Owing to extensive weathering of older rocks during the Jurassic and Triassic, the Dakota strata lie unconformably atop many different formations ranging in age from Precambrian to Early Cretaceous. With a few local exceptions, it is the oldest Cretaceous unit exposed in the northern Great Plains, including Kansas, Nebraska, Iowa, Minnesota, and Wisconsin, as well as the Desert Southwest. It generally consists of sandy, shallow marine or beach deposits with marine-influenced mudflat sediments, and occasional stream deposits.[8][9]
Naming and rank
F.B. Meek and F.V. Hayden first used Dakota in 1862 to name the distinctive red sandstone exposures along the Missouri River near Dakota City, Nebraska. But, with this name, they applied the term "group", which at that time had the meaning of formation rank, as presently used.[6]Dakota Formation is the unit's primary name and rank in the Great Plains. Formation rank is also applied in western extents (e.g., northeast Utah) as the unit thins and exhibits formational characteristics, the marine shales are absent, and fossil pollen species correlate with those found in the unit on the Missouri River.[10] In the San Juan Basin and other intermontane basins and plateaus of the Southwest, Dakota Sandstone is the formal name for the oldest Cretaceous sandstone as well as tongues of that terrestrial sandstone extending into the dark marine shales of the Mancos.[2] However, Dakota Sandstone is everywhere a common informal name for the unit, especially for the sandstone beds.[11]
The Dakota Group rank is employed along the territory of the Dakota Hogback in Colorado and Wyoming, the Colorado Plateau,[4] the Dry Cimarron River,[4] and the Denver Basin. This group ranking recognizes sequences and members that exhibit local formational characteristics, especially marine shales that are less developed or absent further from the center of the seaway. As these locations were at the time of formation the earliest and deepest areas of the seaway, these groups can include older ages of rocks than are usually included elsewhere under the Dakota name. The names of the member formations of the Dakota Group vary between these regions as the geology there is studied further; but, the earliest unit included in Dakota Groups, excluded elsewhere, is the terrestrial Lytle Formation, which is older than any other Cretaceous rock in Colorado or Kansas.[11] The Skull Creek Shale and Plainview Sandstone of Colorado are also included in the Dakota Group, as is the Cedar Mountain Formation of Utah and its Buckhorn Conglomerate member. However, these units represent a separate seaway sequence in the time between the Lytle and "upper Dakota" (Mowry) sequences, and in the plains to the east, the same units are named Kiowa Shale and Cheyenne Sandstone, which are considered separate from the Dakota Formation as defined in Kansas and, moreover, do not appear at the type location in Nebraska.[12] However, subsequent sequence stratigraphic and palynostratigraphic research has demonstrated that the Dakota Formation at the type location includes sand and mudstones covering the same ages and sequences as the "marine shale facies of the Graneros" and "early Late Albian Kiowa-Skull Creek".[5]
In certain places, the classification is undivided; for example, in far southwest Utah, the strata is designated the Dakota Conglomerate without further division.[4]
When nearer the surface (within a couple thousand feet/hundreds of meters), the sandstone beds of the Dakota Formation form various Dakota Aquifers, important water sources in some areas of the Great Plains and the Southwest,[9] far greater in extent than the High Plains Aquifer,[13] and famous for its artesian properties.[14]
Elsewhere, when deeper, especially in the Denver Basin, these same sands have been sought after for hydrocarbon reserves. "Drillers", who navigate deep strata by monitoring material brought to the surface in the drilling mud, alphabetically designated the hydrocarbon "producing sands" of the Dakota in the Denver Basin as (highest) "D", "J", "M", and "O" (lowest). Colorado's "D" and "J" of the driller's Denver Basin have been particularly important to Nebraska, Kansas, and Oklahoma in their efforts of correlating their eastern outcrops with the Dakota units in the Denver Basin and the western units in general.[15][12]
Dakota Formation in Central Kansas
Geological history
Schematic reconstruction of the eastern side of the Cretaceous seaway during deposition of the sediments that eventually became the Dakota Formation. Erosional highlands occur in South Dakota and Minnesota.
