Study: Deadly volcanic eruptions led to twin mass extinctions about 260 million years ago

For this study, the team measured uranium from marine samples collected in the South China Sea. From this, the experts were able able to identify "two pulses" in which the oceans lost their life-giving oxygen. This corresponds to two mass extinctions, one approximately 259 million years ago and another approximately 262 million years ago during the Middle Permian Period.

The researchers highlight that studying ancient extinction events can help them predict the impact of global warming on the ocean's food chain.

"We are studying the biocrisis in the Permian Period, but similar warming is happening today because of human events. Humans are mimicking the effects of volcanic eruptions as a consequence of the release of carbon into the atmosphere,” said Thomas Algeo, a study co-author and University of Cincinnati professor of geosciences, in a statement. 

These massive volcanic eruptions set off a chain of reactions. The event led to a “brief period of cooling from ash in the upper atmosphere reflecting sunlight, followed by much longer periods of global warming,” explains the statement. 

The greenhouse gases emitted by their eruptions heated the oceans. As a result, the warm surface water prevented dissolved oxygen from reaching deeper depths, eventually destroying the food chain of the animals back then.

The results have been published in the journal Earth and Planetary Science Letters. 

Study Abstract:

The timing and causation of the Capitanian (late Middle Permian) biocrisis remain controversial. Here, a detailed uranium-isotopic (238 U) profile was generated for the mid-Capitanian to lower Wuchiapingian of the Penglaitan section (the Guadalupian/Lopingian Permian global stratotype) in South China for the purpose of investigating relationships between the biocrisis and coeval oceanic anoxic events (OAEs). Negative 238 U excursions indicate two distinct OAEs, a mid-Capitanian (OAE-C1) and an end-Capitanian (OAE-C2) event. Mass balance modeling shows that the anoxic sink of uranium (Fanox; i.e., the fraction of the total U burial flux) and anoxic seafloor area (Farea; i.e., the fraction of total seafloor area) increased during each OAE. A dynamic mass balance model yields increases of Fanox from <30% to >60% and Farea from ∼1% to ∼4-7% during each OAE. These two OAEs coincided with two extinction episodes during the Capitanian biocrisis, supporting a causal relationship between oceanic anoxia and mass extinction during the Middle Permian. The most likely driver of middle to late Capitanian global warming and oceanic anoxia was episodic magmatism of the Emeishan Large Igneous Province.