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The Niobrara Formation , also called the Niobrara Chalk, is a
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 ...
in North America that was deposited between 87 and 82 million years ago during the
Coniacian The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by t ...
,
Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. The ...
, and
Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...
stages of the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
. It is composed of two structural units, the Smoky Hill Chalk Member overlying the
Fort Hays Limestone Member The Fort Hays Limestone is a Stratigraphic unit#Member, member of the Niobrara Formation of the Colorado Group exposed in Colorado, Kansas, Nebraska, and South Dakota and is named for the bluffs near the old Fort Hays, a well-known landmark in wes ...
. The chalk formed from the accumulation of
coccoliths Coccoliths are individual plates or scales of calcium carbonate formed by coccolithophores (single-celled phytoplankton such as ''Emiliania huxleyi'') and cover the cell surface arranged in the form of a spherical shell, called a ''coccosphere''. ...
from microorganisms living in what was once the
Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses. The ancient sea, ...
, an inland sea that divided the continent of North America during much of the
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 ...
. It underlies much of the Great Plains of the US and Canada. Evidence of vertebrate life is common throughout the formation and includes specimens of
plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...
s,
mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...
s, and
pterosaurs Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
as well as several primitive aquatic
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s. The type locality for the Niobrara Chalk is the
Niobrara River The Niobrara River (; oma, Ní Ubthátha khe, , literally "water spread-out horizontal-the" or "The Wide-Spreading Water") is a tributary of the Missouri River, approximately long,U.S. Geological Survey. Many early settlers, such as Mari Sando ...
in Knox County in northeastern
Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...
. The formation gives its name to the Niobrara cycle of the Western Interior Seaway.


History of exploration

The Niobrara Chalk was recorded (1857) and named (1862) by Meek, F.B., and Hayden, F.V. It was first studied during an expedition led by
Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
of
Yale University Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the wo ...
in 1870. This and following expeditions to the area in 1871 and 1872 yielded the first of many fossil vertebrate remains commonly attributed with the formation. Excavations continued through the following years up to 1879 under the direction of professional fossil collectors such as B. F. Mudge and S. W. Williston appointed by Marsh. The Niobrara Chalk has been continuously explored ever since, with specimens being found by H. T. Martin of the
University of Kansas The University of Kansas (KU) is a public research university with its main campus in Lawrence, Kansas, United States, and several satellite campuses, research and educational centers, medical centers, and classes across the state of Kansas. Tw ...
and George F. Sternberg, the son of the famous fossil collector
Charles H. Sternberg Charles Hazelius Sternberg (June 15, 1850 – July 20, 1943) was an American fossil collector and paleontologist. He was active in both fields from 1876 to 1928, and collected fossils for Edward Drinker Cope and Othniel C. Marsh, and for the ...
. Much of the best material from the formation is on display at the
Sternberg Museum of Natural History Fort Hays State University (FHSU) is a public university in Hays, Kansas. It is the fourth-largest of the six state universities governed by the Kansas Board of Regents, with a total enrollment of approximately 15,100 students. History FHSU ...
in Hays,
Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
.


Stratigraphy

The Smoky Hill Chalk Member of the Niobrara Chalk contains the majority of the fossils found in the formation, and is subdivided into 23 marker beds. Most vertebrates are present from the upper half of the member. Most of the vertebrate remains were collected and described before the
stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...
of the Niobrara Chalk was fully understood. Specimens were described as being from layers referred to as being either of gray-blue
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 ...
or yellow
chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...
. This dichotomy is not indicative of different stratigraphic units as was previously thought, but rather is seen as a weathering phenomenon that can be found at varying points in the same outcrop. The Fort Hays Limestone Member consists of somewhat harder, massive limestone beds. The Niobrara Formation is overlain by the marine
Pierre Shale The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico. The Pierre Shale was described by Meek and Hayden in 1862 in th ...
and is underlain by the
Carlile Shale The Carlile Shale is a Turonian age Upper/Late Cretaceous series shale geologic formation in the central-western United States, including in the Great Plains region of Colorado, Kansas, Nebraska, New Mexico, North Dakota, South Dakota, and Wyom ...
or
Benton Shale The Benton Shale (also Benton Formation or Benton Group) is a geologic formation name historically used in Montana, Wyoming, North Dakota, South Dakota, Colorado, Kansas, and Nebraska. In the "mile high" plains in the center of the continent, th ...
.


Flora and fauna

During the time of the deposition of the Niobrara Chalk, much life inhabited the seas of the Western Interior Seaway. By this time in the Late Cretaceous many new lifeforms appeared such as mosasaurs, which were to be some of the last of the aquatic lifeforms to evolve before the end of the
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, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
. Life of the Niobrara Chalk is comparable to that of the
Dakota Formation The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Int ...
, although the Dakota Formation, which was deposited during the
Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...
, predates the chalk by about 10 million years.


