Chuska mountains
Encyclopedia
The Chuska Mountains are an elongate range on the Colorado Plateau
and within the Navajo Nation
. The range is about 80 by 15 km (50 by 10 miles), and it trends north-northwest and is crossed by the state line between Arizona
and New Mexico
. The highlands are a dissected plateau
, with an average elevation of about 2740 m (8,989.5 ft), and subdued topography. The highest point is Roof Butte
(36.4601° N, 109.0929° W) at 2994 m (9,822.8 ft), near the northern end of the range in Arizona
. Other high points include the satellite Beautiful Mountain
at 2861 m (9,386.5 ft) and Lukachukai Mountains
at 2885 m (9,465.2 ft), both also near the northern end, and Matthews Peak at 2911 m (9,550.5 ft). The San Juan Basin borders the Chuskas on the east, and typical elevations in nearby parts of that basin are near 1800 m (5,905.5 ft). The eastern escarpment of the mountains is marked by slumps and landslides that extend out onto the western margin of the San Juan Basin. To the north, the Chuskas are separated from the Carrizo Mountains
by Red Rock Valley.
in the San Juan Basin as early as 974 A.D. Logging in the Chuskas was suspended in 1994, but was set to commence again in summer 2008.
The forests of the Chuska Mountains and of the Defiance Uplift receive higher rainfall than the surrounding lowlands, and these highlands typically generate more than half the surface water of the Navajo Nation
. Canyons of Canyon de Chelly National Monument
were cut by streams with headwaters in the Chuskas.
The Chuska Mountains are sparsely populated. Nearby settlements are small, and they include Crystal, New Mexico and Lukachukai, Arizona to the west and Toadlena, New Mexico to the east. Trading posts at Crystal and at Two Grey Hills (about 10 km east of Toadlena), are associated with distinctive patterns used in Navajo rugs. A paved road, New Mexico Highway 134, crosses the range through Narbona Pass. Narbona Pass was formerly named Washington Pass, after Colonel John M. Washington, who commanded a military expedition against the Navajo. Narbona
was a Navajo headman killed in an encounter with Washington's troops in 1849.
. The uplifted region is separated from the San Juan Basin
to the east by the Defiance and associated monocline
s. Relative uplift, basin subsidence, and monocline formation began in the early stages of the Laramide orogeny
about 75 to 80 million years ago. Although the Chuska Mountains can be considered part of the Defiance Uplift, they stand higher. They are capped by an erosional remnant of Chuska Sandstone, a unit locally more than 500 meters thick. The flat-lying Chuska Sandstone rests unconformably
on Mesozoic
rocks deformed in the Defiance monocline. Biotite
in layers of altered volcanic ash
within the Chuska Sandstone has yielded radiometric ages of 35 and 33 million years by argon-argon dating
. The Chuska Sandstone is formed of sand dune
deposits, and it appears to be a remnant of a huge Oligocene
sand sea, the Chuska erg
. The erg hypothesis is consistent with major exhumation of the central Colorado Plateau in the late Oligocene and early Miocene
(e.g., from about 26 to 16 million years ago). If so, then major uplift of the central Colorado Plateau may postdate the Laramide orogeny.
Minette
of the Navajo Volcanic Field intruded and was extruded through the Chuska Sandstone. Minette makes up the two highest points, Roof Butte and Matthews Peak. A maar
complex, containing pyroclastic and extrusive minette, is exposed along New Mexico Highway 134 in Narbona Pass (Brand et al., 2008). Argon-argon dating of four minette samples at Narbona Pass yielded consistent ages of 25 million years. Very little oil
has been produced in Arizona, and much of that production has come from a minette sill
, the reservoir rock of the Dineh-bi-Keyah field in the northwestern Chuska Mountains near Roof Butte. The sill is intruded into lower Pennsylvanian
sedimentary rock
s. The producing rock is both porous and fractured, and it is characterized by large poikilitic
sanidine
grains with inclusions of diopsidic
augite
and biotite: potassium-argon dating
of the biotite yielded 25.7 million years. This pulse of magmatism at about 25 million years may have been accompanied by uplift of the Defiance-Chuska high in addition to the uplift during the Laramide orogeny.
Helium
-rich gas
has been extracted from Devonian
strata in the Dineh-bi-Keyah field. Additional economic resources have included uranium
, mined from some of the Mesozoic strata, particularly from the Morrison Formation
in the Lukachukai Mountains at the northwest end of the Chuska Mountains.
Colorado Plateau
The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...
and within the Navajo Nation
Navajo Nation
The Navajo Nation is a semi-autonomous Native American-governed territory covering , occupying all of northeastern Arizona, the southeastern portion of Utah, and northwestern New Mexico...
. The range is about 80 by 15 km (50 by 10 miles), and it trends north-northwest and is crossed by the state line between Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. The highlands are a dissected plateau
Dissected plateau
A dissected plateau is a plateau area that has been severely eroded so that the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable from orogenic mountain belts by the lack of folding, metamorphism, extensive faulting, or magmatic activity...
