Brian Hynek Green stromatolites bloom at the bottom of a lagoon in Atacama Plateau, ArgentinaBrian Hynek
In the Atacama Plateau, an arid region of northern Argentina that is part of the Andean highlands, an ecosystem composed of lagoons and salt flats could offer a window into Earth’s distant past. In fieldwork carried out in 2022, geophysicist Brian Hynek of the University of Colorado Boulder, USA, noticed a greenish hue on the bed of the lagoons, beneath the crystal-clear water. At the bottom of these water bodies, he identified complex microbial communities that form giant mounds of rock as they grow, in a process similar to how corals form a reef, millimeter by millimeter. The technical name for this type of formation is a stromatolite. Nowadays, it is not uncommon to find stromatolites in salt flats. But despite being relatively modern, those found in Atacama are different to their more current counterparts and look more like fossil stromatolites from billions of years ago. Today’s stromatolites tend to be small. Those in the lagoons of the Atacama Plateau, however, are up to 4.5 meters (m) wide and tall, like older fossil stromatolites. “We think these mounds are actually growing from the microbes, which is what was happening in the oldest ones,” said Hynek, who presented the results of his fieldwork at the annual meeting of the American Geophysical Union in December last year (University of Colorado Newsletter, December 6, 2023).
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