LOGAN — Utah State University geologists are exploring some of the smallest and oldest fossils to find out what happened to life on Earth 740 million years ago, when bacteria was apparently rampant across the planet.

More than a dozen USU scientists are in Denver this week, presenting research at the Geological Society of America's annual meeting. Among their research is evidence of Bavlinella, a bacteria that depleted the world of oxygen, and killed off early plant and animal life, found in fine-grained mudstone of eastern Utah's Uinta Mountains.

"Similar evidence found in the rock record in other areas of the world implies some sort of global phenomenon rather than a localized event," USU doctoral student Dawn Hayes said. She said Bavlinella is similar to Cyanobacteria, a modern blue-green algae that thrives in both fresh water and marine environments.

The geologists say evidence of more complex life, and a "distinct biotic change," exists at the Uinta Mountains site.

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Hayes and faculty mentor Carol Dehler's findings, when combined with discoveries from the Grand Canyon, suggest that widespread die-offs occurred before an intense ice age purportedly spanned the globe. According to a theory known as "Snowball Earth," glaciers encased the planet and led to the demise of early plant and animal life.

"We think something much earlier led to anoxia — lack of oxygen — and caused a ripple effect, enabling bacteria to flourish, further deplete the planet's oceans of oxygen and kill off other species," Dehler said.

— Wendy Leonard