Deposition of the sediments that would become the Dakota Formation began during the late Early Cretaceous (Albian). This deposition marked a reversal from over 100 million years of erosion (most of the Mesozoic).[5] This reversal was due to rising of the mouth of the rivers, called a rise in base level, as the Cretaceous Seaway formed. This rise lowered the gradient of the rivers causing them to deposit sediment inland because their velocity could no longer sustain high volumes of sediment.[16]
Measurements show that the rivers flowed westward and southwestward towards the encroaching sea from source areas near the present-day Great Lakes. The point of deposition slowly moved eastward as the seaway rose. This change is seen by a gradual shift in the composition of sandstones from having a lot of Paleozoic-age rock detritus in Kansas to sandstones having all Precambrian crystalline rock debris in Iowa.[17]
This shift means that the rivers had completely eroded away the Paleozoic rocks in the river source area by the time the Seaway rose high enough for the rivers to deposit sediments in Iowa. The very top of the Dakota Formation was deposited along the coast as indicated by some fossil marine invertebrates. Fossil plants, coal deposits and kaolinite clays show that the climate was warm and wet during deposition of the Dakota Formation.[17] Some of the ancient preserved soils show that an extensive flood plain forest was present.
Western Interior Seaway sequences
This Cretaceous seaway experienced a number of geological sequences (rise and fall cycles of sea level relative to land elevation), which, during partricular lowstands, temporarily reestablished a land connection between the east and west continent at the ancestral Transcontinental Arch. Each sequence represents a cycle of major progression of the seaway into the western interior of North America followed by retreat (see Walther's Law of Facies). The sequences of the seaway typically express facies sequences of, first, a low-stand erosional surface discontinuity (possibly with development of soils), then a transgressive pattern of terrestrial sand and mud followed by near shore marine sediments, a high stand pattern that may establish far-shore marine shale and limestone, a regressive pattern of a return to near shore marine sediments to terrestrial mud and sand, and a final low-stand erosional surface. Five of the first sequences of the Western Interior Seaway are relevant to the Dakota classifications.
The first sequence, typified by the Lytle Formation, did not complete the linkage of the north and south embayments before retreating. The second sequence is typified by the corresponding Skull Creek and Kiowa formations. These first two sequences are not present at the type area along the Missouri River. The sediments broadly considered as Dakota then record the Mowry sequence with the Muddy, J, or Lower Dakota sandstones and the D or Upper Dakota sandstones forming at the discontinuities at the beginning and end of that cycle. In the east the limited marine shales of the Mowry sequence are assigned to the Dakota Formation, while in the center the mudstones and marine shales are commonly assigned a separate unit between upper and lower sandstone units, and in the Southwest, the much thicker marine shales are assigned to tongues of the Lower Mancos. The Greenhorn Cycle is the final relevant sequence as it overlays all Dakota classifications, with the exception of certain sandstones of Graneros age, such as classified in Wisconsin and Iowa.[18][5]
Lithology
Over the range of the usage of the Dakota name, the unit is primarily known for its massive beds of sandstone, which commonly shows shades of red, but also gray, yellow, or white. The sand was carried and deposited by rivers or accumulated in dunes or shoreline strands, and later cemented by red iron oxide or white calcite, depending on the local groundwater conditions that followed the sedimentation. The degree of cementation can range from softly crumbling to resistant to hammering. The sandstone beds can have local conglomerations of gravel. The composition of the sand and gravel varies depending on the sources of the rivers that made each deposit.
The amount of sandstone, averaging 25-50%, can very greatly over short distances between extremes of 5% to 80%. The general remainder of the unit, however, generally in complementary 80% to 5% proportions, is layered mudstone and clay deposited on floodplains, swamps, and estuaries. Similar to the sand, the soil-forming mud was modified by groundwater conditions to accumulate iron oxide or calcite. Coloration can be dark to light red, grey, yellow, and white. Iron oxide accumulation can approach the hardness and luster of hematite.
In evidence of the general low-lying nature of the Dakota's lush, hot-house Earth environment, lignite and coal have formed in various areas.
