Geological Points of Interest - Ashley

Flaming Gorge Scenic Byway
 Sheep Creek Geological Area | Sheep Creek Cave
 Whiterocks Cave

Type

Scenic Byway

Site Name

Wildlife Through the Ages: Flaming Gorge-Uintas National Scenic Byway

Directions

Begin at the Vernal Orientation Center & Utah Field House of Natural History in Vernal, Utah taking highway 191 or at the Flaming Gorge Dam Orientation Center near Dutch John, Utah. You can also begin in Manila City, Utah at the U.S. Forest Service Office & Manila Orientation Center on State Road 44.

Description

You can tour earth's history from your vehicle. You will pass 20 interpretive signs indicating rock formations and fossils they contain. Rocks date Pre-Cambrian to Cretaceous in age representing millions of years of time and transformation. Overlooks, scenic pullouts, visitor centers, and nature trails abound along the way. Pick up a brochure with more information at any of the orientation centers.

The youngest formation exposed in this region is the Mancos Formation. Formed from clay that settled out of a large Cretaceous sea, this formation is home to many sea creature fossils. Next, is the Frontier Formation primarily composed of tropical plants that were buried under river delta sediments? Decomposing plants were placed under enormous amounts of pressure to form coal. The formation of the Mowry Formation followed. Again, an ancient sea covered the area 100 million years ago leaving behind shale composed of hardened clay and volcanic ash. Some fossilized scales and bones remain from fish that lived during this time. Still in the Cretaceous period about 110 million years ago is the Dakota Formation. This formation was composed by soil and rocks deposited in or near streams that entered a vast ocean. Plants and trees are preserved in these layers.

The Jurassic period is made up of five formations in this area. The Morrison Formation, deposited 145 million years ago, is primarily composed of clay, shale, and sandstones in multi-color layers of red, maroon, purple, white, and green. Dinosaurs and other extinct organisms once lived in the extensive low-lying plain with streams and lakes. The Curtis Formation was also deposited by an ancient sea as evidenced from ripple marks and mud cracks. Belemnites, squid-like creatures were abundant in this sea. Next is the Entrada Formation, dominated by windstorms 150 million years ago, this layer is devoid of fossils due to extreme living conditions. Before the Entrada Formation came the Carmel Formation, also a colorful mixture of red, green, and gray siltstone, sandstone, and limestone. Shallow marine deposits and restricted conditions led to the formation of Gypsum, an evaporite. Last in the Jurassic period is the Navajo Formation. Massive sand dunes covered the region and were eventually compacted and cemented to form sandstone. Dinosaur footprints can also be found in this exposed layer.

The Triassic period is composed of the Chinle Formation, deposited by lakes and streams, the Shinarump member, where large amounts of Uranium have been discovered in southern Utah, and the Moenkopi Formation, deposited 200 million year ago made of reddish siltstone, shale, and sandstone. Geodes and Phytosaur teeth can be found in the Chinle in this area. Phytosaur and amphibian tracks can also be seen in the Moenkopi Formation.

The next layer exposed is the Park City Formation of the Permian period. Large deposits of phosphate make this area a prime location for open-pit mining operations. The phosphate formed from the decomposition of marine animals that once inhabited the area. (More mining information and overlooks can be found at the Windy Point Overlook.)

The Pennsylvanian period gives us the Weber and Morgan Formations. The Weber Formation is easily eroded by water due to poor cementation of sand grains resulting in deep gorges in the area. This formation also yields oil fields in Ashley Valley. The Morgan Formation is, once again, evidence of the ever-fluctuating seas across North America. Brachiopods, coral reefs, sea urchins, horsetails, and sponges thrived in the warm shallow seas at this time.

The Madison Formation, from the Mississippian period, and the Lodore Formation, from the Cambrian period, form the next two layers visible on this adventure. Both deposited in ancient seas, the Madison limestone records primitive sea life from 300 million years ago and the trilobite is evident in the Lodore. An unconformity lies between these two formations comprising the missing rock records of the Ordovician, Silurian, and Devonian periods (McKnight and Stewart).

