Porvenir Formation

Porvenir Formation
Stratigraphic range: Middle Pennsylvanian PreꞒ Ꞓ O S D C P T J K Pg N
Porvenir Formation at its type section at Canovas Canyon.
Type	Formation
Underlies	Alamitos Formation
Overlies	Sandia Formation
Thickness	700–1,615 ft (213–492 m)
Lithology
Primary	Limestone
Other	Sandstone, shale
Location
Coordinates	35°42′14″N105°24′18″W / 35.704°N 105.405°W / 35.704; -105.405
Region	New Mexico
Country	United States
Type section
Named for	El Porvenir Campground
Named by	Baltz and Myers
Year defined	1984
Porvenir Formation (the United States) Show map of the United States Porvenir Formation (New Mexico) Show map of New Mexico

The Porvenir Formation is a geologic formation exposed in the southeastern Sangre de Cristo Mountains of New Mexico. It preserves fossils dating back to the middle Pennsylvanian period. ^[1]

Description

The formation is mostly marine and can be divided into three intergrading facies. The first, located primarily to the south, is mostly limestone with some interbedded shale and sandstone. The second facies, located to the north and northwest, is mostly gray shale with some thick limestone and thin sandstone beds. The third facies, found to the northeast, is mostly shale, limestone (including sandy and oolitic limestone) and arkosic sandstone. Thickness is 700–1,615 feet (213–492 meters). ^[1]

The formation rests conformably on the Sandia Formation and is disconformably overlain by the Alamitos Formation. ^[1]

Fossils

The formation contains fusulinids of Desmoinesian (Moscovian) age. ^[1]

History of investigation

The formation was first named by Baltz and Myers in 1984, who considered it correlative with the lower part of the Madera Formation. ^[1] However, in 2004, Kues and Giles recommended restricting the Madera Group to shelf and marginal basin beds of Desmoinean (upper Moscovian) to early Virgilian age, which excluded the Porvenir Formation. ^[2] Spencer G. Lucas and coinvestigators also exclude the Porvenir Formation from the Madera Group. ^[3]

See also

• Earth sciences portal
• Paleontology portal

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

References

1. Baltz, E.H.; Myers, D.H. (1984). "Porvenir Formation (new name); and other revisions of nomenclature of Mississippian, Pennsylvanian, and Lower Permian rocks, southeastern Sangre de Cristo Mountains, New Mexico" (PDF). Contributions to Stratigraphy: U.S. Geological Survey Bulletin. 1537-B: B1–B39. doi:10.3133/b1537B.
2. 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. p. 100.
3. Lucas, Spencer G.; Krainer, Karl; Vachard, Daniel (2016). "The Pennsylvanian section at Priest Canyon, southern Manzano Mountains, New Mexico" (PDF). New Mexico Geological Society Field Conference Series. 67. Retrieved 11 June 2020.