USU Geologist Challenges Views on Earth's 'Snowball Effect'
Thursday, Jun. 04, 2009
View of USU geologist Carol Dehler's study site in the Chuar Group in Grand Canyon. Dehler and her colleagues’ findings challenge long-held views on the effects of "Snowball Earth" glaciations. Photo by Carol Dehler.
Research by Dehler, assistant professor in USU's Geology Department, is featured in the June, 2009, issue of Nature Geoscience.
Peering into Grand Canyon’s ancient rock record, Utah State University geologist Carol Dehler and colleagues are investigating microfossils that challenge long-held views of the effects of “Snowball Earth” glaciations on life millions of years ago.
“The Snowball Earth hypothesis emerged during the 20th century and suggests that Earth was a giant snowball in the sky,” said Dehler, assistant professor in USU’s Geology Department.
According to Snowball Earth theory, the planet underwent an intense ice age between about 750 and 600 million years ago. Glaciers purportedly spanned the globe which, many scientists believe, caused widespread die-offs of plant and animal life. Dehler and colleagues offer an alternative reason for the demise of Earth’s early life.
In a paper published in the June 2009 issue of Nature Geoscience, Dehler, who served as a co-author on the article with scientists from the University of California Santa Barbara and the University of Quebec, suggests that die-offs, driven by the effects of massive levels of organic matter in surface waters, occurred some 16 million or more years before ice nearly enshrouded the planet.
With funding from the National Science Foundation and support from the National Park Service, the authors braved searing heat, rattlesnakes and scorpions to explore a Grand Canyon location called the Chuar Group, which houses, according to the article, “one of the premier archives of mid-Neoproterozoic time.”
Seeking microscopic fossils called “acritarchs,” the scientists noted that the tiny traces of life were present in the lower rocks of the Chuar Group but not in the higher strata. Instead, the geologists found evidence of bacterial blooms, which suggest eutrophication. The process occurs today in Utah waters — including the Great Salt Lake — that receive fertilizer-infused runoff from farming, industrial and residential areas.
“One or a few species of phytoplankton monopolized nutrients at the expense of others,” said co-author Susannah Porter of UCSB when explaining the die-off process of acritarchs. “In addition, the algal blooms resulted in high levels of organic matter production, which we see evidence of in the high organic carbon content in upper Chuar Group rocks.”
Porter said that, as a result of high levels of organic matter, oxygen levels in the water were likely depleted and resulted in widespread “dead zones.”
Dehler joined USU’s Geology Department faculty in 2004. Her research interests include sedimentology and stratigraphy integrated with field mapping, geochemistry and paleontology,
Precambrian geology, regional tectonics and paleoclimate. Her recent endeavors include basin analysis and stable-isotope geochemistry of Meso- and Neoproterozoic strata in North America, basin analysis of Great Basin Devonian strata and related vertebrate evolution in central Idaho, field mapping and aquifer characterization of Permian reefs and K/T boundary in New Mexico and sourcing stone raw materials from Paleo-Indian sites in Colorado.