Bisnis.com, JAKARTA – The Cambrian Explosion about 541 million years ago was when life and organisms actually occurred on planet Earth.
Now new research has revealed how the explosion of life has left its mark deep within the earth.
For scientists, this indicates the interconnected interactions between the Earth’s surface and what lies beneath it, as sediments carrying organic matter are pushed underground over wide geological timescales through subduction.
Launching Science Alert, the new study looked at rare, diamond-filled volcanic rocks called kimberlites. When they’re pushed to the surface, they tell us what’s happening deep in the mantle, and researchers measured the carbon composition in 144 samples taken from 60 locations around the world.
The prevailing view among geologists is that the carbon trapped within diamonds does not vary much over large timescales of hundreds of millions of years.
But here the researchers found a shift in the ratio of specific carbon isotopes about 250 million years ago, about the time the sediments from the Cambrian Explosion would have folded into the mantle. This is a shift potentially caused by major changes in the carbon cycle during a time when the biosphere increased in mass and diversity.
“These observations suggest that biogeochemical processes at the Earth’s surface have a profound influence on the deep mantle, revealing an integral relationship between the deep and shallow carbon cycles,” the researchers wrote.
This relationship between the carbon cycles close to the surface and deeper underground is not easy to measure and has indeed changed significantly over the billions of years the Earth has existed, rather than been fixed.
It seems clear that dead creatures trapped in sediments found their way into the mantle via plate tectonics. Their carbon remains mixed with other materials before eventually reaching the surface again through events such as volcanic eruptions.
The link was confirmed by further observations of strontium and hafnium in the samples. They matched the carbon pattern, narrowing the number of possibilities for how the composition of these rocks was altered.
“This means that the signature for carbon cannot be explained by other processes such as degassing, because otherwise the strontium and hafnium isotopes would not correlate with carbon,” said geochemist Andrea Giuliani of ETH Zurich in Switzerland.
Technically, what we’re dealing with here is sediment subduction fluxes, and these details of the carbon cycle are important for realizing what’s happening on our planet especially as the effects of the climate crisis continue to be felt.
New studies continue to reveal more about how carbon is taken up from and released back into the atmosphere, particularly through the continuous recycling of the tectonic plates that make up the planet’s surface.
Scientists know that relatively small amounts of sediment were once pushed deep into the mantle via subduction zones, meaning the Cambrian Explosion trail must have taken a direct route into the mantle depths.
“This confirms that the subducted rock material in the Earth’s mantle is not homogeneously distributed, but moves along certain trajectories,” Giuliani said.
The research has been published in Science Advances.
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