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 Wyom ...

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

Wyoming Wyoming () is a U.S. state, state in the Mountain states, 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 south ...

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 western

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 ...

.Wasatch Formation
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.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 in ...

dating back to the

Early Eocene In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian i ...

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

. 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 co ...

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 t ...

(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 of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

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 poster ...

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) o ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the 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 rodents. They are na ...

carnivora Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are f ...

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, w ...

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 the ...

and others. A number of birds, several

reptiles Reptiles, as most commonly defined are the animals in the Class (biology), class Reptilia ( ), a paraphyletic grouping comprising all sauropsid, sauropsids except birds. Living reptiles comprise turtles, crocodilians, Squamata, squamates (lizar ...

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% of li ...

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. Alluv ...

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 fluviog ...

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) ...

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, p ...

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. ...

s 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, especial ...

s with

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

lignite Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

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 contro ...

formation in the Uinta 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 pla ...

, 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 Count ...

, the formation overlies the

Williams Fork Formation The Williams Fork Formation is a Campanian ( Edmontonian) geologic formation of the Mesaverde Group in Colorado. Dinosaur remains are among the fossils that have been recovered from the formation, most notably ''Pentaceratops sternbergii'',. Other ...

.Shroba & Scott, 2001, p.18

Description

Definition

The Wasatch Formation was first named as the Wasatch Group by

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 G ...

.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, a ...

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 EncyclopediaVan 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 linguist ...

, 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, easter ...

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 pla ...

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

, 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

, the formation overlies the

. The formation is exposed in the Desolation and Gray Canyons 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

Green River Basin geologic structure map

The Wasatch Formation is found across six states in the northwestern United States, from

Wasatch Formation - Montana
-

and

in the north across

Wasatch Formation - Utah
-

and

in the southwest. The formation is part of several geologic provinces; the eponymous Wasatch uplift,

Uinta uplift The Uinta Mountains ( ) are an east-west trending chain of mountains in northeastern Utah extending slightly into southern Wyoming in the United States. As a subrange of the Rocky Mountains, they are unusual for being the highest range in the con ...

Green River Green River may refer to: Rivers Canada * Green River (British Columbia), a tributary of the Lillooet River *Green River, a tributary of the Saint John River, also known by its French name of Rivière Verte *Green River (Ontario), a tributary of ...

, Piceance, Powder River, Uinta 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 for ...

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 of ...

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 Yellowston ...

province.Wasatch "Group"
-

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

s with subordinate interbedded

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 sma ...

.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 County ...

, 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 the r ...

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 s ...

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 geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth Earth ...

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 nort ...

. 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 North American land mammal age, 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 Bighor ...

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 the ...

core of the Bighorn Mountains. Part of the feldspar has been replaced by

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

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 () m ...

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 in the southwest part of the Uinta Basin.Sanborn, 1981, p.259 The Wasatch Formation is correlated with the Sentinel Butte and

Golden Valley Formation The Golden Valley Formation is a stratigraphic unit of Late Paleocene to Early Eocene age in the Williston Basin of North Dakota.Hickey, 1977 It is present in western North Dakota and was named for the city of Golden Valley by W.E. Benson and W.M ...

s 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.19Pocknall, 1987, p.30

Paleontological significance

The Wasatch Formation is the defining formation for the

, ranging from 55.8 to 50.3 Ma, within the NALMA classification. The Wasatchian followed the

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

, the Wasatch Formation preserved

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 geolo ...

s with pronounced color variegation) are characterized by common ''

Planolites ''Planolites'' is an ichnogenus found throughout the Ediacaran and the Phanerozoic that is made during the feeding process of worm-like animals. The traces are generally small, , unlined, and rarely branched, with fill that differs from the hos ...

'', rare ''

Skolithos ''Skolithos'' (formerly spelled ''Scolithus'' or ''Skolithus'') is a common trace fossil ichnogenus that is, or was originally, an approximately vertical cylindrical burrow. It is produced by a variety of organisms in shallow marine environment ...

'' 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 sediment ...

'', ''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 Mesozoic ...

'') and horizontal (''

Scoyenia ''Scoyenia'' is an ichnogenus found in paleozoic-mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lastin ...

'', ''

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 approx ...

'', '' 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 ...

