Onate Formation

The Onate Formation is a geologic formation that is exposed in most of the highlands of south-central New Mexico.[1] It preserves fossils dating back to the middle Devonian period.[2][3][1]

Onate Formation
Stratigraphic range: middle Devonian
TypeFormation
Lithology
PrimarySiltstone
OtherShale, sandstone
Location
Coordinates32.742°N 106.572°W / 32.742; -106.572
RegionNew Mexico
CountryUnited States
Type section
Named forOnate Mountain
Named byR. Flower
Year defined1955
Onate Formation (the United States)
Onate Formation (New Mexico)

Description

Typically the Onate Formation consists of about 85–95 feet (26–29 m)[3] of orange yellow-weathering dolomitic siltstone with shales and sandstone.[2] The base of the formation is a profound regional unconformity,[1] so that the formation rest on either the Fusselman Dolostone[2] or the Montoya Group.[3] It is overlain by the Sly Gap Formation and thins to the north[2] and south.[3]

Fossils

The formation contains the fossil brachiopod Spirifer acuminatu, as well as crinoids and bryozoans.[2] The brachiopod assemblage includes 34 genera and 41 species. Conodonts are rare but a few tabulate corals, ichnofossils, and the receptaculid Sphaerospongia is present. These give an age of late Givetian. The formation is highly bioturbated.[3]

History of investigation

The formation was defined by Flower in 1955.[2]

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See also

References
  1. Kues 2004
  2. Flower 1955
  3. Cooper and Dutro 1982

References
  • Cooper, G.A.; Dutro, J.T., Jr. (1982). "Devonian brachiopods of New Mexico". Bulletins of American Paleontology. 82-83 (325).
  • Flower, Rousseau (1955). "Pre-Pennsylvanian stratigraphy of southern New Mexico" (PDF). New Mexico Geological Society: 65–70.
  • Kues, B.S. (2004). "Devonian of New Mexico". In Mack, G.H.; Giles, K.A. (eds.). The geology of New Mexico. A geologic history: New Mexico Geological Society Special Volume 11. pp. 59–75. ISBN 9781585460106.

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