, with an average elevation of about 2740 m (8,989.5 ft), and subdued topography. The highest point is Roof Butte
Roof Butte
Roof Butte is a peak of the Chuska Mountains in Arizona, United States. Roof Butte is the highest peak of the Chuska Mountains which run in a north-northwest direction across the Arizona-New Mexico border. Roof Butte is a visible butte for miles around. The mountain has an elevation of . A...
(36.4601° N, 109.0929° W) at 2994 m (9,822.8 ft), near the northern end of the range in Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
. Other high points include the satellite Beautiful Mountain
Beautiful Mountain
Beautiful Mountain is the highest mountain in San Juan County and the highest of the New Mexico Chuska Mountains at 9,388 feet above sea level...
at 2861 m (9,386.5 ft) and Lukachukai Mountains
Lukachukai Mountains
The Lukachukai Mountains are a mountain range in northeast Arizona, entirely within the Navajo Indian Reservation. The highest point of the range is an unnamed point at 9466 feet above sea level...
at 2885 m (9,465.2 ft), both also near the northern end, and Matthews Peak at 2911 m (9,550.5 ft). The San Juan Basin borders the Chuskas on the east, and typical elevations in nearby parts of that basin are near 1800 m (5,905.5 ft). The eastern escarpment of the mountains is marked by slumps and landslides that extend out onto the western margin of the San Juan Basin. To the north, the Chuskas are separated from the Carrizo Mountains
Carrizo Mountains
The Carrizo Mountains are a small range 15 to 20 km in diameter located on the Colorado Plateau in northeastern Arizona. The range is about southwest of the Four Corners. The highest summit, Pastora Peak, is in elevation, whereas elevations on the surrounding plateau are near . The mountains...
by Red Rock Valley.
Peaks
| Rank | Peak Name | Elevation (Feet) | Elevation (Meters) | Subrange |
|---|---|---|---|---|
| 1 | Roof Butte Roof Butte Roof Butte is a peak of the Chuska Mountains in Arizona, United States. Roof Butte is the highest peak of the Chuska Mountains which run in a north-northwest direction across the Arizona-New Mexico border. Roof Butte is a visible butte for miles around. The mountain has an elevation of . A... |
9,823 ft | 2,994 m | |
| 2 | Peak 9778 | 9,778 ft | 2,980 m | |
| 3 | Peak 9566 | 9,566 ft | 2,916 m | |
| 4 | Matthews Peak | 9,550 ft | 2,911 m | Tunitcha Mountains |
| 5 | Lukachukai Mountains HP | 9,466 ft | 2,885 m | Lukachukai Mountains Lukachukai Mountains The Lukachukai Mountains are a mountain range in northeast Arizona, entirely within the Navajo Indian Reservation. The highest point of the range is an unnamed point at 9466 feet above sea level... |
| 6 | Lukachukai BM | 9,416 ft | 2,870 m | Lukachukai Mountains Lukachukai Mountains The Lukachukai Mountains are a mountain range in northeast Arizona, entirely within the Navajo Indian Reservation. The highest point of the range is an unnamed point at 9466 feet above sea level... |
| 7 | Bear BM | 9,396 ft | 2,864 m | |
| 8 | Beautiful Mountain Beautiful Mountain Beautiful Mountain is the highest mountain in San Juan County and the highest of the New Mexico Chuska Mountains at 9,388 feet above sea level... |
9,388 ft | 2,861 m | |
| 9 | Washington Pass BM | 9,370 ft | 2,856 m | |
| 10 | Peak 9280 | 9,280 ft | 2,829 m |
Reservation
Much of the range is Navajo Nation Forest, and ponderosa pine, spruce, and fir are among the important tree varieties. Trees there were cut and transported more than 75 km (about 50 miles) to the east to construct pueblos in Chaco Culture National Historical ParkChaco Culture National Historical Park
Chaco Culture National Historical Park is a United States National Historical Park hosting the densest and most exceptional concentration of pueblos in the American Southwest. The park is located in northwestern New Mexico, between Albuquerque and Farmington, in a remote canyon cut by the Chaco Wash...
in the San Juan Basin as early as 974 A.D. Logging in the Chuskas was suspended in 1994, but was set to commence again in summer 2008.
The forests of the Chuska Mountains and of the Defiance Uplift receive higher rainfall than the surrounding lowlands, and these highlands typically generate more than half the surface water of the Navajo Nation
Navajo Nation
The Navajo Nation is a semi-autonomous Native American-governed territory covering , occupying all of northeastern Arizona, the southeastern portion of Utah, and northwestern New Mexico...
. Canyons of Canyon de Chelly National Monument
Canyon de Chelly National Monument
Canyon de Chelly National Monument was established on April 1, 1931 as a unit of the National Park Service. It is located in northeastern Arizona within the boundaries of the Navajo Nation...
were cut by streams with headwaters in the Chuskas.