Mineral resources

Various exposures of Niobrara Chalk were covered and partially silicified as the Ogallala sediments covered the
Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...
plains. Re-exposed during the
Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
, these cherty materials, known as Smoky Hill Jasper and Smoky Hill silicified chalk, or more recently as Niobrara Jasper or Niobrarite, became source material for stone tools from the earliest human habitation of the High Plains. In some regions, the Niobrara is a commercial hydrocarbon reservoir.
Natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
is produced from the Niobrara in the eastern
Denver Basin The Denver Basin, variously referred to as the Julesburg Basin, Denver-Julesburg Basin (after Julesburg, Colorado), or the D-J Basin, is a geologic structural basin centered in eastern Colorado in the United States, but extending into southeast Wyo ...
. Oil is produced from the Niobrara in the North Park Basin, and new fracturing methods are allowing much larger areas to be tapped for oil. The Fort Hays member was historically quarried on the
High Plains High Plains refers to one of two distinct land regions: * High Plains (United States), land region of the western Great Plains *High Plains (Australia) The High Plains of south-eastern Australia are a sub-region, or more strictly a string of adja ...
for the manufacture of
Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th c ...
at
Superior, Nebraska Superior is a city in Nuckolls County, Nebraska, Nuckolls County, Nebraska, United States. As of the 2010 United States Census, 2010 census, the city population was 1,957. Superior bills itself as the "Victorian Capital of Nebraska", and holds a ...
and
Yocemento, Kansas Yocemento is an unincorporated community in Big Creek Township, Ellis County, Kansas, United States. The settlement lies across the banks of Big Creek against the base of bluffs capped by massive limestone blocks, in which lies the 20th-centur ...
, as well as along the
Dakota Hogback :  North terminus: :  South terminus: The Dakota Hogback is a long hogback ridge at the eastern fringe of the Rocky Mountains that extends north-south from southern Wyoming through Colorado and into northern New Mexico in the United St ...
in Colorado from
Lyons Lyon,, ; Occitan: ''Lion'', hist. ''Lionés'' also spelled in English as Lyons, is the third-largest city and second-largest metropolitan area of France. It is located at the confluence of the rivers Rhône and Saône, to the northwest of th ...
to
Boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In c ...
, and around
Pueblo In the Southwestern United States, Pueblo (capitalized) refers to the Native tribes of Puebloans having fixed-location communities with permanent buildings which also are called pueblos (lowercased). The Spanish explorers of northern New Spain ...
and
Florence Florence ( ; it, Firenze ) is a city in Central Italy and the capital city of the Tuscany region. It is the most populated city in Tuscany, with 383,083 inhabitants in 2016, and over 1,520,000 in its metropolitan area.Bilancio demografico an ...
. Along the Dakota Hogback north of
Laporte, Colorado Laporte (originally spelled La Porte and alternatively spelled LaPorte) is an unincorporated town, a post office, and a census-designated place (CDP) located in and governed by Larimer County, Colorado, United States. The CDP is a part of the For ...
, the Fort Hays Limestone formed a secondary hogback, which was extensively quarried for manufacture of up to 450,000 tons of cement a year. The full depth of the Niobrara was quarried by the Western Portland Cement Company at
Yankton, South Dakota Yankton is a city in and the county seat of Yankton County, South Dakota, United States. The population was 15,411 at the 2020 census, and it is the principal city of the Yankton Micropolitan Statistical Area, which includes the entirety of Y ...
, which supplied cement to the Panama Canal project.


References


Further reading


AAPG Datapages: "Stratigraphy of the Upper Carlile Shale and Lower Niobrara Formation (Upper Cretaceous), Fremont and Pueblo Counties, Colorado"
* Bennett, S. C. 2000. Inferring Stratigraphic Position of Fossil Vertebrates from the Niobrara Chalk of Western Kansas. College of Chiropractic, University of Bridgeport, Bridgeport, CT 06601-2449.

{{Chronostratigraphy of Colorado, Mesozoic state=expanded Geologic formations of Colorado Geologic formations of Kansas Geologic formations of Nebraska Geologic formations of North Dakota Geologic formations of South Dakota Geologic formations of Wyoming Cretaceous Colorado Cretaceous Kansas Cretaceous geology of Nebraska Cretaceous formations of New Mexico Cretaceous geology of North Dakota Cretaceous geology of South Dakota Cretaceous geology of Wyoming Upper Cretaceous Series of North America Coniacian Stage Santonian Stage Campanian Stage Chalk Shale formations of the United States Shallow marine deposits Reservoir rock formations Fossiliferous stratigraphic units of North America Paleontology in Colorado Paleontology in Kansas Paleontology in Nebraska Paleontology in New Mexico Paleontology in North Dakota Paleontology in South Dakota Paleontology in Wyoming