Marine shale is also a part of the Dakota sequences. Less common in the remote extents, particularly in the east, the shale is more representative of the deeper portions of the inland seaway. Moreover, shales on top of the upper Dakota on the plains of the east are usually assigned to the Granola or equivalent units, while in the west the thickest interbedding "tongues" of shale are generally assigned to the lower Marcos. Nevertheless, near the western limits, where the Dakota "pinches out" between the Morrison and the Mowry, the unit returns to the totally terrestrial sand-mud-sand pattern and fossil pollens of the Nebraska type location.[10]
These characteristics of chaotic, land-formed sandbanks and mudflats lying above flinty, whiter marine megacyclic Permian limestones and below grey, rhythmic, chalky shales, persist for thousands of miles, locally variable as they may be, causing common use of the name Dakota in spite of many efforts to apply localized names.[10]
Two sides of the seaway
Historically, Lower Cretaceous strata in the Rocky Mountain region have been called the Dakota Formation based on assumed correlation with the type section of the Dakota of the Great Plains. Witzke and Ludvigson have argued that use of the name "Dakota" must reflect actual, not presumed correlation based on stratigraphy and composition of the sedimentary rock.[17] To the west of the Rocky Mountains, such as on the Colorado Plateau, this sequence of Upper Cretaceous, predominately sandstone, sedimentary rocks was recommended to be known as the Dakota Group,[19] to dispel any suggestion of direct facies correlation. However, few authors of papers on the Dakota west of the Rocky Mountains, especially on the Colorado Plateau, recognize the Dakota as the Dakota Group, instead using the term Dakota Sandstone, of formation rank. Its subdivisions are recognized as members. Many authors have emphasized the fact that the marine Dakota Sandstone on the Colorado Plateau is intertongued with the marine lower part of the Mancos Shale, resulting in valid lithostratigraphic names such as the Whitewater Arroyo Tongue of the Mancos Shale which is directly overlain by the Twowells Sandstone Tongue of the Dakota Sandstone.[2] In the western San Juan Basin, the lowermost part of the Dakota Sandstone, although of marginal marine origin in the eastern San Juan Basin, is a complex of non-marine sandstones. These relationships are especially well displayed in the San Juan Basin of northwestern New Mexico
Beginning in the Early Cretaceous, the Cretaceous Seaway spread south from what is now the Arctic Ocean and connected with a short northward extension from the Gulf of Mexico.[20] This marine transgression of the ocean onto what was formerly land, was completed by the late Albian (~100 MA) thereby dividing North America in half. On the eastern side of the Seaway, sediments that would become the Dakota Formation were deposited as coastal and nearshore marine sands and silts. As the seaway continued to deepen and widen, this eastern shoreline moved progressively eastward; however, accumulation of abundant sediment delivered by massive rivers limited shoreline advancement past the type location throughout the Cenomanian until overtopped by the Greenhorn Seaway in the early Turonian.[5] Meanwhile, on the western side of the seaway, sediments were carried eastwards and northeastwards by rivers from mountains located along what is the Nevada-Utah border.
These western sediments accumulated as nearshore and coastal sands and silts as well, and are counterparts to the Dakota Formation on the eastern side of the Seaway. However, these counterpart sediments originated from the other side of the sea and were carried by rivers flowing in opposite directions. These western sediments are equivalent to the Dakota Formation of the Great Plains, but are not exactly the same strata. Individual formations in the western Dakota Group have local names. In Wyoming, the term Cloverly Formation has been expanded by some authors to include sediments formerly placed within the Dakota Formation.[citation needed] Along the Colorado Front Range, the lower, terrestrial beds, or facies, of the Dakota Group are sometimes called the Lytle Formation, and near-shore marine facies are called the South Platte Formation.[21] In eastern Utah and western Colorado, Young introduced the term Naturita Formation for a series of facies in the larger "Dakota Group".[19] However, despite Witzke and Ludvigson logic, geologist have continued to refer to the Lower Cretaceous sequence of formations on the Colorado Plateau and the Rocky Mountains as the Dakota Group.[22]
Economic geology
The Dakota has provided several resources in the Plains states as well as in parts of the mountainous west.
