The Wasatch Formation (Tw)
[Shroba & Scott, 2001, p.3] is an extensive highly fossiliferous
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 ...
stretching across several basins in
Idaho
Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and W ...
,
Montana
Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...
Wyoming
Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the sou ...
,
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 its ...
and western
Colorado
Colorado (, other variants) is a state in the Mountain states, 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 wes ...
.
[Wasatch Formation]
at Fossilworks
Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world.
History
Fossilworks was cre ...
.org 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 Eocene
In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...
period. The formation defines the
Wasatchian
The Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 55,400,000 to 50,300,000 years BP lasting .
It is usually c ...
or
Lostcabinian (55.8 to 50.3 Ma), a period of time used within the
NALMA classification, but the formation ranges in age from the
Clarkforkian
The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting .
Considered ...
(56.8 to 55.8 Ma) to
Bridgerian
The Bridgerian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 50,300,000 to 46,200,000 years BP lasting .
It is usually c ...
(50.3 to 46.2 Ma).
Wasatch fauna consists of many groups of mammals, including numerous genera of
primate
Primates are a diverse order (biology), order of mammals. They are divided into the Strepsirrhini, strepsirrhines, which include the lemurs, galagos, and lorisids, and the Haplorhini, haplorhines, which include the Tarsiiformes, tarsiers and ...
s,
artiodactyl
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poste ...
s,
perissodactyl
Odd-toed ungulates, mammals which constitute the taxonomic order Perissodactyla (, ), are animals—ungulates—who have reduced the weight-bearing toes to three (rhinoceroses and tapirs, with tapirs still using four toes on the front legs) ...
s,
rodent
Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are roden ...
s,
carnivora
Carnivora is a monophyletic order of placental mammals consisting of the most recent common ancestor of all cat-like and dog-like animals, and all descendants of that ancestor. Members of this group are formally referred to as carnivorans, ...
,
insectivora
The order Insectivora (from Latin ''insectum'' "insect" and ''vorare'' "to eat") is a now-abandoned biological grouping within the class of mammals. Some species have now been moved out, leaving the remaining ones in the order Eulipotyphla, ...
,
hyaenodonta
Hyaenodonta ("hyena teeth") is an extinct order of hypercarnivorous placental pan-carnivoran mammals from mirorder Ferae. Hyaenodonts were important mammalian predators that arose during the early Paleocene in Europe and persisted well into ...
and others. A number of birds, several
reptiles
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephali ...
and
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% ...
and
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s complete the diverse faunal assemblages. Fossil flora and
ichnofossil
A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...
s also have been recovered from the formation.
The formation, first named as Wasatch Group in 1873 by
Ferdinand Vandeveer Hayden
Ferdinand Vandeveer Hayden (September 7, 1829 – December 22, 1887) 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 Ar ...
, was deposited in
alluvial
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Al ...
,
fluvial
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...
and
lacustrine
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...
environment
Environment most often refers to:
__NOTOC__
* Natural environment, all living and non-living things occurring naturally
* Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
s and comprises
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 ...
s,
siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...
s,
mudstones and
shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especia ...
s with
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...
or
lignite beds representing wet
floodplain
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
settings.
The Wasatch Formation is an
unconventional tight gas
Tight gas is natural gas produced from reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates. This natural gas is trapped within rocks with very low permeability, in other ...
reservoir
A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation.
Reservoirs can be created in a number of ways, including control ...
formation in the
Uinta Uinta or Uintah may refer to:
People
* Ute Indian Tribe of the Uintah and Ouray Reservation, Utah
Places
* High Uintas Wilderness
* Uintah and Ouray Indian Reservation, Utah
* Uintah County, Utah
* Uinta County, Wyoming
* Uinta Mountains, in ...
and
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 ...
s of Utah and the coal seams of the formation are mined in Wyoming. At the
Fossil Butte National Monument
Fossil Butte National Monument is a United States National Monument managed by the National Park Service, located west of Kemmerer, Wyoming, United States. It centers on an assemblage of Eocene Epoch (56 to 34 million years ago) animal and ...
