The Golden Valley Formation is a

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers ( strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostr ...

unit of

Late Paleocene The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between . The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age (part ...

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 ...

age in 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 ...

North Dakota North Dakota () is a U.S. state in the Upper Midwest, named after the indigenous Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north and by the U.S. states of Minnesota to the east, S ...

.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. Laird in 1947.Benson, W.E. and Liard, W.M. 1947. Eocene of North Dakota. Geological Society of America Bulletin, vol. 60, pp. 1166–1167. It preserves significant assemblages of

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 ...

plants Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

and

vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...

s,Jepsen, G.L. 1963. Eocene vertebrates, coprolites, and plants in the Golden Valley Formation of western North Dakota. Geological Society of America Bulletin, vol. 74, pp. 673–684. as well as

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is es ...

and insect fossils.

Stratigraphy

The Golden Valley Formation is present as a series of

outliers In statistics, an outlier is a data point that differs significantly from other observations. An outlier may be due to a variability in the measurement, an indication of novel data, or it may be the result of experimental error; the latter a ...

in western North Dakota. It is underlain by the

Sentinel Butte Formation The Sentinel Butte Formation is a geologic formation of Paleocene age in the Williston Basin of western North Dakota. It preserves significant assemblages of non-marine plant and animal fossil A fossil (from Classical Latin , ) is any pre ...

and

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlain by the

White River Group 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, Badlan ...

. It reaches thicknesses of up to and is subdivided into two members: the ''Bear Den Member'' (lower) and the ''Camels Butte Member'' (upper).

Lithologies

The base of the Bear Den Member consists of kaolinitic

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

, mudstone and

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 ...

that weather to white, light grey, orange, and purple. These are overlain by grey or brownish

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

aceous sediments and, in some areas, a bed of lignite (the ''Alamo Bluff lignite''). In places the sequence is capped by a

siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

bed (the ''Taylor bed'') that represents a weathering surface or

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 ...

. The Bear Den Member reaches a maximum thickness of about . The Camels Butte Member consists of montmorillonitic and

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

ceous claystone, siltstone, lignite, poorly cemented sandstone and conglomerate. The upper part includes a massive

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 ...

sandstone that caps many of the major

butte __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and table (landform), tablelands. The word ''butte'' comes from a F ...

s in southwestern North Dakota. The Camels Butte Member reaches a maximum thickness of about .

Depositional environment

The Golden Valley Formation was deposited in a broad swampy lowland crossed by fluvial channels. Deposition occurred during late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

(

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 ...

) to early

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

(

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 ...

) time, a period that spans the Paleocene-Eocene Thermal Maximum.

Paleontology

Plant fossils collected from throughout the formation include floating and rooted aquatic plants such as ''

Salvinia ''Salvinia'', a genus in the family Salviniaceae, is a floating fern named in honor of Anton Maria Salvini, a 17th-century Italian scientist. Watermoss is a common name for ''Salvinia''. The genus was published in 1754 by Jean-François Séguie ...

'', ''

Nelumbo ''Nelumbo'' is a genus of aquatic plants with large, showy flowers. Members are commonly called lotus, though the name is also applied to various other plants and plant groups, including the unrelated genus ''Lotus''. Members outwardly resembl ...

'' and ''

Isoetes ''Isoetes'', commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual ...

'', and lowland forest plants such as the

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except ...

s ''

Onoclea ''Onoclea'' is a genus of plants in the family Onocleaceae, native to moist habitats in eastern Asia and eastern North America. They are deciduous ferns with sterile fronds arising from creeping rhizomes in spring, dying down at first frost. Fert ...

'' and ''

Osmunda ''Osmunda'' is a genus of primarily temperate-zone ferns of family Osmundaceae. Five to ten species have been listed for this genus. Description Completely dimorphic fronds or pinnae (hemidimorphic), green photosynthetic sterile fronds, and n ...

'', the

conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

s ''

Glyptostrobus ''Glyptostrobus'' is a small genus of conifers in the family Cupressaceae (formerly in the family Taxodiaceae). The sole living species, ''Glyptostrobus pensilis'', is native to subtropical southeastern China, from Fujian west to southeast Yun ...