The predominant shales and mudstones are a source of hydrocarbons while the lenses and channels of sandstone form exploitable hydrocarbon reserves. Thus, the Dakota Group is an oil and gas source in the Denver Basin.[23]
When they are near the surface, these same structures function as aquitards and aquifers, respectively. The Dakota sandstones form crucial supplies of water on the Plains, especially on uplands between river valleys wherever it is found outside the boundaries of the Ogallala Aquifer.[24]
As the formation is uniquely terrestrial in origin, in contrast to the vast marine formations of the Plains, the Dakota has additional unique resources. Lignite coal has formed in the unit and was mined briefly in the 19th century. This supply was immediately mined for fuel by early American settlers, but was decidedly inferior to larger supplies of coal in the southeast of Kansas.[25] The widespread bog environments of the Dakota period resulted in concretions of iron, forming hematite, limonite, and beds of "ironstone", which are common in the Janssen clay member of Kansas.[25] Smelting of this limited iron source was only briefly attempted in conjunction with the lignite mining. The iron-cemented sandstone was found to be a durable and colorful building material on the treeless 19th century Plains. Historic 1860s buildings of Fort Harker (Kansas) and Fort Larned are constructed of this stone. The Dakota clays are quarried for tile and brick manufacture.[26]
Uranium is also found concentrated in the Dakota sandstone where percolating uranium-rich water has deposited the mineral in the aquifers.[27]
Paleoenvironment
The sands and muds of the Dakota represent wet lowlands, rivers, flood plains, and beaches with a shoreline deeply undulating between deltas and brackish marine embayments. Ground water flowing from inland reacted with changes in pH, oxygenation, and salinity as it encountered seawater, depositing iron oxide and calcite in underground layers near shorelines. These minerals hardened the material and fossils to preserve evidence of the ecology of those environments.[5] Sandstone with dinosaur tracks in the upper Dakota above the marine Skull Creek Shale near Denver demonstrates that the seaway occasionally retreated from the area.
Dakota Fossils of Land Environments
Iron-cemented leaf imprint (Ellis County, Kansas); evidence of boggy sand near deciduous trees
Marine mollusk shell (Ellis County, Kansas); evidence of sandy wave-washed beach
Dinosaur beach tracks (Dinosaur Ridge); temporary, wide land bridge across the seaway
Vertebrate paleofauna
Dinosaur fossils are very rare in the Dakota Formation and most[citation needed] of them come from Kansas. Some of them are found in Colorado and Nebraska. The most popular site for public viewing of Cretaceous dinosaur fossils in Colorado is Dinosaur Ridge. The best specimen is a partial skeleton of a nodosaurid ankylosaur called Silvisaurus condrayi.[28][29] Other isolated ankylosaur material may also belong to Silvisaurus.[30] Fossil dinosaur tracks are also known and include theropod and ankylosaur.[30] A large ornithopod femur is known from Burt County, Nebraska as well as fossil dinosaur tracks from Jefferson County.[31][32]Goniopholidids are also found here with Dakotasuchus kingi.[33]
2 specimen differing from W. expansolobum in having smaller leaves, thinner secondary veins, a pair of distinctive secondary veins originating from the extreme base of the leaf lamina and running parallel to the primary veins for almost half the lobe length, semi-craspedodromous secondary venation, and a predominantly toothed margin.[37]
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 encountered as one goes westbound along the 40th parallel north across the Great Plains of North America.
The Western Interior Seaway was a large inland sea that split the continent of North America into two landmasses. The ancient sea, which existed from the early Late Cretaceous to the earliest Paleocene, connected the Gulf of Mexico, through the United States and Canada, to the Arctic Ocean. The two land masses it created were Laramidia to the west and Appalachia to the east. At its largest extent, it was 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long.
The Denver Basin, variously referred to as the Julesburg Basin, Denver-Julesburg Basin, or the D-J Basin, is a geologic structural basin centered in eastern Colorado in the United States, but extending into southeast Wyoming, western Nebraska, and western Kansas. It underlies the Denver-Aurora Metropolitan Area on the eastern side of the Rocky Mountains.
