The Buda Limestone is a dense white to yellow sparry limestone with numerous calcite 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 total thickness is about 100 feet (30 m).[1][4] In trans-Pecos Texas, the formation rests on the Grayson Formation and is overlain by the Boquillas Formation.[5]
In the Big Bend National Park area, the formation is divided into three informal members. The lowest is 25 feet (7.6 m) of hard microgranular grayish-white limestone that breaks with a conchoidal fracture. The middle member is about 30 feet (9.1 m) of an argillaceousormarly nodular grayish-white limestone. The upper member is up to 60 feet (18 m) of limestone similar to the lower member.[6]
Foraminifera are poorly preserved, but may include Globigerina.[1] Gastropods, a few Gryphaea oysters,[2] and the bivalveAlectryonia carinata[1] has also been found in the formation. Abundant bivalve fossils are found in the formation east of Big Bend National Park.[6]
The Buda Limestone is an important petroleum reservoir that has been exploited for decades via conventional vertical drilling. It is now being exploited using techniques such as horizontal and underbalanced drilling.[8] 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.[9]
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.[1] By 1935, the formation had been included in the Washita Group.[10]
^ abBarrett, 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. 264pp.[1]
^ abBarnes, V.E. (1977). Geologic atlas of Texas. University of Texas-Austin, Bureau of Economic Geology.
^Roemer, F.A. (1887). "Graptocarcinus texanus, ein Brachyure aus der Kreide von Texas". Neues Jahrbuch für Mineralogie, Geologie, und Paläontologie. 1887: 173–176.
^Davis, G..; Wilcox, G..; Arnone, M..; Bruington, S.. (12 April 2016). "Rejuvenating the Buda Limestone Reservoir in Texas by Using Crude Oil and Nitrogen Injection in Underbalanced Regime: Case History". All Days: SPE–179715–MS. doi:10.2118/179715-MS.
^Ledoux, R; Gottardi, R. (2018). "Characterizing the Natural Fracture System of the Buda Formation, South Texas". Gulf Coast Association of Geological Societies Transactions. 68: 605–610.
^Wilmarth, M.G. (1938). "Lexicon of geologic names of the United States (including Alaska)". U.S. Geological Survey Bulletin. 896.
