Something really stinks...

at the appropriately named Stinking Spring on Onion Creek, Utah, where both hydrologic features sit directly upon the Onion Creek salt diapir. Here's an image of the spring where it joins the creek (click to enlarge), with the contorted beds of gypsum caprock of the Paradox Formation (Pennsylvanian) in the background:

Filamentous green sulfate-reducing bacteria thrive in the hyper-saline water and can be seen here upon close examination of the spring, and they are the source of the hydrogen sulfide gas that produces the strong rotten eggs smell: