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→‎Description: Expand description, add Naming and Rank for correct context of the description. The actual full depth is at most half of the stated 1000ft, but I will have to fix that later.
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[[Fielding Bradford Meek|F.B. Meek]] and [[Ferdinand Vandeveer Hayden|F.V. Hayden]] originated the scientific names for the series of Cretaceous rocks in the central Great Plains of the [[North America|North American Continent]]. They gave the name "Benton" to the great shale deposits between the sandstone bluffs at [[Dakota City, Nebraska]], and the chalk bluffs at the junction of the [[Niobrara River|Niobrara]] and [[Missouri River|Missouri]] rivers. At that time, the early 1860s, Meek and Hayden's "lower Cretaceous" series of the upper Missouri River, ''Dakota-Benton-Niobrara'', was already widely observed from Canada to New Mexico over the Great Plains up to the foothills of the [[Rocky Mountains]].<ref name="meekandhayden1862">{{cite journal |author= [[Fielding Bradford Meek|Meek, F.B.]] and [[Ferdinand Vandeveer Hayden|Hayden, F.V.]] |year= 1862 |title= Descriptions of new Lower Silurian, (Primordial), Jurassic, Cretaceous, and Tertiary fossils, collected in Nebraska, by the exploring expedition under the command of Capt. Wm F. Reynolds, U.S. Top. Engineers, with some remarks on the rocks from which they were obtained |journal= Academy of Natural Sciences of Philadelphia Proceedings |volume= 13 |page= 417-424.|url= https://babel.hathitrust.org/cgi/pt?id=hvd.32044107306102&view=1up&seq=3 }}</ref>
[[Fielding Bradford Meek|F.B. Meek]] and [[Ferdinand Vandeveer Hayden|F.V. Hayden]] originated the scientific names for the series of Cretaceous rocks in the central Great Plains of the [[North America|North American Continent]]. They gave the name "Benton" to the great shale deposits between the sandstone bluffs at [[Dakota City, Nebraska]], and the chalk bluffs at the junction of the [[Niobrara River|Niobrara]] and [[Missouri River|Missouri]] rivers. At that time, the early 1860s, Meek and Hayden's "lower Cretaceous" series of the upper Missouri River, ''Dakota-Benton-Niobrara'', was already widely observed from Canada to New Mexico over the Great Plains up to the foothills of the [[Rocky Mountains]].<ref name="meekandhayden1862">{{cite journal |author= [[Fielding Bradford Meek|Meek, F.B.]] and [[Ferdinand Vandeveer Hayden|Hayden, F.V.]] |year= 1862 |title= Descriptions of new Lower Silurian, (Primordial), Jurassic, Cretaceous, and Tertiary fossils, collected in Nebraska, by the exploring expedition under the command of Capt. Wm F. Reynolds, U.S. Top. Engineers, with some remarks on the rocks from which they were obtained |journal= Academy of Natural Sciences of Philadelphia Proceedings |volume= 13 |page= 417-424.|url= https://babel.hathitrust.org/cgi/pt?id=hvd.32044107306102&view=1up&seq=3 }}</ref>