, the formation
crops out underlying the
Green River Formation
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...
. In the Silt Quadrangle of
Garfield County, Colorado
Garfield County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 61,685. The county seat is Glenwood Springs. The county is named in honor of United States President James A. Garfield. Garfield Coun ...
, the formation overlies the
Williams Fork Formation.
[Shroba & Scott, 2001, p.18]
Description
Definition
The Wasatch Formation was first named as the Wasatch Group by
Ferdinand Vandeveer Hayden
Ferdinand Vandeveer Hayden (September 7, 1829 – December 22, 1887) 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 Ar ...
in the 1873 edition of his original 1869 publication titled "Preliminary field report of the United States Geological Survey of Colorado and New Mexico: U.S. Geological and Geographical Survey of the Territories", based on sections in the Echo and Weber Canyons, of the
Wasatch Mountains
The Wasatch Range ( ) or Wasatch Mountains is a mountain range in the western United States that runs about from the Utah-Idaho border south to central Utah. It is the western edge of the greater Rocky Mountains, and the eastern edge of the ...
.
[Wasatch]
- USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
In the language of the native
Ute people
Ute () are the Indigenous people of the Ute tribe and culture among the Indigenous peoples of the Great Basin. They had lived in sovereignty in the regions of present-day Utah and Colorado in the Southwestern United States for many centuries unt ...
, Wasatch means "mountain pass" or "low pass over high range."
[Wasatch County]
- Utah History Encyclopedia[Van Cott, 1990, p.390] According to
William Bright
William O. Bright (August 13, 1928 – October 15, 2006) was an American linguist and toponymist who specialized in Native American and South Asian languages and descriptive linguistics.
Biography
Bright earned a bachelor's degree in lingui ...
, the mountains were named for a
Shoshoni
The Shoshone or Shoshoni ( or ) are a Native American tribe with four large cultural/linguistic divisions:
* Eastern Shoshone: Wyoming
* Northern Shoshone: southern Idaho
* Western Shoshone: Nevada, northern Utah
* Goshute: western Utah, e ...
leader who was named with the Shoshoni term ''wasattsi'', meaning "blue heron".
[Bright, 2004, p.549]
Outcrops

At the base of
Fossil Butte
Fossil Butte National Monument is a United States National Monument managed by the National Park Service, located west of Kemmerer, Wyoming, United States. It centers on an assemblage of Eocene Epoch (56 to 34 million years ago) animal and pl ...
are the bright red, purple, yellow and gray beds of the Wasatch Formation. Eroded portions of these horizontal beds slope gradually upward from the valley floor and steepen abruptly. Overlying them and extending to the top of the butte are the much steeper buff-to-white beds of the
Green River Formation
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...
, which are about thick. The Wasatch Formation ranges from about in the western part of the Uinta Basin, thinning to in the east.
[ In the Silt Quadrangle of ]Garfield County, Colorado
Garfield County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 61,685. The county seat is Glenwood Springs. The county is named in honor of United States President James A. Garfield. Garfield Coun ...
, the formation overlies the Williams Fork Formation.[ The formation is exposed in the Desolation and ]Gray Canyon
Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...
s pertaining to the Colorado Plateau in northeastern Utah,[Stratigraphy of the Desolation Canyon and Gray Canyon]
/ref> and in Flaming Gorge National Recreation Area
Flaming Gorge National Recreation Area is a United States national recreation area in Wyoming and Utah. Its centerpiece is the long Flaming Gorge Reservoir.
History
The area was given the name "Flaming Gorge" by John Wesley Powell during his ...
at the border of southwestern Wyoming and northeastern Utah.[Stratigraphy of Flaming Gorge National Recreation Area]
/ref>
Extent
The Wasatch Formation is found across six states in the northwestern United States, from Montana
Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...
[Wasatch Formation - Montana]
- USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
and Idaho
Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and W ...
in the north across 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 its ...
