherium 1600
⬍
1800
Orosirium 1800
⬍
2050
Rhyacium 2050
⬍
2300
Siderium 2300
⬍
2500
earlier earlier earlier

The stenium was the seventh period of the Proterozoic . The chronometrically defined period lasted 200 million years. It began 1,200 million years ago BP and ended 1,000 million years ago BP. It followed the ectasium and was replaced by the tonium . With the stenium, the Mesoproterozoic ended and the Neoproterozoic began.

Naming

The name Stenium is derived from ancient Greek στενός (stenos), which means narrow . He alludes to the many, narrow, polymetamorphic mountainous belts that arose during this period.

Geological events

During the stenium, the supercontinent Rodinia ( Russian Родина, (ródina) homeland ) formed, which accreted BP from many cratons between 1300 and 900 million years ago .

After subduction under the eastern continental margin of Laurentia ended around 1,300 million years BP and a northwest-southeast trenching rift had formed in the southwest of the United States by 1,260 million years BP, the sea penetrated after its subsidence from 1210 million years BP from the southeast and sedimented mainly siliciclastic sediments in addition to limestone until 1150 million years ago.

From 1.163 billion years, the cycle of continued Grenville orogeny with strong Magmentätigkeit a (formed were able intrusions , diabase - sills and bimodal plutonic and volcanic rocks), eventually to 1,086 million years BP in a multiphase, transpression continent collision (passed in the area of Van Horn in Texas as early as 1123 million years BP). After the docking of the Rio de la Plata continent (or Amazonia ) around 1086 million years BP, the southwest of Laurentia suffered tensile stresses in the northeast-southwest direction, which evoked mafic plutonism with renewed diabase deposits between 1080 and 1040 million years BP. The stretching regime should last up to 1000 million years BP.

The geology of the Superior Upland. The rocks of the Keweenawan Supergroup are marked in yellow.

Time approximately parallel to the Grenville orogeny proceeded amid Laurentias from about 1.11 billion years BP the emergence of the Midcontinent Rift System (MRS), a huge grave fault system . Over a period of 15 to 22 million years, the Keweenawan Supergroup accumulated in the approximately 2000 kilometers long rift, which stretches from the northeastern edge of Kansas via Iowa to northeast Minnesota in a northeast direction - an accumulation of over 30,000 meters of volcanites, plutonites and sediments! The volcanic rocks alone reach a thickness of 20,000 meters. Shortly before oceanization, the development of the Aulakogen stopped , preventing Laurentia from breaking up completely. The further development of the Grenville Orogeny (Ottawan Orogeny), which burned further to the east, was probably prevented, but the precise connections have not yet been clarified. The origin of the Midcontinent Rift System is assumed to be a mantle diapir , which had created a triple point below Lake Superior .

Biological development

Around 1200 million years BP, in the fossil record, besides eukaryotes, fungal organisms and even microbes can be found on the mainland - which clearly indicates increased oxygen concentrations. As early as 1500 million years BP, simple acritarches appeared in the fossil record , which between 1200 and 1000 million years BP were replaced by much more complex forms, which also spread on the mainland.

stratigraphy

Significant sedimentary basins and geological formations

Geodynamics

Orogenesis

Magmatism

See also

literature

Web links

Individual evidence

  1. ^ Li, ZX et al .: Assembly, configuration and break-up history of Rodinia: a synthesis . In: Precambrian Research . tape 160 , 2008, p. 179-210 .
  2. ↑ Van Schmus, WR and Hinze, WJ: The Midcontinent Rift System . In: Annual Review of Earth and Planetary Sciences . tape 13 (1) , 1985, pp. 345-83 , doi : 10.1146 / annurev.ea.13.050185.002021 .
  3. ^ Ojakangas, RW, GB Morey, and JC Green: The Mesoproterozoic Midcontinent Rift System, Lake Superior Region, USA . In: Sedimentary Geology . tape 141–142 , 2001, pp. 421-442 , doi : 10.1016 / S0037-0738 (01) 00085-9 .
  4. ↑ Parnell, J. et al.: Early oxygenation of the terrestrial environment during the Mesoproterozoic . In: Nature . tape 468 , 2010, p. 290-293 .
  5. ↑ Knauth, LP and Kennedy, MJ: The late Precambrian greening of the Earth . In: Nature . tape 460 , 2009, pp. 728-732 .
  6. ↑ Chaudhuri, AK et al .: Conflicts in stratigraphic classification of the Puranas of the Pranhita-Godavari Valley: review, recommandations and status of the 'Penganga' sequence . In: Geological Society, London, Memoirs . tape 43 , 2014, p. 165-183 .
  7. ↑ Guadagnin, F. et al .: Age constraints on crystal-tuff from the Espinhaço Supergroup - Insight into the Paleoproterozoic to Mesoproterozoic basin cycles of the Congo-São Francisco Craton . In: Gondwana Research . tape 27 , 2015, p. 363-376 .
  8. ^ Davis, DW and Green, JC: Geochronology of the North American Midcontinent rift in western Lake Superior and implications for its geodynamic evolution . In: Canadian Journal of Earth Sciences . tape 34 (4) , 1997, pp. 476-488 .