In southcentral Colorado, southeast of [[Pueblo, Colorado|Pueblo]], this series expresses topographical patterns that inspired subdivision of the Benton shales. Wind and rivers rapidly erode the shales, producing bluffs: massive blocks of Niobrara Chalk cap high slopes of ''non-chalky'' Benton shale leading down a flatter plain that stretches miles to another bluff of ''chalky'' shale with many thin limestones. Particularly, in places where rivers have cut deeply through this lower chalky shale, and furthermore have cut into the bases of the bluffs, {{convert|100|ft|m}} banks of ''non-chalky'' shale can be found. In 1896, [[Grove Karl Gilbert|G.K. Gilbert]] named this lower argillaceous shale "Graneros" for the exposures in Graneros Creek, a tributary of the [[Arkansas River]] near Pueblo.<ref name="Hattin176Strat" /><ref name="cobban-scott-1972"/> Thus, the Graneros records the opening transgression of the Greenhorn Cycle of the [[Western Interior Seaway]], and is therefore the complement of the very similar Blue Hills Shale of the [[Carlile Shale|Carlile Formation]] that records the regression of the same Greenhorn Cycle.
In southcentral Colorado, southeast of [[Pueblo, Colorado|Pueblo]], this series expresses topographical patterns that inspired subdivision of the Benton shales. Wind and rivers rapidly erode the shales, producing bluffs: massive blocks of Niobrara Chalk cap high slopes of ''non-chalky'' Benton shale leading down a flatter plain that stretches miles to another bluff of ''chalky'' shale with many thin limestones. Particularly, in places where rivers have cut deeply through this lower chalky shale, and furthermore have cut into the bases of the bluffs, {{convert|100|ft|m}} banks of ''non-chalky'' shale can be found. In 1896, [[Grove Karl Gilbert|G.K. Gilbert]] named this lower argillaceous shale "Graneros" (from R.C. Hills) for the exposures in Graneros Creek, a tributary of the [[Arkansas River]] near Pueblo.<ref name="Hattin176Strat" /><ref name="cobban-scott-1972"/> Thus, the Graneros records the opening transgression of the Greenhorn Cycle of the [[Western Interior Seaway]], and is therefore the complement of the very similar Blue Hills Shale of the [[Carlile Shale|Carlile Formation]] that records the regression of the same Greenhorn Cycle. By 1938, the Graneros had been mapped into eastern Wyoming, southeastern Montana, South Dakota, Nebraska, Kansas, and northeastern New Mexico.<ref name="wilmarth-1938">{{cite journal |last1=Wilmarth |first1=M.G. |year=1938 |title=Lexicon of geologic names of the United States (including Alaska) |journal=U.S. Geological Survey Bulletin |volume=896 |number=1–2 |url=https://books.google.com/books?id=45fJkycjX6gC&q=graneros#v=snippet&q=graneros&f=false |access-date=13 March 2021}}</ref>


The same Benton topography is also found in the [[Smoky Hills]] of Northcentral Kansas, and the same Graneros Formation is found in the river banks there.<ref name="Hattin176Strat" /> However, north of Kansas, the application of the name has been somewhat different. In 1904, describing the geology of the [[Black Hills]] of South Dakota, [[Nelson Horatio Darton|N.H. Darton]]<ref name=Darton>Darton, N.H. 1904. Comparison of the stratigraphy of the Black Hills, Bighorn Mountains, and Rocky Mountain Front Range. Geological Society of America Bulletin, v. 15, p. 379-448.</ref> applied the name '''Graneros Group''' to descending members; marine [[Belle Fourche Formation|Belle Fourche Shale]] and [[Mowry Shale]], terrestrial [[Newcastle Sandstone]] (a tongue of [[Dakota Formation]] sandstone from the southeast of South Dakota), and marine [[Skull Creek Shale]]. This could have been an original interpretation that these units at the Black Hills represented thickening development of the thin, variable beddings observed in the Graneros of Colorado and Kansas. However, by the 1960s, Darton's definition was recognized as problematic, but many geologists continued to use this classification. It is understood that the listed formations are widely known individually, most with little relationship to the original Graneros definition; and, the same or equivalent units are classified in Wyoming and Colorado as [[Dakota Group]].<ref name="Hattin176Strat" /> As a result, newer reports include the Belle Fourche (Graneros equivalent), Mowry, Newcastle, and Skull Creek within the Dakota Group of this region.
The same Benton topography is also found in the [[Smoky Hills]] of Northcentral Kansas, and the same Graneros Formation is found in the river banks there.<ref name="Hattin176Strat" /> However, north of Kansas, the application of the name has been somewhat different. In 1904, describing the geology of the [[Black Hills]] of South Dakota, [[Nelson Horatio Darton|N.H. Darton]]<ref name=Darton>Darton, N.H. 1904. Comparison of the stratigraphy of the Black Hills, Bighorn Mountains, and Rocky Mountain Front Range. Geological Society of America Bulletin, v. 15, p. 379-448.</ref> applied the name '''Graneros Group''' to descending members; marine [[Belle Fourche Formation|Belle Fourche Shale]] and [[Mowry Shale]], terrestrial [[Newcastle Sandstone]] (a tongue of [[Dakota Formation]] sandstone from the southeast of South Dakota), and marine [[Skull Creek Shale]]. This could have been an original interpretation that these units at the Black Hills represented thickening development of the thin, variable beddings observed in the Graneros of Colorado and Kansas. However, by the 1960s, Darton's definition was recognized as problematic, but many geologists continued to use this classification. It is understood that the listed formations are widely known individually, most with little relationship to the original Graneros definition; and, the same or equivalent units are classified in Wyoming and Colorado as [[Dakota Group]].<ref name="Hattin176Strat" /> As a result, newer reports include the Belle Fourche (Graneros equivalent), Mowry, Newcastle, and Skull Creek within the Dakota Group of this region.