Finally, the Precambrian Uinta Mountain Group is more than three miles thick. Few signs of primitive life are found since it was deposited a billion years ago. It consists of dark-red sandstone with shale and conglomerates. The red cliffs of Red Canyon are made up of these impressive rocks. Basin subsidence is the primary reason such a large volume of clastic sedimentary rocks were deposited (Sprinkel, 2003).

Image(s)

 Photo of a Flaming Gorge Scenic Byway Sign.Photo of Red Canyon - Click on the image to enlarge.
 

Type

Scenic Byways

Site Name

Sheep Creek Geological Area

Directions

This area is located adjacent to the Flaming Gorge National Recreation Area and connects to the Uinta National Scenic Byway described above. You can begin in Manila City, Utah at the U.S. Forest Service Office & Manila Orientation Center on State Road 44.

Description

Named after the Rocky Mountain Bighorn Sheep that inhabit the area, this site is dominated by the Uinta Crest Fault, a section of folded and twisted rock that reveals millions of years of geological history. Along Highway 44, signposts explain the denote formation names and geologic ages as you pass through them.

Along Highway 44, the Uinta fault zone is visible just north of the Sheep Creek Canyon Geological Area loop turnoff. The fault displaced the red Uinta Mountain Group on the south against the gray Madison Limestone. This fault may have formed over 1.5 billion ears ago, but these rocks were probably displaced during the Laramide orogeny about 70 to 40 million years ago (Sprinkel, 2003).

Image(s)

Photo of Sheep Creek Canyon LoopPhoto of Sheep Creek Canyon  - Click the thumbnail to enlarge.Photo of Sheep Creek Canyon Moenkopi - Click the thumbnail to enlarge.

Photo of sheep in Sheep Creek Canyon

 

Type

Caves/Sinkholes

Site Name

Sheep Creek Cave

Directions

Contact the Flaming Gorge Ranger District for more information at 435-784-3445.

Description

This cave is gated. During the summer, however, the cave is open to the public under a permit system. To see the cave, you contact the Manila Ranger District, sign a permit, and pick up the key to the cave gate. Tours are self-guided, with no maps, signs, or other interpretive helps or facilities.

This cave represents the discharge point for a large, very long, but rather narrow karst system that runs under a large and impressive hogback ridge, parallel to the mountain front. The source of the water was dye traced years ago from a sinking stream at Lost Creek Sink, 14 miles to the west and located on the Wasatch-Cache National Forest. The dye trace went 14 miles from sink to spring, running parallel to the mountain front and crossed underneath three completely separate surface drainages in the process with a travel time of about 21 days. (This was probably done during moderate to low flow conditions). Despite the huge karst system, the cave has only about 1,000 feet of known passages. The cave entrance is located at the base of a huge limestone cliff, perhaps 50 feet above the discharge spring (appropriately called Big Spring). This water can be seen within the cave at several locations. Although the cave is generally level, there are numerous large collapse boulders to be negotiated, and several narrow or obscure pits, that make the cave somewhat unsafe for reckless explorers. The air is good, but locally stinky from rodent nests and debris.

Image(s)

 
 

Type

Caves/Sinkholes

Site Name

Whiterocks Cave

Directions

Located 32 miles east of Roosevelt, UT. Contact the Vernal Ranger District for more information at 435-789-1181.

Description

Whiterocks Cave is gated. During the summer, however, the cave is open for free guided public tours. To see the cave, contact the Vernal Ranger District. You will need to enter your name and preferred tour dates into a lottery system. If your group is selected in the lottery, then the Ashley National Forest escorts you up to the cave and provides a high quality guided tour of the cave free of charge. The cave tours see about 2/3 of the known cave, depending on the group and their interest level.

The cave is located about 1,000 feet above the parking spot with a rather strenuous hike along a nice, but narrow trail required to reach the cave. Whiterocks Cave is very scenic, has generally large and level walking passages, and has approximately 1,100 feet of mapped passages. When first discovered in modern times, the cave contained a complete and undisturbed human skeleton. The skull was taken to the local museum, but most of the other bones have slowly been taken because they were not properly protected or managed. This cave represents an abandoned karst system located well above local base level for the surrounding karst area with no running water.

Image(s)

Photo  of Whiterocks Cave

 



Key Contacts

Geology

Joe Gurrieri
Regional Geologist