Valentine Formation

The Valentine Formation is a geologic unit formation or member within the Ogallala unit in northcentral Nebraska near the South Dakota border. It preserves fossils dating to the Neogene period and is particularly noted for Canid fossils.[1][2] A particular feature of the Valentine is lenticular beds of green-gray opaline sandstone that can be identified in other states, including South Dakota, Nebraska, Kansas, and Colorado. Even though three mammalian fauna stages can be mapped throughout the range of the Ogallala, no beddings of the Ogallala are mappable and all attempts of formally applying the Valentine to any mappable lithology beyond the type location have been abandoned. Even so, opaline sandstone[3] has been used to refer to the green-gray opalized conglomerate sandstone that is a particular feature of the lower Ogallala.

Valentine Formation
Stratigraphic range: Neogene
TypeFormation / Member
Unit ofOgallala Formation
OverliesEroded and weathered Miocene units, Pierre Shale (Nebraska), and Niobrara Chalks
Location
Region South Dakota,  Nebraska,  Kansas
Country United States
Type section
Named forValentine Railway Quarries, Valentine, Nebraska

Development, the earliest Ogallala deposits

At the beginning of the Ogallala times, as sediments began washing out from the rising Rocky Mountains into the central plains states, the members of the Pierre Shale[4] and Niobrara Formation outcrop had been largely exposed in their present outcrop range. The Niobrara had been broadly incised by the present river systems, but only to a fraction of their present depths. Therefore, the earliest Ogallala deposits, the time of the Valentine deposits, filled in these shallower valleys; but there was no continuous exposure over the range of the eastern outcrop of the Ogallala.[5][3] Isolated exposures of the Valentine phase have been located along the Niobrara outcrop and quarried along the Smoky Hill River, Solomon River, Republican River, and Niobrara River where these watersheds have cut deeply down through the Niobrara Chalk into the Carlile Shale.

Lithology

The Valentine Formation presents gray to gray-green, unconsolidated, fine-to-coarse grained, fluvial siltstone, channel sandstone, and gravel eroded from uplift of the Rocky Mountains as well as locally eroded materials,[6] particularly Niobrara chalk cobbles and chalk sand.[7] The specific index stone for the Valentine is the lenticular beds of grey-green opaline sandstone.

Distribution

Even as discussed above, the term Valentine is not now formally used outside of Northcentral Nebraska, older literature in other states with Ogallala may refer to the name.

The opaline sandstone of the lower Ogallala is recognized in Kansas in outcrops on hills to the east of the limits of the upper Ogallala (e.g., Rush, Graham, and Rooks counties). These outcrops, which formed in the bottoms of shallow valleys, are now found on the upper slopes of deeper valleys; that is, in inverted topographies. [8] [9]

The Ogallala's opaline sandstone is to be found in Arkansas River gravel at Pueblo, Colorado.[10]

Uses

The silicate cementation makes the opaline sandstone denser and harder than any other local stone, and it has been quarried as ballast, road gravel, and dam outflow rip-rap (e.g., Cedar Bluff Reservoir, Sherman Dam[11]). The opaline sandstone has had limited use in construction, and example being the structures in the city park of Hill City, Kansas. Beds of flint or chert can be found higher in the Valentine and the weathered Niobrara Chalk is also silicified where there is contact with these beds in the Valentine.

Fossil content
Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Bats
Bats reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Cf. Myotis Cf. M. sp. Annies Geese Cross Quarry, Knox County, Nebraska.[12] Crookston Bridge Member.[12] Right dentary lacking posterior end & teeth (UNSM 52004).[12] A mouse-eared bat approximately the size of Myotis septentrionalis.[12]
Potamonycteris P. biperforatus Annies Geese Cross Quarry, Knox County, Nebraska.[12] Crookston Bridge Member.[12] Left half of a rostrum (UNSM 52008).[12] A vespertilionid.