==Description==
==Description==
The Graneros Shale is primarily dark gray [[shale]] with minor [[sandstone]] and [[limestone]]. It rests on the [[Dakota Group]] and is in turn overlain by the [[Greenhorn Limestone]].<ref name="gilbert-1896">{{cite journal |last1=Gilbert |first1=G.K. |author1-link=Grove Karl Gilbert |year=1896 |title=The underground water of the Arkansas Valley in eastern Colorado |journal=U.S. Geological Survey Annual Report |volume=17 |number=2 |pages=551–601 |url=http://pubs.er.usgs.gov/pubs/ar/ar17_2 |access-date=3 September 2020}}</ref><ref name="ziegler-etal-2019">{{cite journal |last1=Ziegler |first1=Kate E. |last2=Ramos |first2=Frank C. |last3=Zimmerer |first3=Matthew J. |title=Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary |journal=New Mexico Geological Society Field Conference Series |date=2019 |volume=70 |issue=4 |pages=47–54 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/70/70_p0047_p0054.pdf |access-date=1 September 2020}}</ref> The thickness varies from {{convert|114-1000|feet|meters}}.<ref name="cobban-scott-1972"/><ref name="cobban-1922">{{cite journal |last1=Collier |first1=A.J. |year=1922 |title=The Osage oil field, Weston County, Wyoming |journal=U.S. Geological Survey Bulletin |volume=736-D |pages=71–110}}</ref>
The Graneros Shale is primarily dark gray [[shale]] with minor [[sandstone]] and [[limestone]], with visible crystalline minerals ([[pyrite]], [[marcasite]], [[selenite]], [[calcite]]). It rests on the [[Dakota Group]] and is in turn overlain by the [[Greenhorn Limestone]].<ref name="gilbert-1896">{{cite journal |last1=Gilbert |first1=G.K. |author1-link=Grove Karl Gilbert |year=1896 |title=The underground water of the Arkansas Valley in eastern Colorado |journal=U.S. Geological Survey Annual Report |volume=17 |number=2 |pages=551–601 |url=https://pubs.er.usgs.gov/publication/ar17_2 |access-date=13 March 2021}}</ref><ref name="ziegler-etal-2019">{{cite journal |last1=Ziegler |first1=Kate E. |last2=Ramos |first2=Frank C. |last3=Zimmerer |first3=Matthew J. |title=Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary |journal=New Mexico Geological Society Field Conference Series |date=2019 |volume=70 |issue=4 |pages=47–54 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/70/70_p0047_p0054.pdf |access-date=1 September 2020}}</ref> The thickness varies from {{convert|114-1000|feet|meters}}.<ref name="cobban-scott-1972"/><ref name="cobban-1922">{{cite journal |last1=Collier |first1=A.J. |year=1922 |title=The Osage oil field, Weston County, Wyoming |journal=U.S. Geological Survey Bulletin |volume=736-D |pages=71–110}}</ref>