[Wasatch Formation - Utah]
- USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
and Wyoming
Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the sou ...
to Colorado
Colorado (, other variants) is a state in the Mountain states, 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 wes ...
in the southwest. The formation is part of several geologic provinces; the eponymous Wasatch uplift, Uinta uplift, Green River, Piceance, Powder River
Powder River may refer to:
Places
* Powder River (Wyoming and Montana), in Wyoming and Montana in the United States
* Powder River Country, the area around the above river
* Powder River (Oregon), in Oregon in the United States
* Powder River Ba ...
, Uinta Uinta or Uintah may refer to:
People
* Ute Indian Tribe of the Uintah and Ouray Reservation, Utah
Places
* High Uintas Wilderness
* Uintah and Ouray Indian Reservation, Utah
* Uintah County, Utah
* Uinta County, Wyoming
* Uinta Mountains, in ...
and 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 ...
s and 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 ...
sedimentary province and Yellowstone
Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellow ...
province.[Wasatch "Group"]
- USGS
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
In Montana, the formation overlies the Fort Union Formation and is overlain by the White River Formation
The White River Formation is a geologic formation of the Paleogene Period, in the northern Great Plains and central Rocky Mountains, within the United States.
It has been found in northeastern Colorado, Dawes County in western Nebraska, Badlands ...
.[Widmayer, 1977, p.18] There is a regional, angular unconformity between the Fort Union and Wasatch Formations in the northern portion of the Powder River Basin.[Widmayer, 1977, p.105]
Subdivision
Many local subdivisions of the formation exist, the following members have been named in the literature:[
]
Lithologies and facies
In the Fossil Basin at the Fossil Butte National Monument, Wyoming, the Wasatch Formation consists primarily of brightly variegated mudstones with subordinate interbedded siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...
s, 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 ...
s, and conglomerates and represents deposition on an intermontane alluvial plain
An alluvial plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the s ...
.[Gunnells et al., 2016, p.984] In Mesa County, Colorado
Mesa County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 155,703. The county seat is Grand Junction. The county was named for the many large mesas in the area, including Grand Mesa.
Mesa Count ...
, the formation comprises interbedded purple, lavender, red, and gray claystones and shales with local lenses of gray and brown sandstones, conglomeratic sandstones, and volcanic sandstones that are predominantly fluvial and lacustrine in origin.[Carrara, 2000, p.8] Along the western margin of the Powder River Basin, the Wasatch Formation contains two thick conglomeratic members (in descending order, the Moncrief Member and Kingsbury Conglomerate Member).[Whipkey et al., 1991, D1]
The Molina Member of the formation is a zone of distinctly sandier fluvial strata. The over- and underlying members of the Molina are the Atwell Gulch and Shire members, respectively. These members consist of infrequent lenses of fluvial-channel sandstones interbedded within thick units of variegated red, orange, purple and gray overbank and paleosol mudstones.[Lorenz et al., 1996, p.3]
The Molina Member represents a sudden change in the tectonic and/or climatic regimes, that caused an influx of laterally-continuous, fine, coarse and locally conglomeratic sands into the basin. The type section of the Molina is located near the small town of Molina on the western edge of the basin and is about thick. These sandy strata of the Molina Member form continuous, erosion-resistant benches that extend to the north of the type section for approximately . The benches are cut by
canyons or "gulches", from which the Atwell Gulch and Shire Gulch members get their names. The Molina forms the principle target within the Wasatch Formation for natural gas exploration, although it is usually called the "G sandstone" in the subsurface.[
]
Provenance
Detrital zircon
Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...
s collected from the middle part of the formation in the Powder River Basin
The Powder River Basin is a geologic structural basin in southeast Montana and northeast Wyoming, about east to west and north to south, known for its extensive coal reserves. The former hunting grounds of the Oglala Lakota, the area is very ...
of Wyoming, where the Wasatch Formation reaches a thickness of more than were gathered for U-Pb geochronological analysis. The detrital zircon age spectrum ranged from 1433-2957 Ma in age, and consisted of more than 95% Archean
The Archean Eon ( , also spelled Archaean or Archæan) is the second of four eon (geology), geologic eons of History of Earth, Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozo ...
age grains, with an age peak of about 2900 Ma. The 2900 Ma age peak is consistent with the age of Archean rocks at the core of the Bighorn Mountains
The Bighorn Mountains ( cro, Basawaxaawúua, lit=our mountains or cro, Iisaxpúatahchee Isawaxaawúua, label=none, lit=bighorn sheep's mountains) are a mountain range in northern Wyoming and southern Montana in the United States, forming a ...