Carnivorans
Carnivorans reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Aelurodon A. ferox Boyd, Cherry, Brown, Knox, Keyapaha & possibly Sheridan counties, Nebraska.[1][13] Crookston Bridge, Cornell Dam, Devil's Gulch, Burge members.[1][13] Numerous specimens.[1] A borophagine dog.
A. mcgrewi Brown, Cherry & Keya Paha counties, Nebraska.[13] Devil's Gulch & Crookston Bridge members.[13] Numerous skull elements.[13] A borophagine dog.
A. stirtoni Cherry County, Nebraska.[1][13] Crookston Bridge & Burge members.[1][13] Numerous remains.[1][13] A borophagine dog, originally reported as Strobodon. Also found in the Tesuque Formation.
?Amphicyonidae Gen. et. sp. indet. Railway Quarry "A", Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Right femur lacking head (UNSM 76638).[1] Large carnivore, possibly a bear-dog.
Bassariscus B. parvus Railway Quarry "A", Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Left ramus (UNSM 25466).[1] A procyonid.
Carpocyon C. compressus Cherry, Brown, Boyd & Keyapaha counties, Nebraska.[13] Cornell Dam, Crookston Bridge & Devil's Gulch members.[13] Numerous specimens.[13] A borophagine dog also known from the Ogallala, Pawnee Creek & Esmeralda formations.
C. cuspidatus Railway Quarry "A", Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Skull elements.[1] A borophagine dog.
C. webbi Brown & Cherry counties, Nebraska.[13] Burge Member.[13] Many skull & jaw elements.[13] A borophagine dog also found in the Ash Hollow, Tesuque & Chamita formations.
Cynarctus C. saxatilis Cherry, Brown, Knox & Webster counties, Nebraska.[1][13] Crookston Bridge, Cornell Dam & Devil's Gulch members.[1][13] Numerous specimens.[1][13] A borophagine dog.
Felidae Gen. et. sp. indet. Railway Quarry "A", Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Partial left maxilla (UNSM 76641).[1] A large cat.
Hyperailurictis H. intrepidus Brown & Cherry counties, Nebraska.[14] Ramus remains.[14] A felid originally reported as Pseudaelurus.
H. marshi Cherry County, Nebraska.[14] Articulated left & right rami (YPM 12865).[14] A felid originally reported as Pseudaelurus.
Ischyrocyon I. gidleyi Cherry, Brown, Knox & Sheridan counties, Nebraska.[15] Devil's Gulch & Burge members.[15] A bear-dog.
Leptarctus L. cf. bozemanensis Railway Quary "A", Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Partial left ramus (UNSM 25467).[1] A mustelid.
Leptocyon L. vafer Brown, Cherry, Keya Paha, Knox & Sheridan counties, Nebraska.[1][16] Cornell Dam, Crookston Bridge, Devil's Gulch, & Burge members.[1][16] Abundant specimens.[1][16] A canine dog.
Mustelidae Gen. et. sp. indet. Railway Quarry "A", Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Left ramus (UNSM 76640).[1] A small carnivore.
Paratomarctus P. euthos Cherry, Brown & Sheridan counties, Nebraska.[13] Burge Member.[13] Abundant remains.[13] A borophagine dog also known from the Ash Hollow Formation.
P. temerarius Brown, Cherry & Webster counties, Nebraska.[13] Cornell Dam, Crookston Bridge & Devil's Gulch members.[13] Abundant remains.[13] A borophagine dog.
Pseudaelurus P. intrepidus Brown & Cherry counties, Nebraska.[14] Ramus remains.[14] Moved to the genus Hyperailurictis.[17]
P. marshi Cherry County, Nebraska.[14] Articulated left & right rami (YPM 12865).[14] Moved to the genus Hyperailurictis.[17]
Pseudocyon P. sp. Brown (Norden Bridge, Lucht & June quarries) & Cherry counties, Nebraska.[15] Burge Member.[15] A bear-dog.
Strobodon S. stirtoni Railway Quarries, Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Right ramus (UNSM 76620) & right maxilla (UCMP 63657).[1] Junior synonym of Aelurodon.
Tomarctus T. near T. euthos Railway Quarries, Cherry County, Nebraska.[1] Crookston Bridge Member.[1] Skull & limb elements.[1] A borophagine dog.