The Perth Basin is a thick, elongated sedimentary basin in Western Australia. It lies beneath the Swan Coastal Plain west of the Darling Scarp, representing the western limit of the much older Yilgarn Craton, and extends further west offshore. Cities and towns including Perth, Busselton, Bunbury, Mandurah and Geraldton are built over the Perth Basin.
The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah and Arizona. Specifically, the basin occupies space in the San Juan, Rio Arriba, Sandoval, and McKinley counties in New Mexico, and La Plata and Archuleta counties in Colorado. The basin extends roughly 100 miles (160 km) N-S and 90 miles (140 km) E-W.
The Naturita Formation is a classification used in western Colorado and eastern Utah for a Cretaceous Period sedimentary geologic formation. This name was "applied to the upper or carbonaceous part of Dakota Group" by R.G. Young in 1960, naming it for Naturita, Colorado. The name is not used by U.S. Geological Survey authors, but has found growing acceptance by the Utah Geological Survey
The geology of Kansas encompasses the geologic history and the presently exposed rock and soil. Rock that crops out in the US state of Kansas was formed during the Phanerozoic eon, which consists of three geologic eras: the Paleozoic, Mesozoic and Cenozoic. Paleozoic rocks at the surface in Kansas are primarily from the Mississippian, Pennsylvanian, and Permian periods.
The Niobrara Formation, also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian stages of the Late Cretaceous. It is composed of two structural units, the Smoky Hill Chalk Member overlying the Fort Hays Limestone Member. The chalk formed from the accumulation of coccoliths from microorganisms living in what was once the Western Interior Seaway, an inland sea that divided the continent of North America during much of the Cretaceous. 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 plesiosaurs, mosasaurs, pterosaurs, and several primitive aquatic birds. The type locality for the Niobrara Chalk is the Niobrara River in Knox County in northeastern Nebraska. The formation gives its name to the Niobrara cycle of the Western Interior Seaway.
Colorado is a geologic name applied to certain rocks of Cretaceous age in the North America, particularly in the western Great Plains. This name was originally applied to classify a group of specific marine formations of shale and chalk known for their importance in Eastern Colorado. The surface outcrop of this group produces distinctive landforms bordering the Great Plains and it is a significant feature of the subsurface of the Denver Basin and the Western Canadian Sedimentary Basin. These formations record important sequences of the Western Interior Seaway. As the geology of this seaway was studied, this name came to be used in states beyond Colorado but later was replaced in several of these states with more localized names.
Dinosaur Ridge is a segment of the Dakota Hogback in the Morrison Fossil Area National Natural Landmark located in Jefferson County, Colorado, near the town of Morrison and just west of Denver.
The Fox Hills Formation is a Cretaceous geologic formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south.
The Mowry Shale is an Early Cretaceous geologic formation. The formation was named for Mowrie Creek, northwest of Buffalo in Johnson County, Wyoming.
The Straight Cliffs Formation is a stratigraphic unit in the Kaiparowits Plateau of south central Utah. It is Late Cretaceous in age and contains fluvial, paralic, and marginal marine (shoreline) siliciclastic strata. It is well exposed around the margin of the Kaiparowits Plateau in the Grand Staircase – Escalante National Monument in south central Utah. The formation is named after the Straight Cliffs, a long band of cliffs creating the topographic feature Fiftymile Mountain.
The Kiowa Formation or Kiowa Shale is a Cretaceous geologic formation in Kansas, diminishing to member status in Colorado and Oklahoma. In Colorado, the Kiowa Shale was classified as a member of the now abandoned Purgatoire Formation. In the vicinity of Longford, Kansas, the local Longford member comprises thinly bedded siltstone, clay, polished gravel, lignite, and sandstone suggests a river and estuary environment.
