The San Rafael Group is a geologic group or collection of related rock

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

s that is spread across the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

s of

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

and

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

. As part of the

Colorado Plateau The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area of ...

, this group of formations was laid down in the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

during the

Bajocian In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age. Stra ...

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. Strat ...

and

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

Stages Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * S ...

Description

The group consists of Jurassic beds younger than the

Navajo Sandstone The Navajo Sandstone is a geological formation in the Glen Canyon Group that is spread across the U.S. states of southern Nevada, northern Arizona, northwest Colorado, and Utah as part of the Colorado Plateau province of the United States.Anonymo ...

and older than the

Morrison Formation The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...

. These show marine influence in their formation in the northwestern exposures at

San Rafael Swell The San Rafael Swell is a large geologic feature located in south-central Utah, United States about west of Green River. The San Rafael Swell, measuring approximately , consists of a giant dome-shaped anticline of sandstone, shale, and limesto ...

, with formations composed of

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 whe ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

, and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...

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) ...

. Further east, the group becomes more continental in character, with the Entrada Formation resembling the underlying clean sandstones of the

Glen Canyon Group The Glen Canyon Group is a geologic group of formations that is spread across the U.S. states of Nevada, Utah, northern Arizona, north west New Mexico and western Colorado. It is called the Glen Canyon Sandstone in the Green River Basin of C ...

. The group is up to thick.

Subunits

Subunits by basin: Black Mesa Basin: *

Entrada Sandstone The Entrada Sandstone is a formation in the San Rafael Group found in the U.S. states of Wyoming, Colorado, northwest New Mexico, northeast Arizona, and southeast Utah. Part of the Colorado Plateau, this formation was deposited during the Jur ...

(youngest) *

Carmel Formation The Carmel Formation is a geologic formation in the San Rafael Group that is spread across the U.S. states of Wyoming, Utah, Colorado, north east Arizona and New Mexico. Part of the Colorado Plateau, this formation was laid down in the Middle J ...

* Page Sandstone (oldest)

Great Basin The Great Basin is the largest area of contiguous endorheic basin, endorheic watersheds, those with no outlets, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja California ...

province: *Entrada Sandstone (youngest) *Page Sandstone *Carmel Formation * Temple Cap Sandstone (oldest) Peterson concluded that the Henrieville Sandstone was simply the bleached upper zone of the Entrada Sandstone and recommended abandoning the formation. Palo Duro Basin/Sierra Grande Uplift: *Entrada Formation (youngest) * Bell Ranch Formation (oldest)

Paradox Basin The Paradox Basin is an asymmetric foreland basin located mostly in southeast Utah and southwest Colorado, but extending into northeast Arizona and northwest New Mexico. The basin is a large elongate northwest to southeast oriented depression for ...

: *

Summerville Formation The Summerville Formation is a geological formation in New Mexico, Colorado, and Utah of the Southwestern United States. It dates back to the Oxfordian stage of the Late Jurassic.Wilcox 2007 Description The formation consists of up to of red m ...

(youngest) *

Curtis Formation The Curtis Formation is a geologic formation in Utah. It preserves fossils dating back to the Callovian age of the Jurassic period. Description The Curtis Formation is composed of shallow marine sandstone, with thin beds of mudstone and m ...

*Carmel Formation *Entrada Sandstone *Page Sandstone (oldest)

Piceance Basin The Piceance Basin is a geologic structural basin in northwestern Colorado, in the United States. It includes geologic formations from Cambrian to Holocene in age, but the thickest section is made up of rocks from the Cretaceous Period. The basi ...

: *Summerville Formation (youngest) *Entrada Sandstone (oldest)

Plateau Sedimentary Province The Colorado Plateau, also known as the Colorado Plateau Province, is a physiographic and desert region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. This province covers an area ...

: * Romana Sandstone (youngest) *Entrada Sandstone *Carmel Formation *Page Sandstone

San Juan Basin The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah a ...

: * Cow Springs Sandstone *

Wanakah Formation The Summerville Formation is a geological Formation (geology), formation in New Mexico, Colorado, and Utah of the Southwestern United States. It dates back to the Oxfordian (stage), Oxfordian stage (stratigraphy), stage of the Late Jurassic.Wilcox ...

*Entrada Sandstone southern San Juan Basin: * Zuni Sandstone (youngest) *

Bluff Formation The Bluff Formation is a geological formation found in the Four Corners area. It was deposited in the late Jurassic Period (geology), Period. Description The Bluff Formation consists of massive wind-deposited (Aeolian processes, eolian) sandston ...

*Summerville Formation * Todilto Formation *Entrada Sandstone (oldest)

History of investigation

There is no designated type locality for the group. It was named for exposures in the

Emery County, Utah Emery County is a county in east-central Utah, United States. As of the 2010 United States Census, the population was 10,976. Its county seat is Castle Dale, and the largest city is Huntington. History Prehistory Occupation of the San Rafael ...

by James Gilluly and J.B. Reeside in 1928. They divided the group into (ascending): Carmel Formation, Entrada Sandstone (new), Curtis Formation (new), and Summerville Formation (new). Areal extent limits were established by Herbert E. Gregory and

Raymond Cecil Moore Raymond Cecil Moore (February 20, 1892, Roslyn, Washington – April 16, 1974, Lawrence, Kansas) was an American geologist and paleontologist.Daniel F. Merriam (2007), "Raymond Cecil Moore: Legendary Scholar and Scientist, World-Class Geologist ...

in 1931. Smith in 1954 revised and divided the group into Entrada, Todilto, and Thoreau (new) formations in the

. In 1959 another revision, this time by Griggs and Read, divided it into Entrada and Bell Ranch (new) formations in the Palo Duro Basin and Sierra Grande Uplift. The Carmel-Navajo contact was revised by Wright and others in 1962 and the Carmel-Entrada contact was revised by Phoenix in 1963. Thompson and Stokes created an overview and named the Henrieville Sandstone in 1970. The Temple Cap Sandstone was revised and the Page Sandstone added (new) by Peterson and Pipiringos in 1979. A revision by O'Sullivan in 1980 divided the group into Carmel, Entrada, and Wanakah formations in

. O'Sullivan revised the upper contact in 1984. In 1988 Peterson revised earlier work and divided the group into Page, Carmel, and Entrada formations in the Black Mesa Basin; divided it into Page, Carmel, Entrada and Romana (new) formations in the

; and divided it into Page, Carmel, Entrada, Curtis, and Summerville formations in Paradox Basin. Condon in 1989 revised the group in

and divided it into Entrada and Wanakah formations in southeastern area; divided it into Entrada, Wanakah, and Cow Springs formations in south-central area; and divided it into Entrada and Cow Springs Sandstones in southwestern area.{{cite journal , last1=Condon , first1=S.M. , title=Revisions of Middle Jurassic nomenclature in the southeastern San Juan Basin, New Mexico , journal=U.S. Geological Survey Bulletin , date=1989 , volume=1808E , pages=E1-E21 , doi=10.3133/b1808EF, doi-access=free

References

Geologic groups of New Mexico Geologic groups of Arizona Geologic groups of Utah Geologic groups of Colorado Middle Jurassic North America