Rinconada Formation | |
---|---|
Stratigraphic range: | |
Type | Formation |
Unit of | Hondo Group |
Underlies | Pilar Formation |
Overlies | Ortega Formation |
Thickness | 600 m (2,000 ft) |
Lithology | |
Primary | Schist |
Other | Quartzite |
Location | |
Coordinates | 36°12′52″N105°48′11″W / 36.2144591°N 105.8030674°W |
Region | Picuris Mountains, New Mexico |
Country | United States |
Type section | |
Named for | Village of Rinconada ( 36°25′43″N106°07′02″W / 36.4287°N 106.1173°W ) |
Named by | Just |
Year defined | 1937 |
The Rinconada Formation is a geologic formation that crops out in the Picuris Mountains of northern New Mexico. Detrital zircon geochronology establishes a maximum age for the Rinconada Formation of about 1723 Mya, placing it in the Statherian period of the Precambrian.
The formation consists of gray to buff quartz-muscovite schist with some inberbedded quartzite and metaconglomerate. [1] which fills an inverted syncline in the northern Picuris Mountains. [2] It is missing from the Hondo Group in the Tusas Mountains. [3] Detrital zircon geochronology establishes a minimum age for the Rinconada Formation of 1762 Mya. However, this reflects the crystallization age of the source rocks, and the true age is likely closer to 1723 Mya based on zircon ages in the underlying Ortega Formation. This indicates a shift in source region between the Ortega Formation and the Rinconada Formation. [4]
The formation is divided into three informal members. [5] The first is composed of staurolite gneiss and schist, from 60 meters (200 feet) to 150 meters (490 feet) thick, which contains porphyroblasts of garnet and staurolite up to 4 centimeters (1.6 in) long. [1] Most of the staurolite from these beds is twinned, and the large crystals are prized by mineral collectors. Where the schist is heavily micaceous and easily eroded, the ground surface is covered with weathered-out staurolite crystals. [6] [5] This member includes spotty basal andalusite-biotite hornfels, from 65 meters (213 feet) to 120 meters (390 feet) thick, consisting of biotite crystals up to 1 centimetre (0.39 inches) in size in a coarsely felted mass of muscovite and quarts. This includes knots of quartz and andalusite up to 25 centimetres (9.8 inches) in diameter. [7]
The staurolite likely crystallized out at a temperature of 532 ± 20 °C and about 3,700 bar total pressure under conditions of water undersaturation. [8]
The second member is a gray-white quartzite, 60 meters (200 feet) to 180 meters (590 feet) thick, with slabby jointing and devoid of sillimanite and kyanite. [9] The third member is a muscovite-rich phyllite with a pearly to greenish gray sheen containing small staurolite and garnet crystals. [10]
The Rinconada Formation is separated from the overlying Pilar Formation by an unconformity representing a gap in geologic time of 200 million years. [4]
The Rinconada Formation is interpreted as deltaic, fluvial, and shallow marine deposition of the regressive sequence of a marine transgression. This was likely part of the northern coast of a back-arc basin associated with the Yavapai orogeny, named the Pilar basin. The quartzite at the upper contact with the Pilar Formation then represents renewed transgression. [4]
The beds making up the unit were originally assigned to the Ortega quartzite by Evan Just during his 1937 survey of pegmatites in northern New Mexico. Evan gave the informal name, Rinconada schist, to these beds and noted the presence of staurolite porphyroblasts. [11] Montgomery formalized the designation of the mixed schist and quartzite beds as the Rinconada member of the Ortega Formation in 1953. [12] The Rinconada Member was promoted to independent formation status by Bauer and Williams in their sweeping revision of the Precambrian stratigraphy of northern New Mexico in 1987. [3]
The Manzano Group is a group of geologic formations in central New Mexico. These have radiometric ages of 1601 to 1662 million years (Ma), corresponding to the late Statherian period of the Paleoproterozoic.
The Mazatzal orogeny was an orogenic event in what is now the Southwestern United States from 1650 to 1600 Mya in the Statherian Period of the Paleoproterozoic. Preserved in the rocks of New Mexico and Arizona, it is interpreted as the collision of the 1700-1600 Mya age Mazatzal island arc terrane with the proto-North American continent. This was the second in a series of orogenies within a long-lived convergent boundary along southern Laurentia that ended with the ca. 1200–1000 Mya Grenville orogeny during the final assembly of the supercontinent Rodinia, which ended an 800-million-year episode of convergent boundary tectonism.