. The sparse Proterozoic
The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...
grains were likely derived from the recycling of Paleozoic sandstone units. The analysis concluded that the Wasatch sandstone is a first cycle sediment, the Archean core of the Bighorn uplift was exposed and shedding sediment into the Powder River Basin during time of deposition of the Wasatch Formation and the Powder River Basin Wasatch detrital zircon age spectra are distinct from the coeval Willwood Formation
The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the NALMA classification.[Bighorn Basin
The Bighorn Basin is a plateau region and intermontane basin, approximately 100 miles (160 km) wide, in north-central Wyoming in the United States. It is bounded by the Absaroka Range on the west, the Pryor Mountains on the north, the Bigh ...]
west of the Bighorn Mountains.[Anderson et al., 2017] Cobbles and pebbles in the Wasatch are rich in feldspathic
Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldspa ...
rock fragments, with individual samples containing as much as 40 percent,[Whipkey et al., 1991, D5] derived from erosion of the Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...
core of the Bighorn Mountains.[ Part of the feldspar has been replaced by ]calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...
cement.[Whipkey et al., 1991, D11] Glauconite
Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable and has very low weathering resistance.
It crystallizes with a monoclinic geometry. Its name is derived from the Greek () ...
is present in the Wasatch, although always in volumes of less than
1 percent of the grains. It most probably was derived from the nearby, friable, glauconite-bearing Mesozoic strata of the eastern Bighorn Mountains.[Whipkey et al., 1991, D15]
The presence of the Kingsbury Conglomerate at the base of the Wasatch Formation indicates that tectonic activity in the immediate vicinity of the Powder River Basin was intensifying. The conglomerate consists of Mesozoic and Paleozoic rock fragments. The lack of Precambrian fragments indicates that the metamorphic core of the Bighorn Mountains had not been dissected by this early deformation.[Widmayer, 1977, p.11] Deformation in the upper part of the formation has been interpreted as the result of the last phase of uplift during the Laramide orogeny
The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the o ...
.[Shroba & Scott, 2001, p.23]
Correlations
The basal part of the Wasatch Formation is equivalent to the Flagstaff Formation
The Flagstaff Formation is a geologic formation in Utah. It preserves fossils dating back to the Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic p ...
in the southwest part of the Uinta Basin.[Sanborn, 1981, p.259] The Wasatch Formation is correlated with the Sentinel Butte
Sentinel Butte is a city in Golden Valley County, North Dakota, United States. The population was 61 at the 2020 census.
Sentinel Butte was founded in 1902 along the transcontinental rail line of the Northern Pacific Railway. The name comes f ...
and Golden Valley Formations of the Williston Basin
The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North Dakota, South Dakota, southern Saskatchewan, and south-western Manitoba that is known for its rich deposits of petroleum and potash. The basin is a ...
.[Widmayer, 1977, p.19][Pocknall, 1987, p.30]
Paleontological significance
The Wasatch Formation is the defining formation for the Wasatchian
The Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 55,400,000 to 50,300,000 years BP lasting .
It is usually c ...
, ranging from 55.8 to 50.3 Ma, within the NALMA classification. The Wasatchian followed the Clarkforkian
The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting .
Considered ...
stage (56.8-55.8 Ma) and is defined by the simultaneous first appearance of adapid and omomyid euprimates, hyaenodontid creodonts, perissodactyls and artiodactyls.[Anemone & Dirks, 2009, p.116] The deposits of the formation were laid down during a period of globally high temperatures during the Paleocene-Eocene Thermal Maximum (PETM). Mean annual temperatures were around and temperature variations were minimal during this time.[Pocknall, 1987, p.172]
At the Fossil Butte National Monument
Fossil Butte National Monument is a United States National Monument managed by the National Park Service, located west of Kemmerer, Wyoming, United States. It centers on an assemblage of Eocene Epoch (56 to 34 million years ago) animal and ...
