Dakota Hogback

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Dakota Hogback
Dinosaur Ridge Open Space Park 03.jpg
The Dakota Hogback viewed south from the Dakota Ridge Trail at the crest of Dinosaur Ridge, just south of Interstate 70.
Highest point
Coordinates 39°40′34″N105°11′34″W / 39.676022°N 105.192688°W / 39.676022; -105.192688
Geography
Parent range Rocky Mountain Front Range
Geology
Orogeny Laramide
Type of rock Cretaceous Dakota Group sandstone and shale anticline

The Dakota Hogback is a long hogback ridge at the eastern fringe of the Rocky Mountains that extends north-south from southern Wyoming through Colorado and into northern New Mexico in the United States. The ridge is prominently visible as the first line of foothills along the edge of the Great Plains. It is generally faulted along its western side, and varies in height, with gaps in numerous locations where rivers exit the mountains. The ridge takes its name from the Dakota Formation, a formation with resistant sandstone beds that cap the ridge. The hogback was formed during the Laramide orogeny, approximately 50 million years (50 my) ago, when the modern Rockies were created. The general uplift to the west created long faulting in the North American Plate, resulting in the creation of the hogback. [1]

While the hogback was created during the Laramide Orogeny, the geologic strata comprising the hogback are much older. For example, fossilized data such as dinosaur footprints have been observed in the exposed strata, created by dinosaurs which lived during the Jurassic Period approximately 150 million years ago. Some of these footprints were attributed to the Diplodocus dinosaur and could be seen on the hogback west of Denver, Colorado as recently as the 1980s. [2]

The ridge forms a barrier between the high plains and the Rocky Mountain foothills. The ridge is pierced by a few water-cut gaps, which have been used to provide road access between the mountains and the plains. The ridge is paralleled by I-25 from north of Cheyenne, Wyoming, through Colorado, into northern New Mexico. The ridge is to the west. North of Denver its major gaps are I-80 in southern Wyoming, U.S. Highway 34 at Loveland, and U.S. 36 to Rocky Mountain National Park. [3] Interstate 70 passes through a highway cut, revealing the numerous layers making up the ridge. South of Denver, the major gaps are U.S. Route 24 in Colorado Springs, U.S. Route 50 in Pueblo, and finally in Colorado, U.S. Route 160 in Walsenburg.

Orogeny

Before the mountains, the region was a shallow sea. As sediments fell to the bottom of the water, they were compressed into soft sedimentary rock. Thus, oyster and clam shells, sand, and mud built slowly into layers of sandstone, shale, limestone, and "mudstone." [3] As the Rocky Mountains rose over the last 67 million years, up to nearly 30,000 feet above sea level, the soft sedimentary rocks were quickly weathered and washed away from the high mountains. But on the edge of the foothills, where the layers were scraped and pushed only slightly upward, the western edge of their remnant still stands at about a 45-degree angle - the Dakota Ridge. [3] The top layer is a hard sandstone, the Dakota Sandstone, from which the ridge gets its name. It protects the softer shales and limestones beneath it from weathering and erosion. [3]

Related Research Articles

<span class="mw-page-title-main">Laramide orogeny</span> Period of mountain building in North America

The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute. The Laramide orogeny occurred in a series of pulses, with quiescent phases intervening. The major feature that was created by this orogeny was deep-seated, thick-skinned deformation, with evidence of this orogeny found from Canada to northern Mexico, with the easternmost extent of the mountain-building represented by the Black Hills of South Dakota. The phenomenon is named for the Laramie Mountains of eastern Wyoming. The Laramide orogeny is sometimes confused with the Sevier orogeny, which partially overlapped in time and space.

<span class="mw-page-title-main">Front Range</span> Mountain range of the Southern Rocky Mountains of North America

The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encountered as one goes westbound along the 40th parallel north across the Great Plains of North America.

The exposed geology of the Bryce Canyon area in Utah shows a record of deposition that covers the last part of the Cretaceous Period and the first half of the Cenozoic era in that part of North America. The ancient depositional environment of the region around what is now Bryce Canyon National Park varied from the warm shallow sea in which the Dakota Sandstone and the Tropic Shale were deposited to the cool streams and lakes that contributed sediment to the colorful Claron Formation that dominates the park's amphitheaters.

<span class="mw-page-title-main">Grand Staircase</span> Landform in Utah and Arizona, United States

The Grand Staircase is an immense sequence of sedimentary rock layers that stretch south from Bryce Canyon National Park and Grand Staircase–Escalante National Monument, through Zion National Park, and into Grand Canyon National Park.

<span class="mw-page-title-main">Geology of the Grand Teton area</span>

The geology of the Grand Teton area consists of some of the oldest rocks and one of the youngest mountain ranges in North America. The Teton Range, partly located in Grand Teton National Park, started to grow some 9 million years ago. An older feature, Jackson Hole, is a basin that sits aside the range.

<span class="mw-page-title-main">Geology of the Capitol Reef area</span>

The exposed geology of the Capitol Reef area presents a record of mostly Mesozoic-aged sedimentation in an area of North America in and around Capitol Reef National Park, on the Colorado Plateau in southeastern Utah.

<span class="mw-page-title-main">Denver Basin</span> Geologic structural basin in the U.S.

The Denver Basin, variously referred to as the Julesburg Basin, Denver-Julesburg Basin, or the D-J Basin, is a geologic structural basin centered in eastern Colorado in the United States, but extending into southeast Wyoming, western Nebraska, and western Kansas. It underlies the Denver-Aurora Metropolitan Area on the eastern side of the Rocky Mountains.

