When T-REX – the massive road-widening project on Interstate 25 – was launched in 2001, Kirk Johnson was psyched.
The chief curator at the Denver Museum of Nature & Science was convinced that somewhere along I-25 at East Evans or East Yale avenues lies the dividing line between the world of dinosaurs and the world of more-modern species.
And he hoped that while the road was dug up, he might have a chance to find it.
But no such luck.
Known as the K-T boundary, the layer of ashy claystone that Johnson sought marks the end of the Cretaceous Period and the beginning of the Tertiary Period (the C was already taken by another epoch so the moniker became K-T).
“Broadway is in the Cretaceous and Lincoln Avenue is in the Tertiary,” Johnson said, based on what he’s found at other sites in the Denver basin.
“It would have been nice to find it on T-REX,” Johnson said of the thin, iridium-rich layer of debris spread worldwide 65.5 million years ago when a huge asteroid slammed in Mexico’s Yucatan Peninsula. Iridium is rare on Earth but more common in space rocks.
The asteroid collision is believed to have played a major role in the demise of dinosaurs. There are dinosaur footprints and fossils on one side of the layer. On the other side, all traces are gone.
The T-REX project moved so fast that paleontology was hard to do.
They uncovered and covered things so quickly “that we did only salvage,” Johnson said.
On one winter night under spotlights, Johnson and a crew crouched behind a concrete barrier and dug into a hillside at I-25 and Evans.
“It’s an area where there was a dip and a bend and it would have been dangerous to be there when there was traffic,” he said.
Nothing in the way of bones emerged, but fossil leaves were uncovered. “They are a little bit ambiguous, although they look Cretaceous,” Johnson said. “We didn’t get enough to know for sure.”
Though T-REX disappointed, Johnson and other scientists continue to add to Colorado’s rich store of paleontologic understanding.
To capture what those long-ago epochs may have resembled, Johnson and artist Jan Vriesen collaborated on the “Ancient Colorado” series.
The 8-by-10-foot paintings depict how various landscapes around Colorado might have looked like 30,000 to 300 million years ago.
The paintings are permanently displayed in the Colorado Convention Center.
Staff writer Ann Schrader can be reached at 303-278-3217 or aschrader@denverpost.com.
