Cecil filter feeders, such as the Carboniferous chronoid, the mushroom chronoid (Agricrocrinus americanus), were significantly less abundant after the Permian-Triassic extinction. Credit: Vasil – Alias Collection, CC BY-SA 3.0
The new study provides an extensive reconstruction of the Permian-Triassic boundary event.
Life on Earth has a long, but very turbulent history. On more than one occasion, all species became extinct and the already highly developed biodiversity shrunk again to a minimum, each time changing the course of evolution. Very widespread mass extinctions occurred about 252 million years ago. It marks the end of the Permian age and its beginning Triassic Era. About three-quarters of all land life and about 95 percent of life at sea disappeared in just a few thousand years.
Massive volcanic activity in today’s Siberia and the release of large amounts of methane from the ocean floor have long been discussed as a potential trigger for the Permian-Triassic extinction. But the true cause and sequence of events that led to the mass extinction remained highly controversial. Now, scientists from Germany, Italy and Canada, in the framework of the project BASE-LiNE Earth funded by the EU, in collaboration with the Helmholtz Center Potsdam GFZ German Research Center GMOR Helmholtz Center for Ocean Research. D Ant. For geosians, for the first time cutting edge-analytic techniques and innovative physico-chemical modeling have been able to definitively recreate the entire cascade of events at that time. The study is published today (October 19, 2020) in an international journal Nature Geoscience is a monthly peer-reviewed scientific journal published by Nature Publishing Group, covering all aspects of Earth science, including theoretical research, modeling and fieldwork. Other related works are also published in fields including meteorology, geology, geology, meteorology, oceanography, paleontology and space science. It was established in January, 2008.
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For their study, the BASE-LiNE Earth team used a previously frequently overlooked environmental archive: the shells of fossilized brachiopods. “These are clam-like organisms that have existed on Earth for millions of millions of years. We were able to use well-preserved brochiopod fossils from the Southern Alps for our analysis. These shells were deposited 252 million years ago at the bottom of the shallow shelf of the Tethys Ocean and recorded environmental conditions shortly before and early extinction, ”explains Dr. Hanna Zurikova. He is the first author of the study, which he conducted as part of the Base-Line Earth Project and as part of his doctoral thesis at Geomer.
By measuring different isotopes of the element boron in fossil shells, the team will be able to detect the evolution of pH values in the ocean 252 million years ago. Since the pH of seawater is closely linked to the concentration of CO2 in the atmosphere, subsequent reconstruction was also possible. For the analysis, the team used high-precision isotope analysis at GAMAR as well as high-resolution micronalysis on a sophisticated large-geometry secondary ion mass spectrometer (SIMS) at GFZ.
“With the help of this technology, we can not only reconstruct the evolution of atmospheric CO2 concentrations, but also clearly detect them in volcanic activity. Dr. Marcus Gutzahr, co-author of the study, explains that the dissolution of methane hydrates, which was suggested as a possible further cause, is not very possible based on our data.
As a next step, the team fed their data from boron and additional carbon isotope-based probes into a computer-based geochemical model that simulated Earth processes at the time. The results showed that the warming and sea acidification associated with abundant volcanic CO2 injection into the atmosphere was already fatal and led to the extinction of marine calcifying organisms as soon as extinction began. However, the CO2 release brought even more results; With rising global temperatures due to the greenhouse effect, the chemical weather on the ground also increased.
Over the thousands of years, increasing amounts of nutrients reached the oceans through rivers and beaches, which then became overly fertile. The result was a massive depletion of oxygen and a change in the entire component cycle. “This domino-like collapse of interconnected survival cycles and processes eventually led to the observed catastrophe of mass extinction on the Permian-Triassic border,” said Dr. Zurikova summarizes.
The study was conducted within the framework of the EU-funded ITN project BASE-LiNE Earth, in which the use of brachiopods as an environmental archive was systematically studied for the first time, and relevant analytical methods were modified and newly developed. “Without these new technologies it would be difficult to reconstruct the processes of the environment 250 million years ago, in the same way that we have done in detail now,” said Prof. Dr .. and co-author of the new study, “In addition, new methods can be applied to other scientific applications.”
References: Hannah Zurikova, Marcus Gutzhar, Klaas v Wall Laman, Saska Flögel, Volker Libetrau, Renato Pozenato, Lucia Angiolini, we van Brandelin, Michael Nice Brandelin, Ant n Brand n Brainn થતીn, by Carr. Powered by Parterbations “, 19 October October 2020, Nature Geoscience.
DOI: 10.1038 / s41561-020-00646-4