Because the Graneros Shale is nearly monolithologic, only one member and one bed have ever been named.<ref name="Hattin176Strat" />
Because the Graneros Shale is nearly monolithologic, only one member and one bed have ever been named.<ref name="Hattin176Strat" />
* Rather than calcite precipitates, the limestones of the Graneros (similar to the limestones of the [[Greenhorn Limestone|Lincoln "Marble"]] just above the formation) are sorted skeletal remains. This skeletal limestone indicates repeated disturbance of the bottom that washed away the silt, leaving mostly ''[[Inoceramus]]'' shell fragments. ''[[Ostrea]] beloiti'' beds are particular index fossils for the formation. The middle limestones of the formation are sufficiently developed in southcentral Colorado and northcentral New Mexico to be named '''Thatcher Limestone Member'''.<ref name= GeolexSigPubThatcher >{{cite web | title = Geologic Unit: Thatcher| series = Geolex — Significant Publications | work = National Geologic Database | publisher = [[United States Geological Survey]] | url = https://ngmdb.usgs.gov/Geolex/Units/Thatcher_10837.html | access-date = 2021-03-12 }}</ref><ref name="Hattin176Strat" /> Ammonites from the Thatcher Limestone Member are indicative of [[Cenomanian]] age.<ref name="cobban-scott-1972"/>
* Rather than calcite precipitates, the limestones of the Graneros (similar to the limestones of the [[Greenhorn Limestone|Lincoln "Marble"]] just above the formation) are sorted skeletal remains. These skeletal limestones indicate repeated disturbances of the bottom that washed away the silt, leaving mostly ''[[Inoceramus]]'' shell fragments. ''[[Ostrea]] beloiti'' beds are particular index fossils for the formation. The middle limestones of the formation are sufficiently developed in southcentral Colorado and northcentral New Mexico to be named '''Thatcher Limestone Member'''.<ref name= GeolexSigPubThatcher >{{cite web | title = Geologic Unit: Thatcher| series = Geolex — Significant Publications | work = National Geologic Database | publisher = [[United States Geological Survey]] | url = https://ngmdb.usgs.gov/Geolex/Units/Thatcher_10837.html | access-date = 2021-03-12 }}</ref><ref name="Hattin176Strat" /> Ammonites from the Thatcher Limestone Member are indicative of [[Cenomanian]] age.<ref name="cobban-scott-1972"/>
* While the formation has several ''thin'' [[bentonite]] beds, one unique bed is sufficiently, thick, widespread, and widely used as a marker bed to be informally named "X bentonite". A feature of bentonite beds is that they mark specific instants in geological time; that is, all locations where a particular bentonite bed is found are therefore known to record the same date in Earth history. At the Graneros type location, which was generally the deepest part of the Western Interior Seaway, the X bentonite is actually in the lowest beds of the Greenhorn Formation. However, progressing eastward, the X bentonite is found within the ''top'' of the Graneros, then lower into the unit, and by Iowa, the X bentonite is found at the ''bottom'' of the Graneros. This pattern is evidence that the Graneros was deposited in different locations in time and space; as the sea levels of the Greenhorn Cycle rose, the Graneros environment moved eastward in space and upwards in geologic time.
* While the formation has several ''thin'' [[bentonite]] beds, one unique bed is sufficiently, thick, widespread, and widely used as a marker bed to be informally named "X bentonite". A feature of bentonite beds is that they mark specific instants in geological time; that is, all locations where a particular bentonite bed is found are therefore known to record the same date in Earth history. At the Graneros type location, which was generally the deepest part of the Western Interior Seaway, the X bentonite is actually in the lowest beds of the Greenhorn Formation. However, progressing eastward, the X bentonite is found within the ''top'' of the Graneros, then lower into the unit, and by Iowa, the X bentonite is found at the ''bottom'' of the Graneros. This pattern is evidence that the Graneros was deposited in different locations in time and space; as the sea levels of the Greenhorn Cycle rose, the Graneros environment moved eastward in space and upwards in geologic time.


