The Manzano Group is a

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

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 New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

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

Statherian The Statherian Period (; , 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 are defined chronometrically. Th ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

of the

Paleoproterozoic The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions ( eras) of the Proterozoic eon, and also the longest era of the Earth's geological history, spanning from (2.5–1.6 Ga). It is further sub ...

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

Permian The Permian ( ) is a geologic period and System (stratigraphy), 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 251.902 Mya. It is the s ...

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

paleontological Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...

time scale of the

in western

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. However, the name was abandoned after 1920.

Description

The group consists of

lithostratigraphic Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneous ...

units 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 ...

and nearby ranges of central New Mexico. These are mostly metarhyolite or

quartzite Quartzite is a hard, non- foliated metamorphic rock that 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 tecton ...

units with some

schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...

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 ...

, and form a sequence in excess of thick. The group records deformation attributed to the

Mazatzal orogeny 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 coll ...

, and the quartzites of the group may be the

provenance Provenance () 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 in a wide range of fields, including archaeology, p ...

of the lower conglomerates of the

Marquenas Formation 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. Description The ...

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 The Yavapai ( ) are a Native American tribe in Arizona. Their Yavapai language belongs to the Upland Yuman branch of the proposed Hokan language family. Today Yavapai people are enrolled in the following federally recognized tribes: * Fort ...

crust. The group was subsequently severely folded and intruded by magma bodies during the

Picuris orogeny 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 ...

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 superimposed ...

in the Los Pinos Mountains. Here the stratigraphy is: : Blue Springs Formation (youngest) :

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. ...

:Estadio Schist : White Ridge Quartzite : Abajo Formation : 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 time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

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, drugs which induce temporary improvements in either mental or physical function or both * ''Upper'', the original film title for the 2013 found f ...

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 extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

fossils that the Abo Formation was Uralian (

Cisuralian The Cisuralian, also known as the Early Permian, is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mou ...

?) 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 The Bursum Formation is a geologic formation in New Mexico.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, Glorieta Sandstone, 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 Quartzite groups Schist groups

Description

Stratigraphy

History of investigation

See also

References