Getting to the Core of the Triassic

For almost two weeks, University of Utah paleontologist Randall Irmis has been pulling all-nighters to watch a drill. The job isn’t as laid back as you might think. Among the purple and red hills of Arizona’s Petrified Forest National Park, a diamond-studded drill is gradually cutting through millions of years of ancient rock, aiming for a depth of 1,700 feet below the surface. Irmis is part of the multi-institution science team collecting the cores as they are hoisted up. The Colorado Plateau Coring Project drill doesn’t stop. “Drilling occurs twenty four hours a day, seven days a week,” Irmis says, with drillers and the science teams split into two shifts.

“I’m on the night shift, so it can get pretty chilly,” Irmis says. Not like there’s much time to sit still and feel the cold. “A length of core comes up every twenty to thirty minutes,” he says, “and then we have to be ready to process it, which can take anywhere from ten to thirty minutes itself.” The details of the core being drawn up are immediately logged in an online database, but there’s more than scientific bookkeeping to worry about. “We also have to ensure that certain tools and equipment are kept clean,” Irmis says, “and that we’re ready to work with the drillers on any challenges that might present themselves.”

The nocturnal schedule can be grueling. But Irmis, his scientific colleagues, and the drillers are continually cutting through the national park’s rock for what the recovered cores can show researchers about a critical time in the history of life on Earth. Triassic secrets await.

Spanning 250 to 200 million years ago, the Triassic Period was a pivot point in life’s evolutionary tale. The early part of the Triassic documents the global recovery from the worst mass extinction the Earth has ever seen, while the middle and later parts record  a flourishing of organisms just before another mass extinction further altered evolutionary history. On land, this was a time when crocodile cousins ruled, early dinosaurs were marginal parts of the ecosystems they inhabited, and our own protomammal relations were just a shadow of the dominant group of vertebrates they were during the Permian. This was a strange time, but, with the benefit of hindsight, one in which we can perceive the foundations of today’s evolutionary diversity.

But there’s more to the story than fossils alone. Even though bones get most of the attention, geological context is an essential to understanding the story of prehistoric organisms. Gaining proper geologic dates, for example, is critical to determining when particular species lived, the speed of evolutionary change, and turnovers in prehistoric ecology. Petrified Forest is an ideal spot to look for answers – the park preserves a wonderfully complete stack of middle and late Triassic strata that the coring team is cutting ever-deeper into. “The core we are recovering, ” Irmis says, “allows us to develop a very high-resolution temporal and environmental context within which we can begin to interpret the changes in Triassic ecosystems that we observe in the fossil record.”

The first step is actually getting the rock out. “We are using the same drilling system that might be used in exploration geology,” Irmis says, called a truck-mounted wireline drilling system. It’s tubes within tubes. Mounted on the end of a long, hollow pipe, a hollow, diamond-studded drill bites into the rock. In this particular case, the core is going through at a 30 degree angle rather than straight down. This creates a five foot long cylindrical core of Triassic rock that is stored in a smaller pipe. When the drill cuts out enough for a new sample, a wire raises the core up to the surface independently of the rest of the apparatus. Pretty handy if you don’t want to pause drilling every half hour.

On the night shift, Irmis and his colleagues rush to take notes on each new core and cap them in their plastic storage liners. These are just the basic details, though. The cores have quite a bit of traveling ahead. First stop – University of Texas, Austin for CT scans of each core. “After that,” Irmis says, “they will travel to the University of Minnesota’s LacCore facility where the cores will be split in half lengthwise, digitally photographed at high resolution, and analyzed quantitatively for color and other characteristics.” Half those split cores will stay there, while the other will go to another lab at Rutgers University for additional analysis. Together, this cooperative effort will pull different clues from the samples. While some researchers will look at geochemical data, others will try to get good Uranium-Lead dates to refine the Triassic timeline and still others will extract fossil plant spores to reconstruct how environments changed through time. That’s just to start. If you know the right questions to ask, the earth can speak volumes.

From this focused, dedicated effort, the cores will allow researchers to get at some major questions about the Triassic. Among the ancient puzzles, Irmis says, are the speed at which Triassic ecosystems changed, how fluctuations in atmospheric carbon dioxide altered environments, what Triassic habitats of western North America shared in common with those elsewhere around the world at the same time, and perhaps what caused the “abrupt change in plant and animal species around 215 million years ago”, near the end of the Triassic. These are big picture mysteries that can’t be answered by the remains of Triassic organisms alone. Details drawn from stone will allow researchers to assemble an unprecedented view on the Triassic.

As of Friday morning, when I received an email update from Irmis, the drill had reached just over 900 feet in depth. That’s a bit more than halfway down. Days of drilling lay ahead, each section raising older and older possibilities of understanding what life was like at a critical time so far distant from our own. “Even though the work is exhausting and sometimes monotonous,” Irmis says, “it’s super exciting because you see something new with each core section that’s brought up. The excitement is just like seeing a fossil for the first time – you can’t wait to see what secrets might be revealed by the new core.”

To learn more about the Colorado Plateau Coring Project, see their official expedition log and their Facebook page. The project is funded by the National Science Foundation and International Continental Drilling Program. Irmis would also like to thank co-PIs  Paul Olsen (Columbia University), John Geissman (University of Texas-Dallas), Dennis Kent (Rutgers University), Roland Mundil (Berkeley Geochronology Center), and George Gehrels (University of Arizona).

Alexandra Witze has also written about this project for Nature News.