Rhus nigricans (Sumac)

The Green River Formation is one of the largest deposits of lacustrine sedimentary rock in the world. The formation was created by three ancient lakes during the Eocene. These lakes covered approximately 25,000 square miles in portions of three states – Wyoming, Utah and Colorado. During the early to middle Eocene, the climate was subtropical in this area much like the southern Atlantic and Gulf Coast states.

The fossil collecting community knows the incredible fauna produced from Fossil Lake which is exposed in the Kemmerer area of SW Wyoming as it is the “fossil fish capital of the world” and the home of Fossil Butte National Monument. Lake Unita was to the south and stretched from eastern Utah to western Colorado. Lake Uinta is known for its plant and insect fossils.

The Green River Formation holds one of the world’s richest deposits of fossil leaves, plants, vines, seeds, and aquatic vegetation. More than 70 species have been identified including sycamore, popular, oak, maple, willow, pine, walnut, rose, tea, hackberry, pea, soapberry, ferns, etc. The preservation is exceptional with excellent color. Small commercial quarries were open in the Cowboy Canyon, Bonanza, Utah and Douglas Pass, Colorado, and supplies appear to be exhausted. I obtained a large collection of these leaves and insects, and these leaves will come with a custom wooden stand and identification label to proudly display these exquisite specimens as shown below.