The Green River Formation is an
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day
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 ...
in
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 ...
,
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 ...
, and
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 ...
. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in the dry season. Each pair of layers is called a
varve
A varve is an annual layer of sediment or sedimentary rock.
The word 'varve' derives from the Swedish word ''varv'' whose meanings and connotations include 'revolution', 'in layers', and 'circle'. The term first appeared as ''Hvarfig lera'' (va ...
and represents one year. The sediments of the Green River Formation present a continuous record of six million years. The mean thickness of a varve here is 0.18 mm, with a minimum thickness of 0.014 mm and maximum of 9.8 mm.
[Bradley, W. H. The varves and climate of the Green River epoch: U.S. Geol. Survey Prof. Paper 158, pp 87–110, 1929.]
The sedimentary layers were formed in a large area named for the Green River, a tributary of the
Colorado River
The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid drainage basin, watershed that encompasses parts of ...
. The three separate basins lie around the
Uinta Mountains
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 c ...
(north, east, and south) of northeastern Utah:
* an area in northwestern Colorado east of the Uintas
* a larger area in the southwest corner of Wyoming just north of the Uintas known as ''Lake Gosiute''
* the largest area, in northeastern Utah and western Colorado south of the Uintas, known as ''Lake Uinta''
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 ...
in
Lincoln County, Wyoming
Lincoln County is a county in the U.S. state of Wyoming. As of the 2020 United States Census, the population was 19,581. Its county seat is Kemmerer. Its western border abuts the eastern borders of the states of Idaho and Utah.
History
Lincoln ...
is in a part of the formation known as ''Fossil Lake'' because of its abundance of exceptionally well preserved
fish fossil
The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fis ...
s.
Lithology and formation
The formation of
intermontane
Intermontane is a physiographic adjective formed from the prefix " inter-" (''signifying among, between, amid, during, within, mutual, reciprocal'') and the adjective "montane" (inhabiting, or growing in mountainous regions, especially cool, moi ...
basin / lake environments during the Eocene resulted from mountain building and uplift of the
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
(late
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
Sevier orogeny
The Sevier orogeny was a mountain-building event that affected western North America from northern Canada to the north to Mexico to the south.
The Sevier orogeny was the result of convergent boundary tectonic activity, and deformation occurred f ...
and the
Paleogene
The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...
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 ...
). Tectonic highlands supplied the Eocene sedimentary basins with sediment from all directions: the
Uinta Mountains
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 c ...
in the center; the
Wind River Mountains
The Wind River Range (or "Winds" for short) is a mountain range of the Rocky Mountains in western Wyoming in the United States. The range runs roughly NW–SE for approximately . The Continental Divide follows the crest of the range and incl ...
to the north; the
Front Range
The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encountere ...
,
Park Range and
Sawatch Range
The Sawatch Range or Saguache RangeThe place name "Saguache” is pronounced “Sawatch” . This name derives from the Ute language noun "''sawup''" meaning "sand dunes" and is spelled using the Spanish language version of this name "Saguach ...
of the Colorado Rockies to the east; the
Uncompahgre Plateau
The Uncompahgre Plateau in western Colorado is a distinctive large uplift part of the Colorado Plateau. is a Ute word that describes the water: "Dirty Water" or "Rocks that make Water Red".
The plateau, with an average elevation of , rises fro ...
and the
San Juan Mountains
The San Juan Mountains is a high and rugged mountain range in the Rocky Mountains in southwestern Colorado and northwestern New Mexico. The area is highly mineralized (the Colorado Mineral Belt) and figured in the gold and silver mining industry ...
to the south and finally, 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 ...
of Utah and the ranges of eastern Idaho to the west.
The
lithology of the lake sediments is varied and includes
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,
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,
siltstones,
oil shale
Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitut ...
s,
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 ...
beds, saline
evaporite
An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean ...
beds, and a variety of lacustrine
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
s and
dolomite Dolomite may refer to:
*Dolomite (mineral), a carbonate mineral
*Dolomite (rock), also known as dolostone, a sedimentary carbonate rock
*Dolomite, Alabama, United States, an unincorporated community
*Dolomite, California, United States, an unincor ...
s.
Volcanic ash
Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...
layers within the various sediments from the then active
Absaroka Volcanic field to the north in the vicinity of
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 ...
and the
San Juan volcanic field
The San Juan volcanic field is part of the San Juan Mountains in southwestern Colorado. It consists mainly of volcanic rocks that form the largest remnant of a major composite volcanic field that covered most of the southern Rocky Mountains in t ...
to the southeast provide
dateable horizons within the sediments.
