Puye Formation

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Puye Formation
Stratigraphic range: Miocene to Pliocene, 7–4  Ma
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Puye escarpment.jpg
Puye Formation at its type area, the Puye Escarpment, near San Ildefonso Pueblo, New Mexico
Type Formation
Unit of Santa Fe Group
Sub-unitsTotavi Lentil
Underlies Tewa Group
Overlies Chamita Formation
Area518 km2
Thickness221 metres (725 feet)
Lithology
Primary Volcaniclastic
Other Ignimbrite
Location
Coordinates 35°53′29″N106°10′23″W / 35.8914°N 106.1730°W / 35.8914; -106.1730 Coordinates: 35°53′29″N106°10′23″W / 35.8914°N 106.1730°W / 35.8914; -106.1730
RegionFlag of New Mexico.svg  New Mexico
CountryFlag of the United States.svg  United States
Type section
Named forPuye Escarpment
Named byH.T.U. Smith
Year defined1938
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Puye Formation (the United States)
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Puye Formation (New Mexico)

The Puye Formation is a geologic formation exposed east of the Jemez Mountains of northern New Mexico. Radiometric dating constrains its age to between 5 and 2 million years, corresponding to the Pliocene epoch.

Contents

Description

The Puye Formation is a fanglomerate containing 25 pyroclastic flows, including pumicious ignimbrites and block and ash flows, erupted by vents of the Tschicoma Formation. It is exposed from the mouth of Ancho Canyon in White Rock Canyon north to Santa Clara Peak, and generally underlies the Bandelier Tuff north and east of the city of Los Alamos, covering an area of 518 square kilometers (200 sq mi). [1] It is best exposed in Guaje Canyon and on the southern end of the Puye Escarpment where it is a cliff-forming formation. It is 71 meters (233 ft) thick at the type section but thickens westward towards the Sierra de los Valles, west of Los Alamos. Drilling has found that the formation is up to 221 meters (725 ft) thick. 1964 [2] The formation was deposited between 7 and 4 million years ago, based on radiometric dating of an ash bed in the upper part of the formation and the absence of Bearhead Rhyolite ash (~7 million years old) in the formation. [3] [4]

The Totavi Lentil is the lowest part of the formation, some 24 meters (79 ft) thick, which consists of pebbles, cobbles, and small boulders of quartzite and granite with only limited volcanic debris, contrasting with the remainder of the formation. [2] This is separated by a significant unconformity from the underlying Chamita Formation. [4] The Totavi Lentil is raised to formation rank by some investigators. [1]

The main body of the Puye Formation consists of fanglomerates in which most of the detritus is volcanic rock of dacitic composition. There are also dacitic tephra beds and some basalt. 1964 The formation shows cyclicity on the scale of 5 to 30 meters representing individual eruptive pulses in the northeastern Jemez highlands. Each sequence shows marked facies changes with increased distance from the eruptive center. Deposition ceased with reduction in Tschicoma volcanism and basinwide pedimentation due to downcutting of the Rio Grande. The formation is remarkably well preserved for a volcanic fanglomerate, due to its deposition in an active graben associated with Rio Grande Rift. [5]

A notable feature of exposures of the formation is the presence of pedestal rocks. [6]

Economic geology

The formation is a high-yield aquifer exploited in the Los Alamos area. [7] Use of potassium dichromate in a power plant created an unusually well-characterized source of chromium contamination in this aquifer, which has been studied to understand natural attenuation of such pollutants. [8]

History of investigation

The formation was first named the Puye Gravel by Harold T.U. Smith in his mapping of the Abiquiu quadrangle in 1938. [9] The name was changed to Puye Conglomerate by Roy Griggs in 1964, since the exposures he studied were consolidated enough to stand as cliffs. Griggs also designated a type section and divided the unit into an upper unnamed fanglomerate and a lower Totavi Lentil, named for a nearby settlement. Griggs assigned the formation to the Santa Fe Group. [10]

Because of its diverse lithology, the formation was renamed the Puye Formation by Bailey, Smith, and Ross in 1969 as part of their work establishing the stratigraphy of the Jemez Mountains. [2]

Footnotes

Related Research Articles

Dacite Volcanic rock intermediate in composition between andesite and rhyolite

Dacite is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz.

