Finlay Limestone

The Finlay Limestone is a geologic formation in western Texas, southern New Mexico, and northern Chihuahua. It preserves fossils dating back to the early Cretaceous period.^[1]^[2]

Finlay Limestone
Stratigraphic range: Albian PreꞒ Ꞓ O S D C P T J K Pg N
Limestone mountains of Finlay Limestone in Aquiles Serdán Municipality near Chihuahua City.
Type	Formation
Unit of	Fredericksburg Group
Underlies	Del Norte Formation
Overlies	Cox Sandstone
Thickness	130–426 feet (40–130 m)
Lithology
Primary	Limestone
Other	Sandstone
Location
Coordinates	31°22′N 105°36′W / 31.36°N 105.60°W / 31.36; -105.60
Region	New Mexico Texas Chihuahua
Country	United States Mexico
Type section
Named for	Finlay Mountains
Named by	G.B Richardson
Year defined	1904
Finlay Limestone (the United States) Show map of the United States Finlay Limestone (Texas) Show map of Texas

Description edit

The formation is composed of massive gray limestone with a few thin beds of brown sandstone, with a total thickness of 130–426 feet (40–130 m).^[1]^[2] It is exposed in the Finlay Mountains (31°22′N 105°36′W / 31.36°N 105.60°W / 31.36; -105.60),^[1] the Sierra de Juarez,^[3] and the Cerro de Cristo Rey uplift (31°47′13″N 106°32′46″W / 31.787°N 106.546°W / 31.787; -106.546).^[2] The formation overlies the Cox Sandstone^[1] and is overlain by the Del Norte Formation.^[2]

The formation is highly fossiliferous, containing fossils characteristic of early Cretaceous Albian and Comanchean age.^[2]

The formation includes carbonate replacement deposits of lead, zinc, and silver in northern Mexico, along the Chihuahua CRD belt.^[4]

The formation was first defined by G.B. Richardson in 1904 and assigned to the Fredericksburg Group.^[1]

^ ^a ^b ^c ^d ^e Richardson 1904
^ ^a ^b ^c ^d ^e Lovejoy 1976
^ Kottlowski 1973
^ Robertson, Ken; Megaw, Peter (June 2009). "Cinco de Mayo: A new silver, lead, and zinc discovery in northern Mexico". The Leading Edge. 28 (6): 730–735. doi:10.1190/1.3148416.

Kottlowski, F.E. (1973). "Pre-Pliocene rocks in La Mesa region, southern Dona Ana County, New Mexico". El Paso Geological Society Field Trip Guidebook. 7: 37–46.
Lovejoy, E.M.P. (1976). "Geology of Cerro de Cristo Rey uplift, Chihuahua and New Mexico" (PDF). New Mexico Bureau of Mines and Mineral Resources Memoir. 31. Retrieved 3 August 2020.
Richardson, G.B. (1904). "Report of a reconnaissance in Trans-Pecos Texas north of the Texas and Pacific Railway". University of Texas, Mineral Survey Bulletin. 9.