Knauth calls the work "isotope geology of carbonates 101."
In order to understand what happened on Earth such a long time ago, researchers have studied the isotopic composition of limestone that formed during that period. Researchers have long studied these rocks, but Knauth said many focused only on the carbon isotopes of Neoproterozoic limestones.
Knauth and Kennedy's study looked at a bigger picture.
"There are three atoms of oxygen for every atom of carbon in limestone," Knauth says. "We looked at the oxygen isotopes as well, which allowed us to see that the peculiar carbon isotope signature previously interpreted in terms of catastrophes was always associated with intrusions of coastal ground waters during the burial transformation of initial limestone muds into rock. It's the same as we see in limestones forming today."
Brave new world
By gathering all of these published measurements and carefully plotting carbon isotopic data against oxygen isotopic data, a process Knauth said took three years, the researchers began to formulate a very different type of scenario for what led to complex life on Earth. Rather than a world subject to periods of life-altering catastrophes, they began to see a world that first greened up with primitive plants.
"The greening of Earth made soils which sequestered carbon and allowed oxygen to rise and get dissolved into sea water," Knauth explained. "Early animals would have loved breathing it as they expanded throughout the ocean of this new world."
A key element to this scenario is not so much what the researchers saw in the data, but what was missing. When they plotted the data for various areas from which it was derived they kept noticing an area on the plots that contained little or no da
|Contact: Skip Derra|
Arizona State University