Tertiary Leaves and Insects of the Green River Formation

Eocene fossils are found in abundance along an ancient lake shore extending throughout western Colorado, eastern Utah and Southwest Wyoming.  Carbon impression fossils of insects, leaves, flowers and seeds are preserved in exquisite detail within mudstone layers of the Green River formation. Lake Uinta existed about 50 million years ago during a period when the climate was warm and subtropical.  Much of the carbon remains bound in shale layers as petroleum fluids and is extracted as gas and oil for energy consumption.  The fossils shown here were collected by us at sites near Douglas Pass in Garfield County, Colorado.