The Madera 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 ide ...

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 northern

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 ...

. Its fossil assemblage dates the formation to the middle to late

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timesca ...

period.

Description

The group consists primarily of marine

limestones Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms when t ...

, and it is exposed in the

Sandia Mountains The Sandia Mountains ( Southern Tiwa: ''Posu gai hoo-oo'', Keres: ''Tsepe,'' Navajo: ''Dził Nááyisí''; Tewa: ''O:ku:p’į'', Northern Tiwa: ''Kep’íanenemą''; Towa: ''Kiutawe'', Zuni: ''Chibiya Yalanne'') are a mountain range located ...

, the Lucero Uplift (), the western

Jemez Mountains The Jemez Mountains are a group of mountains in Rio Arriba, Sandoval, and Los Alamos counties, New Mexico, United States. Numerous Puebloan Indian tribes have lived in the Jemez Mountains region since before the Spanish arrived in New Mexico. ...

, the

Sangre de Cristo Mountains The Sangre de Cristo Mountains ( Spanish for "Blood of Christ") are the southernmost subrange of the Rocky Mountains. They are located in southern Colorado and northern New Mexico in the United States. The mountains run from Poncha Pass in South ...

, and in the

Manzano Mountains The Manzano Mountains are a small mountain range in the central part of the US State of New Mexico. They are oriented north–south and are 30 miles long. The center of the range lies due east of the town of Belen. The name "Manzano" is Spani ...

. The lower section of the group tends to be a gray limestone and the upper an

arkosic Arkose () or arkosic sandstone is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose. Quartz is c ...

limestone, and these have been divided into the

La Pasada Formation The La Pasada Formation is a geologic formation in the southern Sangre de Cristo Mountains of New Mexico. It preserves fossils dating back to the early to middle Pennsylvanian. Description The formation is a cyclic carbonate consisting of a ...

and Alamitos Formation in the southern Sangre de Cristo Mountains. In the Manzano Mountains, the Madera has been divided into the Los Moyos, Wild Cow, and

Bursum Formation The Bursum Formation is a geologic formation in New Mexico.Porvenir and Alamitos Formations. Atrasado Formation

Barry Kues and Katherine Giles have recommended the division of the Madera Group into the

Gray Mesa Formation The Gray Mesa Formation is a geologic formation in New Mexico. Its fossil assemblage dates the formation to the Moscovian age of the Pennsylvanian. The formation as presently defined includes outcrops previously assigned to many local units, inc ...

and

Atrasado Formation The Atrasado Formation is a geologic formation in New Mexico. Its fossil assemblage dates the formation to the Kasimovian age of the Pennsylvanian. It was formerly known locally as the Wild Cow Formation or the Guadelupe Box Formation. Descripti ...

in its western and southern exposures, which extend from the

Nacimiento Mountains The Sierra Nacimiento (official name), or Nacimiento Mountains, are a mountain range in the northwestern part of the U.S. state of New Mexico. They are just west of the more prominent Jemez Mountains near the town of Cuba, and are separated ...

through the Lucero Uplift to the Los Robles Mountains. For the eastern exposures of the Sandia and Manzano Mountains and Estancia Basin, they recommend division into the Los Moyos Formation and Wild Cow Formation. They recommend abandoning the name Madera Group in the Sangre de Cristo Mountains. More recently,

Spencer G. Lucas Spencer George Lucas is an American paleontologist and stratigrapher, and curator of paleontology at the New Mexico Museum of Natural History and Science. His main areas of study are late Paleozoic, Mesozoic and early Cenozoic vertebrate fo ...

and coinvestigators have recommended abandoning the names Los Moyos Formation and Wild Cow Formation and using Grey Mesa Formation and Atrasado Formation throughout the Madera Group. The group is underlain at most locations by the

Sandia Formation The Sandia Formation is a geologic formation in New Mexico, United States. Its fossil assemblage is characteristic of the early Pennsylvanian. Description The Sandia Formation is mostly shale with some sandstone and conglomerate but only minor ...

, with its base typically placed at the first massive marine limestone bed above the shales of the Sandia Formation. It is overlain everywhere by the

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 chann ...

or its equivalents, with the transition typically gradational, with the base of the Abo placed at the top of the last massive marine limestone bed below the fluvial redbeds typical of the Abo. The transitional zone between the Madera Group and the Abo Formation is sometimes assigned to the Bursum Formation, which is not included in the Madera Group.

Fossils

The exposures near Jemez Springs include some of the richest

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...

fossil beds in North America.

Crinoid Crinoids are marine animals that make up the Class (biology), class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or coma ...

stems and

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

ns are also part of the fossil assemblage. The formation is also exposed in the canyon of Rio Grande del Rancho south of

Talpa, New Mexico Talpa is a settlement in Taos County, New Mexico, located south of the town of Taos along New Mexico Highway 518. History First named Rio Chiquito for the river running through the area, Talpa was settled during the early-18th century during th ...

, where brachiopods, crinoids,

rugose coral The rugosa, also called the tetracorallia or horn coral, are an extinct order of solitary and colonial corals that were abundant in Middle Ordovician to Late Permian seas. Solitary rugosans (e.g., '' Caninia'', '' Lophophyllidium'', '' Neozap ...

, and

graptolite Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through the L ...

fossils can be found. The fossil assemblage dates the Madera Group to the middle to late

History of investigation

In 1903, C.R. Keyes applied the name, Madera

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

, to what he identified as upper Carboniferous beds in the Sandia Mountains. The unit was named for the town of La Madera. The name was subsequently applied to Pennsylvanian marine limestones throughout central and northern New Mexico. D.A. Myers first proposed that the unit be raised to group rank in 1973. The Pennsylvanian stratigraphy of New Mexico has historically been unusually complex and inconsistent, with dozens of names for groups, formations, and members. Kues and Giles recommended that the name Madera Group be applied to similar exposures of shelf and marginal basin beds of Desmoinean (upper Moscovian) to early

Virgilian Publius Vergilius Maro (; traditional dates 15 October 7021 September 19 BC), usually called Virgil or Vergil ( ) in English, was an ancient Roman poet of the Augustan period. He composed three of the most famous poems in Latin literature: th ...

age found from north-central and central New Mexico south along the west side of the Orogrande Basin as far as the

Caballo Caballo may refer to: Places * Caballo, New Mexico * Caballo Island (in the Philippines) * Caballo Lake * Caballo Mountain, Spain * Caballo Mountains The Caballo Mountains, (Spanish: "horse") are a mountain range located in Sierra and Doña A ...

and

Robledo Mountains The Robledo Mountains are a mountain range in Doña Ana County, New Mexico just northwest of Las Cruces. They are an uplifted block of Paleozoic rocks on the west side of the Rio Grande Rift. The range was named for Pedro Robledo, who died on Ma ...

Footnotes

References

* * * * * * * * * * * {{Chronostratigraphy of Colorado, Paleozoic state=expanded Carboniferous formations of New Mexico Carboniferous southern paleotropical deposits Geologic groups of New Mexico

Description

Fossils

History of investigation

See also

Footnotes

References