The Lead Camp Limestone is a

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 ...

in 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 north to south, but are only about wide at their widest. The highest peak ...

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 ...

. 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 ...

dating back to the

middle Pennsylvanian The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, on the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period (or the upper of two subsystems of the Carboniferous System). It last ...

Description

The Lead Camp Limestone consists of 75% medium- to dark-gray

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 ...

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

and 21-24%

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

. The base of the formation contains minor

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. The limestone forms prominent cliffs capping the southern San Andres Mountains. The total thickness is . The formation rests

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

on the

Lake Valley Limestone The Lake Valley Limestone is a geologic formation widely exposed in southwestern New Mexico. It preserves fossils dating back to the lower to middle Mississippian. Description The Lake Valley Limestone consists of gray cherty limestone with thi ...

to the south and conformably on the Sandia Formation to the north. Deposition began in the late Morrowan (

Bashkirian The Bashkirian is in the International Commission on Stratigraphy geologic timescale the lowest stage (stratigraphy), stage or oldest age (geology), age of the Pennsylvanian (geology), Pennsylvanian. The Bashkirian age lasted from to Mega annu ...

) to the south, spread to the north in the Atokan (early

Moscovian Moscovian may refer to: *An inhabitant of Moscow, the capital of Russia *Something of, from, or related to Moscow *Moscovian (Carboniferous) The Moscovian is in the International Commission on Stratigraphy, ICS geologic timescale a stage (strat ...

, and continued into the Missourian (

Kasimovian The Kasimovian is a geochronologic age or chronostratigraphic stage in the ICS geologic timescale. It is the third stage in the Pennsylvanian (late Carboniferous), lasting from to Ma.; 2004: ''A Geologic Time Scale 2004'', Cambridge Unive ...

)

Age Age or AGE may refer to: Time and its effects * Age, the amount of time someone has been alive or something has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

Fossils

The formation contains marine fossils in the calcareous shale beds. It contains

fusulinid The Fusulinida is an extinct order within the Foraminifera in which the tests are traditionally considered to have been composed of microgranular calcite. Like all forams, they were single-celled organisms. In advanced forms the test wall was d ...

s characteristic of the middle Pennsylvanian.

History of investigation

The formation was first defined by George Bachman and Donald Myers in 1969, for exposures near the confluence of Lead Camp and San Andres Canyons.

Footnotes

References

* * {{cite book , last1=Kues , first1=B.S. , last2=Giles , first2=K.A. , year=2004 , chapter=The late Paleozoic Ancestral Rocky Mountain system in New Mexico , editor1-last=Mack , editor1-first=G.H. , editor2-last=Giles , editor2-first=K.A. , title=The geology of New Mexico. A geologic history: New Mexico Geological Society Special Volume 11 , pages=95–136 , isbn=9781585460106 Carboniferous formations of New Mexico Carboniferous southern paleotropical deposits Limestone formations of the United States Shale formations of the United States

Description

Fossils

History of investigation

See also

Footnotes

References