The
trona
Trona (trisodium hydrogendicarbonate dihydrate, also sodium sesquicarbonate dihydrate, Na2CO3•2NaHCO3•3H2O) is a non-marine evaporite mineral. It is mined as the primary source of sodium carbonate in the United States, where it has replaced ...
(hydrated sodium bicarbonate carbonate) beds of
Sweetwater County, Wyoming are noted for a variety of rare evaporite minerals. The Green River Formation, is the
type locality for eight rare minerals:
bradleyite,
ewaldite,
loughlinite,
mckelveyite-(Y),
norsethite,
paralabuntsovite-Mg,
shortite
Shortite is a sodium-calcium carbonate mineral, with the chemical formula Na2Ca2(CO3)3. It was discovered by J. J. Fahey in well cuttings from the Green River Formation, Sweetwater County, Wyoming, US, and was named to honor Maxwell N. Short (1 ...
and
wegscheiderite. It also has a natural occurrence of
moissanite
Moissanite () is naturally occurring silicon carbide and its various crystalline polymorphs. It has the chemical formula SiC and is a rare mineral, discovered by the French chemist Henri Moissan in 1893. Silicon carbide is useful for commercial ...
(SiC) and 23 other valid mineral species.
Cyclicity
The beds display a pronounced
cyclicity, with the precession, obliquity, and eccentricity orbital components all clearly detectable. This enables the beds to be internally dated with a high degree of accuracy, and
astrochronological dates agree very well with
radiometric
Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which ch ...
dates.
File:Green River Fm.jpg, Unnamed middle member, Green River Formation along U.S. Highway 191 near Indian Canyon Summit, Duchesne County, Utah.
File:Upper Green River.jpg, Unnamed upper member, saline facies, Green River Formation, along U.S. Highway 191 in lower Indian Canyon, Duchesne County, Utah. Left: typical exposure; right: exposure in roadcut.
File:Transition facies GR (4).jpg, Transition facies, unnamed upper member of the Green River Formation along U.S. Highway 191, lower Indian Canyon, Duschesne County, Utah.
File:Transition facies GR (7).jpg, Tranisition facies exposed in road cut along U.S. Highway 191, lower Indian Canyon, Duchesne County, Utah.
Fossil zones
Within the Green River Formation of southwest Wyoming in the area known as ''Fossil Lake'', two distinct zones of very fine-grained lime muds are particularly noted for preserving a variety of complete and detailed
fossil
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 ...
s. These layers are an Eocene
Lagerstätte
A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...
, a rare place where conditions were right for a rich accumulation of undisturbed fossils. The most productive zone—called the ''split fish layer''—consists of a series of laminated or
varve
A varve is an annual layer of sediment or sedimentary rock.
The word 'varve' derives from the Swedish word ''varv'' whose meanings and connotations include 'revolution', 'in layers', and 'circle'. The term first appeared as ''Hvarfig lera'' (va ...
d lime muds about thick, which contains abundant fish and other fossils. These are easily split along the layers to reveal the fossils. This thin zone represents some 4000 years of deposition. The second fossil zone, the ''18 inch layer'', is an unlaminated layer about thick that also contains abundant detailed fossils, but is harder to work because it is not composed of fissile laminae.
The limestone matrix is so fine-grained that fossils include rare soft parts of complete insects and fallen leaves in spectacular detail. Some 35,000 fossiliferous rocks from the Green River Formation are housed at the
Smithsonian Institution
The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...
in Washington, D.C.
Fish fossils of ''
Diplomystus
''Diplomystus'' is an extinct genus of freshwater clupeomorph fish distantly related to modern-day extant herrings, alewives, and sardines. The genus was first named and described by Edward Drinker Cope in 1877. There are seven species of ' ...
'' and ''
Knightia
''Knightia'' is an extinct genus of clupeid bony fish that lived in the freshwater lakes and rivers of North America and Asia during the Eocene epoch. The genus was erected by David Starr Jordan in 1907, in honor of the late University of Wyom ...
'' are found in Fossil Lake but not in Lake Gosiute. Only Lake Gosiute has fossils of catfish (''
Ictaluridae
The Ictaluridae, sometimes called ictalurids, are a family of catfish native to North America, where they are an important food source and sometimes fished for sport. The family includes about 51 species, some commonly known as bullheads, madt ...
