Monday, 21 September 2020

Another Mass Extinction!

 Another Mass Extinction!

Mike Benton of Bristol University wrote THIS ARTICLE last week. So, rather belatedly, it appears here.

The extinction event was rather difficult to recognise. We knew of 5 such events - now we have 6. It happened 233million years ago, in the middle of the Triassic, and is called the Carnian Pluvial Episode (CPE) and seems to have killed off as many species as the asteroid at the end of the Cretaceous.

The ending of the tetrapods left a space which the dinosaurs filled for the next 165million years.

A timeline of mass extinction events. D. Bonadonna/MUSE, Trento, Author provided

The CPE was first noticed in Europe, to which, it was thought to be restricted. Then its time correlation with the eruption of the Wrangellia basalts was noticed. I had not noticed the concept of Wrangellia until now, but it seems to be one of the terranes welded onto the west coast of North America.

The Wrangellian eruptions led to acid rain - it is a Pluvial event! - which acidified the oceans and cleaned off the land surface. When the eruptions stopped so did the rain but temperatures remained high - dinosaur weather!

The effects in the oceans were great. Before the CPE carbonates in the oceans came from microbes. After it was coral reefs and plankton.

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