The Yavapai orogeny was an orogenic (mountain-building) event in what is now the Southwestern United States that occurred between 1710 and 1680 million years ago (Mya), in the Statherian Period of the Paleoproterozoic. Recorded in the rocks of New Mexico and Arizona, it is interpreted as the collision of the 1800-1700 Mya age Yavapai island arc terrane with the proto-North American continent. This was the first in a series of orogenies within a long-lived convergent boundary along southern Laurentia that ended with the ca. 1200–1000 Mya Grenville orogeny during the final assembly of the supercontinent Rodinia, which ended an 800-million-year episode of convergent boundary tectonism.
The Picuris orogeny was an orogenic event in what is now the Southwestern United States from 1.43 to 1.3 billion years ago in the Calymmian Period of the Mesoproterozoic. The event is named for the Picuris Mountains in northern New Mexico and interpreted either as the suturing of the Granite-Rhyolite crustal province to the southern margin of the proto-North American continent Laurentia or as the final suturing of the Mazatzal crustal province onto Laurentia. According to the former hypothesis, this was the second in a series of orogenies within a long-lived convergent boundary along southern Laurentia that ended with the ca. 1200–1000 Mya Grenville orogeny during the final assembly of the supercontinent Rodinia, which ended an 800-million-year episode of convergent boundary tectonism.
The Vadito Group is a group of geologic formations that crops out in most of the Precambrian-cored uplifts of northern New Mexico. Detrital zircon geochronology and radiometric dating give a consistent age of 1700 Mya for the group, corresponding to the Statherian period.
The Big Rock Formation is a formation that crops out in the Tusas Mountains of northern New Mexico. Detrital zircon geochronology gives a maximum age for the formation of 1665 Mya, corresponding to the Statherian period.
The Burned Mountain Formation is a geologic formation that crops out in the Tusas Mountains of northern New Mexico. It has a U-Pb radiometric age of 1700 Mya, corresponding to the Statherian period.
The Picuris Mountains are a mountain range in northern New Mexico. They are considered a subrange of the Sangre de Cristo Mountains.
The Glenwoody Formation is a geological formation that is exposed in the cliffs southeast of the Rio Grande Gorge near the town of Pilar and in a few other locations in the Picuris Mountains. Its minimum age from detrital zircon geochronology is 1.693 Mya, corresponding to the Statherian period.
The Hondo Group is a group of geologic formations that crops out in most of the Precambrian-cored uplifts of northern New Mexico. Detrital zircon geochronology gives a maximum age for the lower Hondo Group of 1765 to 1704 million years (Mya), corresponding to the Statherian period.
The Ortega Formation is a geologic formation that crops out in most of the mountain ranges of northern New Mexico. Detrital zircon geochronology establishes a maximum age for the formation of 1690-1670 million years (Mya), in the Statherian period of the Precambrian.
The Pilar Formation is a geologic formation that crops out in the Picuris Mountains of northern New Mexico. It has a radiometric age of 1488 ± 6 million years, corresponding to the Calymmian period.
The Piedra Lumbre Formation is a geologic formation that crops out in the Picuris Mountains of northern New Mexico. Detrital zircon geochronology yields a maximum age of 1475 million years, corresponding to the Calymmian period.
The Marquenas Formation is a geological formation that crops out in the Picuris Mountains of northern New Mexico. Detrital zircon geochronology gives it a maximum age of 1435 million years, corresponding to the Calymmian period.
The Uncompahgre Formation is a geologic formation in Colorado. Its radiometric age is between 1707 and 1704 Ma, corresponding to the Statherian period.
The Trampas Group is a group of geologic formations that crops out in the Picuris Mountains of northern New Mexico. Detrital zircon geochronology yields a maximum age of 1475 million years, corresponding to the Calymmian period.
The White Ridge Quartzite is a geologic formation in central New Mexico. It has a maximum age of 1650 million years (Ma), corresponding to the Statherian period.
The Sais Quartzite is a geologic formation exposed in the Los Pinos Mountains of central New Mexico.
The Abajo Formation is a geologic formation in the Los Pinos Mountains of central New Mexico. It was deposited about 1660 million years (Ma) ago, corresponding to the Statherian period.
The White Ledges Formation is a geologic formation that crops out in central Arizona, US. Detrital zircon geochronology establishes a maximum age for the formation of 1726 million years (Mya), in the Statherian period of the Precambrian. The formation is typical of quartzites deposited around 1650 million years ago in the southwestern part of Laurentia, the ancient core of the North American continent.