The Manzano Group is a group of

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 ...

s in central

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

. These have radiometric ages of 1601 to 1662 million years ( Ma), corresponding to the late

Statherian The Statherian Period (; grc, σταθερός, statherós, meaning "stable, firm") is the final geologic period in the Paleoproterozoic Era and lasted from Mya to Mya (million years ago). Instead of being based on stratigraphy, these dates ar ...

period of the Paleoproterozoic. The name ''Manzano Group'' was previously applied to a group of sedimentary formations of

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

age in roughly the same geographical area. The original Manzano Group was historically important in the establishment of the paleontological time scale of the

period in western

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. However, the name was abandoned after 1920.

Description

The group consists of

lithostratigraphic units exposed in the Los Pinos Mountains and nearby ranges of central New Mexico. These are mostly metarhyolite or

quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tect ...

units with some

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 o ...

and

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose (flaky ...

, and form a sequence in excess of thick. The group records deformation attributed to the Mazatzal orogeny, and the quartzites of the group may be the

provenance Provenance (from the French ''provenir'', 'to come from/forth') is the chronology of the ownership, custody or location of a historical object. The term was originally mostly used in relation to works of art but is now used in similar senses i ...

of the lower conglomerates of the Marquenas Formation to the north, which was previously problematic. Study of the group also provides evidence in favor of the hypothesis that the Mazatzal Province was formed by continental arc volcanism from Yavapai crust. The group was subsequently severely folded and intruded by magma bodies during the Picuris orogeny.

Stratigraphy

The group is best exposed in an overturned

syncline In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimpose ...

in the Los Pinos Mountains. Here the stratigraphy is: : Blue Springs Formation (youngest) : Sais Quartzite :Estadio Schist : White Ridge Quartzite :

Abajo Formation 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. History of investigation The unit was first defined by S. ...

: Sevilleta Metarhyolite :Bootleg Canyon Sequence : Tijeras Greenstone The Estadio Schist is a garnet + staurolite + biotite schist, described as a marker bed separating the Sais Quartzite from the White Ridge Quartzite.

History of investigation

The Manzano Series was first named by Herrick in 1900. Herrick correctly placed the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

boundary just below the base of this unit and identified Permian fossils in overlying beds, but could find no fossils within the series itself. Gordon assigned the underlying beds to the (now-abandoned) Magdalena Group and added the overlying limestone beds now assigned to the San Andres Formation, and placed the Manzano Group in the

upper Carboniferous Upper may refer to: * Shoe upper or ''vamp'', the part of a shoe on the top of the foot * Stimulant Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those ...

based on fossils reported by Lee and Girty. The name continued in use at least as late as 1920, when Boese concluded from

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

fossils that the Abo Formation was Uralian (

Cisuralian The Cisuralian is the first Series (stratigraphy), series/Epoch (geology), epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian (geology), Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the w ...

?) in age. This placed the fossils in the upper Pennsylvanian as defined in western North America at that time, and Boese recommended abandonment, or at least heavy revision, of the Manzano Group. The modern units corresponding to the original Manzano Group are (in ascending stratigraphic order) the Bursum Formation,

Abo Formation The Abo Formation is a geologic formation in New Mexico. It contains fossils characteristic of the Cisuralian epoch of the Permian period. Description The Abo Formation consists of fluvial redbed mudstones and sandstones, including river channel ...

Yeso Formation The Yeso Group is a group of geologic formations in New Mexico. It contains fossils characteristic of the Kungurian Age of the early Permian Period. Description The Yeso Group is lithologically complex, ranging from marine shelf carbonate ...

Glorieta Sandstone The Glorieta Sandstone is a geologic formation in New Mexico. It preserves fossils characteristic of the Kungurian age of the Permian geology. Description The Glorietta Sandstone is a massive yellowish brown to light gray, cliff-forming, fine to ...

, and San Andres Formation. The Yeso Formation has itself been promoted to group rank, though this has not been universally accepted. The name ''Manzano Group'' was revived in 2006 to refer to latest

formations in the Manzano Mountains, a usage that has since become more widely adopted.

References

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

Description

Stratigraphy

History of investigation

See also

References