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 ...
found the
Caballo Mountains
The Caballo Mountains, (Spanish: "horse") are a mountain range located in Sierra and Doña Ana Counties, New Mexico, United States. The range is located east of the Rio Grande and Caballo Lake, and west of the Jornada del Muerto; the south of ...
of
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 ...
. It preserves
fossils
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 preserved in ...
late Pennsylvanian
The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the ICS geologic timescale, the younger of two subperiods (or upper of two subsystems) of the Carboniferous Period. It lasted from roughly . As with most oth ...
.
Description
The Bar B formation is mostly cyclic beds of
shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...
and
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 whe ...
, with shale making up about 80% of the formation and limestone the other 20%.
Chert
Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
is present in some of the limestone. The upper include reddish-brown
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, p ...
calcareous
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
In zoology
''Calcareous'' is used as an adje ...
siltstone. The total thickness is about . The formation rests on the Nakaye Formation and is unconformably overlain by the
San Andres Mountains
The San Andres Mountains are a mountain range in the southwestern U.S. state of New Mexico, in the counties of Socorro, Sierra, and Doña Ana. The range extends about 75 miles (120 km) north to south, but are only about 12 miles (19 ...
Caswell Silver
Caswell Silver (June 25, 1916 – October 18, 1988) was an American geologist and entrepreneur who was President of Sundance Oil Company from 1960 to 1984. In addition to the business of oil and gas exploration, he was active in the American Assoc ...
in 1952. Bachman and Myers criticized its definition in 1975, but it is accepted by Kues and Giles, though they restrict it to the Caballo Mountains.
See also
*
List of fossiliferous stratigraphic units in New Mexico
This article contains a list of fossil-bearing stratigraphic units in the state of New Mexico, U.S.
Sites
See also
* Paleontology in New Mexico
References
*
{{DEFAULTSORT:Fossiliferous stratigraphic units in New Mexico
New Mexico
Stra ...
*
Paleontology in New Mexico
Paleontology in New Mexico refers to paleontological research occurring within or conducted by people from the U.S. state of New Mexico. The fossil record of New Mexico is exceptionally complete and spans almost the entire stratigraphic column. ...