Paleontology in Iowa refers to paleontological research occurring within or conducted by people from the U.S. state of Iowa. The paleozoic fossil record of Iowa spans from the Cambrian to Mississippian. During the early Paleozoic Iowa was covered by a shallow sea that would later be home to creatures like brachiopods, bryozoans, cephalopods, corals, fishes, and trilobites. Later in the Paleozoic, this sea left the state, but a new one covered Iowa during the early Mesozoic. As this sea began to withdraw a new subtropical coastal plain environment which was home to duck-billed dinosaurs spread across the state. Later this plain was submerged by the rise of the Western Interior Seaway, where plesiosaurs lived. The early Cenozoic is missing from the local rock record, but during the Ice Age evidence indicates that glaciers entered the state, which was home to mammoths and mastodons.
The Graneros Shale is a geologic formation in the United States identified in the Great Plains as well as New Mexico that dates to the Cenomanian Age of the Cretaceous Period. It is defined as the finely sandy argillaceous or clayey near-shore/marginal-marine shale that lies above the older, non-marine Dakota sand and mud, but below the younger, chalky open-marine shale of the Greenhorn. This definition was made in Colorado by G. K. Gilbert and has been adopted in other states that use Gilbert's division of the Benton's shales into Carlile, Greenhorn, and Graneros. These states include Kansas, Texas, Oklahoma, Nebraska, and New Mexico as well as corners of Minnesota and Iowa. North Dakota, South Dakota, Wyoming, and Montana have somewhat different usages — in particular, north and west of the Black Hills, the same rock and fossil layer is named Belle Fourche Shale.
The Greenhorn Limestone or Greenhorn Formation is a geologic formation in the Great Plains Region of the United States, dating to the Cenomanian and Turonian ages of the Late Cretaceous period. The formation gives its name to the Greenhorn cycle of the Western Interior Seaway.
The geology of Nebraska is part of the broader geology of the Great Plains of the central United States. Nebraska's landscape is dominated by surface features, soil and aquifers in loosely compacted sediments, with areas of the state where thick layers of sedimentary rock outcrop. Nebraska's sediments and sedimentary rocks lie atop a basement of crystalline rock known only through drilling.
The geology of North Dakota includes thick sequences oil and coal bearing sedimentary rocks formed in shallow seas in the Paleozoic and Mesozoic, as well as terrestrial deposits from the Cenozoic on top of ancient Precambrian crystalline basement rocks. The state has extensive oil and gas, sand and gravel, coal, groundwater and other natural resources.
References
↑ "Geologic Unit: Woodbury". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved November 27, 2020.
↑ Monroe, James S. and Wicander, Reed (1997) The Changing Earth: Exploring Geology and Evolution (2nd edition) Wadsworth Publishing Company, Belmont, California, page 610, ISBN0-314-09577-2
1 2 3 Douglas A. Sprinkel; Scott K. Madsen; James I. Kirkland; Gerald L. Waanders; Gary J. Hunt (2012). "Cedar Mountain and Dakota Formations around Dinosaur National Monument—evidence of the first incursion of the Cretaceous Western Interior Seaway into Utah"(PDF). Utah Geological Survey Special Study. Utah Geological Survey (143): 9, 12–15. Retrieved February 21, 2021. The Dakota Formation ... has undergone a colorful history of nomenclature changes. ... Naturita has generally not been an accepted name for this section of rocks on the Colorado Plateau. ... The term Dakota Sandstone has been formally used in geologic maps and reports in the eastern Uinta Mountains (...); however, we revise the descriptive term to formation to reflect the lithologic heterogeneity of the Dakota in this region and to be consistent with usage elsewhere in Utah.
1 2 "The Geologic Framework of the Dakota Aquifer". The Dakota Aquifer Program Annual Report. Kansas Geological Survey (FY89): Part 3b. (The report concludes that the Lytle Sequence is not present in Kansas or eastern Colorado, and observes that the Kiowa and Cheyenne correlate with the Skull Creek and Plainview. )
↑ P. Allen Macfarlane; John H. Doveton; Donald O. Whittemore. "User's Guide to the Dakota Aquifer in Kansas". Technical Series. Kansas Geological Survey (FY89): 2. Retrieved April 2, 2021. .... Across the Continental Divide, the Dakota aquifer is present in many of the intermontane basins. Thus, the Dakota is an important source of water in many areas of the North American continent.
