Tiny fossils yield big surprises at Florissant Fossil Beds
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- Created on Wednesday, 10 November 2010 07:00
- Written by Dave Philipps
By DAVE PHILIPPS, THE GAZETTE
The first sign visitors encounter at Florissant Fossil Beds National Monument steels them against disappointment. It reads, “Where are the fossils?”
Sure, the park boasts a small group of enormous, petrified redwood stumps. But beyond that, well …
“People are expecting big dinosaur bones,” said Jeff Wolin, a ranger at the monument just west of Pikes Peak in Teller County. “We don’t have that here. And a lot of what we do have, you can’t see. It’s hidden.”
That hidden ancient history — among the richest and most diverse collections of fossils on Earth — is what makes Florissant Fossil Beds both so challenging to enjoy and so hard to resist. It offers a glimpse into a lost world, but one that takes some deliberate imagining to bring into focus.
Fall and winter are a good time to try because the crowds disappear and a simplifying snow often covers the distracting present.
A good place to start on a recent visit was the cramped office of Herbert Meyer, a paleontologist who works for the monument. He’s a leading expert on the fossil beds.
It all started at the tail end of the Eocene epoch, a warm, lush time on Earth about 34.07 million years ago — give or take a few millennia.
“First you have to realize that the area did not look then like it does now,” Meyer said. “There was a large volcano to the west.”
Instead of a high, dry valley dotted with meadows and small ponderosa pines, the area was lush and fairly wet. A stream ran south along what is now Teller 1, and groves of giant redwoods, some reaching 25 stories into the sky, crowded the shore.
Above the highest reaches of the trees, the silhouette of the Guffey Volcano, rising thousands of feet above the surrounding forest, stood on the horizon.
Beneath the high evergreen canopy, the ancestors of modern laurels, birches, oaks, ginkgoes, hickories, poplars, elms and other geneses now lost to time crowded toward the light. Butterflies floated through the dappled light and spiders scuttled along the leaves.
Ferns and moss grew thick in the granite soil, disturbed by the movements of primitive rabbits and possums. A 3-foot-tall horse ancestor called mesohippus nibbled at the grass, and a beast bigger than a rhinoceros, called brontothere, browsed branches. The animals’ snouts sported a Y-shape bone protruding from the tip. And the forest may have echoed with the sound of 8-foot-tall male brontotheres butting heads.
All these details would almost certainly have been lost in time if not for the Guffey Volcano.
“It was a lot like Mount Saint Helens in Washington,” Meyer said. Sometimes it would periodically spew tons of ash and pumice. Sometimes lava and other debris would avalanche down the slopes into the forested valley of the monument.
One of these muddy flows created a dam across a stream flowing through the monument and formed a lake. The lake is the reason we know anything about what life in the forest 34.07 million years ago was like.
“Things fell into the lake, just like they would today,” Meyer said.
All kinds of things: butterflies, dragonflies, damselflies, bees, spiders, leaves, flowers, cones, branches, ants, beetles, clams, even a possum or two.
Then they sank to the bottom, where, once again, the volcano played a critical role.
Fine volcanic ash settled over the forest. A steady supply washed into the lake. Microscopic, single-celled algae called diatoms living in the lake feasted on the ash, causing regular algae booms and die-offs.
When the algae died, billions and billions of their skeletons drifted like fine powder through the water, gently covering everything on the lake bottom.
This delicate cycle continued, off and on, for about 5,000 years, until the lake eventually dried up. The result is a layer of shale that preserves, in almost unheard-of detail, untold thousands of fossils that, together, form a snapshot of life in the ancient forest.
“Each layer was literally paper thin,” Meyer said. “And the details preserved can be microscopic.”
A brush-footed butterfly not only has its tiny antennae preserved, even the pattern on its wings somehow is imprinted in the shale. It is such an exemplary specimen that, where it resides now, at Harvard University, it holds the honor of being the holotype — the example of a species with which all other fossils are compared.
In all, 1,700 fossil species have been unearthed from the ancient lake, making Florissant Fossil Beds one of the most diverse paleontological sites in the world.
The giant redwood stumps that catch most visitors’ eyes were preserved through a different process, when mud flows barreling down from the volcano buried the trees.
The problem with fossils, of course, is that they are hidden underground. You can’t see them until you dig them up.
And, historically, the scientists who dug up fossils in Florissant carted them away to museums. For the most part, only the redwood stumps, which were too large to move, remained. Unfortunately, the delicate process that preserved so many insects was not as good at fossilizing giant brontotheres (only bits and pieces have been found).
None of this makes Florissant Fossil Beds any less amazing, it just makes it less appealing as a tourist stop.
It’s still exciting for paleontologists, Meyer said. “Every time you split open a piece of shale, it is almost like scratching a lottery ticket. You never know when you are going to hit the jackpot.”
Each species helps fill in a critical chapter in the history of the Earth between the Eocene and Oligocene epochs, when the planet suddenly cooled dramatically.
“Florissant gives us important information about how species reacted to rapid climate change, which could be useful,” Meyer said.
Visitors can see park staff split shale in the monument’s fossil lab, which is open to the public sporadically throughout the winter, and might even catch the staff cracking open something amazing.
Beyond that, to really enjoy the secrets of the past at the fossil beds, visitors need a good imagination. Take time to linger over the fabulous — though small — fossils in the visitors center, then, with visions of a steamy ancient Eocene forest in mind, head out to walk the trails in the current epoch’s chilly air.
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