Evolution: timing the Triassic extinction (Introduction)

by David Turell , Monday, November 16, 2020, 22:26 (1466 days ago) @ David Turell

200 million years ago with volcanic activity:

https://cosmosmagazine.com/history/palaeontology/volcano-link-to-end-of-triassic-extinc...

"Two hundred million years ago, the Triassic period was brought to a devastating end by extensive volcanic eruptions from the Central Atlantic magmatic province (CAMP), which formed as Pangea broke apart. As carbon dioxide spewed into the atmosphere, the Earth’s carbon cycle was disrupted, and the oceans became acidified.

"Delicate marine ecosystems collapsed, and a sweep of prehistoric creatures such as conodonts and phytosaurs went extinct – though somehow, plants, dinosaurs, pterosaurs and mammals scraped through. This new world allowed dinosaurs to expand their ecological niche and reign supreme for the next 135 million years.

"Evidence for this end-Triassic extinction event comes from two major compositional shifts observed in the carbon isotope record 200 million years ago, as extensive volcanism could have released isotopically light methane into the atmosphere.

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“'Through our analysis of the chemical signature of these microbial mats, in addition to seeing sea-level change and water column freshening, we discovered the end-Triassic mass extinction occurred later than previously thought.”

"A drop in sea level in European basins – which may have been indirectly driven by volcanic activity on CAMP – caused localised environmental changes. The marine ecosystem became a brackish, shallow-water environment where microbial mats thrived.

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"It is currently unclear exactly how much later the extinction event occurred. Grice says their new interpretation requires further reanalysis of the carbon isotope record, in order to gain a better understanding of the regional versus global effects of the CAMP.

"This research may also reshape our understanding of other mass extinction events – particularly those linked to volcanic activity – and could alert us to future potential mass extinctions on modern Earth."

Comment: The big extinctions certainly allowed marked shifts in the course of evolution. It is obvious that tectonic plate activity played a major role and is a requirement for a planet to host life.