Lagomorphs
Lagomorphs reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Alilepus A. sp. Stewart Quarry.[18] Crookston Bridge Member.[18] Teeth.[18] A leporid.
Hypolagus H. fontinalis Railway Quarries.[18] Crookston Bridge Member.[18] Dentaries & a maxilla.[18] A leporid.
H. parviplicatus Railway Quarries.[18] Crookston Bridge Member.[18] Dentaries.[18] A leporid.
Leporinae Indeterminate Stewart Quarry.[18] Crookston Bridge Member.[18] 4 isolated premolars.[18] A leporid.
Pronotolagus P. albus Stewart Quarry.[18] Crookston Bridge Member.[18] Teeth & jaw elements.[18] A leporid.

Proboscideans
Proboscideans reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Gomphotherium G. osborni Boyd County, Nebraska.[19] Near-complete skeleton.[19] A gomphothere.
Tetrabelodon T. osborni Boyd County, Nebraska.[19] Near-complete skeleton.[19] Junior synonym of Gomphotherium.

Rodents
Rodents reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Anchitheriomys A. fluminis Norden Bridge Quarry, Brown County, Nebraska.[20] Crookston Bridge Member.[20] A castorid.
Ceratogaulus C. rhinocerus Crookston Bridge Quarry, Cherry County, Nebraska.[21] Crookston Bridge Member.[21] UNSM 122005, 122007, 122010 & 122009.[21] A mylagaulid.
C. sp., cf. C. rhinocerus Northcentral Nebraska.[21] Burge Member.[21] Multiple specimens.[21] A mylagaulid.
Cupidinimus C. nebraskensis Cherry County, Nebraska.[22] Crookston Bridge Member.[22] Several mandibles.[22] A heteromyid.
Eucastor E. tortus Brown, Cherry & Knox counties, Nebraska.[23] Cornell Dam, Crookston Bridge & Devil's Gulch members.[23] Skull elements.[23] A castorid.
Megasminthus M. tiheni Norden Bridge Quarry, Brown County, Nebraska.[24] Jaw elements & teeth.[24] A zapodine.
Monosaulax M. skinneri Cherry County, Nebraska.[23] Cornell Dam, Crookston Bridge & Devil's Gulch members.[23] Teeth, mandibles & cranial material.[23] A castorid.
Nothodipoides N. stirtoni Cherry & Brown counties, Nebraska.[25] Burge Member.[25] A skull (FAM 65276) & 2 mandibles (FAM 65277 & 65279).[25] A castorid.
?Plesiosminthus ?P. sp. Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[24] Mandibles & teeth.[24] A sicistine.
Prodipoides P. burgensis Brown, Cherry & Knox counties, Nebraska.[23] Burge, Crookston Bridge & Devil's Gulch members.[23] Mandibles & partial skull.[23] A castorid.
P. dividerus Brown & Cherry counties, Nebraska.[23] Burge, Devil's Gulch & Crookston Bridge members.[23] Mandibles (UCMP 29691, FAM 64314, 64319, 64316, & 64318) & partial cranium (FAM 64324).[23] A castorid also known from the Ash Hollow & Esmeralda formations.
Temperocastor T. valentinensis Cherry & Webster counties.[23] Crookston Bridge Member.[23] Skull elements, scapula & radius.[23] A castorid.

