Green River Field Trip August 11-13, 2017

Lead by Dr. Ron Surdam-Retired Wy State Geologists

Wilmot H. Bradley left Yale and New Haven, Connecticut in 1920 and headed west to Wyoming to examine the economic potential of the oil shale deposits in the Green River Basin as an employee the USGS. He found a lot more than oil. He found an ancient lake that showed a clear connection between geologic sedimentation and the changing of Earth’s orbit providing evidence to support the recently proposed Milankovitch theory. Each year left a varve and the varves formed patterns.  He found numerous insect fossils and saline deposits (Trona). The Trona conceivably formed with help from the Absaroka volcanoes which were active at the same time as the formation of the lake. He wrote up his results and Yale gave him a Ph.D. for the effort. Bradley went on to become a significant geologist in the US but he never lost his interest in the Green River Basin.

The Milankovitch theory and the oil shale both had their marketing ups and downs but the Green River Basin continued to attract scientists and businesses. We have all seen the fish fossils from the Lagerstatte (earth treasure) and some of us have even gone down in the Trona mine. Ron Surdam went to the Green River Basin in the 1970’s to continue the exploration started by Bradley. Ron will show us fossil river deltas, the famous varves and the fossil lake Gosiute. A reminder that the world was full of drama long before we entered the scene. Ron used the knowledge he gained to explore many other parts of the world but eventually he came back to Wyoming to be the state geologist.

Trip Report

Photos show examples of fossils and sediments from the fossil lake.

Green River Sedimentary layers

Green River Sedimentary Layers


Green River Fish

Green River Fish