Boquillas Formation

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Boquillas Formation
Stratigraphic range: Cenomanian to Santonian
Type Formation
Unit of Eagle Ford Group / Terlingua Group
Sub-units Ernst Member, San Vicente Member, Terrell Member, Lozier Canyon Member, Antonio Creek Member, Scott Ranch Member, Langtry Member[1]
Underlies Austin Chalk or Aguja Formation
Overlies Buda Limestone
Primary Marl
Other Limestone, volcanic ash beds
Region West Texas
Country United States
Type section
Named for Boquillas post office, Big Bend National Park, Texas[2]
Named by J. A. Udden[2]

The Boquillas Formation is a geologic 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 named for outcrops near the former Boquillas post office in Big Bend National Park.[2] The term Boquillas Formation has been used for rocks that outcrop from Del Rio, Texas to as far west as Doña Ana County, New Mexico.[3]

Vertebrate fossils found in the Boquillas Formation include mosasaurs, fish bones, and shark's teeth.[4][5] Invertebrate fossils found in the formation include ammonites, swimming crinoids, inoceramid clams, sea urchins, oysters, and foraminifera[1]


  1. ^ a b Denne, R. A., Breyer, J. A., Callender, A. D., Hinote, R. E., Kariminia, M., Kosanke, T. H., Kita, Z., Lees, J. A., Rowe, H., Spaw, J. M., and Tur, N. (2016). Biostratigraphic and geochemical constraints on the stratigraphy and depositional environments of the Eagle Ford and Woodbine Groups of Texas: in Breyer, J. A. (ed.), The Eagle Ford Shale: A renaissance in U.S. oil production, AAPG Memoir 110, p. 1-86.
  2. ^ a b c Udden, J. A., 1907, A sketch of the geology of the Chisos country, Brewster County, Texas: University of Texas Bulletin 93, 101 p.
  3. ^ Lovejoy, E.M.P., 1976, Geology of Cerro de Cristo Rey uplift, Chihuahua and New Mexico: New Mexico Bureau of Mines and Mineral Resources Memoir, no. 31.
  4. ^ Gorden L. Bell, Jr., Kenneth R. Barnes and Michael J. Polcyn (2013) Late Cretaceous mosasauroids (Reptilia, Squamata) of the BigBend region in Texas, USA. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, Available onCJO 2013 doi:10.1017/S1755691013000406
  5. ^ Hunt, ReBecca K., Vincent L. Santucci and Jason Kenworthy (2006) A preliminary inventory of fossil fish from National Park Service units, in S.G. Lucas, J.A. Spielmann, P.M. Hester, J.P. Kenworthy, and V.L. Santucci (eds.), Fossils from Federal Lands. New Mexico Museum of Natural History and Science Bulletin 34, p. 63–69.