Valles Caldera Volcanic caldera in the Jemez Mountains of northern New Mexico, United States

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Jemez Mountains Mountain range in New Mexico, United States

The Jemez Mountains are a group of mountains in Rio Arriba, Sandoval, and Los Alamos counties, New Mexico, United States.

Chicoma Mountain Mountain in New Mexico, United States

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Redondo Peak Mountain in New Mexico, United States

Redondo Peak is a conspicuous summit in the Jemez Mountains of New Mexico, in the southwestern United States. It is located entirely within the Valles Caldera National Preserve. It is the second highest summit in the Jemez after Chicoma Mountain. It is the most visually prominent peak in the range when viewed from the south, for example, from Albuquerque. From many other directions it is less prominent or not visible, due to its location in the center of the Valles Caldera, well away from the caldera's rim.

Pajarito Plateau

The Pajarito Plateau is a volcanic plateau in north central New Mexico, United States. The plateau, part of the Jemez Mountains, is bounded on the west by the Sierra de los Valles, the range forming the east rim of the Valles Caldera, and on the east by the Puye escarpment, which rises about 300 to 400 feet above the Rio Grande valley about a mile west of the river. The Rio Grande passes through White Rock Canyon to the southeast, and the Caja del Rio across the river is sometimes regarded as part of the plateau. The plateau is occupied by several notable entities, including Bandelier National Monument, the town of Los Alamos and its remote suburb White Rock, and Los Alamos National Laboratory. Elevations range from about 5600 feet at the river to about 7800 feet where the plateau merges into the mountain range.

Zuni-Bandera volcanic field Volcanic field in New Mexico, United States

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Abiquiu Formation A geologic formation in New Mexico

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Santa Fe Group (geology) Group of geologic formations filling the Rio Grande rift

The Santa Fe Group is a group of geologic formations in New Mexico and Colorado. It contains fossils characteristic of the Oligocene through Pleistocene epochs. The group consists of basin-filling sedimentary and volcanic rocks of the Rio Grande rift, and contains important regional aquifers.

Bandelier Tuff A geologic formation in New Mexico

The Bandelier Tuff is a geologic formation exposed in and around the Jemez Mountains of northern New Mexico. It has a radiometric age of 1.85 to 1.25 million years, corresponding to the Pleistocene epoch. The tuff was erupted in a series of at least three caldera eruptions in the central Jemez Mountains.

Ritito Conglomerate A geologic formation in New Mexico

The Ritito Conglomerate is a geologic formation in northern New Mexico dating to the Oligocene epoch.

Polvadera Group A group of geologic formations in New Mexico

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Keres Group A group of geologic formations in New Mexico

The Keres Group is a group of geologic formations exposed in and around the Jemez Mountains of northern New Mexico. Radiometric dating gives it an age of 13 to 6 million years, corresponding to the Miocene epoch.

Cochiti Formation A geologic formation in New Mexico

The Cochiti Formation is a geologic formation exposed near the southwest Jemez Mountains of northern New Mexico. Its age is estimated as 10 to 2.6 million years, corresponding to the middle Miocene to Pliocene.

Tewa Group A group of geologic formations in New Mexico

The Tewa Group is a group of geologic formations exposed in and around the Jemez Mountains of northern New Mexico. Radiometric dating gives it an age of 1.85 million to 72 thousand years, corresponding to the Pleistocene epoch.

Gilman Conglomerate A geologic formation in New Mexico

The Gilman Conglomerate is a geologic formation in northern New Mexico dating to the Oligocene epoch.

Espanola basin Structural basin in northern New Mexico, US

The Espanola basin is a structural basin in northern New Mexico. It is located in the Rio Grande watershed and is part of the Rio Grande rift. The definition of its boundaries is not fully settled, but the basin is usually defined such that it includes the cities of Santa Fe, Los Alamos, and Espanola.

References