Vadito Group | |
---|---|
Stratigraphic range: | |
Type | Group |
Sub-units | Big Rock Formation Burned Mountain Formation Glenwoody Formation |
Underlies | Hondo Group |
Overlies | Moppin Complex |
Lithology | |
Primary | Metasedimentary rock |
Other | Metavolcanic rock |
Location | |
Coordinates | 36°11′35″N105°47′49″W / 36.193°N 105.797°W |
Region | Picuris and Tusas Mountains, New Mexico |
Country | United States |
Type section | |
Named for | Vadito, New Mexico |
Named by | A. Montgomery |
Year defined | 1953 |
Map of Vadito Group outcroppings |
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 Vadito Group is an extensive sequence of supracrustal rocks dominated by feldspathic gneisses, feldspathic schists, and metamorphosed sandstones and conglomerates. Its lower section includes amphibolites, though mafic beds make up less than 10% of the unit. It is found in the Picuris Mountains, the Tusas Mountains, the Truchas Range, the Mora River area, the Rincon Mountains ( 36°04′42″N105°21′01″W / 36.0784234°N 105.3502279°W ), the northern Taos Range, and in the Cimarron Range. [1] [2] Detrital zircon geochronology establishes that the principal source regions for the sediments that became the Vadito Group had ages of 1765 to 1704 Mya. [3] The absolute age of the Burned Mountain Formation constituting the upper part of the Vadito Group in the Tusas Mountains is 1700 Mya, based on uranium-lead dating. [4]
The Vadito Group is divided into the Big Rock Formation and Burned Mountain Formation in the Tusas Mountains, and the upper Vadito Group is assigned to the Glenwoody Formation in the Picuris Mountains. The Burnt Mountain Formation probably correlates with the Glenwoody Formation while the Big Rock Conglomerate corresponds to a disconformity in the Picuris Mountains. Detrital zircon dating indicates that the Marquenas Formation, formerly assigned to the Vadito Group, has a maximum age of 1435 Mya and is not part of the Vadito Group. [3]
The Vadito Group lies structurally above the Hondo Group in the Picuris Mountains. However, both groups have been severely deformed and metamorphosed, and the Vadito Group is thought to actually be the older of the two groups. Cross-bedding indicates that the Vadito Group has been overturned. [2]
Three metamorphic episodes are recognized in the group. Only the third is well constrained in time, occurring around 1420 Mya and reaching the amphibolite facies. [3] This is likely associated with the Picuris orogeny. [5]
The Vadito Group is interpreted to have been deposited in deep water in a volcanic back-arc basin (the Pilar basin) that opened during the Yavapai orogeny. [3]
The Vadito Group is intruded by the pegmatite of the Harding Pegmatite Mine, [6] an historically important source of lithium, beryllium, and tantalum. The Vadito Group has also been mined for kyanite on Mesa La Jara ( 36°32′39″N106°04′55″W / 36.5443°N 106.082°W ). [7] Some 1500 tons of kyanite were extracted from Big Rock in 1928, and further prospecting took place in 1948–1949. However, there was no further development of the deposits. [8] The kyanite pods have been interpreted as either metamorphosed pelitic silt lenses, [9] as unusual pegmatites, [10] or as hydrothermal systems. [7] [11]
The unit was designated as the Vadito Formation in 1953 by Arthur Montgomery, [12] who had first taken interest in the geology of the Picuris Mountains as a result of his wartime operation of the Harding Pegmatite Mine. [13] P.E. Long recommended raising it to group rank in 1976 [14] and this was adopted by Bauer and Williams in their sweeping revision of northern New Mexico Precambrian stratigraphy. [1]
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 geology of New Mexico includes bedrock exposures of four physiographic provinces, with ages ranging from almost 1800 million years (Ma) to nearly the present day. Here the Great Plains, southern Rocky Mountains, Colorado Plateau, and Basin and Range Provinces meet, giving the state great geologic diversity.
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 Moppin Complex is a Precambrian geologic complex found in the Tusas Mountains of northern New Mexico. It has not been directly dated, but is thought to be Statherian based on a minimum age of 1.755 Gya from radiometric dating of magmatic intrusions.
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 Harding Pegmatite Mine is a former adit mine that extracted lithium, tantalum, and beryllium from a Precambrian pegmatite sill. It ceased operations in 1958 and its owner, Arthur Montgomery, donated it to the University of New Mexico, which runs the site as an outdoor geology laboratory with mineral collecting permitted on a small scale.
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 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 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 Tres Piedras Orthogneiss is a pluton in northern New Mexico. It has a U-Pb radiometric age of 1693 Mya, placing it in the Statherian 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.