The Chuska Mountains are sparsely populated. Nearby settlements are small, and they include Crystal, New Mexico and Lukachukai, Arizona to the west and Toadlena, New Mexico to the east. Trading posts at Crystal and at Two Grey Hills (about 10 km east of Toadlena), are associated with distinctive patterns used in Navajo rugs. A paved road, New Mexico Highway 134, crosses the range through Narbona Pass. Narbona Pass was formerly named Washington Pass, after Colonel John M. Washington, who commanded a military expedition against the Navajo. Narbona
Narbona
Narbona was a Navajo chief who participated in the Navajo Wars. He was killed in a confrontation with U.S. soldiers on August 30th, 1849....
was a Navajo headman killed in an encounter with Washington's troops in 1849.
Geology
The Chuska Mountains and the Defiance Uplift immediately to the southwest form one of the prominent uplifted highs of the Colorado PlateauColorado Plateau
The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...
. The uplifted region is separated from the San Juan Basin
San Juan Basin
The San Juan Basin is a geologic structural basin in the Four Corners region of the Southwestern United States; its main portion covers around , encompassing much of northwestern New Mexico, southwest Colorado, and parts of Arizona and Utah....
to the east by the Defiance and associated monocline
Monocline
A monocline is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence.-Formation:Monoclines may be formed in several different ways...
s. Relative uplift, basin subsidence, and monocline formation began in the early stages of the Laramide orogeny
Laramide orogeny
The Laramide orogeny was a 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, as is the cause. The Laramide...
about 75 to 80 million years ago. Although the Chuska Mountains can be considered part of the Defiance Uplift, they stand higher. They are capped by an erosional remnant of Chuska Sandstone, a unit locally more than 500 meters thick. The flat-lying Chuska Sandstone rests unconformably
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
on Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
rocks deformed in the Defiance monocline. Biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
in layers of altered volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
within the Chuska Sandstone has yielded radiometric ages of 35 and 33 million years by argon-argon dating
Argon-argon dating
Argon-argon dating is a radiometric dating method invented to supersede potassium-argon dating in accuracy. The older method required two samples for dating while the newer method requires only one...
. The Chuska Sandstone is formed of sand dune
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
deposits, and it appears to be a remnant of a huge Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
sand sea, the Chuska erg
Erg (landform)
An erg is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover. The term takes its name from the Arabic word ʿarq , meaning "dune field"...
. The erg hypothesis is consistent with major exhumation of the central Colorado Plateau in the late Oligocene and early Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
(e.g., from about 26 to 16 million years ago). If so, then major uplift of the central Colorado Plateau may postdate the Laramide orogeny.
Minette
Minette
Minette may refer to:*the Haitian actress Minette *Henrietta Anne of England also nicknamed Minette*Minette is an archaic rock term used to locally describe a particular type of lamprophyre...
of the Navajo Volcanic Field intruded and was extruded through the Chuska Sandstone. Minette makes up the two highest points, Roof Butte and Matthews Peak. A maar
Maar
A maar is a broad, low-relief volcanic crater that is caused by a phreatomagmatic eruption, an explosion caused by groundwater coming into contact with hot lava or magma. A maar characteristically fills with water to form a relatively shallow crater lake. The name comes from the local Moselle...
complex, containing pyroclastic and extrusive minette, is exposed along New Mexico Highway 134 in Narbona Pass (Brand et al., 2008). Argon-argon dating of four minette samples at Narbona Pass yielded consistent ages of 25 million years. Very little oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
has been produced in Arizona, and much of that production has come from a minette sill
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...
, the reservoir rock of the Dineh-bi-Keyah field in the northwestern Chuska Mountains near Roof Butte. The sill is intruded into lower Pennsylvanian
Pennsylvanian
The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
s. The producing rock is both porous and fractured, and it is characterized by large poikilitic
Poikilitic
Poikilitic texture refers to crystals, typically phenocrysts, in an igneous rock which contain small grains of other minerals. The texture is most easily observed in petrographic thin sections....
sanidine
Sanidine
Sanidine is the high temperature form of potassium feldspar 4O8. Sanidine most typically occurs in felsic volcanic rocks such as obsidian, rhyolite and trachyte. Sanidine crystallizes in the monoclinic crystal system. Orthoclase is a monoclinic polymorph stable at lower temperatures...
grains with inclusions of diopsidic
Diopside
Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class...
augite
Augite
Augite is a single chain inosilicate mineral, 2O6. The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees.-Characteristics:Augite is a solid solution in the pyroxene group...
and biotite: potassium-argon dating
Potassium-argon dating
Potassium–argon dating or K–Ar dating is a radiometric dating method used in geochronology and archeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium into argon . Potassium is a common element found in many materials, such as micas, clay minerals,...
of the biotite yielded 25.7 million years. This pulse of magmatism at about 25 million years may have been accompanied by uplift of the Defiance-Chuska high in addition to the uplift during the Laramide orogeny.
Helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
-rich gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
has been extracted from Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
strata in the Dineh-bi-Keyah field. Additional economic resources have included uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
, mined from some of the Mesozoic strata, particularly from the Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
in the Lukachukai Mountains at the northwest end of the Chuska Mountains.