CRFS Connections

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Uplift

All of Capitol Reef’s rock layers were deposited around sea level (0 feet), with one on top of the other. The layers were uplifted between 70-50 MYA during a mountain-building event called the Laramide Orogeny. Most of the Colorado Plateau was uplifted uniformly, but in Capitol Reef, an ancient bedrock fault was reactivated and caused an uplift higher on the west side than the east. This nearly 100-mile long uplift is called the Waterpocket Fold, named by the Powell Expedition.

The uplift has been slowly eroding away, and the layers have been made visible within the last 15-20 million years. The name Waterpocket Fold comes from the many water pockets, depressions which often form in the sandstone layers, that fill with rainwater and snowmelt. For the early explorers, the waterpockets were essential to their travel, since they were in a land that was new to them. Fold refers to the eroded monocline, a fold or wrinkle in the earth’s crust.

the red and white vertical line is the Waterpocket Fold

In the center of the image, the red and white vertical line is the Waterpocket Fold, with the Fremont River running through the upper center of it, before joining the Dirty Devil River. To the left (west) of it is Thousand Lake Mountain, and Boulder Mountain. To the right (east) are the Henry Mountains. To the lower right (southeast) is the Colorado River and Lake Powell. Image from Landsat-7, courtesy of NASA.

 

The Waterpocket Fold is so large that it can be seen from the International Space Station! For a bird’s eye view of the Fold, the Larb’s Hollow Overlook on Scenic Highway 12 is a great place to get a sense of the magnitude. The Notom-Bullfrog Road on the east side of Capitol Reef offers a close-up view of the Fold, and the farther south you drive, the more impressive and visible the uplift is. If you drive up the Burr Trail Switchbacks, the views from the top illustrate the Fold and the "strike valleys" that have formed parallel to it. Strike valleys form from the erosion of softer layers within harder sediments. As Tom Morris explains, “In an area with tilted strata [rock layers], erosion will erode some rock units faster than others. These weaker units erode into valleys between the layers of more resistant rock.” From the Burr Trail, some of the ridges along the strike valleys are formed in Dakota Sandstone and a fossilized oyster shell reef (from an inland sea about 100 MYA).

A view of the Waterpocket Fold from Strike Valley Overlook

A view of the Waterpocket Fold from Strike Valley Overlook in the southern portion of Capitol Reef National Park. In the middle distance are the grey slopes of Mancos Shale (90 MYA) and in the foreground is the white Navajo Sandstone (180 MYA). Between are "strike valleys" running parallel towards the south, and to the east is the southern end of the Henry Mountains. - Photo courtesy of NPS/Jacob Frank.

Uplift in Pleasant Creek

From the field station you can look up and down Pleasant Creek Valley. To the west you can see upstream through Miner’s Mountain to Boulder Mountain and the Aquarius Plateau. Miner’s Mountain is an anticline (as opposed to a monocline) but was formed around the same time as the Waterpocket Fold. Anticlines are arch-like formations with the oldest rocks in the center, and younger rocks on either side. According to University of Kansas Professor Dr. Diane Kamola, when “you look west, the vista is dominated by the east-dipping vegetated surface (which geologists call a ‘dip slope’ because the dipping surface reflects the structural dip of the beds). The dip slope is the eastern half of the Monocline. Where is flattens out, in the center of Miners Mountain - that is along the axis of the anticline, and the trend of the ‘flat area’ corresponds to the placement of the axis of the structure.”

Dr. Kamola continues, “As you look east from the field station, and you see the Page Sandstone (see annotated photo of Stratigraphy), you are looking at the western-most part of the Fold. If the strata was not folded, the Page Sandstone should be located way above the Wingate Sandstone (which forms the cliffs at the Field Station). When looking to the east, you can see the Page Sandstone at about the same elevation as the Wingate, and that can only happen if it were in the foot wall of a normal fault (which it isn’t), or if it is exposed in the limb of the monocline (which it is).”

Pleasant Creek is in the middle of the Waterpocket Fold, and since the Fold is so large, only a few layers are typically visible at any given location.

Pleasant Creek Valley

Photo and annotation by Dr. Diane Kamola.

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