Navajo section
Encyclopedia
The Navajo Section is a physiographic section
Physiographic regions of the world
The physiographic regions of the world are a means of defining the Earth's landforms into distinct regions based upon classic 1916 three-tiered approach defining divisions, provinces, and sections...

 of the larger Colorado Plateaus
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,...

 province, which in turn is part of the larger Intermontane Plateaus
Intermontane Plateaus
Physiographic regions of the U.S. InteriorSee:legendIn some places,high plateaus lie between the mountain ranges, for example,the plateau of Anatolia in Turkey and the plateau of Tibet.These are called "Intermontane plateaus"....

 physiographic division. It is located in northeastern 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 northwestern 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...

, is named for 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...

 reservation, with about half of the area of the section in the reservation, and are characterized by broad rolling plains carved on easily eroded rocks, and cuesta
Cuesta
In structural geology and geomorphology, a cuesta is a ridge formed by gently tilted sedimentary rock strata in a homoclinal structure. Cuestas have a steep slope, where the rock layers are exposed on their edges, called an escarpment or, if more steep, a cliff...

s and tablelands
Tablelands
Tablelands may refer to:* Areas also called plateaus* The Tablelands in Gros Morne National Park, Newfoundland and Labrador, Canada...

 capped by gently dipping resistant sandstone beds. The lowest point in the section is about 4,700 ft., near the Four Corners area, where the boundary between the Navajo Section and the Canyon Lands
Canyon Lands
The Canyon Lands Section of the Colorado Plateaus is a physiographic section of the larger Colorado Plateaus province, which in turn is part of the larger Intermontane Plateaus physiographic division. They are a desolate but spectacularly scenic sandstone area of southeastern Utah...

 section is, is in the San Juan River channel. The highest point in the New Mexico part of the Navajo Section is at Chromo Mountain (elevation 9,916 ft) on the Continental Divide
Continental Divide
The Continental Divide of the Americas, or merely the Continental Gulf of Division or Great Divide, is the name given to the principal, and largely mountainous, hydrological divide of the Americas that separates the watersheds that drain into the Pacific Ocean from those river systems that drain...

 near Chama
Chama, New Mexico
Chama is a village in Rio Arriba County, New Mexico, United States. The population was 1,199 at the 2000 census. It is a small village, but tourism is starting to help the town's economy .-Geography:...

. One of the most prominent features of the Navajo Section is the Ship Rock, near the town of Shiprock.

Geology and physiography

The area is predominately generally horizontal sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

 beds with some shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

 sequences of late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 and early Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

 age. A few areas of the section also have abundant volcanic necks and buttes
Buttes
Buttes was a municipality in the district of Val-de-Travers in the canton of Neuchâtel in Switzerland. On 1 January 2009, the former municipalities of Boveresse, Buttes, Couvet, Fleurier, Les Bayards, Môtiers, Noiraigue, Saint-Sulpice and Travers merged to form Val-de-Travers....

, but due to the arid weather and soft sandstone, many of the rock formations of the area have eroded to form distinctive features of long cuesta
Cuesta
In structural geology and geomorphology, a cuesta is a ridge formed by gently tilted sedimentary rock strata in a homoclinal structure. Cuestas have a steep slope, where the rock layers are exposed on their edges, called an escarpment or, if more steep, a cliff...

s, shallow canyons and valleys, narrow fan terraces, undulating plateaus, isolated mesas, steep hills, and some shale badlands
Badlands
A badlands is a type of dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded by wind and water. It can resemble malpaís, a terrain of volcanic rock. Canyons, ravines, gullies, hoodoos and other such geological forms are common in badlands. They are often...

.

Near the Four Corners area is a steeply tilted 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...

 known as The Hogback, which trends southwestward from where the San Juan River enters the area. Here the San Juan River flows into an area known as 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....

, where the western San Juan Basin is typified by exposures of the Fruitland
Fruitland Formation
The Fruitland Formation is a sedimentary geological formation containing layers of sandstone, shale, and coal. It was laid down in marshy delta conditions, with poor drainage and frequent flooding, under a warm, humid and seasonal climate...

 and Menefee Formations. A stepped sequence of high stream terraces, present above the San Juan River and its tributaries, represents abandoned Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

flood plains.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK