The Muleros Formation 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
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 ...
, which is particularly well exposed at Cerro de Cristo Rey near
El Paso, Texas
El Paso (; "the pass") is a city in and the county seat, seat of El Paso County, Texas, El Paso County in the western corner of the U.S. state of Texas. The 2020 population of the city from the United States Census Bureau, U.S. Census Bureau w ...
. 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 ...
dating back to the
early Cretaceous
The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.
Geology
Pro ...
period.
Descriptiom
The formation consists of highly fossiliferous nodular
argillaceous (
clay
Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4).
Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
-rich)
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 ...
at its base and in its upper portion, with
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 ...
dominating the middle section and
interbedding with the limestone towards the top of the formation. Total thickness is . The formation conformably overlies the
Smeltertown Formation and grades into the overlying
Mesilla Valley Formation.
The formation is interpreted as an outer
shelf
Shelf ( : shelves) may refer to:
* Shelf (storage), a flat horizontal surface used for display and storage
Geology
* Continental shelf, the extended perimeter of a continent, usually covered by shallow seas
* Ice shelf, a thick platform of ice f ...
formation that later experienced shallowing and deposition of limestone in an inner shelf environment subject to storm influence, then deepened again to deposit shale with some storm layers.
Fossils
The formation contains at least 20 genera and 23 species of fossils. These include the molluscs ''
Lima
Lima ( ; ), originally founded as Ciudad de Los Reyes (City of The Kings) is the capital and the largest city of Peru. It is located in the valleys of the Chillón River, Chillón, Rímac River, Rímac and Lurín Rivers, in the desert zone of t ...
wacoensis'' Roemer, ''Lima mexicana'' Bose, ''
Pecten texanus'' var. ''elongatus'' Bose, ''Pecten subalpinus'' Bose, ''
Plicatula
Plicatula is a genus of saltwater clams, marine bivalve molluscs, known commonly as kitten's paws or kittenpaws in the family Plicatulidae. MolluscaBase eds. (2022). MolluscaBase. Plicatula Lamarck, 1801. Accessed through: World Register of M ...
incongrua'' Conrad, ''
Ostrea quadriplicata'' (Shumard), ''
Texigryphaea
''Texigryphaea'' is an extinct genus of oyster belonging to the order Ostreida and family Gryphaeidae. It dates to the Albian to Cenomanian Ages of the Cretaceous period and is primarily found in Texas and the southern Western Interior of North A ...
washitaensis''. ''
Trigonia emery'' Conrad, ''
Helicocryptus mexicanus'' Bose, and ''
Turritella granulata'' Sowerby var. ''cenomanensis'' d'Orbigny and the echinoderm ''
Heteraster bravoensis'' (Bose). These are characteristic of the
Albian age
Age or AGE may refer to:
Time and its effects
* Age, the amount of time someone or something has been alive or has existed
** East Asian age reckoning, an Asian system of marking age starting at 1
* Ageing or aging, the process of becoming older ...
. The formation is highly fossiliferous, with some beds consisting almost entirely of fossils of the oyster ''Texigryphaea washitaensis''.
History of investigation
The beds making up the formation were first described by E. Bose in 1906 as subdivision 5 of his
stratigraphic section
A stratigraphic section is a sequence of layers of rocks in the order they were deposited. It is based on the principle of original horizontality, which states that layers of sediment are originally deposited horizontally under the action of gr ...
. W.S. Strain assigned the name Muleros Formation to this subdivision in 1976.
See also
*
List of fossiliferous stratigraphic units in New Mexico
*
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. ...
Footnotes
References
*
*
* {{cite journal , last1=Strain , first1=W.S. , year=1976 , title=New formation names in the Cretaceous at Cerro de Cristo Rey, Dona Ana County, New Mexico; Appendix 2 , journal=New Mexico Bureau of Mines and Mineral Resources Memoir , volume=31 , pages=77–82 , url=https://geoinfo.nmt.edu/publications/monographs/memoirs/downloads/31/Memoir-31.pdf , accessdate=5 August 2020
Cretaceous formations of New Mexico