45-54.1 millon years ago...
The Colton Formation consists mostly of floodplain and channel sediments that are less resistant and more highly colored than the adjacent beds of the Flagstaff and Green River Formations. Its red, yellow, or brown, fine- to medium-grained, sandstones that are crossbedded distinguish the Colton Formation. In other places by its red, green, or purple, sandy mudrocks and shales that are poorly bedded. In some place by its limestone beds of variegated colors, that are generally less than 1 foot thick, tough, and poorly bedded. Lacustrine beds are bound to the Colton Formation and are characterized by the following features; pale grey, fine-grained sandstones that are not crossbedded. In other places its yellow-brown or gray, thin-bedded, tough shales that are interbedded with limestone and dolomite units. In places by its limestones and dolomites of several types that are two feet thick or more. From a thickness of 800 feet at South Maple Canyon, it thins to less that 550 feet at Wales Canyon, which most northerly portions have been removed by erosion.