THE ROCKS OF CAPITOL REEF

If you use this book, an ability to recognize some of the rock layers is important. Diagnostic features are mentioned here and the layers are listed from oldest to youngest (west to east). Some terms are defined below:

SANDSTONE - A cemented sediment composed predominantly of quartz sand grains. The size of the grains and colors of the rock vary.

SILTSTONE - A very fine grained consolidated rock composed predominantly of silt size particles.

SHALE - A thinly layered sediment in which the particles are clay (smallest) size.

CONGLOMERATE - Rounded, waterworn fragments of rock or pebbles cemented together.

LIMESTONE - A bedded sedimentary deposit consisting chiefly of calcium carbonate from limy mud, limy sand or shell fragments.

MUDSTONE - A rock that may include clay, silt and sand size particles mixed together in changing percentages.

GYPSUM - A mineral that is very common in Capitol Reef. The mineral is included in rock layers as a thin, vertically striated, opaque, white (sometimes color stained) band or as a shiny clear crystalline band or mound. In the Carmel Formation it forms a thick massive layer many feet thick.

CROSSBEDDING - The arrangement of layers transverse or oblique to the main planes of stratification.

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MEMBER -- Rock formations often consist of distinguishable sections. These sections will be different colors, rock types, hardness or have some feature that is diagnostic. These distinguishable sections are referred to as Members.

The White Rim Sandstone, the oldest rock layer in the Park, can be found in the Fremont River gorge, Grand Wash, Capitol Wash and Sulpher Creek, in each case, west of the scenic drive. These rocks were deposited in the early Permian Period, more than 250 million years ago, and are up to 800 feet thick. The diagnostic features are light yellow to gray, sandstone with some cross-bedding. This formation covers only the lower walls and stream bed of the canyons.

The Kaibab Limestone is the next formation up and includes some thin sandstone and siltstone layers. It is not visible from very many places but is easily seen on the Fremont River Gorge trail and from the Goosenecks Overlook. Diagnostic features are light brown or gray to white limestone usually forming cliffs up to 200 feet thick.

The Moenkopi Formation is about 225 million years old and was deposited in the early Triassic Period. There are no rocks of the late Permian time here so there is a time gap between the Kiabab and the Moenkopi. The low red brown formation south of the campground and along the scenic drive is the Moenkopi. It is also the main red brown rock seen along the low areas as you drive into the Park from Torrey. The formation consists mostly of chocolate-colored sandstones, siltstones and shales that are about 850 feet thick. The one glaring exception to the above is the Sinbad Limestone which is in the lower portion of the formation, though not the bottom. The Sinbad is yellowish in color and weathers as limestone typically does, with sharp ridges and points on each rock. Ripple marks are common and mud cracks frequent in the bottom and top Moenkopi layers. This formation is layered in a way that reminds some people of a torte cake. Another period of erosion occurred after the deposition of the Moenkopi so there is another time break before the next formation was deposited in late Triassic. Diagnostic features of the Moenkopi are the chocolate color, ripple marks, and a slope forming nature.

The Chinle Formation is next up and is the most colorful of the Capitol Reef layers. It forms the slopes at the campground entrance, behind the picnic area and behind the blacksmith shop. The lowest layer in the Chinle is the Shinarump Conglomerate. This layer is discontinuous here, so will not be present everywhere. From many locations the Shinarump can be followed with the eye to a place where it disappears, then on to where it reappears. The majority of the Chinle is soft, slope forming, clay, shale, siltstone and sandstone. The clay is often color banded and weathers to a texture of packed popcorn on the surface. The main sandstone layer is about half way up and is a brown ledge former called the Capitol Reef Bed. The rest is purple, orange, green, blue or other colors visible from the campground and along the west side of "The Reef". The Chinle is about 450 feet thick and again there is a time gap before the next formation was deposited. Diagnostic features are the colorful slopes above the Shinarump cliffs.

The Wingate Sandstone is the orange brown rock that forms the cliffs in the Headquarters area of Capitol Reef. It is about 350 feet thick and makes similar cliffs all along the Waterpocket Fold. There is a tendency for holes to form in exposed surfaces so that in places it looks like Swiss cheese. Cliff walls are stable for thousands of years and often develop water stains and a patina that make the walls almost glow with beauty. The diagnostic feature is the sheer orange brown cliff. Note! Wingate can be yellow or tan.

The Kayenta Formation is easy to miss in Capitol Reef. The color is similar to the Wingate Sandstone, though more purplish red, and it seems to get lost between the Wingate and the Navajo Sandstone. It is quite thick (350 feet) but grades out of the Wingate and into the Navajo so the contacts are not always sharp. Diagnostic features are the more purplish red color than the Wingate and a tendency to form small sandstone cliffs with thin softer beds of siltstone or mudstone weathering out between.