<span class="mw-page-title-main">Geology of the Rocky Mountains</span> Discontinuous series of North American mountain ranges with distinct geological origin

The geology of the Rocky Mountains is that of a discontinuous series of mountain ranges with distinct geological origins. Collectively these make up the Rocky Mountains, a mountain system that stretches from Northern British Columbia through central New Mexico and which is part of the great mountain system known as the North American Cordillera.

<span class="mw-page-title-main">Hogback (geology)</span> Long, narrow ridge

In geology and geomorphology, a hogback or hog's back is a long, narrow ridge or a series of hills with a narrow crest and steep slopes of nearly equal inclination on both flanks. Typically, the term is restricted to a ridge created by the differential erosion of outcropping, steeply dipping, homoclinal, and typically sedimentary strata. One side of a hogback consists of the surface of a steeply dipping rock stratum called a dip slope. The other side is an erosion face that cuts through the dipping strata that comprises the hogback. The name "hogback" comes from the Hog's Back of the North Downs in Surrey, England, which refers to the landform's resemblance in outline to the back of a hog. The term is also sometimes applied to drumlins and, in Maine, to both eskers and ridges known as "horsebacks".

<span class="mw-page-title-main">Laramie Formation</span>

The Laramie Formation is a geologic formation of Late Cretaceous (Maastrichtian) age, named by Clarence King in 1876 for exposures in northeastern Colorado, in the United States. It was deposited on a coastal plain and in coastal swamps that flanked the Western Interior Seaway. It contains coal, clay and uranium deposits, as well as plant and animal fossils, including dinosaur remains.

<span class="mw-page-title-main">Dakota Formation</span> Rock units in midwestern North America

The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.

Colorado is a geologic name applied to certain rocks of Cretaceous age in the North America, particularly in the western Great Plains. This name was originally applied to classify a group of specific marine formations of shale and chalk known for their importance in Eastern Colorado. The surface outcrop of this group produces distinctive landforms bordering the Great Plains and it is a significant feature of the subsurface of the Denver Basin and the Western Canadian Sedimentary Basin. These formations record important sequences of the Western Interior Seaway, and as the geology of this seaway was studied, this name came to be used in states beyond Colorado, but was later replaced in several of these states with more localized names.

<span class="mw-page-title-main">Dinosaur Ridge</span>

Dinosaur Ridge is a segment of the Dakota Hogback in the Morrison Fossil Area National Natural Landmark located in Jefferson County, Colorado, near the town of Morrison and just west of Denver.

Prehistory of Colorado provides an overview of the activities that occurred prior to Colorado's recorded history. Colorado experienced cataclysmic geological events over billions of years, which shaped the land and resulted in diverse ecosystems. The ecosystems included several ice ages, tropical oceans, and a massive volcanic eruption. Then, ancient layers of earth rose to become the Rocky Mountains.

<span class="mw-page-title-main">Grand Hogback</span>

The Grand Hogback is a 70-mile long, curving, spine-like ridge in Western Colorado that extends from near McClure Pass in Pitkin County through Garfield County and then to near Meeker in Rio Blanco County. The hogback is significant because it marks part of the boundary between the Colorado Plateau to the west and the Southern Rocky Mountains to the east.

The geology of Alberta encompasses parts of the Canadian Rockies and thick sedimentary sequences, bearing coal, oil and natural gas, atop complex Precambrian crystalline basement rock.

The geology of Wyoming includes some of the oldest Archean rocks in North America, overlain by thick marine and terrestrial sediments formed during the Paleozoic, Mesozoic and Cenozoic, including oil, gas and coal deposits. Throughout its geologic history, Wyoming has been uplifted several times during the formation of the Rocky Mountains, which produced complicated faulting that traps hydrocarbons.

The geology of Utah, in the western United States, includes rocks formed at the edge of the proto-North American continent during the Precambrian. A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism, and the formation of the basin and range terrain in the Cenozoic.

The bedrock of Colorado was assembled from island arcs accreted onto the edge of the ancient Wyoming Craton. The Sonoma orogeny uplifted the ancestral Rocky Mountains in parallel with the diversification of multicellular life. Shallow seas covered the regions, followed by the uplift current Rocky Mountains and intense volcanic activity. Colorado has thick sedimentary sequences with oil, gas and coal deposits, as well as base metals and other minerals.

<span class="mw-page-title-main">Greater Green River Basin</span> River basin in southwestern Wyoming, United States

The Greater Green River Basin (GGRB) is a 21,000 square mile basin located in Southwestern Wyoming. The Basin was formed during the Cretaceous period sourced by underlying Permian and Cretaceous deposits. The GGRB is host to many anticlines created during the Laramide Orogeny trapping many of its hydrocarbon resources. It is bounded by the Rawlins Uplift, Uinta Mountains, Sevier overthrust belt, Sierra Madre Mountains, and the Wind River Mountain Range. The Greater Green River Basin is subdivided into four smaller basins, the Green River Basin, Great Divide Basin, Washakie Basin, and Sand Wash Basin. Each of these possesses hydrocarbons that have been economically exploited. There are 303 named fields throughout the basin, the majority of which produce natural gas; the largest of these gas fields is the Jonah Field.

References

  1. Dakota Group in Northern Front Range Foothills, Colorado; Karl M. Waage; A Shorter Contribution to General Geology, Geological Survey Professional Paper 274-B; A revised subdivision and terminology for the Dakota group and local details of its Stratigraphy; United States Government Printing Office, Washington: 1955
  2. Guidebook on the Geology, History, and Surface-Water Contamination and Remediation in the Area from Denver to Idaho Springs, Colorado; Edited K.C. Stewart and R.C. Severson; U.S. Geological Survey Circular 1097; United States Government Printing Office, Washington, D.C. 1994
  3. 1 2 3 4 "The Dakota Hogback - Rocky Mountain National Park (U.S. National Park Service)".