At that time, most life was concentrated in the oceans. They were rich in fantastic creatures such as armored trilobites, meter-long shrimps and giant spiny worms.

cause of extinction

For many years, the prevailing view was that this sudden extinction was caused mainly by a sharp decrease in oxygen content. One theory is that this event was triggered by a sudden burst of Cambrian life that covered the seafloor with decaying organic material. In addition, a large number of animals and plants died and decomposed, absorbing a large amount of oxygen from the water, which did not have time to restore it.

But a study recently published in the journal Geophysical Research Letters shows that: The death wave may have been caused by the release of hydrogen sulfide, a chemical gas that suffocates marine life.

This chemical is lethal to all marine animals. No animal can survive for long in such an environment.
says study co-author Chao Chang, a geochemist at Northwestern University in Xi’an, China.

The keys to this extinction are found in the Cambrian geological formation of the Yangtze Platform, a vast once-submerged plateau in southern China. The conclusion was made based on the molybdenum content: it is durable, and its concentration in sediments varies depending on the chemical composition of the surrounding water.

Samples taken from the mass extinction period contained high levels of molybdenum. This suggests that the water may contain hydrogen sulfide because molybdenum can “combine with sulfur to form insoluble compounds and then settle in sediments,” Chang said. This happens much faster in sulphide waters than in normal waters, “especially when the concentration of hydrogen sulfide is high.” In other words, higher molybdenum concentrations may be associated with more hydrogen sulfide in the sea.

What triggered this toxic spread?

At this stage, no one can say exactly what causes the expansion of sulfur waters, but there is a hypothesis. As the microbes fed on the decaying material, they also absorbed naturally occurring sulfate in seawater. During this process, the growing population of microbes can convert sulfates into a byproduct called hydrogen sulfide. It also filled the water, causing a poisonous wave.

Although the researchers only took samples from what is now China, they believe this toxic spread occurred on a global scale. Scientists say such studies help inform the limits of suitability for life on Earth.