Green River Formation
The Green River Formation contains the largest oil shale deposits in the world. The 213 billion tons of oil shale contain an estimated 2.38 × 10¹¹ m³ (1.5 trillion US barrels) of shale oil. This is a tribute to the high volume of organic material that was buried. The source of the organic material was probably cyanobacteria, which thrive in warm alkaline lake conditions.