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The Buda Limestone is a geological
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The Buda Limestone is a dense white to yellow sparry
The Buda Limestone is a geological formation
Formation may refer to:
Linguistics
* Back-formation, the process of creating a new lexeme by removing or affixes
* Word formation, the creation of a new word by adding affixes
Mathematics and science
* Cave formation or speleothem, a secondar ...
in the High Plains High Plains refers to one of two distinct land regions:
* High Plains (United States), land region of the western Great Plains
*High Plains (Australia)
The High Plains of south-eastern Australia are a sub-region, or more strictly a string of adja ...
and Trans-Pecos
The Trans-Pecos, as originally defined in 1887 by the Texas geologist Robert T. Hill, is the portion of Texas that lies west of the Pecos River. The term is considered synonymous with Far West Texas, a subdivision of West Texas. The Trans-Peco ...
regions of West Texas
West Texas is a loosely defined region in the U.S. state of Texas, generally encompassing the arid and semiarid lands west of a line drawn between the cities of Wichita Falls, Abilene, and Del Rio.
No consensus exists on the boundary betwee ...
and in southern 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 ...
, whose strata date back to the Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
. Pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
remains are among the 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 preserved ...
s that have been recovered from the formation.Barrett, P.M., Butler, R.J., Edwards, N.P., & Milner, A.R. Pterosaur distribution in time and space: an atlas. p61-107. in Flugsaurier: Pterosaur papers in honour of Peter Wellnhofer. 2008. Hone, D.W.E., and Buffetaut, E. (eds). Zitteliana B, 28. 264p/ref>
Description
The Buda Limestone is a dense white to yellow sparry 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 numerous calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
veins that weathers to yellowish or pinkish due to its iron content. In far western Texas, the formation overlies the Del Rio Formation and is in turn overlain by the Eagle Ford Group
The Eagle Ford Group (also called the Eagle Ford Shale) is a Sedimentary rock, sedimentary rock formation deposited during the Cenomanian and Turonian ages of the Late Cretaceous over much of the modern-day state of Texas. The Eagle Ford is pr ...
. The total thickness is about . In trans-Pecos Texas, the formation rests on the Grayson Formation and is overlain by the Boquillas Formation
The Boquillas Formation is a geologic Formation (geology), formation deposited during the Late Cretaceous in modern-day West Texas. It is typically composed of alternating marls and limestones with thin volcanic ash beds (bentonites). It was nam ...
.
In the Big Bend National Park
Big Bend National Park is an American national park located in West Texas, bordering Mexico. The park has national significance as the largest protected area of Chihuahuan Desert topography and ecology in the United States, and was named after ...
area, the formation is divided into three informal members. The lowest is of hard microgranular grayish-white limestone that breaks with a conchoidal fracture. The middle member is about of an argillaceous
Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces.
Clay minerals ...
or marly nodular grayish-white limestone. The upper member is up to of limestone similar to the lower member.
Fossils
Foraminifera
Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular Ectoplasm (cell biology), ectoplasm for catching food and ot ...
are poorly preserved, but may include ''Globigerina
''Globigerina'' () is a genus of planktonic Foraminifera, in the order of Rotaliida.Glo ...
''. Gastropods, a few ''Gryphaea
''Gryphaea'', one of the genera known as devil's toenails, is a genus of extinct oysters, marine bivalve mollusks in the family Gryphaeidae.
These fossils range from the Triassic period to the middle Paleogene period, but are mostly restric ...
'' oysters, and the bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...
''Alectryonia
''Lopha'' is a genus of marine bivalve molluscs in the family Ostreidae.
The genus ''Lopha'' is present from the Triassic period in the Lower Norian age (216.5 ± 2.0 – 203.6 ± 1.5 Mya) to the recent age.
Description
''Lopha'' species ha ...
carinata'' has also been found in the formation. Abundant bivalve fossils are found in the formation east of Big Bend National Park.
Exposures in Hays County, Texas
Hays County is located on the Edwards Plateau in the U.S. state of Texas. Hays County is part of the Austin-Round Rock metropolitan area. As of the 2020 census, its official population had reached 241,067. The county seat is San Marcos. Ha ...
have yielded fossil remains of ''Pterodactyloidea
Pterodactyloidea (derived from the Greek words ''πτερόν'' (''pterón'', for usual ''ptéryx'') "wing", and ''δάκτυλος'' (''dáktylos'') "finger" meaning "winged finger", "wing-finger" or "finger-wing") is one of the two traditional ...
'', ''Ornithocheiroidea
Ornithocheiroidea (or ornithocheiroids) is a group of pterosaurs within the extinct suborder Pterodactyloidea. They were typically large pterosaurs that lived from the Early to Late Cretaceous periods (Valanginian to Maastrichtian stages), with f ...
'' and ''Ornithocheiridae
Ornithocheiridae (or ornithocheirids, meaning "bird hands") is a group of pterosaurs within the suborder Pterodactyloidea. These pterosaurs were among the last to possess teeth. Members that belong to this group lived from the Early to Late Cr ...
''.
Economic resources
The Buda Limestone is an importantpetroleum reservoir
A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations.
Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...
that has been exploited for decades via conventional vertical drilling. It is now being exploited using techniques such as horizontal and underbalanced drilling
Underbalanced drilling, or UBD, is a procedure used to drill oil and gas wells where the pressure in the wellbore is kept lower than the static pressure of the formation being drilled. As the well is being drilled, formation fluid flows into the w ...
. While the vertical wells relied on the porosity of the formation (up to 6%), the horizontal wells exploit a system of natural vertical fractures in the formation.
History of investigation
The formation was originally named the Shoal Creek Limestone, but this name was preempted, and the formation was renamed the Buda Limestone by T.W. Vaughan in 1900. By 1935, the formation had been included in the Washita Group.See also
*List of pterosaur-bearing stratigraphic units
This is a list of stratigraphic units, where pterosaur fossils have been recovered from. Units listed are all either formation rank or higher (e.g. group).
See also
* Pterosaur
* List of fossil sites
This list of fossil sites is a worldw ...
References
Limestone formations of the United States Cretaceous formations of New Mexico Cretaceous geology of Texas {{paleo-site-stub