The Ceja Formation is a

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

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 near

Albuquerque, New Mexico Albuquerque ( ; ), also known as ABQ, Burque, the Duke City, and in the past 'the Q', is the List of municipalities in New Mexico, most populous city in the U.S. state of New Mexico, and the county seat of Bernalillo County, New Mexico, Bernal ...

, United States.

Description

The formation consists of weakly consolidated

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

and conglomerate, varying in color from light yellowish-brown to reddish-yellow or pink. It consists of

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

deposits with

paleocurrent A paleocurrent or paleocurrent indicator is a geological feature (typically a sedimentary structure) that helps one determine the direction of flowing water in the geologic past. This is an invaluable tool in the reconstruction of ancient deposi ...

directions from the west. The lower beds are predominantly interbedded

and

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

while the upper beds are predominantly

to conglomerate with occasional small boulders. The formation lies disconformably on the Arroyo Ojito Formation and its top beds are gravels capping the Llano de Albuquerque

geomorphic Geomorphology () is the scientific study of the origin and evolution of topography, topographic and bathymetry, bathymetric features generated by physical, chemical or biological processes operating at or near Earth#Surface, Earth's surface. Ge ...

surface. The lower beds sometimes contain white micritic carbonate pebbles interpreted as reworked

caliche Caliche () is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or se ...

of the underlying Arroyo Ojito Formation. Total exposed thickness is . Well logs indicate that the Ceja thickens to more than in the subsurface on the western margin of the

Rio Grande valley Lower Rio Grande Valley (), often referred to as the Rio Grande Valley (RGV) of South Texas, is a region located in the southernmost part of Texas, along the northern bank of the Rio Grande. It is also known locally as the Valley or the 956 (the ...

, where it likely interfingers with the Sierra Ladrones Formation. Data from

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s and radioisotope measurements indicate that the formation is

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58ash bed correlated to the 3.28 Ma Nomlaki Tuff. At Cat Mesa, the formation overlies a

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

with a Ar-Ar age of 3.00 ± 0.01 Ma. A second flow within the formation has an Ar-Ar age of 2.68 ± 0.04 Ma. The formation is overlain by a third flow with a K-Ar age of 2.68 ± 0.04 Ma. A fossil

pocket gopher Pocket gophers, commonly referred to simply as gophers, are burrowing rodents of the family Geomyidae. The roughly 41 speciesSearch results for "Geomyidae" on thASM Mammal Diversity Database are all endemic to North and Central America. They ar ...

is also consistent with a Pliocene age. Interbedded flows near

Los Lunas Los Lunas is a village in Valencia County, New Mexico, United States. As of the 2020 census, the village has a population of 17,242. It is the county seat of Valencia County. Los Lunas is part of the Albuquerque Metropolitan Statistical Area. ...

give ages of 1.25 ± 0.02 Ma and 3.80 ± 0.04 Ma, extending the formation into the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. The formation is divided into the Atrisco

Member Member may refer to: * Military jury, referred to as "Members" in military jargon * Element (mathematics), an object that belongs to a mathematical set * In object-oriented programming, a member of a class ** Field (computer science), entries in ...

, Rio Puerco Member, and Santa Ana Mesa member. The Atrisco Member is reddish-brown mudstone and sandstone, some thick, mostly found in the subsurface but distinctive on well logs and discernible as a gradational boundary at the

type section In geology, a stratotype or type section is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the ...

and as a sharper boundary further north. This is overlain by the Rio Puerco Member. Santa Ana Member of the Ceja Formation

The Santa Ana Mesa Member consists of reddish-brown sandstone and conglomerate conspicuous in the flanks of Santa Ana Mesa. It contains a 7.1 Ma

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...

bed. The unit is typically redder than the other members of the Ceja Formation. The Rio Puerco Member named for the Rio Puerco. It forms a very poorly sorted mesa-capping gravel along Ceja del Rio Puerco. It disconformably overlies the Atrisco Member to the north but interfingers with the Atrisco Member further south.

History of investigation

The unit was first defined by V.C. Kelley in 1977 for beds formerly assigned to the upper buff member of the Santa Fe Formation (now the Santa Fe Group) by Kirk Bryan and Franklin T. McCann in 1936. S.D. Connell and coinvestigators reassigned the member to the Arroyo Ojito Formation in 1999. In 2007, Williams and Cole recommended that the Arroyo Ojito Formation be abandoned, because the name was being used inconsistently and because the formation straddled a significant regional unconformity since named the Rincones paleosurface. They raised the Ceja Member, which lay above the Rincones paleosurface, to formation rank, a recommendation with which Connell subsequently concurred.

References

Bibliography

* * * * * {{cite journal , last1=Williams , first1=P.L. , last2=Cole , first2=J.C. , year=2007 , title=Geologic map of the Albuquerque 30' x 60' quadrangle, north-central New Mexico , journal=U.S. Geological Survey Scientific Investigations Map , series=Scientific Investigations Map , volume=SIM-2946 , doi=10.3133/sim2946 , hdl=2027/mdp.39015049951992 , url=https://pubs.usgs.gov/sim/2007/2946/downloads/pdf/2946_pamphlet_508.pdf , accessdate=11 August 2020, doi-access=free Neogene formations of New Mexico Pliocene Series of North America Piacenzian Zanclean Messinian Tortonian Sandstone formations of the United States Fluvial deposits Mudstone formations of the United States Conglomerate formations of the United States

Description

History of investigation

See also

References

Bibliography