↑ Herbert F. Wang (2020). "2 Saga of the Dakota Aquifer". Groundwater Storage in Confined Aquifers. Guelph, Ontario, Canada: The Groundwater Project. ISBN978-1-7770541-7-5. Retrieved April 5, 2021. While the Dakota sandstone is one of the most important of the known artesian reservoirs, .... – Powell testimony (1890) ... The Dakota aquifer in South Dakota is one of the classic artesian aquifers. Many modern ideas concerning artesian aquifers stem from N. H. Darton's investigation of the Dakota aquifer in the 1890s and early 1900s. - John D. Bredehoeft et al. (1983)
↑ Boreing, M.J., 1953, Geology of the Denver basin, IN Moore, C.A., ed., Proceedings of the third subsurface geological symposium: University of Oklahoma, Norman, OK, March 3–4, 1953, p. 72-81. "The two main producing sands in the basin are accordingly called the 'D' (upper) and the 'J' (middle). The basal sand members of the Cretaceous we shall call the 'M' and 'O' sands."
↑ Bejnar, C. R. and Lessard, R. H. (1976) "Paleocurrents and depositional environments of The Dakota Group, San Miguel and Mora Counties, New Mexico" in Ewing, Rodney C. and Kues, Barry S. (eds.) (1976) Guidebook of Vermejo Park, Northeastern New Mexico: Twenty-seventh Field Conference, September 30, October 1 and 2, 1976 New Mexico Geological Society, Socorro, N.M., pp. 157–163, OCLC2754478
1 2 3 Witzke, B.J., and Ludvigson, G.A. 1994. The Dakota Formation in Iowa and its type area. In Shurr, G.W., Ludvigson, G.A., and Hammond, R.H. (eds). Perspectives on the eastern margin of the Cretaceous Western Interior Basin. Geological Society of America, Special Paper 287:43–78.
1 2 Young, Robert G. (1960) "Dakota Group of Colorado Plateau" American Association of Petroleum Geologists Bulletin 44(2): pp 156–194
↑ Kauffman, E.G. 1984. Paleobiogeography and evolutionary response dynamic in the Cretaceous Western Interior Seaway of North America. In Westermann, G.E.G. (ed), Jurassic-Cretaceous Biochronology and Paleogeography of North America, Geological Association of Canada Special Paper 27: 273–306.
↑ For example in east-central and northeast New Mexico the Dakota Group consists of the Mesa Rica Sandstone, the Pajarito Shale, and the Romeroville Sandstone, and includes the underlying Tucumcari Shale in the Tucumcari area and Glencairn Formation in Union County. "Dakota Group" U.S. Geological Survey
↑ "Welcome to Kansas Brick and Tile". Retrieved April 19, 2020. Our three brick plants are nestled in the Dakota clay deposits right here in the heart of Kansas.
↑ Eaton, T.H. 1960. A new armored dinosaur from the Cretaceous of Kansas. University of Kansas Paleontological Contributions, Vertebrata, 8:1–24.
↑ Carpenter, K. and J.I. Kirkland. 1998. Review of Lower and Middle Cretaceous ankylosaurs from North America. Lucas, S.G., Kirkland, J.I. and Estep, J.W., (eds.), Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History and Science Bulletin No. 14:249–270.
1 2 Liggett, G.A. 2005. A review of the dinosaurs from Kansas. Transactions of the Kansas Academy of Science 108(1–2), p.1-14.
↑ Barbour, E. H. 1931. Evidence of dinosaurs in Nebraska. Bulletin of University of Nebraska State Museum, 1:187–190.
↑ Joeckel, R. M., Cunningham, J. M., Corner, R. G., Brown, G. W., Phillips, P. L. and Ludvigson, G. A. 2004. Late Albian Dinosaur Tracks from the Cratonic (eastern) Margin of the Western Interior Seaway, Nebraska, USA. Ichnos, 11:275-284.