'' and ''
Hypsidoridae'') and suckers (''
Catostomidae
The Catostomidae are the suckers of the order Cypriniformes, with about 78 species in this family of freshwater fishes. The Catostomidae are almost exclusively native to North America. The only exceptions are '' Catostomus catostomus,'' found in ...
''). The catfish are found mostly in the deepest parts of the lake.
[Morton, Glenn R., 2003]
Creationist Misuse of the Green River Formation
, accessed May 2, 2009
The various fossil beds of the Green River Formation span a 5 million year period, dating to between 53.5 and 48.5 million years old. This span of time includes the transition between the moist early Eocene climate and the slightly drier mid-Eocene. The climate was moist and mild enough to support
crocodiles, which do not tolerate frost, and the lakes were surrounded by
sycamore
Sycamore is a name which has been applied to several types of trees, but with somewhat similar leaf forms. The name derives from the ancient Greek ' (''sūkomoros'') meaning "fig-mulberry".
Species of trees known as sycamore:
* ''Acer pseudoplata ...
( e.g. ''Platanus wyomingensis'' ) forests. As the lake configurations shifted, each Green River location is distinct in character and time. The lake system formed over underlying river deltas and shifted in the flat landscape with slight tectonic movements, receiving sediments from the Uinta highland and the
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
to the east and north. The lagerstätten formed in anoxic conditions in the fine carbonate muds that formed in the lakebeds. Lack of oxygen slowed bacterial decomposition and kept scavengers away, so leaves of palms, ferns and sycamores, some showing the insect damage they had sustained during their growth, were covered with fine-grained sediment and preserved. Insects were preserved whole, even delicate wing membranes and spider spinnerets.
Vertebrates were preserved too, including the osteoderms of ''
Borealosuchus
''Borealosuchus'' (meaning "boreal crocodile") is an extinct genus of crocodyliforms that lived from the Late Cretaceous to the Eocene in North America. It was named by Chris Brochu in 1997 for several species that had been assigned to '' Leidyo ...
'', the crocodile that was an early clue to the mild Eocene climate of Western North America. Fish are common. The fossils of the herring-like ''Knightia'', sometimes in dense layers, as if a school had wandered into anoxic water levels and were overcome, are familiar to fossil-lovers and are among the most commonly available fossils on the commercial market. There were two genera of indigenous freshwater
stingray, ''
Heliobatis'' and ''
Asterotrygon''. Approximately sixty vertebrate taxa in all have been found at Green River. Besides fishes they include at least eleven species of reptiles, and some birds and one
armadillo-like mammal, ''
Brachianodon westorum'', with some scattered vertebrae of others, like the dog-sized ''
Meniscotherium'' and ''
Notharctus'', one of the first primates. The earliest known
bat
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...
s (''
Icaronycteris index''
,
and ''
Onychonycteris finneyi''
), already full-developed for flight, are found here. Even a snake, ''
Boavus idelmani'', found its way into a lake and was preserved in the mudstone.
Discovery of the fossil beds
The first documented records of (invertebrate) fossils from what is now called the Green River Formation are in the journals of early missionaries and explorers such as S. A. Parker, 1840, and J. C. Fremont, 1845.
Geologist Dr. John Evans collected the first fossil fish, described as ''Clupea humilis'' (later renamed ''
Knightia
''Knightia'' is an extinct genus of clupeid bony fish that lived in the freshwater lakes and rivers of North America and Asia during the Eocene epoch. The genus was erected by David Starr Jordan in 1907, in honor of the late University of Wyom ...
eocaena''), from the Green River beds in 1856.
Edward Drinker Cope collected extensively from the area and produced several publications on the fossil fish from 1870 onwards.
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 ...
(geologist-in-charge of the United States Geological and Geographical Survey of the Territories, the forerunner of the
United States Geological Survey
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, ...
) first used the name "Green River Shales" for the fossil sites in 1869.
Millions of fish fossils have been collected from the area, commercial collectors operating from legal quarries on state and private land have been responsible for the majority of Green River vertebrate fossils in public and private collections all over the world.
Oil shale
The Green River Formation contains the largest
oil shale
Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitut ...
deposit in the world. It has been estimated that the
oil shale reserves could equal up to of
shale oil
Shale oil is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas. The resulting oil c ...
