La Tuna Formation

La Tuna Formation
Stratigraphic range: Bashkirian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Underlies	Berino Formation
Overlies	Rancheria Formation, Helms Formation
Thickness	340–423 ft (104–129 m)
Lithology
Primary	Limestone
Other	Chert, shale
Location
Coordinates	31°58′0″N106°31′30″W / 31.96667°N 106.52500°W / 31.96667; -106.52500
Region	New Mexico
Country	United States
Type section
Named for	La Tuna (Anthony, New Mexico)
Named by	L.A. Nelson
Year defined	1937
La Tuna Formation (the United States) Show map of the United States La Tuna Formation (New Mexico) Show map of New Mexico

The La Tuna Formation is a geologic formation in the Franklin Mountains of southern New Mexico and western Texas and the Hueco Mountains of western Texas. It preserves fossils dating back to the Bashkirian Age of the early Pennsylvanian. ^{[1] [2]}

Description

The unit consists mostly of massive gray limestone with minor interbedded shale. The limestone is locally cherty ^{[2] [3]} and the upper beds include some thin shale lenses and algal mounds. ^[4] The total thickness is 340–423 ft (104–129 m). ^{[5] [1]} The formation lies on the Helms Formation ^[5] or Rancheria Formation ^[2] and is overlain by the Berino Formation. ^[5]

The formation contains detrital zircon grains of Cambrian age, which provides supporting evidence for a landmass thought to be present in Pennsylvanian time in the location of the modern Florida Mountains. ^[6] It is thought to have been laid down in the Horquilla Seaway, a continental shelf environment on the southwest coast of Pangaea. ^[3]

Fossils

The formation contains crinoids and other fossils consistent with deposition in the Morrowan (Bashkirian). ^[1] The upper beds include some algal mounds. ^[4] The formation contains a diverse gastropod fauna, ^[7] as well as the foraminiferan Millerella , the demosponge Chaetetes . ^{[8] [9]} and the coral Petalaxis . ^[3] The base of the formation contains earliest Morrowan conodonts. ^[10] The red alga Masloviporidium delicatum has been reported in the formation. ^[11] Cordaites has been reported within a sandstone bed within the formation. ^[3]

History of investigation

The unit was designated the La Tuna Member of the Magdalena Group by L.A. Nelson in 1937. ^[12] In 2001, B. Kues recommended abandoning the Magdalena Group and raising its members, including the La Tuna, to formation rank. ^[4] Spencer G. Lucas and Karl Krainer have recommended demoting the La Tuna Formation in New Mexico to member rank within the Horquilla Formation. ^[3]

See also

• Earth sciences portal
• Paleontology portal

• List of fossiliferous stratigraphic units in New Mexico
• Paleontology in New Mexico

Footnotes

1. Harbour 1972.
2. Kues & Giles 2004.
3. Lucas & Krainer 2020.
4. Kues 2001.
5. Nelson 1940.
6. Amato 2019.
7. Metcalf & Johnson 1971.
8. West & Kershaw 1991.
9. Batten 1995.
10. Lane 1974.
11. Groves & Mamet 1985.
12. Nelson 1937.

References

• Amato, Jeffrey M. (1 May 2019). "Detrital zircon ages from Proterozoic, Paleozoic, and Cretaceous clastic strata in southern New Mexico, U.S.A.". Rocky Mountain Geology. 54 (1): 19–32. doi:10.24872/rmgjournal.54.1.19. S2CID   182592316.
• Batten, Roger L. (4 April 1995). "Pennsylvanian (Morrowan) Gastropods from the Magdalena Formation of the Hueco Mountains, Texas". American Museum Novitates (3122). hdl:2246/3564 . Retrieved 18 September 2020.
• Groves, J. R.; Mamet, B. L. (1985). "Masloviporidium, a Cosmopolitan Middle Carboniferous Red Alga". Paleoalgology: 85–90. doi:10.1007/978-3-642-70355-3_8. ISBN   978-3-642-70357-7.
• Harbour, R.L. (1972). "Geology of the northern Franklin Mountains, Texas and New Mexico". U.S. Geological Survey Bulletin. 1298. doi: 10.3133/b1298 .
• Kues, B.S. (2001). "The Pennsylvanian System in New Mexico; Overview with suggestions for revisions of stratigraphic nomenclature" (PDF). New Mexico Geology. 23 (4): 103–122. Retrieved 18 September 2020.
• Kues, B.S.; Giles, K.A. (2004). "The late Paleozoic Ancestral Rocky Mountain system in New Mexico". In Mack, G.H.; Giles, K.A. (eds.). The geology of New Mexico. A geologic history (Special Volume 11). New Mexico Geological Society. pp. 95–136.
• Lane, H.Richard (1974). "Mississippian of Southeastern New Mexico and West Texas--A Wedge-on-Wedge Relation". AAPG Bulletin. 58. doi:10.1306/83D913D0-16C7-11D7-8645000102C1865D.
• Lucas, Spencer G.; Krainer, Karl (Fall 2020). "Gallery of Geology: The Pennsylvanian section at Bishop Cap, Doña Ana County, New Mexico" (PDF). New Mexico Geology. 42 (2): 79-81. Retrieved 11 February 2021.
• Metcalf, Artie L.; Johnson, Walter E. (23 July 1971). "Gastropods of the Franklin Mountains, El Paso County, Texas". The Southwestern Naturalist. 16 (1): 85. doi:10.2307/3670100. JSTOR   3670100.
• Nelson, L.A. (1937). "Gastropoda from the Pennsylvanian (Magdalena) of the Franklin Mountains of west Texas [abstract of thesis]". Colorado University Studies. 25 (1): 89–91.
• Nelson, L.A. (1940). "Paleozoic stratigraphy of the Franklin Mountains, West Texas". American Association of Petroleum Geologists Bulletin. 24 (1): 157–172. doi:10.1306/3D93319A-16B1-11D7-8645000102C1865D.
• West, R. R.; Kershaw, S. (1991). "Chaetetid Habitats". Fossil and Recent Sponges: 445–455. doi:10.1007/978-3-642-75656-6_36. ISBN   978-3-642-75658-0.