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.'' * '' Wyonycteris sp.'' ;Taeniodonta * '' Stylinodon mirus''Schoch & Lucas, 1981 ;Theriiformes * '' Copedelphys innominata''Gunnell et al., 2016, p.984 * '' Herpetotherium knighti'' * '' H. innominatum'' * '' Peradectes elegans'' * '' P. chesteri'' * '' Peratherium edwardi'' * '' P. marsupium'' * '' Ectoganus sp.'' * '' Oodectes sp.'' * '' Paleotomus sp.''Alroy, 2002 * '' Stylinodon sp.''Schoch, 1986 * '' Uintacyon sp.'' * Epoicotheriidae indet. * Leptictidae indet. * Marsupialia indet. * Metacheiromyidae indet. * Nyctitheriidae indet. * Oxyaenidae indet. * Pantolestidae indet. * Stylinodontidae indet.

Birds

* '' Eocrex primus''Wetmore, 1931 * '' Limnofregata hutchisoni''Stidham, 2014 * '' Presbyornis sp.''

Invertebrates

;Bivalves * '' Asimina vesperalis''Brown, 1962 * '' Davidia antiqua''Manchester, 2002 * '' Unio wasatchensis''Yen, 1948 ;Gastropods * '' Viviparus paludinaeformis'' * '' Ferrissia cf. minuta'' ;Mollusks * Mollusca indet.Dorr & Steidtmann, 1970

Flora

* '' Allantodiopsis erosa''Wilf, 2000 * '' Allophylus flexifolia'' * '' Ampelopsis acerifolia'' * '' Beringiaphyllum cupanioides''Manchester et al., 1999 * '' Carya antiquorum'' * '' Castanea intermedia'' * '' Cercidiphyllum arcticum'' * '' Cissus marginata'' * '' Dillenites garfieldensis'' * '' Dombeya novimundi'' * '' Ficus artocarpoides'' * '' Ficus planicostata'' * '' Fraxinus eocenica'' * '' Hovenia cf. oregonensis'' * ''

Metasequoia occidentalis ''Metasequoia occidentalis'' is an extinct redwood species of the family Cupressaceae that is found as fossils throughout the Northern Hemisphere. It is one of three extinct species of ''Metasequoia'' that are currently recognized as valid.Stocke ...

'' * '' Nyssa alata'' * '' Osmunda greenlandica'' * '' Penosphyllum cordatum'' * '' Platanus raynoldsi'' * ''

Platycarya americana ''Platycarya'' is a genus of flowering plants in the family Juglandaceae native to eastern Asia in China, Korea, and Japan.Flora of China''Platycarya''/ref>Flora of China''Platycarya strobilacea''/ref> It is a deciduous tree growing to 15 m ta ...

'' * '' Populus wyomingiana'' * '' Prunus corrugis'' * '' Rhamnus goldiana'' * '' cf. Schoepfia republicensis'' * '' Stillingia casca'' * '' Syzygioides americana'' * '' Ternstroemites aureavallis'' * '' Zizyphus fibrillosus'' * '' Alnus sp.'' * '' Celtis sp.'' * '' Cinnamomophyllum sp.''Wilf et al., 2006 * '' Sloanea sp.'' * Apocynaceae indet. * Dicotyledonae indet. * Lauraceae indet. * cf. Magnoliales indet.

Ichnofossils

* '' Lunulichnus tuberosus''Zonneveld et al., 2006, p.90 * ''

'' * '' Camborygma'' * '' Celliforma'' * '' Palaeophycus'' * ''

'' * ''

'' * '' Spongeliomorpha'' * '' Taenidium'' * ''

'' * cf. ''

Herbivore expansion

The mammal fauna of the formation is part of the fourth phase of herbivore expansion spanning about 115 Ma from the

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

,Labandeira, 2006, p.421 and correlated with the Wind River and

Wilcox Formation The Wilcox Formation is a geologic formation in Tennessee. It preserves fossils dating back to the Paleogene period. The first hydrocarbon discover in the formation occurred in 1928, onshore Texas. Subsequent field discoveries included the Sev ...

s of the United States and the Laguna del Hunco Formation of Argentina.Labandeira, 2006, p.434

Economic geology

Petroleum geology

The Wasatch Formation is a

reservoir rock A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...