The Navajo Sandstone is the king of the rock layers- in Capitol Reef. It forms the top of more ridges and has more surface acres than any other sandstone in the Park. It is up to 1100 feet thick. It is highly cross-bedded and is essentially a mass of sand dunes that were hardened into rock. Highway 24 winds through the Navajo Sandstone from near Hickman Bridge parking lot past the waterfall to the east. The peaks above Hickman Bridge including Walker Peak (except for the very top), Navajo Dome and Capitol Dome are made of this resistant tan rock. A fresh surface of the formation is usually a bright white. Weathered surfaces may be tan, light brown or stained a reddish brown. Many canyon hikes end at a pour-over in the Navajo Formation. Diagnostic features are the light color and strong cross-bedding. Note! The Navajo can be reddish brown.

The Page Sandstone is sometimes listed next above the Navajo but is discontinuous in Capitol Reef and where present hard to differentiate from the Navajo or basal Carmel Formation. In this book any tan sandstone below the Carmel Formation is called Navajo.

Next comes the most varied formation in the Park, the Carmel. It is composed of sandstone, siltstone, mudstone, limestone and gypsum. Hikers who walk west from the Notom Road or South Desert are destined to walk through a long stretch of this amazing rock. The formation is up to 1,000 feet thick in the north part of the Park but thins to as little as 300 feet in the south. The wide variety of rock types reflect the wide variety of conditions under which it was deposited. The diagnostic features vary. From a distance, in the south part of the Park, the distinctive feature is the red chevrons marching on the lower slopes of the Waterpocket Fold. In the north the expanses of un-vegetated gypsum "moonscape" and the layer cake cliffs are distinctive.

The overlying Entrada Sandstone is largely a valley or slope formed in Capitol Reef but the exceptions are significant. The Cathedrals of Cathedral Valley are erosional remnants composed of Entrada. Jailhouse Rock and Temple Rock in South Desert are mostly Entrada with a cap of Curtis. The expressions of the Entrada differ greatly between the north part of the Park and the south but the color is quite consistently earthy red. The diagnostic features are the color and the location above the Carmel.

The Curtis Formation is a nice marker. It is light gray and separates two red brown formations. It is not extensive or thick (150 feet maximum in the north) and does not exist in the south part of the Park but is a "protector" of many of the Cathedrals because it forms the top layer and shields the less resistant Entrada that the Cathedrals are made of. The diagnostic feature is the light gray color. The Summerville is one of the less noticeable formations. It is up to 250 feet thick, red brown, and very even bedded which to me looks even more like a torte cake than the Moenkopi. It is extensive out of the Park east of the Notom Road. The diagnostic feature is the even bedded layer that separates the Curtis and Morrison Formations.

The Morrison Formation is almost impossible to escape from anywhere on the east side of the Fold. The Hartnet and Cainville Wash roads wind through its colorful rounded clay hills and conglomerate cliffs for miles. South of Cedar Mesa the conglomerate forms many ridge tops and the clay is in the slopes below. It may be as thick as 700 feet and contain colors of gray accented by reds, browns, yellows, and greens. The colorful clays make driving impossible, or nearly so, when wet and are best displayed in Bentonite Hills on the Hartnet Road. The diagnostic features include the colorful clays and the conglomerate ledges. Note that this formation is well above the Navajo Sandstone while the similar colorful clays of the Chinle are well below the Navajo.

The Cedar Mountain Formation is on top of the Morrison but is commonly indistinguishable from it.

The Dakota Sandstone (0 - 150 feet thick) is significant mainly because it is loaded with fossils - mainly good size bivalves - that can be seen throughout the Park. They are most easily seen along "Oyster Shell Reef" just east of part of the Notom Road. Fossils are the diagnostic feature.

Last comes the Mancos Shale. It is mostly blue gray shales up to 3,000 feet thick with two prominent sandstone layers to break it up. A drive from Halls Creek Overlook north or from the east Park boundary to Hanksville in the late afternoon can engender an appreciation of the Mancos that might otherwise not exist. The low angle light and shadows at that time of day bring life to the rocks. Boring and hot to walk through, it adds an almost alien dimension to the east side of the Park and east of the Park. The Ferran Sandstone member is the lowest sandstone and not always distinctive in the Park while the Emery Sandstone member (More recent books may refer to this layer as the Mule Canyon member.) is thicker and forms the east Park boundary for a few miles south of Cedar Mesa Campground. The diagnostic feature is the blue gray shale wall.

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