Popotosa Formation

The Popotosa Formation is a geologic formation in New Mexico. It preserves fossils dating back to the Neogene period.

Popotosa Formation
Stratigraphic range: Neogene
TypeFormation
Unit ofSanta Fe Group
UnderliesSierra Ladrones Formation
Thickness1,447 m (4,747 ft)
Lithology
PrimaryVolcaniclastics
OtherTuff
Location
Coordinates34.30000°N 107.04386°W / 34.30000; -107.04386
RegionNew Mexico
CountryUnited States
Type section
Named forCanada Popotosa
Named byC.S. Denny
Year defined1940
Popotosa Formation (the United States)
Popotosa Formation (New Mexico)

Description

The Popotosa Formation is a thick (up to 1,447 meters (4,747 feet)) sequence of volcanic debris beds with a few interspersed ash beds. It is exposed along the Rio Grande rift from the Socorro area. Radiometric dating of interbedded flows gives it an age of 26.4 to 7 Ma, corresponding to the late Oligocene to Miocene.[1]

The formation is interpreted as deposition of fanglomerates (mostly derived from the Datil-Mogollon volcanic field to the southwest) and playa sediments in a closed basin in the early stages of rifting along the Rio Grande rift. It is thus typical of the lower Santa Fe Group.[1]

History of investigation

The unit was first described by C.S. Denny in 1940, who named it for exposures near Canada Popotosa.[2] It was assigned to the lower Santa Fe Group by Machette in 1978.[3]

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See also

Footnotes
  1. Asher-Bolinder 1988
  2. Denny 1940
  3. Machette 1978

References
  • Asher-Bolinder, Sigrid (1988). "Stratigraphy of reference sections in the Popotosa Formation, Socorro County, New Mexico" (PDF). U.S. Geological Survey Bulletin. 1800. doi:10.3133/b1800. Retrieved 10 June 2020.
  • Denny, Charles S. (January 1940). "Tertiary Geology of the San Acacia Area New Mexico". The Journal of Geology. 48 (1): 73–106. doi:10.1086/624862.
  • Machette, M.N. (1978). "Geologic map of the San Acacia quadrangle, Socorro County, New Mexico". U.S. Geological Survey Geologic Quadrangle Map. GQ-1415. Retrieved 10 June 2020.
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