The Finlay Limestone is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in western

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

, southern

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

, and northern

Chihuahua Chihuahua may refer to: Places *Chihuahua (state), a Mexican state **Chihuahua (dog), a breed of dog named after the state **Chihuahua cheese, a type of cheese originating in the state **Chihuahua City, the capital city of the state **Chihuahua Mun ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

.Richardson 1904Lovejoy 1976

Description

The formation is composed of massive gray

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

with a few thin beds of brown

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

, with a total thickness of . It is exposed in the Finlay Mountains (), the

Sierra de Juarez Sierra (Spanish for " mountain range" and " saw", from Latin ''serra'') may refer to the following: Places Mountains and mountain ranges * Sierra de Juárez, a mountain range in Baja California, Mexico * Sierra de las Nieves, a mountain rang ...

,Kottlowski 1973 and the Cerro de Cristo Rey uplift (). The formation overlies the Cox Sandstone and is overlain by the

Del Norte Formation The Del Norte Formation is a geologic formation in Mexico, New Mexico and Texas near the city of El Paso. It preserves fossils dating back to the early Cretaceous period. Description The formation is divided into two informal members. The lowe ...

Fossils

The formation is highly fossiliferous, containing fossils characteristic of early Cretaceous

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± ...

and Comanchean age.

Economic resources

The formation includes carbonate replacement deposits of lead, zinc, and silver in northern Mexico, along the

CRD belt.

History of investigation

The formation was first defined by G.B. Richardson in 1904 and assigned to the

Fredericksburg Group The Fredericksburg Group is a geologic group in Texas, United States. It preserves fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples inc ...

Footnotes

References