in the Greater Natural Buttes Field in the

Uinta Basin The Uinta Basin (also known as the Uintah Basin) is a physiographic section of the larger Colorado Plateaus province, which in turn is part of the larger Intermontane Plateaus physiographic division. It is also a geologic structural basin in ...

of Utah and Colorado. The formation is characterized by

porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

ranging from 6 to 20% and permeability of up to 1 mD. Based on 409 samples from the Wasatch Formation, average porosity is 8.75 percent and average permeability is 0.095 mD.Nelson & Hoffman, 2009, p.8 The production rates after 2 years are 100–1,000 mscf/day for gas, 0.35–3.4 barrel per day for oil, and less than 1 barrel per day for water. The water:gas ratio ranges from 0.1 to 10 barrels per million standard cubic feet, indicating that free water is produced along with water dissolved in gas in the reservoir.Nelson & Hoffman, 2009, p.5 Oil in the Bluebell-Altamont Field in the Uinta Basin and gas in the Piceance Creek Field in the Piceance Basin are produced from the Wasatch Formation.Sanborn, 1981, p.260 As of May 2019, tight gas from the Wasatch Formation and underlying

Mesaverde Group The Mesaverde Group is a Late Cretaceous stratigraphic group found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States. History The Mesaverde Formation was first described by W.H.Holmes in 1877 during the Hayden ...

has been produced more than 1.76 trillion cubic feet (TCF) of gas from over 3,000 wells in the

, mostly from the Natural Buttes gas field in the eastern part of the basin. In the

, the Mesaverde Group and Wasatch Formation produced more than 7.7 TCF from over 12,000 wells, mostly from the central part of the basin.Drake II et al., 2019, p.1

Mining

Coal

Coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

is mined from the Wasatch Formation in Wyoming. Together with the Fort Union Formation, the Wasatch Formation represents the thickest coal bed deposits in the state.Wyoming's Coal Geology
- Wyoming State Geological Survey

Uranium

The fluvial sandstones contain

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

roll front deposits. The formation is the main producer of uranium in the state.Langden, 1973 Ore zones contain

uraninite Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2 but because of oxidation typically contains variable proportions of U3O8. Radioactive decay of the uranium causes t ...

and

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...

. Oxidized ores include

uranophane Uranophane ( Ca( U O2)2( SiO3O H)2·5 H2O), also known as uranotile, is a rare calcium uranium silicate hydrate mineral that forms from the oxidation of other uranium-bearing minerals. It has a yellow color and is radioactive. Alice Mary Weeks, a ...

, meta-

autunite Autunite (hydrated calcium uranyl phosphate), with formula Ca(UO2)2(PO4)2·10–12H2O, is a yellow-greenish fluorescent phosphate mineral with a hardness of 2–. Autunite crystallizes in the orthorhombic system and often occurs as tabular square ...

, and

phosphuranylite Phosphuranylite is a uranyl phosphate mineral with formula KCa(H3O)3(UO2)7(PO4)4O4·8(H2O). It was first described in 1879 by Frederick Augustus Genth, from an occurrence in the Flat Rock pegmatite in Mitchell County, North Carolina Mitchell ...

.Heinrich, 1958

Wasatchian correlations

References

Bibliography

Wasatch publications

* *

Geology publications

* * * * * * * * * * * * * *

= Maps

= ;State maps * * ;Quadrangle maps * * * * ;Other maps * *

Paleontology publications

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * {{Chronostratigraphy of Colorado, Cenozoic state=expanded Geologic formations of the United States Geologic formations of Colorado Geologic formations of Idaho Geologic formations of Montana Geologic formations of Utah Geologic formations of Wyoming Eocene Series of North America Paleogene Colorado Paleogene Idaho Paleogene Montana Paleogene geology of Utah Paleogene geology of Wyoming Bridgerian Clarkforkian Ypresian Stage Sandstone formations of the United States Conglomerate formations Mudstone formations Siltstone formations Shale formations of the United States Coal formations Coal in the United States Alluvial deposits Fluvial deposits Lacustrine deposits Ichnofossiliferous formations Reservoir rock formations Source rock formations Unconventional gas Fossiliferous stratigraphic units of North America Paleontology in Colorado Paleontology in Utah Paleontology in Wyoming Shoshone