California Park Ranger Discovers Massive Cache of Miocene Epoch Fossils
Paleontologists excavating a site in northern California have unearthed one of the largest and most astonishing collections of Miocene fossils ever discovered in the state. Dating to the Miocene Epoch, these 10-million-year-old remains include samples from a broad range of species, all of which have long been extinct.
Amazingly, this incredible site was found entirely by accident, reports SFGate.
Stumbling into a Lost Epoch
In the summer of 2020, a park ranger working for the East Bay Municipal Utility District stumbled across something completely unexpected. While walking near the Mokelumne River watershed southeast of Sacramento in the Sierra Nevada foothills, ranger Greg Francek spotted something hard and shiny half buried in the earth. He bent over to examine it more closely. After a short inspection, he realized it was something rare and remarkable.
"I happened upon a petrified tree," Francek said in a statement issued by EBMUD. "This tree was partially encased in the burial sediments, and because one end was exposed, I could actually see the tree rings inside." When wood is covered in fine-grained sediment, such as that deposited during floods or following volcanic eruptions, it is protected from decay. Over the course of millions of years, it will gradually turn to stone.
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Petrified tree uncovered by Greg Francek in Sierra Nevada foothills. (EBMUD)
Searching further, Francek found many more such specimens. He soon realized he was standing in the midst of an ancient petrified forest.
But that interesting discovery was only the tip of the iceberg.
Francek returned to the site near the watershed many times over the next few weeks, to continue his explorations. In among the petrified trees, which numbered in the hundreds, he was delighted to discover a wide range of vertebrate fossils.
Francek contacted numerous paleontologists and geologists, to inform them of what he’d found. Eventually, a small team of researchers organized by California State University-Chico Russell Shapiro arrived to examine the site. During an initial exploratory excavation, they were astonished to discover a beautifully preserved and fully intact mastodon skull, with the long tusks still attached.
A complete mastodon skull complete with teeth was found. (EBMUD)
Mastodons resembled short, thick elephants, although they were only distantly related to the evolutionary forerunners of the elephant species that survive in the modern era. These powerful creatures roamed North America in large numbers from the late Miocene (10 million years ago or so) until the end of the Pleistocene era (approximately 11,000 years ago, when North America’s glacial cover melted at the end of the last Ice Age).
"What you hope to find is a tip of a tusk," Shapiro told the student paper Chico State Today when discussing the find. "Not only do we have the tip, but we have the entire thing. And it's just beautiful ivory. It's mind-blowing."
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The mastodon’s tusks were found almost complete. (Jason Halley / Chico State Today)
A Landscape Full of Miocene Fossils
As exciting as this discovery was, it was only the beginning. Excavations at multiple spots near the watershed uncovered the fossilized remains from dozens of animals, all of which walked the Earth or swam in its waters during the Miocene Epoch.
The Cal State Chico team were astonished and delighted to find the spiny fossilized bones of a 400-pound monster proto-salmon, which would have inhabited the seacoast adjacent to the lands where the mastodon grazed. They also unearthed Miocene period fossils from ancient and gigantic versions of camels, horses, tapirs, rhinos, tortoises, and a long-extinct four-tusked elephant cousin known as the gomphothere.
Skeletal reconstruction of Gomphotherium productum. (Ryan Somma, CC BY-SA 2.0)
“The discovery is highly significant because of both the sheer number and diversity of specimens found,” the experts explained in the EBMUD statement. “Few other fossil discoveries like this exist in California. The bones paint a clearer picture of life 10 million years ago when animals evolved from living in forests to grassland as the landscape changed.”
The man responsible for discovering this remarkable treasure trove of fossilized artifacts marvels at how events have unfolded over the past year.
"I located the first vertebrate fossils," Greg Francek said. "What I didn't comprehend at the time was the amazing fact that I was looking at the bones of great beasts that had roamed this landscape millions of years ago."
10 Million Years’ Worth of Questions Waiting to Be Answered
This fossil discovery site will be fully protected under the auspices of the United States Paleontology Preservation Act. In the coming months, institutions from around the nation and the world will dispatch experts to contribute to the ongoing excavations and analysis of what has already been found.
“Researchers still have a lot of questions,” the EBMUD statement noted, acknowledging that the study of this massive Miocene fossil field is still in its early stages. “Like why are all these fossils in this location? How did they die? What happened and when? The study of this site may take years.”
The scientists know that the Miocene animal fossils and petrified trees may not have originated in the area where they were found. They could have been carried to their current location from somewhere inland, either during a huge flood or possibly by lava flow from an ancient volcanic eruption. This could have happened at the end of the last Ice Age, when flooding was common, or millions of years in the past, when the geography of the region was vastly different. The trees are believed to have been oak, and they would have been growing not far the edges of an ancient ocean. Some of the animals may have lived among the oaks, but others may have survived by grazing in more open areas.
The Mokelumne River watershed provides drinking water for more than 1.4 million people living in the Bay Area of northern California. It is now on the verge of providing new and exciting answers to paleontologists, natural historians, and other scientists who want to know what life was like on Earth in the unimaginably distant past.
Top image: Teeth from a mastodon skull unearthed in the foothills of the Sierra in California. Source: Jason Halley/California State University
By Nathan Falde