CODY, Wyo. — As the planet enters a new phase of climate change, scientists in two countries are working with core samples drilled in Wyoming to understand what caused a pattern of runaway warming, sometimes called the “fever period,” 56 million years ago.
For reasons unknown, during the transition between the Paleocene and Eocene epochs, a sudden surge of carbon dioxide into the atmosphere prompted an extreme version of global warming, producing droughts and floods, widespread species extinctions and a redistribution of planetary life.
Whatever caused the mass release of C02 remains a mystery. Scientists wonder if it could happen again, and if the human release of C02, now estimated at 300 billion tons over the last two centuries, could help trigger another period of runaway warming.
“Obviously, today, we’re undergoing our own experiment with climate change and the release of carbon via fossil fuels and greenhouse gases,” said Will Clyde of the University of New Hampshire, who heads the Bighorn Basin Coring Project. “We still don’t know where this carbon came from in the past. We’re missing an understanding on the long-term carbon cycle of the earth.”
Clyde and a team of 27 scientists from several universities in the United States and Germany believe that answers may lie in the red and tan soils of Wyoming’s Bighorn Basin, a large swath of semi-desert east of Yellowstone National Park.
An inland sea turned steamy savannah turned desert, the region is rich in unweathered strata dating back to the Paleocene-Eocene Thermal Maximum — a period of intense warming that occurred 56 million years ago.
The material scattered across the basin may reveal past temperature shifts, carbon cycling and pollen and soil changes that took place during the PETM. It could provide further evidence that C02 levels are a driver of climate change.
“To get a pristine geochemical sampling, we want fresh material that hasn’t been exposed to the elements on the surface,” said Clyde. “The basin has that. We’ll look in detail at how this terrestrial system changed during these hyperthermals (warming events), and get more clues on the source of the carbon.”
Last summer, the team drilled a series of cores to depths of 500 feet. They worked on the Polecat Bench north of Powell, at Gilmore Hill east of Cody and at a site near Basin.
The rock samples arrived intact at the Bremen Core Repository in Germany. In a first-of-its kind study, scientists from across the country will converge at the center this month, including Scott Wing, a paleobotanist from the Smithsonian National Museum of Natural History.
“We know the PETM was about 180,000 years long, and that it took place about 56 million years ago,” said Wing. “I expect the data from the cores to help us improve our ability to recognize environmental and ecological changes that took place during the PETM.”
Wing specializes in fossil plants — leaves in particular — and studies past global warming episodes. While many hypotheses have been posed over what caused the sudden surge in carbon during the PETM, he said, evidence proving any one of them has been hard to come by.
What is known is that temperatures rose on average around 9 degrees Fahrenheit during the PETM. Before the event, Wing said, the Bighorn Basin was home to palm, redwood, sycamore and katsura trees. The ground underfoot was as wet as a Louisiana swamp, inhabited by cousins to the alligator and other reptiles.
But as temperatures climbed, the region grew dry and the canopy of trees opened up. New plant species moved north and the soils dried out. Iron began to oxidize, leaving the red striations seen today across the Bighorn Basin.
The basin’s geological history makes it perfect for the study, and the core samples taken last summer are rich in possibility. If the cores were a movie, Wing said, they would reveal more frames per second than samples taken anywhere else in the world.
“We can sample the rocks in the cores at fine intervals — every few inches if we want,” Wing said. “Small vertical distances translate into small time differences. A rock column we sample every foot means there is, on average, about one sample for every 1,000 years, since a foot of rock equals roughly 1,000 years of deposition.”
The cores are narrow in diameter and Wing doesn’t expect to find any plant or mammal fossils contained within them.
Rather, he’s looking for chemicals and microfossils, such as pollen and spores from plants. He also expects to find pieces of waxy cuticle covering ancient leaves and bits of fossilized charcoal.
“The microfossils will tell us something about what kind of plants were living in the Bighorn Basin during the PETM,” Wing said. “The chemical fossils help with that, too, but we also hope they will give us information on temperature, fire frequency, and possibly the pH of the soils at the time.”
While scientists aren’t sure what caused the warming event, they have a growing understanding of its far-reaching consequences.
Clyde said the dramatic change in climate killed most single-cell life in the world’s oceans. Mammals present at the time dispersed across land bridges in northern latitudes.
“We see a major turnover in mammal assemblages and new immigrants coming in,” Clyde said. “Even before we discovered the event, we knew about this mammal change.”
Near the PETM, he said, scientists have recorded the first appearance of primates in the fossil record. They’ve also noted the arrival of early horses, known as hyracotheriums, and doacodexis, a hoofed mammal related to today’s deer.
“Every place we’ve found it, it’s the same pattern,” said Clyde. “For a lot of us, that’s what got us interested. There’s a clear link between climate change and mammalian dispersal.”
The study, funded by the National Science Foundation, includes the Bureau of Land Management, the Smithsonian, the Royal Netherlands Institute for Sea Research and the Denver Museum of Nature and Science.
The universities of Michigan, New Hampshire, Wyoming, Colorado and Birmingham are involved, along with Purdue, Penn State and ExxonMobil Co.
Results may be available this spring, when the scientific team begins to summarize their findings in research papers.
Contact Martin Kidston at email@example.com or 307-527-7250.