Crevasse Canyon Formation
Encyclopedia
The Crevasse Canyon Formation is a coal-bearing Cretaceous
bedrock
formation in New Mexico
and Arizona
.
The formation is divided into three members, in ascending stratigraphic order: Dilco Coal Member, Dalton Sandstone Member, and Gibson Coal Member. The Dilco Coal Member is described by Cather (2010) as "Drab mudstone
, fine- to medium-grained sandstone
, and coal
. Sandstone is commonly crossbedded
or ripple laminated." The Dalton Sandstone Member is described as "Gray to yellowish gray, fine- to medium-grained, cliff-forming sandstone." The Gibson Coal Member is described as "Drab mudstone, buff, brown, and greenish gray sandstone (commonly cross-bedded
), and coal," with the coals typically less than 0.5 m thick.
remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus
.
Petrified wood is common in the Gibson Coal Member.
and Santonian
by palynology
of coal and shale.
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...
bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
formation in 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 Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
.
Description
The formation was originally described in 1954 by Allen and Balk as part of the Mesaverde Group.The formation is divided into three members, in ascending stratigraphic order: Dilco Coal Member, Dalton Sandstone Member, and Gibson Coal Member. The Dilco Coal Member is described by Cather (2010) as "Drab mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
, fine- to medium-grained 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 coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
. Sandstone is commonly crossbedded
Cross-bedding
In geology, the sedimentary structures known as cross-bedding refer to horizontal units that are internally composed of inclined layers. This is a case in geology in which the original depositional layering is tilted, and the tilting is not a result of post-depositional deformation...
or ripple laminated." The Dalton Sandstone Member is described as "Gray to yellowish gray, fine- to medium-grained, cliff-forming sandstone." The Gibson Coal Member is described as "Drab mudstone, buff, brown, and greenish gray sandstone (commonly cross-bedded
Cross-bedding
In geology, the sedimentary structures known as cross-bedding refer to horizontal units that are internally composed of inclined layers. This is a case in geology in which the original depositional layering is tilted, and the tilting is not a result of post-depositional deformation...
), and coal," with the coals typically less than 0.5 m thick.
Fossils
DinosaurDinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
.
Petrified wood is common in the Gibson Coal Member.
Age
Tschudy (1976) identified the Crevasse Canyon formation as ConiacianConiacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma...
and Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
by palynology
Palynology
Palynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...
of coal and shale.