Marinoan glaciation

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The Marinoan glaciation, sometimes also known as the Varanger glaciation,

gas hydrates[5] and might have been hastened by the release of methane from equatorial permafrost.[6][7]

Origin of name and history of terminology

The name is derived from the

Adelaide Geosyncline (Adelaide Rift Complex) in South Australia and is taken from the Adelaide suburb of Marino. The term Marinoan Series was first used in a 1950 paper by Douglas Mawson and Reg Sprigg to subdivide the Neoproterozoic rocks of the Adelaide area and encompassed all strata from the top of the Brighton Limestone to the base of the Cambrian.[8] The corresponding time period, referred to as the Marinoan Epoch, spanned from the middle Cryogenian to the top of the Ediacaran in modern terminology. Mawson recognised a glacial episode within the Marinoan Epoch which he referred to as the Elatina glaciation after the 'Elatina Tillite' (now Elatina Formation) where he found the evidence.[9] However, the term Marinoan glaciation came into common usage because it was the glaciation that occurred during the Marinoan Epoch, as distinct from the earlier glaciation during the Sturtian Epoch (the time period of deposition of the older Sturtian Series[8]
).

The term Marinoan glaciation was later applied globally to any glaciogenic formations assumed (directly or indirectly) to correlate with Mawson's original Elatina glaciation in South Australia.[10] Recently, there has been a move to return to the term Elatina glaciation in South Australia because of uncertainties regarding global correlation and because an Ediacaran glacial episode (Gaskiers) also occurs within the wide-ranging Marinoan Epoch.[11]

Cryogenian Snowball Earth

Further information: Cryogenian, Snowball Earth, and Neoproterozoic

Emerging evidence suggests that the Earth underwent a number of glaciations during the Neoproterozoic era.[12] There were three (or possibly four) significant ice ages during the late Neoproterozoic. These periods of nearly complete glaciation of Earth are often referred to as "Snowball Earth", where it is hypothesized that at times the planet was covered by ice 1–2 km (0.62–1.24 mi) thick.[13] Of these glaciations, the Sturtian glaciation was the most significant, whereas the Marinoan was a shorter, but still worldwide glaciation. Other Cryogenian glaciations were probably small and not global as compared to the Marinoan or Sturtian glaciations.

During the Marinoan glaciation, characteristic glacial deposits indicate that Earth suffered one of the most severe ice ages in its history. Glaciers extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator.[14][15]

The Earth may not have been fully covered in ice, as some computer simulations show an extreme slowdown of the hydrological cycle that inhibited new glacial formation before the Earth was fully ice-covered.[16]

The melting of the Snowball Earth is associated with greenhouse warming due to the accumulation of high levels of carbon dioxide in the atmosphere.[17] Deglaciation likely started in the mid-latitudes, as in the tropics, the intense hydrological cycle replenished snow rapidly. As the mid-latitudes became ice free, dust was blown from them into other regions, lowering albedo and speeding up deglaciation.[18]

Evidence

Flinders Ranges NP
, South Australia. A$1 coin for scale.
Diamictite of the Neoproterozoic Pocatello Formation, a 'Snowball Earth'—type deposit

Even though much evidence has been lost through geological changes, field investigations show evidence of the Marinoan glaciation in China,

barite), and other unusual sedimentary structures.[13] Two diamictite-rich layers in the top 1 km (0.62 mi) of the 7 km (4.3 mi) Neoproterozoic strata of the northeastern Svalbard archipelago represent the first and final phases of the Marinoan glaciation.[19] In Uruguay, evidence of the Marinoan glaciation is known from dropstones, diamictites, rhythmites, clast layers, and varve-like deposits.[2]

According to Eyles and Young, the Marinoan is a second episode of

Cordillera."[20]

See also

References

  1. S2CID 129706604
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    doi:10.1016/S1342-937X(05)70644-4
    . Retrieved 16 October 2022.
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  4. doi:10.1016/j.gloplacha.2023.104071
    . Retrieved 1 June 2023.
  5. S2CID 253430013
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  6. doi:10.1038/ngeo214
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  7. S2CID 4416812
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  8. ^ a b Mawson, D.; Sprigg, R.C. (1950). "Subdivision of the Adelaide System". Australian Journal of Science. 13: 69–72.
  9. Transactions of the Royal Society of South Australia
    . 73: 117–121.
  10. doi:10.1016/j.precamres.2015.10.006
    .
  11. doi:10.1016/j.precamres.2007.12.001
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  12. doi:10.1038/ngeo355
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  13. ^ a b "New Evidence Supports Three Major Glaciation Events In The Distant Past". ScienceDaily. 2004-04-22. Retrieved 2011-06-18.
  14. ^ Dave Lawrence (2003). "Microfossil lineages support sloshy snowball Earth". Geotimes. Retrieved 2011-06-18.
  15. ^ "Global Glaciation Snowballed Into Giant Change in Carbon Cycle". ScienceDaily. 2010-05-02. Retrieved 2011-06-18.
  16. doi:10.1029/2000JD900221
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  17. S2CID 2205883
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  18. doi:10.1038/s43247-021-00160-4
    .
  19. S2CID 53588955. Archived from the original
    (PDF) on 2012-03-20. Retrieved 2011-06-18.
  20. ISBN 978-0521548038
    .
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