An eMTB exploration of Onion Creek...

was huge fun, especially because of the interesting geology exposed along the way. Read more here:

GEOSIGHTS: THE ONION CREEK SALT DIAPIR, GRAND COUNTY.

Although the sky looks threatening, it was a pleasant and warm day for riding the 10 mile-long road with 1,600 feet of elevation gain. This panoramic image caught where Onion Creek is incising through sandstone beds of the Cutler Formation. (Click image to enlarge.)

Stinking Spring emerging from the gypsum caprock of the Paradox Formation (Pennsylvanian) that constitutes the body of the salt diapir. Note the white bacteria in the spring water.

Stinking Spring emerging from the gypsum caprock of the Paradox Formation (Pennsylvanian) that constitutes the body of the salt diapir. Note the white bacteria in the spring water.

Filamentous sulfur-reducing bacteria living in the discharge of appropriately-named Stinking Spring.

Filamentous sulfur-reducing bacteria living in the discharge of appropriately-named Stinking Spring.

At the head of Onion Creek looking north across the olive-colored gypsum caprock of the Paradox Formation diapir. Red beds in near-right foreground are part of the Cutler Formation (Permian).

At the head of Onion Creek looking north across the olive-colored gypsum caprock of the Paradox Formation diapir. Red beds in near-right foreground are part of the Cutler Formation (Permian).