'' and ''

Metasequoia ''Metasequoia'', or dawn redwoods, is a genus of fast-growing deciduous trees, one of three species of conifers known as redwoods. The living species ''Metasequoia glyptostroboides'' is native to Lichuan county in Hubei province, China. Altho ...

'', and the dicots ''

Platanus ''Platanus'' is a genus consisting of a small number of tree species native to the Northern Hemisphere. They are the sole living members of the family Platanaceae. All mature members of ''Platanus'' are tall, reaching in height. All except f ...

'' and ''

Cercidiphyllum ''Cercidiphyllum'' is a genus containing two species of plants, both commonly called katsura. They are the sole members of the monotypic family Cercidiphyllaceae. The genus is native to Japan and China and unrelated to '' Cercis'' (redbuds). De ...

''. The

fossils have come primarily from the upper, early Eocene Camels Butte Member. They include the remains of mammals such as ''

Coryphodon ''Coryphodon'' (from Greek κορῦφὴ, "point", and ὀδοὺς, "tooth", meaning ''peaked tooth'', referring to "the development of the angles of the ridges into points n the molars") is an extinct genus of pantodonts of the family Coryph ...

'', ''

Hyracotherium ''Hyracotherium'' ( ; " hyrax-like beast") is an extinct genus of very small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation. This small, fox-sized animal was once considered to be the earliest ...

'', ''

Homogalax ''Homogalax'' (from the Greek "ομογάιαξ") is an extinct genus of tapir-like odd-toed ungulate. It was described on the basis of several fossil finds from the northwest of the USA, whereby the majority of the remains come from the state o ...

'', ''

Sinopa ''Sinopa'' ("swift fox") is a genus of hyaenodontid mammal from family Sinopidae, that lived in North America and Asia during the early to middle Eocene. Description ''Sinopa'' was a small genus of hyaenodontid mammals. Its carnassial teeth w ...

'', ''

Didymictis ''Didymictis'' ("double weasel") is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America and Europe from the late Paleocene to middle Eocene. Description ''Di ...

'', '' Hyopsodus'', ''

Paramys ''Paramys'' is an extinct genus of rodents from North America, Europe, and Asia. It is one of the oldest genera of rodents known and probably lived in trees. While the genus name literally means "near a mouse", it coexisted with ''Thisbemys'', ...

'' and others; there are also remains of

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% ...

, amphibians, and reptiles such as ''

Trionyx ''Trionyx'' is a genus of softshell turtles belonging to the family Trionychidae. In the past many species in the family were classified in this genus, but today '' T. triunguis'', the African or Nile softshell turtle, is the only extant softshe ...

'', '' Peltosaurus'', and four genera of

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...

ns.

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 ...

fossils include shells of freshwater mollusks such as '' Viviparus'', ''

Unio Unio may refer to: * ''Unio'' (bivalve), a genus of freshwater mussels * ''Unio'' (sternwheeler), a steamboat that operated in Oregon, United States, in 1861, before being renamed ''Union'' * UNI/O, an asynchronous serial bus * UNIO Satu Mare, a ...

'', ''

Hydrobia ''Hydrobia'' is a genus of very small brackish water snails with a gill and an operculum, aquatic gastropod mollusks in the family Hydrobiidae.Gofas, S. (2011). Hydrobia Hartmann, 1821. Accessed through: World Register of Marine Species ...

'', and ''

Planorbis ''Planorbis'' is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails, or planorbids. All species in this genus have sinistral or left-coiling shells.Bouchet, P.; R ...

'', and the wing casing of a crabid beetle.

References

Bibliography

* {{ISBN, 0-8137-1150-9 Geologic formations of North Dakota Eocene Series of North America Paleogene geology of North Dakota Ypresian Stage Thanetian Stage Wasatchian Clarkforkian Mudstone formations Siltstone formations Sandstone formations of the United States Coal formations Conglomerate formations Fluvial deposits Fossiliferous stratigraphic units of North America Paleontology in North Dakota