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Green River Fossil Hunting - Fossilera Adventures


Eocene Fish

Kemmerer, WY Forecast

Article written by: Jayson Kowinsky -


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Fossil Lake Safari by FossilEra Adventures - Kemmerer, Wyoming

Dig for world famous fish fossils on a Fossil Lake Safari in the Green River Formation with FossilEra Adventures!

FossilEra, one of the highest quality and largest online fossil retailers, now has a fossil quarry in the Green River formation of Wyoming! At FossilEra Adventures you can dig and find your own world famous Green River fossils. Fossil digs include Full day, Half day, 2 Hour, and Exclusive options.

Green River fosisl hunting

Green River fossil hunting

Geology and Paleontology of the Green River Formation

The Green River Formation, situated predominantly in Wyoming but also extending into parts of Colorado and Utah, is renowned as one of the world's most significant fossil formations. Dating back to the Eocene Epoch, approximately 56 to 34 million years ago, the Green River Formation represents a time when lush forests and extensive connected lakes and rivers covered much of the landscape in what is now the western United States.

One of the most remarkable aspects of the Green River Formation is its exceptional fossil preservation. The fine-grained sedimentary rocks of the formation, particularly its limestone layers, have yielded an extraordinary array of exquisitely preserved fossils, including plants, insects, fish, reptiles, birds, and mammals that lived in a sub-tropical environment.

This exceptional preservation is attributed to the rapid burial of organisms in anoxic (oxygen-deprived) conditions at the bottom of the ancient lakes, which inhibited decay and scavenging, allowing delicate structures to be remarkably well-preserved. Even soft tissues and remains of animals' last meals are often preserved. Things that are rarely preserved in other fossil deposits.

The Fossils


The most celebrated fossils of the Green River are its remarkably detailed fish preserved in the lake environments. There is a staggering diversity of fish fossils to be found, with hundreds of different taxa identified to date. These include small minnows, large predatory fish, and even freshwater stingrays. Well known fish genera found in the formation include Knightia, Diplomystus, Phareodus, Mioplosus, and Priscacara.

Green River fish with Mioplosus and Knightia

Green River Fish: Mioplosus and Knightia.


The Green River Formation is not only renowned for its exceptional preservation of fish fossils but also for its diverse array of other fossilized organisms, including insects, vertebrates, and plants. Within the fine-grained sedimentary layers of the formation, a wealth of insect fossils has been discovered, ranging from beetles and dragonflies to various fly species.

A fossil insect - a fly of the Diptera order. from the Eocene Green River Formation.

A fossil fly of the Diptera order. from the Eocene Green River Formation.


In addition to insects, the Green River Formation also has a rich assortment of vertebrate fossils, including early mammals, birds, reptiles, and amphibians. Some examples include freshwater turtles, crocodiles, and incredibly rare early horses!

Extremely rare Early Horse (Protorohippus sp.) from the Eocene Green River Formation.

Extremely rare Early Horse (Protorohippus sp.) from the Eocene Green River Formation. (Public Domain - National Park Service)


Plants that grew in this sub-tropical environment are also found preserved in the lake sediments. Most plants are preserved as individual leaves or branches. Well known plant fossils include huge palm fronds, and stems with leaves and flowers still preserved!

Palm Frond from the Green River Formation

Palm Frond from the Green River Formation (Public Domain - National Park Service)

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The Green River formation is centered near Kemmerer, Wyoming. FossilEra Adventures is about 30 minutes north-west of Kemmerer. The closest airport is Salt Lake City in Utah, which is about a 2.5 hour drive from the quarry.

The Digs:

FossilEra Adventures offers a wide array of digs, from full day, half day, 2 hour, to exclusive tours. The quarry is open from Spring to Fall 7 days a week.

You are also provided with the fossil tools to split the fine grained limestones and experts are present to help you out and identify your finds. Best of all, you can keep what you find! Be prepared to ship home lots of Eocene fish!

Pre-Booking is not required, but recommended during the busy season.

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