"This study presents the first physical evidence that Snowball Earth reached the heart of continents at the equator," said Liam Courtney-Davies, the study's lead author and postdoctoral researcher in CU Boulder's Department of Geological Sciences.
The research, set to be published during the week of Nov. 11 in the *Proceedings of the National Academy of Sciences*, includes contributions from Rebecca Flowers, a CU Boulder geological sciences professor, as well as experts from Colorado College, and the Universities of California at Santa Barbara and Berkeley.
The study centered on Colorado's Front Range in the Rocky Mountains, where unique rock formations known as the Tavakaiv, or "Tava," sandstones hold crucial insights into this ice-laden epoch. The team employed a technique called laser ablation mass spectrometry to date the rocks, revealing that they had been buried beneath massive glaciers between approximately 690 and 660 million years ago.
Courtney-Davies noted that this research sheds light on a pivotal time in Earth's history that also coincides with the rise of multicellular life in oceans after the glacial thaw. "You have the climate evolving, and you have life evolving with it. All of these things happened during Snowball Earth upheaval," he said. "We have to better characterize this entire time period to understand how we and the planet evolved together."
The concept of "Snowball Earth" was first introduced by geologist Joseph Kirschvink in a 1992 paper. Yet, despite decades of investigation, the theory remains debated. Evidence of thick ice from this era has typically been found along ancient coastal regions, but proof within the interiors of continents near the equator has been scarce - until now.
Colorado's position during this period was notably different. Rather than occupying its current northern latitude, it lay over the equator within the ancient supercontinent Laurentia. If glaciers formed here, it would support the hypothesis that ice sheets could have spread globally.
The research team focused on the Tava sandstones, visible along Colorado's Front Range, including around Pikes Peak. These formations, appearing as vertical bands of yellow-brown rock, are known to geologists for their distinct characteristics. The team hypothesized that these sandstones were connected to ancient ice sheets and calculated the ages of mineral veins within them, using iron oxide-rich samples exposed to laser zapping to release uranium atoms. By measuring the decay of uranium to lead, the team accurately dated the rocks.
The findings confirmed that the Tava sandstone was buried during the Snowball Earth era, likely by glaciers pressing down on the surface, forcing the sands deeper into the bedrock.
"We're excited that we had the opportunity to unravel the story of the only Snowball Earth deposits that have so far been identified in Colorado," said Flowers.
The team aims to extend this research, suggesting that similar formations might be found elsewhere across North America. "We want to get the word out so that others try and find these features and help us build a more complete picture of Snowball Earth," added Courtney-Davies.
Research Report:Hematite U-Pb dating of Snowball Earth meltwater events
Related Links
University of Colorado at Boulder
Beyond the Ice Age
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