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==Fossils==
==Fossils==
The upper part of the formation contains abundant oyster fossils<ref name="cobban-scott-1972"/> and the [[ammonoid]]s ''Tarrantoceras sellardsi'' Adkins, ''[[Desmoceras]]'', ''[[Anthoceras]]'', and ''Borissiakoceras''. The mollusks ''[[Inoceramus]] rutherfordi'' Warren, ''[[Ostrea]] beloiti'' Logan, and ''[[Turrilites]] acutus americanus'' are also present. Fossils become more scarce in Wyoming.
The upper part of the formation contains abundant oyster fossils<ref name="cobban-scott-1972"/> and the [[ammonoid]]s ''Tarrantoceras sellardsi'' Adkins, ''[[Desmoceras]]'', ''[[Anthoceras]]'', and ''Borissiakoceras''. The mollusks ''[[Inoceramus]] rutherfordi'' Warren, ''[[Ostrea]] beloiti'' Logan, and ''[[Turrilites]] acutus americanus'' are also present. Fossils become more scarce in Wyoming.
<ref name="cobban-1988">{{cite journal |last1=Cobban |first1=W.A. |title=Professional Paper |journal=USGS Professional Paper |date=1988 |volume=1473 |doi=10.3133/pp1473 |url=https://pubs.er.usgs.gov/publication/pp1473 |access-date=3 September 2020|doi-access=free }}</ref>
<ref name="cobban-1988">{{cite journal |last1=Cobban |first1=W.A. |title=''Tarrantoceras'' Stephenson and related ammonoid genera from Cenomanian (Upper Cretaceous) rocks in Texas and the Western Interior of the United States |journal=U.S. Geological Survey Professional Paper |date=1988 |volume=1473 |doi=10.3133/pp1473 |url=https://pubs.er.usgs.gov/publication/pp1473 |access-date=13 March 2021|doi-access=free }}</ref>

==History of investigation==
The unit was first named by R.C. Hills in 1896 for exposures in eastern Colorado.<ref name="gilbert-1896"/> By 1938 it had been mapped into eastern Wyoming, southeastern Montana, South Dakota, Nebraska, Kansas, and northeastern New Mexico. <ref name="wilmarth-1938">{{cite journal |last1=Wilmarth |first1=M.G. |year=1938 |title=Lexicon of geologic names of the United States (including Alaska) |journal=U.S. Geological Survey Bulletin |volume=896 |number=1–2 |url=https://books.google.com/books?id=45fJkycjX6gC&q=+Wilmarth,+M.G.,+1935,+%5BSelected+Geologic+Names+Committee+remarks+(ca.+1935-1938)+on+Cretaceous+rocks+of+the+U.S.%5D,+IN+Wilmarth,+M.G.,+1938,+Lexicon+of+geologic+names+of+the+United+States+(including+Alaska):+U.S.+Geological+Survey+Bulletin,+896,+pts.+1-2,+&pg=PA1243 |access-date=3 September 2020}}</ref>


==See also==
==See also==

Revision as of 21:09, 14 March 2021

Graneros Shale
Stratigraphic range: Cenomanian
Graneros Shale at outlet of El Vado Reservoir, New Mexico, USA
TypeFormation
Sub-unitsSee text
UnderliesGreenhorn Formation
OverliesDakota Formation
Thickness114–1,000 feet (35–305 m)
Lithology
PrimaryShale
OtherSandstone, limestone
Location
Coordinates38°16′35″N 104°42′44″W / 38.2763°N 104.7121°W / 38.2763; -104.7121
RegionCO,IA,KS,MN,MT,NM,NE,ND,OK,SD,WY
Country United States
Type section
Named forGraneros Creek, Walsenburg quadrangle, Pueblo Colorado
Named byR.C.Hills
Year defined1896
Graneros Shale is located in the United States
Graneros Shale
Graneros Shale (the United States)
Graneros Shale is located in Colorado
Graneros Shale
Graneros Shale (Colorado)

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.[1]. It is defined as the argillaceous or clayey marine shale that lies above the older, non-marine Dakota sand and mud and below the younger, chalky 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. The states include Kansas, Texas, Oklahoma, Nebraska, and New Mexico as well as corners of Minnesota and Iowa.[2][3] 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.[4]

Naming and Rank

F.B. Meek and F.V. Hayden originated the scientific names for the series of Cretaceous rocks in the central Great Plains of the North American Continent. They gave the name "Benton" to the great shale deposits between the sandstone bluffs at Dakota City, Nebraska, and the chalk bluffs at the junction of the Niobrara and Missouri rivers. At that time, the early 1860s, Meek and Hayden's "lower Cretaceous" series of the upper Missouri River, Dakota-Benton-Niobrara, was already widely observed from Canada to New Mexico over the Great Plains up to the foothills of the Rocky Mountains.[5]

