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The Flechado Formation is a geologic formation in the northern
Sangre de Cristo Mountains ) , country= United States , subdivision1_type= States , subdivision1= , parent= Rocky Mountains , geology= , orogeny= , area_mi2= 17193 , range_coordinates= , length_mi= 242 , length_orientation= north-south , width_mi= 120 , w ...
of New Mexico. 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 Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early ...
to
middle 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 o ...
.


Description

The Flechado Formation consists of low- feldspar sandstone and
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 ...
alternating with thin beds of limestone. The total thickness is . It overlies the Tererro Formation and is overlain by the Alamitos Formation. The formation is well to extremely well cemented in the type area, so that it can be difficult to distinguish from the
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
Ortega Formation The Ortega Formation is a geologic formation that crops out in most of the mountain ranges of northern New Mexico. Detrital zircon geochronology establishes a maximum age for the formation of 1690-1670 million years ( Mya), in the Statherian peri ...
. The formation grades laterally 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 ...
to the south of the Rio Pueblo, with the
clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...
beds of the Flechado abruptly thinning and transitioning to carbonate beds of the La Pasada over a distance of about . The terrigenous sediments of the Flechado Formation were likely derived from the southern part of Uncompahgre uplift during uplift on the west side of the Picuris-Pecos fault. File:Flechado Formation type closeup.jpg, Close view of Flechado Formation at its type section.


Fossils

Fossils are scarce in the upper portion of the Flechado Formation, but middle Desmoinesian (upper
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 (strati ...
) brachiopods are found about below the top of the formation. Atokan (lower Moscovian) fusulinids and brachiopods are found in the lower part, which also contains broken crinoid, bryozoan, and algal remains.


History of investigation

The formation was first described by P.K. Sutherland in 1963.


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 encyclopedia , last1=Sutherland , first1=P.K. , year=1963 , title=Paleozoic rocks , editor1-last=Miller , editor1-first=J.P. , editor2-last=Montgomery , editor2-first=Arthur , editor3-last=Sutherland , editor3-first=P.K. , encyclopedia=Geology of part of the southern Sangre de Cristo Mountains, New Mexico: New Mexico Bureau of Mines and Mineral Resources Memoir 11 , pages=22-44 , url=https://geoinfo.nmt.edu/publications/monographs/memoirs/downloads/11/Memoir-11.pdf , accessdate=29 July 2020 Carboniferous formations of New Mexico Carboniferous southern paleotropical deposits