by Alex Gugel , all rights reserved

Capitol Reef

Geology and Stratigraphy Column

brochure Capitol Reef - Geology and Stratigraphy Column
Capitol Reef National Park National Park Service U.S. Department of the Interior Geology “Geology knows no such word as forever.” —Wallace Stegner Capitol Reef National Park’s geologic story reveals a nearly complete set of Mesozoic-era sedimentary layers. For 200 million years, rock layers formed at or near sea level. About 75-35 million years ago tectonic forces uplifted them, forming the Waterpocket Fold. Forces of erosion have been sculpting this spectacular landscape ever since. Deposition Uplift If you could travel in time and visit Capitol Reef 245 million years ago, you would not recognize the landscape. Imagine a coastal park, with beaches and tidal flats; the water moves in and out gently, shaping ripple marks in the wet sand. This is the environment in which the sediments of the Moenkopi Formation were deposited. Visiting Capitol Reef 180 million years ago, when the Navajo Sandstone was deposited, you would have been surrounded by a giant sand sea, the largest in Earth’s history. In this hot, dry climate, wind blew over sand dunes, creating large, sweeping crossbeds now preserved in the sandstone of Capitol Dome and Fern’s Nipple. Now jump ahead 20 million years, to 225 million years ago. The tidal flats are gone and the climate supports a tropical jungle, filled with swamps, primitive trees, and giant ferns. The water is stagnant and a humid breeze brushes your face. Oxygen-rich river water oxidized the iron in the sediments, giving the Chinle Formation its lavender and red colors, while the reducing environment of stagnant bogs gave it the greens and grays. All the sedimentary rock layers were laid down at or near sea level. Younger layers were deposited on top of older layers. The Moenkopi is the oldest layer visible from the visitor center, with the younger Chinle Formation above it. The Castle is Wingate Sandstone; the Kayenta Formation that formerly capped it has eroded away, but is still visible atop the red cliffs behind it. White domes of Navajo Sandstone comprise the highest and youngest layer seen from the visitor center. The movement of, and the interaction between, Earth’s tectonic plates created the different environments in which Capitol Reef’s nineteen rock layers were formed. Few of these sedimentary layers would be visible, however, if not for the Laramide Orogeny, a massive mountain building event that likely reactivated an ancient buried fault between 75 and 35 million years ago. The compression associated with the Laramide Orogeny gave rise to a one-sided fold, or monocline, in the earth’s crust within the Colorado Plateau. area of otherwise nearly horizontal layers. The layers on the west side of the Fold have been lifted more than 7,000 feet (2134 m) higher than corresponding layers on the east. The Waterpocket Fold is the longest exposed monocline in North America and is nearly 90 miles in length. It is the main reason Capitol Reef National Monument was established in 1937. The Waterpocket Fold is a classic monocline: an enlongated fold with one steep side in an Erosion Capitol Reef’s spectacular scenery reflects not only the underlying structure of the Waterpocket Fold, but also the differing degrees of resistance to weathering and erosion seen in each rock layer. Water is the dominant erosional force in Capitol Reef, with wind playing only a minor The folding and tilting of the rock layers allow you to travel through 280 million years of Capitol Reef’s geologic history in just fifteen miles by driving through the park on State Route 24. role. Flash floods are the most dramatic display of erosion in action. Floodwaters propel debris, sediment, cobbles, and boulders, increasing water’s carving power. Deposition and uplift in Capitol Reef have created a unique window into Earth’s history, revealed through the power of erosion. Cenozoic andesite Wingate Sandstone Navajo Sandstone and Kayenta Formation Sandstone Deeply-buried fault Additional information on the geology of Capitol Reef National Park is available on our website (www.nps.gov/care) which also links to the Capitol Reef Natural History Association, a non-profit cooperating association that sells publications on Capitol Reef ’s natural and cultural history. Marine Transition between tidal flats and dune fields Shallow marine, tidal flats, & sabkhas (sandy salt flats) Vast region of sand dunes West-flowing rivers Sand dunes Forested basin with rivers, swamps, & lakes River channels Gently sloping coastal plain, fluctuating sea level Grayish-green sandstone & siltstone Earthy, red, very fine-grained sandstone & gypsum Interlayered red sandstone, siltstone, & gypsum Tan sandstone White crossbedded sandstone Interlayered white sandstone & red siltstone Sandstone, often stained dark red Interlayered sandstone, siltstone, & bentonitic mudstone White sandstone Mostly dark red siltstone & mudstone; minor yellowish limestone Gray dolomitic limestone White crossbedded sandstone 0-80 feet 450-750 feet 300-100 feet 50-100 feet 800-1100 feet 350 feet 350 feet 350-550 feet 0-90 feet 500-1000 feet 70-100 feet 400+ feet www.nps.gov/care Beach & dune sands Marine Sand dunes Fremont River Gorge & Goosenecks of Sulphur Creek Fremont River Gorge Miners Mountain, Egyptian Temple, & base of Chimney Rock Discontinuous; cap of Chimney Rock Slopes below Fruita Cliffs; contains petrified wood & uranium Fruita Cliffs & Circle Cliffs Top, ledgy portion of Fruita Cliffs; Hickman Bridge Capitol Dome, Navajo Dome, & Grand Wash Narrows Cap of Golden Throne Forms red V-shaped chevrons on east side of Waterpocket Fold Cathedrals of Cathedral Valley Caps cathedrals of Cathedral Valley Cliffs at east park entrance Tidal flats Thinly-bedded, reddish siltstone; thick, wavy gypsum on top 206 MYA 248 MYA 290 MYA MYA = Million Years Ago Shinarump Member White Rim Sandstone Kaibab Limestone Moenkopi Formation Chinle Formation Wingate Sandstone Kayenta Formation Navajo Sandstone Page Sandstone Carmel Formation Entrada Sandstone Curtis Formation Summerville Formation Salt Wash Member Brushy Basin Member 150-300 feet Morrison Formation Bentonite Hills; along Notom-Bullfrog Road north of Burr Trail Vast river systems; bentonite clays from altered volcanic ash White crossbedded sandstone (Salt Wash) & candy-striped mudstone (Brushy Basin) 180-700 feet 144 MYA Jurassic Triassic Permian Coastal Cedar Mountain Formation Conglomerate and mudstone layers 0-100 feet Mancos Shale North and east of the Hartnet Road river ford Tan sandstone, oyster shell fossils 0-50 feet Factory Butte and badlands near Caineville Muley Canyon Sandstone Masuk Formation Tarantula Mesa Sandstone Capitol Reef Stratigraphy Column Rivers and Floodplains Mostly dark gray shale interlayered with sandstone 2000-3000 feet 65 MYA Age Dakota Dakota Sandstone Sandstone Shallow sea that bisected North America Shale interlayered with sandstone West side of Henry Mtns., east of Strike Valley Landforms Oyster Shell Reef; locally absent Floodplains, coastal areas, and marine 1200-1450 feet (combined) Location / Remarks Cretaceous Paleoenvironment Rock Type Thickness San Rafael Group Glen Canyon Group EXPERIENCE YOUR AMERICA™ 11/15

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