The Blue Springs Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

exposed in the

Los Pinos Mountains The Los Pinos Mountains are a small mountain range in the central part of New Mexico, US. They are the southernmost part of a mountain front, running north to south, that also includes the Sandia Mountains and the Manzano Mountains. The Los Pinos ...

of central

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

Description

The formation consists of almost of metasedimentary rock. The lower beds are massive gray to red

slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic ro ...

and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

, while the central portion mostly is greenish

sericite Sericite is the name given to very fine, ragged grains and aggregates of white (colourless) micas, typically made of muscovite, illite, or paragonite. Sericite is produced by the alteration of orthoclase or plagioclase feldspars in areas th ...

schist Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...

with occasional slate and siltstone beds. The uppermost beds are again red to gray slate. The formation is underlain by the

Sais Quartzite The Sais Quartzite is a geologic formation exposed in the Los Pinos Mountains of central New Mexico. Description The formation consists of up to of massive gray quartzite beds, thick, interbedded with thinner sericite-bearing quartzite beds. A ...

and overlain by

Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 538.8 million years to the present, and it began with the Cambrian Period, when anima ...

units. The middle schist is interpreted as a metarhyolite (a

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained ( aphanitic) in texture, but may be porphyritic, containing larger mineral crystals ( phenocrysts) in an otherwise fine-grained groundmass. The min ...

). The crystallization age of the formation is placed at 1588 ± 7 million years ( Ma), corresponding to the earliest

Calymmian The Calymmian Period (from grc, κάλυμμα, kálymma, meaning "cover") is the first geologic period in the Mesoproterozoic Era and lasted from Mya to Mya (million years ago). Instead of being based on stratigraphy, these dates are defined ...

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

of the

Mesoproterozoic The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic ...

History of investigation

The formation was originally described as the Blue Springs schist by J.T. Stark and E.C. Dapples in 1946 and named for Blue Springs, a seepage area just north of Highway 60. The formation was first assigned to the

Manzano Group 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 name ''Manzano Group'' was pr ...

in 2006.

References

{{Reflist Permian formations of New Mexico Precambrian formations of New Mexico

Description

History of investigation

See also

References