Report a correction
The Green River lakes
The Green River Formation is the deposit of three great lakes that covered parts of Wyoming, Utah and Colorado in the Eocene. The annual layers, varves, make Green River one of the few places where geological time can be counted directly rather than estimated. The fauna documents a subtropical North America: crocodiles in Wyoming, palms in Colorado. The formation also holds the world's largest known oil shale deposit, which for a century has been declared the energy source of the future at intervals without extraction ever proving economic.
Factual errors are corrected without argument once documented. What you send is read by a person and checked against sources — nothing changes automatically. See the editorial policy.