Ectasium

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Aeonothem Arathem system Age
( mya )
later later later
P
r
o
t
e
r
o
z
o
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k
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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 ectasium , derived from ancient Greek ἔκτασις (éktasis) = expansion, spread , is the second, chronometrically defined period of the Mesoproterozoic . It lasted 200 million years and followed BP to the Calymmium 1,400 million years ago , and 1,200 million years ago BP it passed into the stenium .

Naming

The name indicates the further expansion of the cratons and their sediment shells.

geology

The ectasium is geodynamically shaped by two major events - the breakup of Columbia and the beginning amalgamation of the supercontinent Rodinia .

The collapse of Columbia, which began around 1600 million years BP, was accompanied by widespread, anorogenic magmatism , the so-called AMCG consequences ( anorthosite - mangerite - charnockite) between 1600 and 1300 million years BP in Laurentia, Baltica , Amazonia and northern China - granite ). The decay process ended between 1300 and 1200 million years BP, as the intrusion of mafic gang swarms suggests ( Mackenzie gang swarm around 1270 million years BP, Sudbury gang swarm around 1240 million years BP).

The Grenville orogeny , the precursor of which, the Elzevirian orogeny , had already begun towards the end of the Ectasium (1240 to 1220 million years BP), is of decisive importance for the amalgation process of Rodinia . In the period 1300 to 1200 million years BP, an island arc was accreted along a subduction zone of the B-type on the eastern, active continental margin of Laurentia , which finally docked during the Elzevirian Orogeny (around 1230 million years BP).

On the south and south-east edge of Laurentia, the north-west subduction that preceded the mountain formation had already started around 1,500 million years ago and was fading again between 1,400 and 1,300 million years BP. A consequence of this subduction process was widespread, anorogenic magmatism in southwest Laurentia (for example, the Ruin Granite in Arizona intruded around 1440 million years BP and the World Beater Complex formed in Death Valley around 1400 million years BP ). A backarc basin was created behind the approaching arch of the island , in which the rocks of the Carrizo Mountain Group were deposited around 1380 million years ago . The arch of the island itself is represented by rocks from the Sierra del Cuervo in northern Mexico .

Between 1300 and 1260 million years BP, a northwest-southeast trending rift collapsed on the mainland behind the subduction zone, stretching from western Texas to southeastern California . Around 1260 million years BP compression began, which led to crust constrictions and elevations in rift sequences (recognizable by the Hakatai Shale of the Unkar Group in the Grand Canyon ). Between 1210 and 1150 million years BP, the rising sea penetrated the sinking rift and filled the previously formed rift fractures (for example, formations such as the Lanoria Formation , the Troy Quartzite and the Shinumo Quartzite formed ).

Biological evolution

The oldest evidence of eukaryotic unicellular organisms in the form of red algae comes from the ectasium . w. S. of the species Bangiomorpha pubescens , which were found in the Canadian Hunting Formation on Somerset Island . As early as 1500 million years BP, very simple acritarches appeared in the fossil record , which were then to be replaced by much more complex forms between 1200 and 1000 million years BP, which were also common on the mainland. Towards the end of the ectasium around 1200 million years BP, fungus-like organisms can be detected in addition to eukaryotes and even microbes on the mainland - which clearly indicates increased oxygen concentrations.

stratigraphy

Significant sedimentary basins and geological formations

The 1210 million year old Hakatai Shale of the Unkar Group with intruding basalt dike, Grand Canyon

Geodynamics

Magmatism

The Franklin Mountains in West Texas, dating back to 1280 million years BP

Terrane

Orogenesis

See also

literature

Web links

Individual evidence

  1. ↑ Anderson, JL and Morrison, J .: Ilmenite, magnetite and peraluminous Mesoproterozoic anorogenic granites of Laurentia and Baltica . In: Lithos . tape 80 , 2005, pp. 45-60 .
  2. ↑ Nicholas J. Butterfield: Bangiomorpha pubescens n. Gen., N. Sp .: implications for the evolution of sex, multicellularity, and the Mesoproterozoic / Neoproterozoic radiation of eukaryotes. In: Paleobiology , 26 (3), 2000, pp. 386-404, Jacksonville NY, doi : 10.1666 / 0094-8373 (2000) 026 <0386: BPNGNS> 2.0.CO; 2
  3. ↑ Knauth, LP and Kennedy, MJ: The late Precambrian greening of the Earth . In: Nature . tape 460 , 2009, pp. 728-732 .
  4. ↑ Parnell, J. et al.: Early oxygenation of the terrestrial environment during the Mesoproterozoic . In: Nature . tape 468 , 2010, p. 290-293 .
  5. ↑ 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 .
  6. ↑ 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 .