San Rafael Group
Encyclopedia
The San Rafael Group is a geologic group of formations that is spread across the U.S. state
s of New Mexico
, Arizona
, Utah
and Colorado
. Part of the Colorado Plateau
, this group of formations was laid down in the Middle Jurassic
during the Bajocian
, Bathonian
and Callovian
stages.
Asterisks (*) indicate usage by the U.S. Geological Survey.
for the group. It was named for exposures in the San Rafael Swell
in Emery County, Utah
by Gilluly and Reeside in 1928. That same year they divided the group into (ascending): Carmel Formation, Entrada Sandstone (new), Curtis Formation (new), and Summerville Formation (new). Areal extent limits were established by Gregory and Moore in 1931. Smith in 1954 revised and divided the group into Entrada, Todilto, and Thoreau (new) formations in the San Juan Basin
. 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 Paradox Basin
. 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 Plateau sedimentary province; and divided it into Page, Carmel, Entrada, Curtis, and Summerville formations in Paradox Basin. Condon in 1989 revised the group in San Juan Basin
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.
Parklands (incomplete list):
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
s of 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...
, 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...
, Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
and 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...
. Part of the Colorado Plateau
Colorado Plateau
The Colorado Plateau, also called the Colorado Plateau Province, is a physiographic region of the Intermontane Plateaus, roughly centered on the Four Corners region of the southwestern United States. The province covers an area of 337,000 km2 within western Colorado, northwestern New Mexico,...
, this group of formations was laid down in the Middle Jurassic
Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger....
during the Bajocian
Bajocian
In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....
, Bathonian
Bathonian
In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 167.7 Ma to around 164.7 Ma...
and Callovian
Callovian
In the geologic timescale, the Callovian is an age or stage in the Middle Jurassic, lasting between 164.7 ± 4.0 Ma and 161.2 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the Oxfordian....
stages.
Asterisks (*) indicate usage by the U.S. Geological Survey.
Subunits
Subunits (alphabetical):- Bell Ranch Formation (NM),
- Bluff Sandstone (AZ,NM),
- Carmel FormationCarmel FormationThe 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...
(AZ*,CO*,NM*,UT*,WY*), - Cow Springs Sandstone (AZ),
- Curtis Formation (CO*,UT*),
- Entrada SandstoneEntrada SandstoneThe Entrada Sandstone is a formation in the San Rafael Group that is spread across the U.S. states of Wyoming, Colorado, northwest New Mexico, northeast Arizona and southeast Utah...
(AZ*,CO*,NM*,UT*), - Henrieville Sandstone (UT),
- Page Sandstone (AZ*,UT*,WY*),
- Romana Sandstone (AZ*,UT*),
- Summerville FormationSummerville FormationThe Summerville Formation is a geological formation in New Mexico, Colorado, and Utah of the Southwestern United States. It dates back to the Middle Jurassic.-Dinosaurs:Theropod tracks geographically located in Utah, New Mexico, and Colorado, USA....
(AZ,CO,NM,UT), - Temple Cap Sandstone (UT*) or Temple Cap Formation (UT),
- Thoreau Formation (NM),
- Todilto Limestone (AZ,CO*,UT*) or Todilto Formation (AZ,CO,NM,UT),
- Wanakah Formation (AZ*,CO*,NM*,UT*).
History of investigation
There is no designated type localityType locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
for the group. It was named for exposures in the San Rafael Swell
San Rafael Swell
The San Rafael Swell is a large geologic feature located in south-central Utah, USA about 30 miles west of Green River, Utah. The San Rafael Swell, approximately by , consists of a giant dome-shaped anticline of sandstone, shale, and limestone that was pushed up during the Paleocene Laramide...
in Emery County, Utah
Emery County, Utah
Emery County is a county located in the U.S. state of Utah. As of 2000 the population was 10,860, and by 2009 had been estimated to decrease to 10,629. It was named for George W. Emery, governor of the Utah Territory in 1875...
by Gilluly and Reeside in 1928. That same year they divided the group into (ascending): Carmel Formation, Entrada Sandstone (new), Curtis Formation (new), and Summerville Formation (new). Areal extent limits were established by Gregory and Moore in 1931. Smith in 1954 revised and divided the group into Entrada, Todilto, and Thoreau (new) formations in the San Juan Basin
San Juan Basin
The San Juan Basin is a geologic structural basin in the Four Corners region of the Southwestern United States; its main portion covers around , encompassing much of northwestern New Mexico, southwest Colorado, and parts of Arizona and Utah....
. 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 Paradox Basin
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 formed during the late Paleozoic Era...
. 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 Plateau sedimentary province; and divided it into Page, Carmel, Entrada, Curtis, and Summerville formations in Paradox Basin. Condon in 1989 revised the group in San Juan Basin
San Juan Basin
The San Juan Basin is a geologic structural basin in the Four Corners region of the Southwestern United States; its main portion covers around , encompassing much of northwestern New Mexico, southwest Colorado, and parts of Arizona and Utah....
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.
Places found
Geologic Province:- Black Mesa Basin*
- Great BasinGreat BasinThe Great Basin is the largest area of contiguous endorheic watersheds in North America and is noted for its arid conditions and Basin and Range topography that varies from the North American low point at Badwater Basin to the highest point of the contiguous United States, less than away at the...
province* - Palo Duro Basin*
- Paradox BasinParadox BasinThe 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 formed during the late Paleozoic Era...
* - Piceance BasinPiceance BasinThe 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...
* - Plateau sedimentary province*
- San Juan BasinSan Juan BasinThe San Juan Basin is a geologic structural basin in the Four Corners region of the Southwestern United States; its main portion covers around , encompassing much of northwestern New Mexico, southwest Colorado, and parts of Arizona and Utah....
* - Sierra Grande Uplift*
Parklands (incomplete list):
- Canyonlands National ParkCanyonlands National ParkCanyonlands National Park is a U.S. National Park located in southeastern Utah near the town of Moab and preserves a colorful landscape eroded into countless canyons, mesas and buttes by the Colorado River, the Green River, and their respective tributaries. The park is divided into four districts:...
- see geology of the Canyonlands areaGeology of the Canyonlands areaThe exposed geology of the Canyonlands area is complex and diverse; 12 formations are exposed in Canyonlands National Park that range in age from Pennsylvanian to Cretaceous. The oldest and perhaps most interesting was created from evaporites deposited from evaporating seawater... - Capitol Reef National ParkCapitol Reef National ParkCapitol Reef National Park is a United States National Park, in south-central Utah. It is 100 miles long but fairly narrow. The park, established in 1971, preserves 378 mi² and is open all year, although May through September are the most popular months.Called "Wayne Wonderland" in the 1920s...
- see geology of the Capitol Reef areaGeology of the Capitol Reef areaThe exposed geology of the Capitol Reef area presents a record of mostly Mesozoic-aged sedimentation in an area of North America in and around Capitol Reef National Park. Nearly 10,000 feet of sedimentary strata are found in the Capitol Reef area, representing nearly 200 million years of...
Works cited
- GEOLEX database entry for San Rafael Group, USGS (viewed 20 March 2006)
- GEOLEX database Bibliographic References for Glen Canyon, USGS (viewed 20 March 2006)