, up to half of which may be recoverable by
shale oil extraction
Shale oil extraction is an industrial process for unconventional oil production. This process converts kerogen in oil shale into shale oil by pyrolysis, hydrogenation, or thermal dissolution. The resultant shale oil is used as fuel oil or up ...
technologies (
pyrolysis
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...
,
hydrogenation
Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organ ...
, or
thermal dissolution Thermal dissolution is a method of liquefaction of solid fossil fuels. It is a hydrogen-donor solvent refining process. It may be used for the shale oil extraction and coal liquefaction.
Other liquids extraction processes from solid fuels are py ...
of
kerogen
Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It ...
in oil shale).
However, the estimates of recoverable oil has been questioned, back in 2013, by geophysicist Raymond T. Pierrehumbert, who argued that the technology for recovering oil from the Green River oil shale deposit had not been developed and had not been profitably implemented at any significant scale.
Green River oil shale is
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 ...
type
lamosite. The
organic matter
Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...
is from
blue-green algae (cyanobacteria).
[
]
Notable mineral deposits
The unusual chemistry of the lakes in which it was deposited makes the Green River Formation a major source of sodium carbonate. In southwest Wyoming the formation contains the world's largest deposits of trona
Trona (trisodium hydrogendicarbonate dihydrate, also sodium sesquicarbonate dihydrate, Na2CO3•2NaHCO3•3H2O) is a non-marine evaporite mineral. It is mined as the primary source of sodium carbonate in the United States, where it has replaced ...
, and in Colorado, the world's largest deposits of nahcolite
Nahcolite is a soft, colourless or white carbonate mineral with the composition of sodium bicarbonate ( Na H C O3) also called thermokalite. It crystallizes in the monoclinic system.
Nahcolite was first described in 1928 for an occurrence in ...
. Another unusual mineral, currently only known from the Parachute Creek member is the crystalline nickel porphyrin mineral abelsonite
Abelsonite is a nickel porphyrin mineral with chemical formula C31H32N4Ni. It was discovered in 1969 in the U.S. State of Utah and described in 1975. The mineral is named after geochemist Philip H. Abelson. It is the only known crystalline geo ...
.[ ]
See also
* Florissant Formation (Florissant Fossil Beds National Monument
The Florissant Formation is a sedimentary geologic formation outcropping around Florissant, Teller County, Colorado. The formation is noted for the abundant and exceptionally preserved insect and plant fossils that are found in the mudstones and ...
), a similarly fossiliferous, but younger freshwater Eocene formation in the Colorado Rocky Mountains.
* History of the oil shale industry in the United States
* Lagerstätte
A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...
* List of fossil sites
This list of fossil sites is a worldwide list of localities known well for the presence of fossils. Some entries in this list are notable for a single, unique find, while others are notable for the large number of fossils found there. Many of t ...
''(with link directory)''
References
Further reading
* ''Geologic Atlas of the Rocky Mountain Region'', Rocky Mountain Association of Geologists, 1972, Denver Colorado
* King, Philip B., 1977, ''The Evolution of North America'', Revised edition, Princeton University Press
* Gaggiano, Tom, ''The Green River Formation'
Accessed March 18, 2006.
* Carrol, Alan, 2001, ''Green River'' research project, http://www.geology.wisc.edu/~carroll/green_river.html Accessed March 18, 2006.
External links
Minerals of the Green River Formation, Sweetwater County, Wyoming, Mindat
UCMP Berkeley website
Eocene fossils from the Green River Formation
Paleobiology Database: Icaronycteris Type Locality: Wasatchian, Wyoming, aka Fossil Lake, Green River
Paleobiology Database Green River Quarry: Kimmeridgian - Tithonian, Utah
Paleobiology Database: BYU Locality #712, Uintah Basin, Green River Formation, Utah: Eocene - Eocene, Utah
* Green River Formation and Shale Oil, Research Brief by Ran
{{Authority control
Geology of the Rocky Mountains
Geologic formations of Colorado
Geologic formations of Utah
Geologic formations of Wyoming
Green River (Colorado River tributary)
Eocene United States
Lagerstätten
Oil shale in the United States
Oil shale formations
Paleogene Colorado
Paleogene geology of Utah
Paleogene geology of Wyoming
Paleontology in Colorado
Paleontology in Utah
Paleontology in Wyoming
Geological type localities
Eocene Series of North America