Ectasian

The Ectasian Period (from Ancient Greek: ἔκτασις, romanized: éktasis, meaning "extension") is the second geologic period in the Mesoproterozoic Era and lasted from 1400 Mya to 1200 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.

Geologically, the name refers to the continued expansion of platform covers during this period. In the early Ectasian period, a day was 17 hours and 32 minutes. At the end of the Ectasian, it was 18 hours and 28 minutes.

## Contents

* 1 Geology
* 2 Biology
* 3 Climate
* 4 See also
* 5 References
* 6 Further reading

## Geology

A possible configuration of continents in the supercontinent Columbia before breaking up.

The early Ectasian has the supercontinent Columbia intact until at least 1.35 Ga with rifting around the western side of Laurentia.[1] Columbia slowly destabilized until it fully broke up around 1.3-1.2 Ga at the mid to end Ectasian with multiple dyke swarms including the Mackenzie dike swarm at in Canada and the Galiwinku dyke swarm in Australia.[1][2] Evidence from metamafic rocks from 1.37 to 1.35 Ga suggests that a superplume formed around that time and affected 3 provinces, causing expansion and the breakup of Columbia.[3]

## Biology

The Dismal Lakes group ranging from 1590 to 1270 Mya hosts microfossils that are interpreted to be eukaryotes, with various species appearing in the grouping.[4]

Continued appearances of acritarchs are present in the Ectasian period with a moderate amount of eukaryotes.[5]

## Climate

The very beginning of the Ectasian had the end of the Mesoproterozoic Oxidation Event which lasted from 1.59 to 1.36 Ga, with estimations going up to 3.6% current levels of oxygen[6][7]. Besides this, the Ectasian had oxygen conditions typical of the Boring Billion, from 0.1% to 1% of current oxygen levels in most conditions.[8]

The seafloor during the Ectasian is around 50-80% oxidated at the beginning of the period and declined afterwards.[6] The ocean was mostly ferruginous in lower depths with a minority surface area being oxic and recurring euxinic conditions in mid-depth waters.[6]

The water temperature during the Mesoproterozoic is reported to be 26.9 ± 0.4 degrees Celsius with the water being lighter than the current ocean water.[9] Shallow seafloors may have "oxygen oases" by microbial mats oxygenating the seafloor, allowing aerobic organisms to survive.[10]

## See also

* Earth:Boring Billion - Earth history, 1.8 to 0.8 billion years ago
* Earth:Jotnian
* Earth:Riphean (stage)

## References

1. ↑ 1.0 1.1 Zhao, G.; Sun, M.; Wilde, S. A.; Li, S. (2004). "A Paleo-Mesoproterozoic supercontinent: assembly, growth and breakup". Earth-Science Reviews 67 (1): 91–123. doi:10.1016/j.earscirev.2004.02.003. Bibcode: 2004ESRv...67...91Z. https://www.gt-crust.ru/jour/article/download/518/355. Retrieved 14 February 2016.
2. ↑ Hou, Guiting; Santosh, M.; Qian, Xianglin; Lister, Gordon S.; Li, Jianghai (2008-10-01). "Tectonic constraints on 1.3-1.2 Ga final breakup of Columbia supercontinent from a giant radiating dyke swarm". Gondwana Research 14 (3): 561–566. doi:10.1016/j.gr.2008.03.005. ISSN 1342-937X. https://www.sciencedirect.com/science/article/pii/S1342937X08000749.
3. ↑ Lv, Pei; Yu, Shengyao; Peng, Yinbiao; Wang, Chunyu; Li, Sanzhong; Liu, Yongjiang; Gao, Xiangyu; Sun, Deyou et al. (2022-08-01). "A plume broke up Columbia supercontinent: Evidence from the Mesoproterozoic metamafic rocks in the Tarim Craton, NW China". Precambrian Research 377. doi:10.1016/j.precamres.2022.106719. ISSN 0301-9268. https://www.sciencedirect.com/science/article/pii/S0301926822001632.
4. ↑ Loron, Corentin C.; Halverson, Galen P.; Rainbird, Robert H.; Skulski, Thomas (July 2021). "Shale-hosted biota from the Dismal Lakes Group in Arctic Canada supports an early Mesoproterozoic diversification of eukaryotes". https://www.researchgate.net/publication/353087643_Shale-hosted_biota_from_the_Dismal_Lakes_Group_in_Arctic_Canada_supports_an_early_Mesoproterozoic_diversification_of_eukaryotes.
5. ↑ Knoll, Andrew H., Emmanuelle J. Javaux, David Hewitt, and Phoebe A. Cohen. 2006. Eukaryotic organisms in Proterozoic oceans. Philosophical Transactions\- Royal Society of London Series B Biological Sciences 361(1470): 1023-1038. https://doi.org/10.1098/rstb.2006.1843
6. ↑ 6.0 6.1 6.2 Yan, Hao; Qin, Zheng; Xu, Lingang; Mao, Jingwen; Tang, Dongjie; Huang, Qin; Yang, Xiuqing; Li, Zhiquan et al. (2025-11-26). "An expansive global oxygenation of Earth's surface environments 1.4 billion years ago" (in en). Nature Communications 16 (1): 10535. doi:10.1038/s41467-025-65551-z. ISSN 2041-1723. https://www.nature.com/articles/s41467-025-65551-z.
7. ↑ Zhang, Shuichang; Wang, Huajian; Wang, Xiaomei; Ye, Yuntao (25 October 2021). "The Mesoproterozoic Oxygenation Event". Science China Earth Sciences 64 (12): 2043–2068. doi:10.1007/s11430-020-9825-x. Bibcode: 2021ScChD..64.2043Z. https://link.springer.com/article/10.1007/s11430-020-9825-x?idp_error=cookies_not_supported&error=cookies_not_supported&code=d00a2df1-dd21-4c70-9125-9588afcda877. Retrieved 9 May 2023.
8. ↑ Planavsky, Noah J.; Cole, Devon B.; Isson, Terry T.; Reinhard, Christopher T.; Crockford, Peter W.; Sheldon, Nathan D.; Lyons, Timothy W. (9 August 2018). "A case for low atmospheric oxygen levels during Earth's middle history". Emerging Topics in Life Sciences 2 (2): 149–159. doi:10.1042/etls20170161. ISSN 2397-8554. PMID 32412619.
9. ↑ "Science" (in en). doi:10.1126/sciadv.adu6693. https://www.science.org/action/cookieAbsent.
10. ↑ Jia, Tianyi; Wang, Ruimin; Huang, Tianzheng; Lang, Xianguo; Ma, Haoran; Shen, Bing (2022-07-15). "Constraining the redox landscape of Mesoproterozoic mat grounds: A possible oxygen oasis in the 'Boring Billion' seafloor". Precambrian Research 376. doi:10.1016/j.precamres.2022.106681. ISSN 0301-9268. https://www.sciencedirect.com/science/article/pii/S0301926822001255.

## Further reading

* James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale". Lethaia 37 (2): 183–199. doi:10.1080/00241160410006492.

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kya = thousands years ago. Mya = millions years ago. Gya = billions years ago.
See also: Geologic time scale

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