Huronian glaciation

The Huronian glaciation (or Makganyene glaciation)^[1] was a period where at least 3 ice ages occurred during the deposition of Huronian Supergroup. Deposition of this largely sedimentary succession extended from approximately 2.5 to 2.2 billion years ago (Gya), during the Siderian and Rhyacian periods of the Paleoproterozoic era. Evidence for glaciation is mainly based on the recognition of diamictite, that is interpreted to be of glacial origin. Deposition of the Huronian succession is interpreted to have occurred within a rift basin that evolved into a largely marine passive margin setting.^[2] The glacial diamictite deposits within the Huronian are on par in thickness with Quaternary analogs.

Description

The three glacial diamictite-bearing units of the Huronian are, from the oldest to youngest, the Ramsay Lake, Bruce, and Gowganda formations. Although there are other glacial deposits recognized throughout the world at this time, the Huronian is restricted to the region north of Lake Huron, between Sault Ste. Marie, Ontario, and Rouyn-Noranda, Quebec. Other similar deposits are known from elsewhere in North America, as well as Australia and South Africa.^[3]

The Huronian glaciation broadly coincides with the Great Oxygenation Event, a time of increased atmospheric oxygen and decreased atmospheric methane. The oxygen reacted with the methane to form carbon dioxide and water, both much weaker greenhouse gases than methane, greatly reducing the efficacy of the greenhouse effect, especially as water vapor readily precipitated out of the air with dropping temperature.^[4] This caused an icehouse effect and, possibly compounded by the low solar irradiation at the time as well as reduced geothermal activities, the combination of increasing free oxygen (which causes oxidative damage to organic compounds) and climatic stresses likely caused an extinction event, the first and longest lasting in the Earth's history, which wiped out most of the anaerobe-dominated microbial mats both on the Earth's surface and in shallow seas.^[5][6]

Discovery and name

In 1907, Arthur Philemon Coleman first inferred a "lower Huronian ice age"^[7][8] from analysis of a geological formation near Lake Huron in Ontario. In his honour, the lower (glacial) member of the Gowganda Formation is referred to as the Coleman member. These rocks have been studied in detail by numerous geologists and are considered to represent the type example of a Paleoproterozoic glaciation.^[9][10]

The confusion of the terms glaciation and ice age has led to the more recent impression that the entire time period represents a single glacial event.^[11] The term Huronian is used to describe a lithostratigraphic supergroup and should not be used to describe glacial cycles, according to The North American Stratigraphic Code, which defines the proper naming of geologic physical and chrono units.^[12] Diachronic or geochronometric units should be used.

Geology and climate

The Gowganda Formation (2.3 Gya) contains "the most widespread and most convincing glaciogenic deposits of this era", according to Eyles and Young. In North America, similar-age deposits are exposed in Michigan, the Medicine Bow Mountains, Wyoming, Chibougamau, Quebec, and central Nunavut. Globally, they occur in the Griquatown Basin of South Africa, as well as India and Australia.^[13]

The tectonic setting was one of a rifting continental margin. New continental crust would have resulted in chemical weathering. This weathering would pull CO₂ out of the atmosphere, cooling the planet through the reduction in greenhouse effect.^{[citation needed]}

Popular perception is that one or more of the glaciations may have been snowball Earth events, when all or most of Earth's surface was covered in ice.^[11][14][15] However the palaeomagnetic evidence that suggests ice sheets were present at low latitudes is contested,^[16][17] and the glacial sediments (diamictites) are discontinuous, alternating with carbonate and other sedimentary rocks, indicating temperate climates, providing scant evidence for global glaciation.

Implications

Before the Huronian Ice Age, most organisms were anaerobic, relying on chemosynthesis and retinal-based anoxygenic photosynthesis for production of biological energy and biocompounds. But around this time, cyanobacteria evolved porphyrin-based oxygenic photosynthesis, which produced dioxygen as a waste product. At first, most of this oxygen was dissolved in the ocean and afterwards absorbed through the reduction by surface ferrous compounds, atmospheric methane and hydrogen sulfide. However, as the cyanobacterial photosynthesis continued, the cumulative oxygen oversaturated the reductive reservoir of the Earth's surface^[11] and spilt out as free oxygen that "polluted" the atmosphere, leading to a permanent change to the atmospheric chemistry known as the Great Oxygenation Event.

The once-reducing atmosphere, now an oxidizing one, was highly reactive and toxic to the anaerobic biosphere. Further more, atmospheric methane was depleted by oxygen and reduced to trace gas levels, and replaced by much less powerful greenhouse gases such as carbon dioxide and water vapor, the latter of which was also readily precipitated out of the air at low temperatures. Earth's surface temperature dropped significantly, partly because of the reduced greenhouse effect and partly because solar luminosity and/or geothermal activities were also lower at that time,^[6] leading to an icehouse Earth.

