Did a big impact in Australia end a super ice age 2 billion years ago?

[lpetrich]

• An Impact-Driven End to ‘Snowball Earth’?
• New research finds Earth’s oldest asteroid strike linked to ‘big thaw’ - News and Events | Curtin University, Perth, Western Australia
• Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognised meteorite impact structure | Nature Communications - journal article
•  Huronian glaciation

From Centauri Dreams:

The oldest preserved impact structure on Earth appears to be at Yarrabubba in Western Australia, where a magnetic anomaly about 20 kilometers in diameter has been interpreted to be a remnant of an original impact crater 70 kilometers across. Here, what had been an approximate age of 2.65 to 1.075 billion years has now been constrained to 2.229 billion years, making Yarrabubba 200 million years older than the next oldest impact.

From the Nature paper:

The oldest record of impacts on Earth are Archaean to Palaeoproterozoic ejecta deposits found within the Kaapvaal craton of southern Africa and the Pilbara Craton in Western Australia, spanning ca. 3470 (ref. 6) to 2460 Ma7; however, no corresponding impact craters have been identified. Currently only two precisely dated Precambrian-age impact structures are known, the 2023 ± 4 Ma, >250 km Vredefort Dome in South Africa8,9, and the 1850 ± 1 Ma, >200 km Sudbury structure in Canada10. Other purported Palaeoproterozoic-age impact structures have either poorly constrained ages11 or highly contentious impact evidence12,13.

The Yarrabubba impact was dated by doing uranium-lead radiometric dating on shock-recrystallized bits ("neoblasts") of zircon and monazite crystals.

 

[lpetrich]

The Yarrabubba impact's age, 2229 ± 5 Ma, is about the time of the end of the Huronian glaciation, which started about 2.5 billion years ago.

The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis | PNAS

The oldest known midlatitude glaciation is the Pongola one, at 2.9 Gya, billion years ago.

There were three Huronian glaciations, from 2.45 Gya to a little over 2.2 Gya, and after those events the Makganyene snowball-Earth glaciation, which ended at 2.2 Gya -- the time of the Yarrabubba impact.

The Makganyene snowball was likely provoked by the release of enough atmospheric oxygen to destroy the atmosphere's methane, thus reducing the Earth's atmosphere's greenhouse effect, thus provoking the formation of that snowball.

The Yarrabubba impact could have ended that snowball by putting a lot of water vapor into the air. It would then have acted as a greenhouse gas, heating up the atmosphere and melting the snowball ice.

 

[Treedbear]

• An Impact-Driven End to ‘Snowball Earth’?
• New research finds Earth’s oldest asteroid strike linked to ‘big thaw’ - News and Events | Curtin University, Perth, Western Australia
• Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognised meteorite impact structure | Nature Communications - journal article
•  Huronian glaciation

From Centauri Dreams:

The oldest preserved impact structure on Earth appears to be at Yarrabubba in Western Australia, where a magnetic anomaly about 20 kilometers in diameter has been interpreted to be a remnant of an original impact crater 70 kilometers across. Here, what had been an approximate age of 2.65 to 1.075 billion years has now been constrained to 2.229 billion years, making Yarrabubba 200 million years older than the next oldest impact.

From the Nature paper:

The oldest record of impacts on Earth are Archaean to Palaeoproterozoic ejecta deposits found within the Kaapvaal craton of southern Africa and the Pilbara Craton in Western Australia, spanning ca. 3470 (ref. 6) to 2460 Ma7; however, no corresponding impact craters have been identified. Currently only two precisely dated Precambrian-age impact structures are known, the 2023 ± 4 Ma, >250 km Vredefort Dome in South Africa8,9, and the 1850 ± 1 Ma, >200 km Sudbury structure in Canada10. Other purported Palaeoproterozoic-age impact structures have either poorly constrained ages11 or highly contentious impact evidence12,13.

The Yarrabubba impact was dated by doing uranium-lead radiometric dating on shock-recrystallized bits ("neoblasts") of zircon and monazite crystals.

Coincidently the Carolina bays in SW Australia seem to align perfectly with the impact site.