Glendonites after the end Permian mass extinction

Observer

15-05-2025

The end of Permian mass extinction occurred 251.9 million years ago, marking the close of a geological period known as Permian. This extinction event is known as the greatest mass extinction recorded in the Earth's history. It is often called the Great Dying - an event when life was on the brink of vanishing, stranding few survivors stumbling both on land and in the ocean. Scientists believe this extinction event was triggered by an enormous volcanic eruption known as the Siberian Traps Large Igneous Province. The volcanic eruption emitted massive amounts of greenhouse gases into the atmosphere, warming the planet drastically and leading to substantial environmental changes that had a profound impact on life.
Our recent field-based research has explored marine carbonate rock exposures dating back to this extinction event in the vicinity of the Qurayat area, Oman, and revealed the occurrence of unusual clusters of calcite aggregates that look like glendonites.
Glendonites are altered forms of carbonate crystals formed from another mineral called ikaite.
What is fascinating is that glendonites have never been reported from this specific time interval before, making our findings the first report. Normally, ikaite forms in near-freezing water conditions and is typically found in polar or nearby areas. However, the time of the extinction event was marked by extreme global warming, and the sediments we examined were laid down in warmer tropical conditions.
To us, this presents a fascinating puzzle about how these unusual calcite crystal aggregates ended up in such a warm environment during such extreme warming.
Musaab Al Sarmi
Scientists have few ideas about why glendonites might appear during warmer periods. One idea is that cold spells (short bursts of very cold weather) could have played a role. Another possibility is that upwelling (rising water from the ocean's depth) of very cold water or cold water masses coming from polar regions allows glendonites to form in unusual places.
Additionally, experiments in the lab have shown that ikaite crystals can form at much higher temperatures, as high as 35°C, which is far beyond its typical temperature for their formation when the water is very alkaline (with a pH above 9). This raises the question of whether one of these cases could explain why these carbonate crystal aggregates were found during the end of the Permian mass extinction.
It seems less likely that a short pulse of a very cold period contributed to the formation of identified carbonate crystal aggregates. This is supported by research on oxygen isotopes from conodont remains - ancient eel-like marine animals that lived in the ocean million years ago - which shows that the ancient temperature of surface seawater rose quickly back then.
However, through microscopic analysis of these calcite crystal aggregates, our study has shown that the ocean's conditions during that time were quite unusual. Seawater had a higher alkalinity level and a pH level above 9, meaning the ocean water was much more basic back then. This could mean that the calcite aggregates could have formed at higher temperatures, as shown in experiments. However, there is no evidence that glendonites can naturally form in highly alkaline water, and those made in the lab were formed under conditions that do not occur in nature. We also found evidence of the upwelling process indicated by fossil content. This suggests that unusual ocean chemical states, possibly along with the upwelling of very cold water, may have played a role in the formation of these intriguing carbonate crystal aggregates.
Overall, this research, along with many others, highlight how unusual ocean chemistry was during the End-Permian mass extinction, driven by extreme global warming, which critically impacted ocean life.