↑ "Table 17.1," in Weishampel, et al. (2004). Page 365.
↑ Vaughn, Peter Paul (1956). "A Second Specimen of the Cretaceous Crocodile Dakotasuchus from Kansas". Transactions of the Kansas Academy of Science. 59 (3): 379–381. doi:10.2307/3626613. ISSN0022-8443. JSTOR3626613.
1 2 3 4 Lockley, M.; Harris, J.D.; and Mitchell, L. 2008. "A global overview of pterosaur ichnology: tracksite distribution in space and time." Zitteliana. B28. p. 187-198. ISSN1612-4138.
Robert G. Raynolds; James W. Hagadorn (2016). "Colorado Stratigraphic Chart". Colorado Geological Survey. Colorado School of Mines. Retrieved September 12, 2021.: Isochronous stratigraphic chart correlates current usage from the eastern plains to the western border of Colorado. While the entire succession is illustrated, the reader can see the interaction of the West Shore Dakota stage with the Mesozoic discontinuities that preceded the seaway as well as the mountain building stages after the seaway.
"Cretaceous Chart and Fossils". Colorado Stratigraphy. 2018. Retrieved September 12, 2021.: Isochronous stratigraphic chart based on the CGS's chart and other sources, the focus entirely on the complex sequences of the Western Interior Seaway. By thereby expanding the vertical scale, the mechanism for vertically changing age of the West Shore Dakota over horizontal distances is clearly illustrated. Missing is the details of the Skull Creek/Kiowa sequence embodied within Colorado's particular definition of the Dakota Group.
Isochronous: The vertical scale is evenly progressing time rather than thickness; everything at the same level happened at the same time.
Paul C. Franks (1979). "Paralic to Fluvial Record of an Early Cretaceous Marine Transgression--Longford Member, Kiowa Formation, North-Central Kansas". Kansas Geological Survey Bulletin. Kansas Geological Survey (219): Introduction. Retrieved April 23, 2021.: Provides detailed descriptions of the processes, as understood at that time, that formed the first deposits of the Cretaceous on the Plains as the Western Interior Seaway made its first advance to the east, with mention of similar faces observed on the western shore. It was not yet recognized that the sequence that deposited the Skull Creek/Kiowa also deposited the lowest sands of the Dakota in eastern Nebraska.
"The Geologic Framework of the Dakota Aquifer". The Dakota Aquifer Program Annual Report. Kansas Geological Survey (FY89): Part 3b.: Original classifications in Kansas were Lithostratigraphic. This study of potential hydrostratigraphic coupling of Colorado and Kansas aquifers commences correlative application of advanced west shore sequence stratigraphy to the east shore lithostratigraphy. This correlation was later supported by subsequent palynostratigraphy (Ludvigson - Witzke, 2010).
R.l. Brenner; G.A. Ludvigson; B.J. Witzke; A.N. Zawistoski; E.P. Kvale; R.L. Ravn; R.M. Joeckel (2000). "Late Albian Kiowa-Skull Creek Marine Transgression, Lower Dakota Formation, Eastern Margin of Western Interior Seaway". Papers in Natural Resources. School of Natural Resources, University of Nebraska–Lincoln. 70 (1009): 868. Bibcode:2000JSedR..70..868B. doi:10.1306/2DC4093E-0E47-11D7-8643000102C1865D. Retrieved September 9, 2021.: Application of sequence and palynostratographic methods matured on the West Shore to the East Shore. Reports new understandings of the marine influences on the development of the Dakota units, particularly at the Nebraska/Iowa type location. Identifies previously unreported discontinuity in the Dakota type, extending the upper Dakota/Woodbury member into the late Albian. Charts the Dakota unit and adjacent units with the new understanding of the discontinuities from the Kansas west border through the type location to Minnesota.
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Iron-cemented leaf imprint (Ellis County, Kansas); evidence of boggy sand near deciduous trees
Marine mollusk shell (Ellis County, Kansas); evidence of sandy wave-washed beach
Dinosaur beach tracks (Dinosaur Ridge); temporary, wide land bridge across the seaway