, the Wasatch Formation preserved ichnofossil
A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...
s attributed to arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
s and described as '' Lunulichnus tuberosus''.[ Trace fossils are common within the upper part of the Main Body Member. These traces occur in three distinct alluvial depositional settings: flood basin/alluvial plain, crevasse splay, and fluvial channel. Flood basin deposits (dominated by alluvial ]paleosol
In the geosciences, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The precise definition of the term in geology and paleontology is slightly different from its use in soil science.
In geol ...
s with pronounced color variegation) are characterized by common '' Planolites'', rare '' Skolithos'' and small, meniscate plug-shaped burrows, possibly '' Celliforma''.[Zonneveld et al., 2006, p.88]
Crevasse splay deposits (current-rippled to planar laminated, fine-grained sandstone to siltstone) are characterized by a mixed assemblage of vertical (''Arenicolites
''Arenicolites'' is a U-shaped ichnotaxon (trace fossil) dating from Ediacaran times onwards in South Australia. The trace shown by this fossil, is a pair of closely spaced circles on a bedding plane
In geology, a bed is a layer of sedimen ...
'', ''Skolithos'', unwalled sinuous shafts, shafts with discoidal lenses of sediment), sub-vertical ('' Camborygma'' and ''Thalassinoides
''Thalassinoides'' is an ichnogenus of trace fossil used to refer to "dichotomously or T-branched boxworks, mazes and shafts, unlined and unornamented". Facies of ''Thalassinoides'' increased suddenly in abundance at the beginning of the Mesoz ...
'') and horizontal (''Scoyenia
''Scoyenia'' is an ichnogenus found in paleozoic-mesozoic strata
In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjac ...
'', ''Rusophycus
''Rusophycus'' is a trace fossil ichnogenus allied to '' Cruziana''. ''Rusophycus'' is the resting trace, recording the outline of the tracemaker; ''Cruziana'' is made when the organism moved. The sculpture of ''Rusophycus'' may reveal the app ...
'', '' Taenidium'', ''Planolites'' and '' Palaeophycus'') burrows. Large, vertically oriented burrows (''Camborygma'', cf. ''Ophiomorpha
''Ophiomorpha'' is an ichnotaxon, usually interpreted as a burrow of an organism (specifically a crustacean) living in the near-shore environment. The burrow lining is more or less smooth on the inside, and densely to strongly mammalated or nod ...
'', '' Spongeliomorpha'' and ''Thalassinoides'') are the dominant forms within fluvial channel deposits.[
]
Fossil content
Among the following fossils have been found in the formation:[
]
Mammals
;Primates
* '' Absarokius abbotti''[Covert & Hamrick, 1993]
* '' A. gazini''[Bown & Rose, 1987]
* '' Anaptomorphus aemulus''[West & Dawson, 1973]
* '' Anemorhysis sublettensis''[
* '' Arapahovius gazini''
* '' Artimonius nocerai''][
* '' A. witteri''][Muldoon & Gunnell, 2002]
* ''Cantius frugivorus
''Cantius frugivorus'' is a species of adapiform primate that lived in North America during the early Eocene.
Morphology
This species had a dental formula of . The incisors are small and vertical in ''Cantius frugivorus'', and the canines ar ...
