Wyoming Rockhounding: Fishing the Fossil Lake! Green River Formation, Kemmerer, WY
Hey friends! Welcome back to Rock Talk with Angel.
I'm so excited to tell you about our most recent rockhounding trip, and what ended up being one of our favorite trips for rocks or fossils in our entire mining journey thus far.
If you, like me, grew up in the Jurassic Park era, your younger self surely fantasized about life as a paleontologist. Brushing dust from the bones of ancient creatures beyond your wildest dreams, in exotic locations, while studying and making new discoveries about long-dead life. No? Just me?? Paleontology has held a fascination for me all my life, and my dreams of paleontology finally started to come true: we finally took a trip to the bucket-list and awe-inspiring Green River Formation quarries in Kemmerer, Wyoming. If you enjoy fossils and rockhounding, this is a MUST VISIT spot. If you're anywhere near this area and it's digging season (approx. May-September, weather depending), PLEASE do yourself a favor and work in a visit to the quarries.
Our trip began at the Kemmerer Fossil & Mineral Expo, a small yet fascinating local gem show in Kemmerer, Wyoming. We were recommended by friends to join this show as a vendor, and it was a worthy show to explore! The show itself was filled with unique minerals and fossils from around the world. My favorites were the Hell Creek formation T-Rex teeth and Triceratops brow horn. Holding a t-rex tooth made dino-loving heart beat a whole lot faster! I'm already looking forward to next year's show.
The longer drive from Colorado to Kemmerer made this show a bit of a jaunt for us, but it also gave us the perfect excuse to work in a rockhounding adventure after our work was done. (Our trip to American Fossil Quarry was arranged by the Kemmerer show promoter, Keely Brook Sweeney--thanks Keely!) American Fossil is one of several quarries that operate in the Fossil Lake, Wyoming's most fossil rich zone and arguably the most famous section of the world-famous Green River Formation which covers parts of Colorado, Utah, and Wyoming.
History of the Green River Formation:
About 50 million years ago, the 25,000 square mile Green River formation was a series of three subtropical inland lakes, existing for a span of around 2 million years. After the catastrophic mass extinction at the end of the Cretaceous period, the end of the dinosaurs and most other life forms on earth, the Eocene epoch marked the recovery and rise of the remaining life on the planet. Birds and mammals thrived, and the Green River area was an ideal habitat for these as well as fish, reptiles, insects, and plants.
The climate of the Kemmerer area is dusty and dry today, but during the Eocene, it resembled modern-day Florida, creating the perfect environment for life. The creatures inhabiting the great inland lakes were amazingly diverse: many species of fish, including ancestors of freshwater herrings and perch, stingrays, gars, and paddlefish, swam here. Also in attendance were crocodiles, turtles, palms, bats, birds, insects, and even a miniature sized 3 toed horse! This ecosystem was even attended by one of the earliest primate species. Unlike many other famous fossil localities, the creatures of the Green River formation all lived during the same approximate period, rather than being separated by vast spans of geologic time.
In the lake itself, anoxic layers spelled death for the unfortunate souls that wandered there. Whole schools of fish could be trapped forever in the oxygen-depleted zones, never to reemerge. But the lack of oxygen that doomed the lake's victims also protected their remains from decay and scavenging, and allowed calcium carbonate to be deposited from the surrounding hills, preserving the many life forms of the Green River Formation in an amazing "fossil lake". The fossil lake remains today, providing us a snapshot of the early Eocene unlike anywhere else in the world.
American Fossil Quarry
There are several quarries closely packed into the hillsides around Kemmerer, and our visit took us to American Fossil. American Fossil is dominated by the "split fish layer", which is filled to the brim with fish fossils of all sizes and species, as well as rarities. A unique aspect of this quarry is the allowance for visitors to keep any fossils they find, even rarities up to $100,000 in value! This gives visitors the opportunity to find (and keep, sell, or donate) something truly special, truly unusual, in addition to the more common fossils that pack the layers of the quarry. American Fossil staff members are on-site to provide help and identification, and assistance with tricky fossil extractions. After digging, on-site tile saws allow guests over 18 years of age to trim and begin prep on their treasures. In my opinion, American Fossil has a wonderful set-up for guests, and streamlined the experience greatly! Helpful advice and assistance from staff made this novice feel like a seasoned fossil hunter in little to no time.
