From Mexico City, at the 60th annual meeting of the Society of Vertebrate Paleontology
While wildfires raced out of control across much of the western United States this summer, evidence of a blaze that occurred about 74 million years ago was coming to light in the Bighorn Basin of central Wyoming.
During 10 days of fieldwork this August, Marilyn D. Wegweiser, a geologist at Ball State University in Muncie, Ind., collected numerous remains from a 1-centimeter-thick layer of ash that appears in outcrops and sediments of the area. Walking along a mile of the layer, she filled two medium-size canvas bags with fossils that included fragments of large bones and scraps of petrified wood.
About one-third of the bones and most of the fossilized wood showed distinct signs of having burned, she says. Also, the thick layer of sediment atop the ash contained charred, petrified logs up to 3 feet thick, which had burned in the fire and fell later.
According to forensic analysts, the pattern and type of color changes in the bones indicate there was meat on them when they burned, which suggests the animals died either during the wildfire or just before, Wegweiser says.
The small size of the fragments—none of which was more than an inch across—indicate that an extended, hot, bone-consuming conflagration swept across a mature forest chock full of fuel—and of large animals. “There were small pieces of bone every 50 or 60 feet along the outcrop for more than a mile, but there wasn’t much left of any single animal,” she notes.
During future field research in the area, Wegweiser plans to look for more outcrops of ash so she can better determine the extent of the fire. She’ll also look for fossil teeth that might help identify what type of animals died in the blaze.
In the meantime, she intends to use her samples of petrified wood to identify the trees that populated this particular forest. At the time of the wildfire, central Wyoming was a coastal lowland covered with sequoia, sassafras, fig, and other trees.