''[Honey, 1988][Gunnell et al., 2016, p.991]
* '' C. mckennai''[
* '' C. nunienus''][
* '' Carpodaptes cf. hazelae''][
* '' Chiromyoides minor''][Gunnell, 1994]
* '' Chlororhysis knightensis''[
* '' Copelemur australotutus''][Beard, 1988][
* '' C. praetutus''][
* '' C. tutus''][Gunnell et al., 2016, p.992]
* '' Ignacius frugivorus''[
* '' Loveina minuta''][
* '' L. sheai''][
* '' L. zephyri''][Bown, 1979]
* '' Microsyops angustidens''[
* '' M. knightensis''][
* '' M. latidens''][Gunnell et al., 2016, p.990]
* '' M. cf. elegans''[
* '' M. cf. scottianus''][
* '' Notharctus robinsoni''][
* '' N. venticolus''][
* '' Omomys carteri''][
* '' O. lloydi''][
* '' Plesiadapis dubius''][Holroyd & Rankin, 2014]
* '' Plesiadapis cf. cookei''[Gazin, 1942]
* '' Plesiadapis cf. rex''[
* '' Simpsonlemur cf. jepseni''][
* '' Smilodectes sororis''][Gunnell, 2002]
* '' Steinius cf. vespertinus''[
* '' Tetonius matthewi''][
* '' Tetonoides pearcei''][
* '' cf. Trogolemur myodes''][
* '' Uintanius rutherfurdi''][
* '' Utahia carina''][
* '' Walshina mcgrewi''][
* '' Washakius insignis''][
* '' W. izetti''][
* '' cf. Choctawius sp.''][
* '' Cantius sp.''][
* '' Carpolestes sp.''][
* '' Chlororhysis sp.''][
* '' Loveina sp.''
* '' Microsyops sp.''][
* '' Notharctus sp.''][Roehler, 1991]
* '' Omomys sp.''[
* '' Phenacolemur sp.''][
* '' Picrodus sp.''][Scott & Fox, 2005]
* '' Tetonius sp.''
* '' Trogolemur sp.''[
* '' Uintasorex sp.''
* Phenacolemurinae indet.][
;Artiodactyls
* '' Antiacodon pygmaeus''][
* '' Bunophorus cf. etsagicus''][
* '' B. grangeri''][
* '' B. macropternus''][
* '' B. sinclairi''][Stucky & Krishtalka 1990]
* '' Diacodexis secans''[Krishtalka & Stucky, 1985][
* '' Gagadon minimonstrum''][Stucky & Covert, 2014]
* '' Hexacodus pelodes''[
* '' H. uintensis''][Gunnell et al., 2016, p.1004]
* '' Antiacodon sp.''[
* '' Bunophorus sp.''][
* '' Diacodexis sp.''][
* '' Hexacodus sp.''][
* '' Microsus sp.''][
* Dichobunidae indet.][
;Perissodactyls
* '' Arenahippus pernix''][Gingerich, 1991]
* '' Cardiolophus semihians''[
* '' cf. Dilophodon destitutus''][Zonneveld & Gunnell, 2003]
* '' Eotitanops borealis''[
* '' Heptodon calciculus''][Gunnell et al., 2016, p.1003]
* '' H. posticus''[
* '' Homogalax protapirinus''][
* '' Hyrachyus modestus''][
* '']Hyracotherium vasacciense
''Eohippus'' is an extinct genus of small equid ungulates. The only species is ''E. angustidens'', which was long considered a species of '' Hyracotherium''. Its remains have been identified in North America and date to the Early Eocene ( Ypre ...
''[Dorr, 1978]
* '' Lambdotherium popoagicum''[
* '' Minippus index''][
* '' Orohippus proteros''][
* '' Orohippus cf. pumilus''][Clyde et al., 1997]
* '' Palaeosyops fontinalis''[
* '' Protorohippus venticolum''][Froehlich, 2002][
* '' Xenicohippus craspedotum''][Gunnell et al., 2016, p.1001]
* '' Eotitanops borealis''[
* '' Helaletes sp.''][
* '' Heptodon sp.''][
* '' Homogalax sp.''][
* '' Hyrachyus sp.''][
* '' Hyracotherium sp.''][
* '' Lambdotherium sp.''][
* '' Orohippus sp.''][
* '' Palaeosyops sp.''][
* Equidae indet.][
* Helaletidae indet.][
* Isectolophidae indet.][
* Perissodactyla indet.][
* Tapiroidea indet.][Gazin, 1965]
;Hyaenodonta
* '' Gazinocyon vulpeculus''[Polly, 1996]
* '' Iridodon datzae''[Morlo & Gunnell, 2003]
* '' Prolimnocyon antiquus''[
* '' Prototomus secundarius''][
* '' Tritemnodon cf. strenuus''][
* '' Prolimnocyon sp.''][
* '' Sinopa sp.''][
* '' Thinocyon sp.''][
* '' Tritemnodon sp.''][
* Hyaenodontidae indet.][Gunnell, 1998]
;Acreodi
* '' Dissacus cf. praenuntius''[
* '' Hapalodectes leptognathus''][
* '' Pachyaena ossifraga''][
* '' Wyolestes dioctes''][Gingerich, 1982]
* '' Dissacus sp.''
