Plant Fossils from Green River Formation

Description: During the Eocene, a lake complex covered some 50,000 square miles of land in Colorado, Wyoming, and Utah. This complex resulted in some of the most impressive lacustrine fossil deposits famed throughout the world as the Green River Formation. While the preservation of fauna in the form of fish and insects is quite impressive, an extensive variety of plant material was preserved as well, with over 150 genera represented. While many taxa characteristic of much of the Northern Hemisphere have been found are indicative of a land link with both Europe and Asia, some 30% of the genera are endemic to the region. The climate appears to have been more subtropical than at present, much more like the Gulf Coast region of today. There are also woodland forms, such as hackberry, sycamore and sumac as well as lakeside forms like willow and cottonwood to be found as well, providing clues to the diverse environments to be found within this extensive region.