After the combined impact of oxidization and climate change devastated the anaerobic biosphere (then likely dominated by archaeal microbial mats), aerobic organisms capable of oxygen respiration were able to proliferate rapidly and exploit the ecological niches vacated by anaerobes in most environments. The surviving anaerobe colonies were forced to adapt a symbiotic living among aerobes, with the anaerobes contributing the organic materials that aerobes needed, and the aerobes consuming and "detoxing" the surrounding of oxygen molecules lethal to the anaerobes. This might have also caused some anaerobic archaea to begin invaginating their cell membranes into endomembranes in order to shield and protect the cytoplasmic nucleic acids, allowing endosymbiosis with aerobic eubacteria (which eventually became ATP-producing mitochondria), and this symbiogenesis contributed to the evolution of eukaryotic organisms during the Proterozoic.^{[citation needed]}

See also

• Timeline of glaciation

References

1. Tang, Haoshu; Chen, Yanjing (1 September 2013). "Global glaciations and atmospheric change at ca. 2.3 Ga". Geoscience Frontiers. 4 (5): 583–596. Bibcode:2013GeoFr...4..583T. doi:10.1016/j.gsf.2013.02.003.
2. Young, Grant M; Long, Darrel G.F; Fedo, Christopher M; Nesbitt, H.Wayne (June 2001). "Paleoproterozoic Huronian basin: product of a Wilson cycle punctuated by glaciations and a meteorite impact". Sedimentary Geology. 141–142: 233–254. Bibcode:2001SedG..141..233Y. doi:10.1016/S0037-0738(01)00076-8.
3. Bekker, Andrey (2020), "Huronian Glaciation", in Gargaud, Muriel; Irvine, William M.; Amils, Ricardo; Claeys, Philippe (eds.), Encyclopedia of Astrobiology, Berlin, Heidelberg: Springer, pp. 1–9, doi:10.1007/978-3-642-27833-4_742-5, ISBN 978-3-642-27833-4, S2CID 245528915, retrieved 16 March 2022
4. EPA.gov page "Understanding Global Warming Potentials"
5. "Geologists uncover ancient mass extinction from 2 billion years ago". 5 September 2019.
6. Plait, Phil (28 July 2014). "When a Species Poisons an Entire Planet". Slate Magazine. Retrieved 16 March 2022.
7. Coleman, A. P. (1 March 1907). "A lower Huronian ice age". American Journal of Science. s4-23 (135): 187–192. Bibcode:1907AmJS...23..187C. doi:10.2475/ajs.s4-23.135.187. ISSN 0002-9599.
8. Bekker, Andrey (2014). "Huronian Glaciation". Encyclopedia of Astrobiology. pp. 1–8. doi:10.1007/978-3-642-27833-4_742-4. ISBN 978-3-642-27833-4.
9. Young, Grant M. (April 1970). "An extensive early proterozoic glaciation in North America?". Palaeogeography, Palaeoclimatology, Palaeoecology. 7 (2): 85–101. Bibcode:1970PPP.....7...85Y. doi:10.1016/0031-0182(70)90070-2.
10. Nesbitt, H. W.; Young, G. M. (October 1982). "Early Proterozoic climates and plate motions inferred from major element chemistry of lutites". Nature. 299 (5885): 715–717. Bibcode:1982Natur.299..715N. doi:10.1038/299715a0. ISSN 0028-0836. S2CID 4339149.
11. Kopp, Robert (14 June 2005). "The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis". PNAS. 102 (32): 11131–6. Bibcode:2005PNAS..10211131K. doi:10.1073/pnas.0504878102. PMC 1183582. PMID 16061801.
12. "NORTH AMERICAN STRATIGRAPHIC CODE: North American Commission on Stratigraphic Nomenclature" (PDF). AAPG Bulletin. 89 (11): 1547–1591. November 2005. doi:10.1306/07050504129. ISSN 0149-1423.
13. Eyles, Nicholas; Young, Grant (1994). Deynoux, M.; Miller, J.M.G.; Domack, E.W.; Eyles, N.; Fairchild, I.J.; Young, G.M. (eds.). Geodynamic controls on glaciation in Earth history, in Earth's Glacial Record. Cambridge: Cambridge University Press. pp. 3–5. ISBN 978-0-521-54803-8.
14. Rasmussen, Birger; et al. (5 November 2013). "Correlation of Paleoproterozoic glaciations based on U–Pb zircon ages for tuff beds in the Transvaal and Huronian Supergroups". Earth and Planetary Science Letters. 382: 173–180. Bibcode:2013E&PSL.382..173R. doi:10.1016/j.epsl.2013.08.037.
15. Kurucz, Sophie; et al. (October 2021). "Earth's first snowball event: Evidence from the early Paleoproterozoic Huronian Supergroup". Precambrian Research. 365: 106408. Bibcode:2021PreR..36506408K. doi:10.1016/j.precamres.2021.106408. S2CID 244217078.
16. Williams, George E.; Schmidt, Phillip W. (2 December 1997). "Paleomagnetism of the Paleoproterozoic Gowganda and Lorrain formations, Ontario: low paleolatitude for Huronian glaciation". Earth and Planetary Science Letters. 153 (3): 157–169. Bibcode:1997E&PSL.153..157W. doi:10.1016/S0012-821X(97)00181-7. ISSN 0012-821X.
17. Kopp, Robert E.; Kirschvink, Joseph L.; Hilburn, Isaac A.; Nash, Cody Z. (9 August 2005). "The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis". Proceedings of the National Academy of Sciences. 102 (32): 11131–11136. Bibcode:2005PNAS..10211131K. doi:10.1073/pnas.0504878102. ISSN 0027-8424. PMC 1183582. PMID 16061801.