Tectonic processes could have triggered past mass extinctions, said PSI Senior Scientist John Goodge, a co-author of a new paper showing a tectonic trigger to the first Paleozoic extinction event on Earth, based on geological and paleontological relationships in Antarctica and Australia.
“First, plausible explanations for a known extinction event were lacking, made particularly puzzling because it took place during a time of general biotic expansion, and second, there are few examples where tectonic processes appear to be the trigger – neither exogenic nor purely environmental causes that are commonly called on to explain extinction events. The coincidence of events in both Antarctica and Australia is remarkable,” said Goodge, coauthor of “Tectonic trigger to the first major extinction of the Phanerozoic: The early Cambrian Sinsk event” that appears in Science Advances. Paul M. Myrow is lead author.
The so-called Cambrian ‘explosion’ is arguably the most dramatic expansion of species in Earth history. The Cambrian is the first period in the Paleozoic era, between the end of the Precambrian eon and the beginning of the Ordovician period, lasting from about 540-485 million years ago. This is when the first representatives of our modern animal phyla appear in the fossil record (including our line with backbones) and larger multicellular organisms with hard body parts began to flourish (such as the first trilobites and brachiopods).
“Despite the success stories, there were some setbacks, including the extinction event we cite called the Sinsk event, which is known from fossil occurrences in Russia. As with other prominent extinctions – like the dramatic loss of dinosaurs and the earlier ‘mother of mass extinctions’ at the end of the Permian when approximately 90% of marine species were lost – there is a lot of debate about causation,” Goodge said.
Common explanations include bolide impacts, hothouse/icehouse fluctuations, and environmental degradation or catastrophe (such as atmospheric change due to volcanism, or seawater changes such as loss of oxygen). So some can be rapid or more gradual changes. In this case, the authors suggest that it was plate tectonics that triggered a major upset in the marine environment (first whammy) that was then exacerbated by follow-on changes in atmosphere and seawater composition (second whammy) that sealed the deal.
“This was a tremendously fun paper to write and illustrates how important Antarctica’s geology is to understanding global problems,” Goodge said.