* '' ?Mesonyx sp.''[
* Mesonychidae indet.][
;Carnivora
* '']Miacis latidens
''Miacis'' is a genus of extinct Carnivoramorpha, carnivorous mammals that appeared in the late Paleocene and continued through the Eocene. The genus ''Miacis'' is not monophyletic but a diverse collection of species that belong to the Stem gro ...
''[
* '' Vulpavus australis''][Gunnell et al., 2016, p.1000]
* '' V. canavus''[Guthrie, 1971]
* '' Miacis sp.''[
* '' Vulpavus sp.''][
* Miacidae indet.][Roehler, 1987]
;Cimolesta
* '' Amaramnis gregoryi''[
* '' Esthonyx acutidens''][
* '' Esthonyx cf. bisulcatus''][Gunnell et al., 2016, p.989]
* '' Palaeoryctes cruoris''
* '' Palaeoryctes cf. punctatus''
* '' ?Trogosus cf. latidens''[
* '' Esthonyx sp.''][
* '' Trogosus sp.''][
;Dinocerata
* '' cf. Bathyopsis fissidens''][
* '' Probathyopsis cf. harrisorum''][
* '' Bathyopsis sp.''][
;Erinaceomorpha
* '' Adunator meizon''
;Eutheria
* '' Aceroryctes dulcis''][Rankin & Holroyd, 2014]
* '' Arctocyon nexus''[Gazin, 1956]
* '' Bessoecetor cf. septentrionalis''[Scott et al., 2002]
* '' Chriacus oconostotae''
* '' Lambertocyon gingerichi''
* '' Palaeosinopa incerta''[Bown & Schankler, 1982]
* '' P. lacus''[
* '' Palaeosinopa cf. didelphoides''][
* '' cf. Palaeosinopa lutreola''][
* '' Thryptacodon australis''
* '' T. pseudarctos''][Secord, 2008]
* '' Chriacus sp.''[
* '' Claenodon sp.''
;Ferae
* '' Ambloctonus major''][
* '' Brachianodon westorum''][
* '' Didymictis altidens''][
* '' D. cf. protenus''][Gunnell et al., 2016, p.999]
* '' Oxyaena forcipata''[
* '' O. lupina''][Gunnell, 1998]
* '' Protictis agastor''
* '' P. paralus''
* '' Raphictis cf. gausion''
* '' Tubulodon pearcei''[
* '' Tytthaena parrisi''
* '' Uintacyon asodes''
* '' Viverravus cf. acutus''][
* '' V. gracilis''][
* '' V. lutosus''][
* '' V. minutus''][
* '' V. sicarius''][
* '' Didymictis sp.''][
* '' Patriofelis sp.''][
* '' Viverravus sp.''][
;Glires
* '' Acritoparamys francesi''][
* '' Knightomys depressus''][Korth, 1984]
* '' K. huerfanensis''[Gunnell et al., 2016, p.998]
* '' Leptotomus parvus''[
* '' Lophiparamys murinus''][
* '' Microparamys hunterae''][
* '' M. minutus''][
* '' Mysops fraternus''][
* '' ?Notoparamys blochi''][
* '' Paramys copei''][
* '' P. delicatior''][
* '' P. delicatus''][
* '' P. excavatus''][
* '' P. taurus''][
* '' P. wyomingensis''][
* '' Pauromys schaubi''][
* '' Pseudotomus robustus''][Black & Sutton, 1984]
* '' Reithroparamys delicatissimus''[
* '' R. huerfanensis''][
* '' R. cf. debequensis''][
* '' Sciuravus bridgeri''][
* '' S. nitidus''][
* '' S. wilsoni''][