When we arrived to dig with our group of fellow vendors, the American Fossil staff gave us a quick yet thorough introduction, provided tools, and let us explore the available areas. There are 3 major zones here: the main area of rock carried from the wall and deposited by heavy machinery, the area of softest and easiest to split cast-off rocks from previous hunters, and the area of harder rocks for more intrepid hunters. Unlike much rockhounding, and with the exception of the hard rock zone, power and strength is no real advantage here. The trick to finding the fossils lies in careful splitting of the rocks into finer and finer slices, with a careful hand and watchful eyes for any sign of fossils within. A careful strike from hammer to thin chisel opens the rock layers as if it were a huge book, revealing the fossils preserved between its pages. Hit it too hard or in the wrong zone, and anything you would have found is either damaged beyond repair or hidden forever in an invisible layer. A little practice goes a long way in this environment, and we practiced in all 3 zones to start to learn how to hunt here. Before long, we were gleefully collecting the bony remains of Knightia Eocaena and other common Green River fish. "Fishing the Fossil Lake", as we heard it called. Fish fossils of all varieties were abundant, though finding an intact fish in good condition was a prize among the many partials.
The Last Rock of the Day
If you've read my account of previous rockhounding trips, you may know that my husband Keith can have an almost supernatural sense for rockhounding. What appears to be good luck, is also a day that starts at opening time and ends at closing time, careful practice, VERY hard work, research done ahead of time...and of course, good luck! As this particular day pressed on and folks headed home after a long weekend of work, we continued to dig, piling our treasures on the provided shelves to be trimmed at day's end. The day was near its end and we were eventually the last ones digging at the quarry, trying for a few more fish as the guests still in attendance trimmed their finds. True to form, Keith decided to split one last large rock to finish out the day...to our delight, 3 good sized fish stood out along its smooth face! He also noticed an imprint in the rock next to it, but wrote it off as only a feature of the rock itself (as a previous piece had proven to be upon inspection.) American Fossil staff had recommended we call for help cutting down larger slabs to prevent damage, so we called for help to trim the slab down and liberate the fishy trio. Cooper came to assist but immediately froze, taking a careful look at the slab.
After a gentle laugh, he said "It's a good thing you called me over to help...there's a stingray in this slab!"
He carefully outlined the subtle shape of a stingray which now stood out in relief, perfectly positioned in the center of the slab and the matching negative imprint of the next layer. Excitedly (and with no lack of surreality), we gathered friends and other staff to take a look at the find. Sure enough, not only was the stingray there in the rock, but the American Fossil crew suggested we have the entire slab prepped as a scenic display, with the stingray flanked by the fish and the natural edge preserved. We were a bit overwhelmed, and more so, our tiny rental car was already packed with both our own inventory and the smaller fossils we had already found. We were certainly out of our element (like fish out of water?) trying to navigate the unexpected adventure of preserving a rare, and very large, fossil specimen!
Luckily for us, we had the perfect crew on hand to help us proceed with the next steps! Keely, the Kemmerer show promoter, also happens to professionally prep fossils--she has a reputation among the vendors and locals for being one of the best at this detailed and highly specialized work. We were relieved to hire her on the spot to preserve and prepare the specimen! While the exact species and condition of the stingray will be unknown until it's dry enough to start exploratory prep, the experts suggested that the stingray appears to be quite large and likely well-preserved. While hiding under the rock may have made its appearance a bit anti-climactic, the protective layer of rock protecting the fossil will probably make it a much better preserved fossil in the long run. Certainly the final find of the day greatly exceeded any expectation we could have, and we're so grateful to Keely and her husband, as well as Cooper and the American Fossil crew, for all of their help and expertise.
At the end of the day, this trip was a dream come true long before our end-of-the-day find. We were fortunate enough to be able to come out, live the paleontology dream, and dig with old friends and new. While we're learning the basics of fossil prep to work on the fish we found, Keely will be starting professional work on the stingray, and I'll definitely be keeping you updated on how it's all shaping up!
Thanks for tuning in to Rock Talk! Follow the blog for more modern lore and history of the gems we love, as well as a firsthand perspective on some classic rockhounding localities around the US. Catch us on Facebook, Instagram, and Tiktok @phenomenalgems for more of our adventures, and to check out more of our finds! Rock on, my friends!