In southcentral Colorado, southeast of Pueblo, this series expresses topographical patterns that inspired subdivision of the Benton shales. Wind and rivers rapidly erode the shales, producing bluffs: massive blocks of Niobrara Chalk cap high slopes of non-chalky Benton shale leading down a flatter plain that stretches miles to another bluff of chalky shale with many thin limestones. Particularly, in places where rivers have cut deeply through this lower chalky shale, and furthermore have cut into the bases of the bluffs, 100 feet (30 m) banks of non-chalky shale can be found. In 1896, G.K. Gilbert named this lower argillaceous shale "Graneros" (from R.C. Hills) for the exposures in Graneros Creek, a tributary of the Arkansas River near Pueblo.[4][1] Thus, the Graneros records the opening transgression of the Greenhorn Cycle of the Western Interior Seaway, and is therefore the complement of the very similar Blue Hills Shale of the Carlile Formation that records the regression of the same Greenhorn Cycle. By 1938, the Graneros had been mapped into eastern Wyoming, southeastern Montana, South Dakota, Nebraska, Kansas, and northeastern New Mexico.[6]

The same Benton topography is also found in the Smoky Hills of Northcentral Kansas, and the same Graneros Formation is found in the river banks there.[4] However, north of Kansas, the application of the name has been somewhat different. In 1904, describing the geology of the Black Hills of South Dakota, N.H. Darton[7] applied the name Graneros Group to descending members; marine Belle Fourche Shale and Mowry Shale, terrestrial Newcastle Sandstone (a tongue of Dakota Formation sandstone from the southeast of South Dakota), and marine Skull Creek Shale. This could have been an original interpretation that these units at the Black Hills represented thickening development of the thin, variable beddings observed in the Graneros of Colorado and Kansas. However, by the 1960s, Darton's definition was recognized as problematic, but many geologists continued to use this classification. It is understood that the listed formations are widely known individually, most with little relationship to the original Graneros definition; and, the same or equivalent units are classified in Wyoming and Colorado as Dakota Group.[4] As a result, newer reports include the Belle Fourche (Graneros equivalent), Mowry, Newcastle, and Skull Creek within the Dakota Group of this region.

Description

The Graneros Shale is primarily dark gray shale with minor sandstone and limestone, with visible crystalline minerals (pyrite, marcasite, selenite, calcite). It rests on the Dakota Group and is in turn overlain by the Greenhorn Limestone.[8][9] The thickness varies from 114–1,000 feet (35–305 m).[1][10]

Because the Graneros Shale is nearly monolithologic, only one member and one bed have ever been named.[4]

  • Rather than calcite precipitates, the limestones of the Graneros (similar to the limestones of the Lincoln "Marble" just above the formation) are sorted skeletal remains. These skeletal limestones indicate repeated disturbances of the bottom that washed away the silt, leaving mostly Inoceramus shell fragments. Ostrea beloiti beds are particular index fossils for the formation. The middle limestones of the formation are sufficiently developed in southcentral Colorado and northcentral New Mexico to be named Thatcher Limestone Member.[11][4] Ammonites from the Thatcher Limestone Member are indicative of Cenomanian age.[1]
  • While the formation has several thin bentonite beds, one unique bed is sufficiently, thick, widespread, and widely used as a marker bed to be informally named "X bentonite". A feature of bentonite beds is that they mark specific instants in geological time; that is, all locations where a particular bentonite bed is found are therefore known to record the same date in Earth history. At the Graneros type location, which was generally the deepest part of the Western Interior Seaway, the X bentonite is actually in the lowest beds of the Greenhorn Formation. However, progressing eastward, the X bentonite is found within the top of the Graneros, then lower into the unit, and by Iowa, the X bentonite is found at the bottom of the Graneros. This pattern is evidence that the Graneros was deposited in different locations in time and space; as the sea levels of the Greenhorn Cycle rose, the Graneros environment moved eastward in space and upwards in geologic time.

