There have been five known major extinctions in the last 540 million years. The most important of these occurred at the end of the Permian geological period, about 252 million years ago, and caused the disappearance of many marine (about 80%) and terrestrial (about 75%). Today it is established that this biological crisis is mainly associated with the release of greenhouse gases as a result of large volcanic eruptions. Their remnants represent in modern Siberia (Russia) huge plateaus of volcanic rocks, called traps, with an area 13 times larger than the area of metropolitan France. These greenhouse gas emissions then caused a global rise in temperature, which led to a drop in oxygen levels in the oceans and acidification. However, the exact timing of this extinction is still being debated. As part of this discussion, a group of paleontologists published an article on September 6, 2022 in the journal Paleontology that examines the evolution of ocean temperatures before and after the peak of the extinction crisis.
Small crustaceans to determine past temperatures
Paleontologists decided to study ostracods, small shell-like crustaceans, to study past temperatures. They were collected in the Araks Valley (Iran) in rocks dated exactly at the time of the crisis, about 252 million years ago, with an interval of about 300,000 years. From 163 ostracods, the researchers wanted to know the concentration of different types of oxygen atoms, its isotopes, in ostracod shells using a technique called secondary ion mass spectrometry. Indeed, the concentration of these oxygen isotopes in shells depends on the temperature of the organisms’ habitat. The obtained results made it possible to obtain new elements about the time of the crisis and the degree of temperature increase.
Disaster scenario: 12°C slow warming
Similar previous studies have already been carried out on fossils from the Caucasus or China.