CHICO — A remarkably rich trove of fossilized animal and plant remains is undergoing evaluation and identification by a crew of Chico State paleontologists.
The site, whose specific location the scientists do not want to publicize to avoid having it picked over by collectors and others, sits in the Mokelumne River watershed southeast of Sacramento. What the Chico State researchers have found is impressive, according to Sean Nies, an instructional support technician in the university's Earth and Environmental Science Department.
It also provides materials for the Gateway Science Museum's current exhibit, "Fossils and Formations," open to the public through early June at 625 The Esplanade in Chico. The exhibit also has an unusual feature — a fossil lab, open from noon to 3 p.m. Fridays, where people can watch paleontologists in action. The public can also bring rocks and fossils to the lab, where paleontologists can answer questions and identify the specimens.
Nies, who graduated from Chico State in 2016 with a degree in geology, said the fossils they're finding southeast of Sacramento date from the Miocene epoch — approximately 8 million years ago. It was during this period that continental configurations and mountain topography made their transition toward modern conditions, and animal and plant life began to evolve into forms recognizable today.
"It was a significant find," Nies explained. "The ranger/naturalist who discovered the site found petrified wood and bones."
Russell Shapiro, professor in the Earth Department at Chico State, along with Todd Green, department head, and Nies visited the site and began finding other fragments, skulls, teeth, and more, Nies recalled.
"The site has an impressive diversity of animals," he said. "We've found two or three different species of horses, camels and rhinos, along with mastodons (ancient ancestral elephants), tortoises, turtles, pronghorn (a type of deer with pincer-like horns), and a few small rodent bones. There was also a large fish fossil.
"What made the site impressive is that it's widespread and hasn't been studied," Nies said. "It's a more diverse ecosystem we're finding."
Nies said the sites help the scientists "get an idea of the paleological history, where we can start to suss out ecology and what it was at the time and how it was changing compared to other parts of California. This shows us the evolution of California."
What makes this site more scientifically valuable than, say, a site just a few miles away with no fossil deposits?
"A lot of it has to do with the type of deposit it is," Nies explained. "This deposit came from debris flows and riverbeds. It took place during the leveling out of the Sierra Nevada. There was vulcanism taking place.
"As those were traveling through the steeper canyons of foothills, it picked up animals that had already perished," he said. "Then it flooded out, leveled out and settled — really, the end of a paleochannel, where everything settles out. There was sediment from water and the bones got buried in a way that allows them to fossilize."
The museum exhibit features items discovered within a three-hour radius of Chico. "It shows how we use paleontology to show how our area developed during other geological times," Nies said.
For museum visitors, it provides an interactive way to see the methods scientists use when evaluating fossils.
"The community can see us prepping fossils. We identify them and then put them on display," Nies explained. "There's nothing else locally where people can see this process."
Gateway Science Museum is open 11 a.m. to 4 p.m. Thursdays through Saturdays. Adult admission is $7 with youths getting in for $5 each. Chico State and Butte College students can visit at no charge, as can people with Gateway memberships.