* '' Thisbemys perditus''][
* '' Tuscahomys ctenodactylops''][Anemone et al., 2012]
* '' Microparamys sp.''[
* '' Paramys sp.''][Rose, 1981]
* '' Reithroparamys sp.''[Gazin, 1962]
* '' Tillomys sp.''[
* Cylindrodontidae indet.][
* Paramyidae indet.][
* Rodentia indet.][Gunnell, 1998]
* Sciuravidae indet.[
;Insectivora
* '' Apatemys bellulus''][
* '' A. bellus''][
* '' A. cf. whitakeri''][Gunnell et al., 2016, p.987]
* '' Labidolemur soricoides''
* '' Unuchinia dysmathes''
* '' Apatemys sp.''[Savage et al., 1972][
;Leptictida
* '' Palaeictops cf. bicuspis''][
* '' Prodiacodon cf. concordiarcensis''
* '' Prodiacodon cf. furor''
* '' Prodiacodon cf. tauricinerei''][
;Lipotyphla
* '' Cedrocherus aceratus''
* '' Eoictops novaceki''][Gunnell et al., 2016, p.985]
* '' Entomolestes sp.''[Hamrich & Covert, 1991]
* Adapisoricinae indet.[
;Macroscelidea
* '' Aletodon cf. quadravus''
* '' Apheliscus nitidus''][
* '' Apheliscus cf. insidiosus''][Gunnell et al., 2016, p.994]
* '' Dorraletes diminutivus''
* '' Haplomylus speirianus''[
* '' Haplomylus cf. scottianus''][
* '' Litocherus lacunatus''
* '' Scenopagus priscus''][
* '' Scenopagus sp.''][
;Multituberculata
* '' Ectypodus cf. powelli''
* '' Neoplagiaulax cf. hazeni''
* '' Neoplagiaulax cf. hunteri''
* '']Ptilodus kummae
''Ptilodus'' (meaning "soft-haired") is a genus of mammals from the extinct order of Multituberculata, and lived during the Paleocene in North America.
''Ptilodus'' was a relatively large multituberculate of in length, which is about the same ...
''
* '' Mesodma sp.''
* '' Ectypodus sp.''[
* '' Parectypodus sp.''][
* '' ?Prochetodon sp.''][
* '' Ptilodus sp.''
;Pantodonta
* '' Barylambda faberi''][
* '' Coryphodon armatus''][Lucas, 1998]
* '' C. lobatus''[
* '' C. radians''][
* '' Coryphodon sp.''][
;Pholidota
* '' Palaeanodon sp.''][
;Placentalia
* '' Copecion brachypternus''][Thewissen, 1990]
* '' Ectocion collinus''
* '' E. osbornianus''[
* '' E. superstes''][Gunnell et al., 2016, p.995]
* '' Hyopsodus loomisi''[Alroy, 2002]
* '' H. minor''[
* '' H. minusculus''][
* '' H. paulus''][
* '' H. powellianus''][
* '' H. wortmani''][
* '' H. cf. mentalis''][
* '' H. cf. walcottianus''][
* '' Meniscotherium chamense''][Williamson & Lucas, 1992]
* '' M. cf. robustum''[
* '' M. cf. tapiacitum''][
* '' Phenacodus grangeri''
* '' P. intermedius''][
* '' P. trilobatus''][
* '' P. vortmani''][
* '' Ectocion sp.''
* '' Hyopsodus sp.''][
* '' Phenacodus sp.''][
;Soricomorpha
* '' Leptacodon cf. munusculum''
* '' Nyctitherium serotinum''][
* '' Leptacodon sp.''][
* '' ]