As discussed in the previous Naming and Rank section, the Graneros name was applied to a group of other units; however, this has no relation to the description of the Graneros Shale formation.[4]

Fossils

The upper part of the formation contains abundant oyster fossils[1] and the ammonoids Tarrantoceras sellardsi Adkins, Desmoceras, Anthoceras, and Borissiakoceras. The mollusks Inoceramus rutherfordi Warren, Ostrea beloiti Logan, and Turrilites acutus americanus are also present. Fossils become more scarce in Wyoming. [12]

See also

References

  1. ^ a b c d e Cobban, W.A.; Scott, G.R. (1972). "Stratigraphy and ammonite fauna of the Graneros Shale and Greenhorn Limestone near Pueblo, Colorado". U.S. Geological Survey Professional Paper. Professional Paper. 645. doi:10.3133/pp645. Retrieved 3 September 2020.
  2. ^ "Geologic Unit: Graneros". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved 2021-03-12.
  3. ^ Siliciclastic and calcareous sedimentary rocks of early Late Cretaceous age in the Western Interior of the United States have been assigned to, in ascending order, the Graneros Shale, Greenhorn Formation, Carlile Shale, Niobrara Formation, and their lateral equivalents (including members of the Frontier Formation and overlying formations). Merewether, E. Allen; Cobban, William A.; Obradovich, John D. (2007). "Regional disconformities in Turonian and Coniacian (Upper Cretaceous) strata in Colorado, Wyoming, and adjoining states - Biochronological evidence". Rocky Mountain Geology. 42 (2): 95–122. doi:10.2113/gsrocky.42.2.95.
  4. ^ a b c d e f g Donald E. Hattin (1975). Stratigraphy and Depositional Environment of Greenhorn Limestone (Upper Cretaceous) of Kansas, Kansas Geological Survey, Bulletin 176. University of Kansas Publications, State Geological Survey of Kansas. p. Stratigraphy. The Graneros Shale was named by Gilbert (1896, p. 564) for 200 to 210 feet of argillaceous or clayey shale lying between the top of the Dakota and the base of the overlying Greenhorn Limestone." "[In northwestern Nebraska and around the Black Hills] the thicknesses are for the combined Mowry and Belle Fourche shales but, as noted above, only the Belle Fourche is lithologically equivalent to the Graneros.
  5. ^ Meek, F.B. and Hayden, F.V. (1862). "Descriptions of new Lower Silurian, (Primordial), Jurassic, Cretaceous, and Tertiary fossils, collected in Nebraska, by the exploring expedition under the command of Capt. Wm F. Reynolds, U.S. Top. Engineers, with some remarks on the rocks from which they were obtained". Academy of Natural Sciences of Philadelphia Proceedings. 13: 417-424.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ Wilmarth, M.G. (1938). "Lexicon of geologic names of the United States (including Alaska)". U.S. Geological Survey Bulletin. 896 (1–2). Retrieved 13 March 2021.
  7. ^ Darton, N.H. 1904. Comparison of the stratigraphy of the Black Hills, Bighorn Mountains, and Rocky Mountain Front Range. Geological Society of America Bulletin, v. 15, p. 379-448.
  8. ^ Gilbert, G.K. (1896). "The underground water of the Arkansas Valley in eastern Colorado". U.S. Geological Survey Annual Report. 17 (2): 551–601. Retrieved 13 March 2021.
  9. ^ Ziegler, Kate E.; Ramos, Frank C.; Zimmerer, Matthew J. (2019). "Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary" (PDF). New Mexico Geological Society Field Conference Series. 70 (4): 47–54. Retrieved 1 September 2020.
  10. ^ Collier, A.J. (1922). "The Osage oil field, Weston County, Wyoming". U.S. Geological Survey Bulletin. 736-D: 71–110.
  11. ^ "Geologic Unit: Thatcher". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved 2021-03-12.
  12. ^ Cobban, W.A. (1988). "Tarrantoceras Stephenson and related ammonoid genera from Cenomanian (Upper Cretaceous) rocks in Texas and the Western Interior of the United States". U.S. Geological Survey Professional Paper. 1473. doi:10.3133/pp1473. Retrieved 13 March 2021.


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