The Raton Formation is a geological formation of Upper Cretaceous and Paleocene

Paleocene

The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

 age which outcrops in the Raton Basin

Raton Basin

The Raton Basin is a geologic structural basin in southern Colorado and northern New Mexico. It takes its name from Raton Pass and the town of Raton, New Mexico. In extent, the basin is approximately east-west, and north-south, in Huerfano and Las Animas Counties, Colorado, and Colfax County,...

 of northeast New Mexico

New Mexico

New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...

 and southeast Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

.

The Raton Formation was originally named "Raton Hills Group" by Hayden

Ferdinand Vandeveer Hayden

Dr. Ferdinand Vandeveer Hayden was an American geologist noted for his pioneering surveying expeditions of the Rocky Mountains in the late 19th century. He was also a physician who served with the Union Army during the Civil War.-Early life:Ferdinand Hayden was born in Westfield, Massachusetts...

 in 1869 for coal beds in the Raton Hills in Colfax County, New Mexico

Colfax County, New Mexico

-2010:Whereas according to the 2010 U.S. Census Bureau:*83.8% White*0.5% Black*1.5% Native American*0.4% Asian*0.1% Native Hawaiian or Pacific Islander*3.6% Two or more races*10.1% Other races*47.2% Hispanic or Latino -2000:...

. In 1913, Lee changed the name to Raton Formation. Lee described the formation as a coal with carbonaceous shale with brown to buff sandstone and conglomerate (usually at the base). The Raton Formation is about 1140 feet thick at the type locality. The formation unconformably overlies the Vermejo Formation

Vermejo Formation

The Vermejo Formation is a geologic formation of Upper Cretaceous age which outcrops in the Raton Basin of northeastern New Mexico and southeastern Colorado....

, and unconformably (?) underlies the Poison Canyon Formation.

In 1954, Brown determined that the Raton Formation was of Late Cretaceous and Paleocene age.

Pillmore measured the formation thickness as 2000 feet, and divided the Raton Formation into three divisions. The lowest division is a basal sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

 and conglomerate of quartzite

Quartzite

Quartzite is a hard metamorphic rock which was originally sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to gray, though quartzites often occur in various shades of pink...

, chert

Chert

Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...

 and gneiss

Gneiss

Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...

 pebbles and cobbles in a coarse-grained quartzose to arkosi sandstone matrix. The middle division is fine to coarse grained sandstone, with some siltstone, mudstone, and coal. The upper division is coal-bearing and contains sandstone, siltstone, mudstone, shale, and mineable coal.

Because the Raton Formation is a well-preserved sequence of rocks spanning the Cretaceous-Tertiary boundary, it has been studied for evidence of a large meteor impact at the end of the Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 that is thought to have caused the Cretaceous–Tertiary extinction event. The boundary is represented by a 1-cm thick tonstein

Tonstein

Tonsteins are a distinctive type of rock, composed largely of the mineral kaolin. Tonsteins occur in association with coals in the Carboniferous strata of Europe.The individual beds of tonstein are thin but laterally very extensive...

 clay layer which has been found to contain anomalously high concentrations of iridium

Iridium

Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...

. The boundary clay layer is accessible to the public at Trinidad Lake State Park

Trinidad Lake State Park

Trinidad Lake State Park is a state park near Trinidad, Colorado, United States. The park protects Trinidad Lake, a dammed reservoir. There are hiking trails, and camping and boating opportunities. The park features historical attractions such as the coal mining ruins at Cokedale...

, among other places in the Raton Basin.