Fantasy Canyon, UT
In October of 2008, I took a group of students to Fantasy Canyon, Utah. Fantasy Canyon is an area composed of unique erosional features located about 40 km south of Vernal, in northeastern Utah. Even though the area is somewhat small (10 acres and it is not really a canyon) it contains some of the most unique geologic features in the world.
With intricate rock formations, eroded by wind and rain over millions of years, the dramatic stone figures stand out from the many other rock formations in Utah’s eastern wilderness.
The stunning pinnacles, pillars, arches, and knobs that form Fantasy Canyon are formed from the sandstone layer formed from ancient river channel sediment deposits, (pictured below).
Pictured above, both the rock above and below the sandstone trapped the sandstone layer resulting in the classic badland topography found in and around the main Canyon.
During the Eocene Epoch, 55 to 34 million years ago, the Fantasy Canyon area was at the fringe of a vast subtropical lake – Lake Uinta – that at peak level stretched from the Wasatch Plateau to western Colorado.
Lake Uinta was in a drying phase and retreating westward by the end of the Eocene.
Rivers en route to the dwindling lake deposited sand, silt, and clay shed from nearby mountains.
Eventually more and more sediment was deposited in lake Uinta, and the once-loose sands, silts and clays were forged into rocks of sandstone, siltstone and shale.
Collectively these rocks are a part of the Uinta Formation that spans extensive areas of the Uinta Basin and nearby Colorado.
Differences in the rate of weathering and erosion between dissimilar rock types ultimately shaped Fantasy Canyon.
Pictured above and below, the mudstone and claystone have been stripped away by water and wind, leaving the slightly more durable sandstone to be carved into bizarre, melted wax-like forms.
Although the sandstone is more resistant to erosion relative to adjacent rocks, it is in fact extremely fragile.
The sandstone is fine grained, porous, soft, poorly cemented, brittle, and crumbly.
Because of different rates of weathering, the more durable sandstone remain while the more easily weathered siltstone and shale washed away, yielding this spectacular scenery at Fantasy Canyon.
Today’s geologic formations of Fantasy Canyon will eventually give way to weather and then topple and erode into sand, but new formations will appear as the topsoil washes away.
Because the delicate formations are so fragile the area is referred to as “Nature’s China Shop.”
There are inch-wide, black-colored, subvertical, northwest-southeast trending gilsonite dikes that have intruded the rocks at Fantasy Canyon.
Gilsonite, named after U.S. Marshall Samuel H. Gilson, is a type of asphaltite – solidified hydrocarbons. Gilsonite was discovered in the early 1860s.
The Eocene-aged Uinta Formation is fossiliferous. It contains widely scattered bones, mostly mammals, which roamed the Basin during the Eocene. Fossilized turtle shells are visible in the area.
A similar ancient lake, named Lake Gosiute, existed to the north in the Green River and Washakie Basins of Wyoming.
Some seams of iron staining do appear but they are very oxidized. The mineral being oxidized could be magnetite or hematite.
The rocks of the Eocene Green River Formation preserve a record of these ancient lakes, including world famous fish and leaf fossils, (pictured below).
Additionally, Utah’s much-talked-about oil shale resources, as well as significant conventional oil and gas reserves, are within the strata that accumulated in ancient Lake Uinta.
Within Fantasy Canyon boundaries, you can see 5 different gas-wells in all directions.
Because rocks from these ancient lake systems are major oil and gas sources and reservoirs, research conducted here by the University of Utah will help us predict the petroleum development potential of ancient lake deposits in Utah and around the world.
Fantasy Canyon is one of Utah’s most unique and delicate destinations.