The deposition of Trona in Wyoming started about 50-60 million years ago during the Eocene Age in the Wilkins Peak Member of the Green River Formation. A large freshwater lake, Lake Gosiute, covered an estimated 15,000 square miles in a basin in southwestern Wyoming. The lake was fairly shallow, and it evaporated rapidly and repeatedly. Therefore, the climate would change back and forth between arid and humid, trapping the once abundant life. All the minerals and mud settled in the bottom of the lake. Sodium, alkaline and bicarbonate were transported to the lake by runoff water. It is believed the sodium came from the volcanoes in northwestern Wyoming. The mixture of all these elements formed the trona deposits we mine today.
For millions of years, the climate in southwestern would change from wet to dry. The wet periods would wash mud into the lake that would cover a trona bed. The dry periods would create trona beds. This is the reason we now have numerous beds of trona, marlstone, oil shale, and sandstone that can be found in areas as deep as 3,500 feet. · In Wyoming, large deposits of Trona are found in the Green River formation. There are 42 beds of Trona that cover about 1,300 square miles. Approximately eleven of these seams are at least six feet in thickness, and 25 of them exceed 3 feet thick. · The most common bed for Trona mining, bed 17, is 1,600 feet deep. Amazingly, the bed is 12 feet thick and is of very high quality. soda ash derived from trona. Current challenges to the industry include a slump in export demand due to the Asian economic slump, and new competition for the export market, particularly from China.