Ungulates
Ungulates reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Calippus C. proplacidus Brown County, Nebraska.[26] Devil's Gulch Member.[26] Skull elements.[26] An equid.
C. regulus Penny Creek localities, Webster County, Nebraska.[27] Multiple specimens.[27] An equid.
Colbertchoerus C. niobrarensis Deep Creek Quarry, Brown County, Nebraska.[28] Devil's Gulch Member.[28] Partial skull (UNSM 2604).[28] A peccary also known from the Calvert & Choptank formations.
Cormohipparion C. johnsoni Burge Quarry, Nebraska.[29] Burge Member.[29] Skull elements.[29] An equid.
C. merriami June & Midway quarries, Nebraska.[29] Burge Member.[29] Skull elements.[29] An equid.
C. quinni Brown County, Nebraska.[30] Devil's Gulch, Cornell Dam & Crookston Bridge members.[30] Multiple specimens.[30] An equid.
Hemiauchenia H. sp. June Quarry, Brown County, Nebraska.[31] Burge Member.[31] A metacarpal.[31] A camelid.
Protohippus P. perditus Brown County, Nebraska.[26] Devil's Gulch & Crookston Bridge members.[26] Numerous specimens.[26] An equid.
Pseudhipparion P. retrusum Cherry & Brown counties, Nebraska.[32] Burge & Devil's Gulch members.[32] Numerous specimens, including many skulls & mandibles.[32] An equid.
Stirtonhyus S. xiphidonticus Cherry & Knox counties, Nebraska.[28] Crookston Bridge & Devil's Gulch members.[28] Numerous specimens.[28] A peccary.
Tapiravus T. cf. polkensis Webster & Cherry counties, Nebraska.[33] Mandibles.[33] Moved to the genus Tapirus.
Tapiridae Genus & species undetermined Cherry County, Nebraska.[33] Crookston Bridge Member.[33] Teeth.[33] A tapir.
Tapirus T. cf. polkensis Webster & Cherry counties, Nebraska.[33] Mandibles.[33] A tapir.
Ustatochoerus U. medius Brown & Cherry counties, Nebraska.[34] Numerous specimens.[34] A merycoidodontid.
U.? schrammi Boyd & Brown counties, Nebraska.[34] Jaw elements.[34] A merycoidodontid.

Birds
Birds reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Dissourodes D. milleri Cherry County, Nebraska.[35] Crookston Bridge Member.[36] Distal end of left tibiotarsus (UNSM 5780).[35] Lumped into the genus Mycteria.[36]
Heterochen H. pratensis Devil's Gulch, Brown County, Nebraska.[37] Nearly complete left tarsometatarsus (UNSM 5781).[37] A goose-like anseriform.
Mycteria M. milleri Cherry County, Nebraska.[35][36] Crookston Bridge Member.[36] Distal end of left tibiotarsus (UNSM 5780).[35][36] A stork, originally reported as Dissourodes.
Palaeonerpes P. shorti Driftwood Creek, Hitchcock County, Nebraska.[38] Equivalent to the top of the formation.[38] Distal end of left tibiotarsus (AMNH 1641).[38] A woodpecker.

Squamates
Squamates reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Ameiseophis A. cf. A. robinsoni Norden Bridge Quarry, Brown County, Nebraska.[39] Trunk vertebra (MSUVP 891). A colubrid snake.
Amphisbaenidae? Indeterminate Norden Bridge Quarry, Brown County, Nebraska.[40] A centrum of a dorsal vertebra (UNSM 61029).[40] A worm lizard.
Anguidae Unidentified Norden Bridge Quarry, Brown County, Nebraska.[40] 3 large osteoscutes (UNSM 61028).[40] An anguid lizard.
Boidae Indeterminate Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[40] Vertebrae & a fragmentary dentary.[40] Seems to be near the Ogmophis-Calamagras-Charina group.
Boinae Gen. et. sp. indet. Norden Bridge locality, Brown County, Nebraska.[41] Caudal vertebra.[41] Similar to Charina.
cf. Cnemidophorus cf. C. sp. Cherry County, Nebraska.[40] A right dentary.[40] A whiptail lizard.
Colubridae Indeterminate Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[40] Vertebrae.[40] At least 4 forms, including at least 1 natricine.
Colubrinae Gen. et. sp. indet. Norden Bridge locality, Brown County, Nebraska.[41] 2 precaudal vertebrae.[41] May represent an extinct genus or one found in Central or South America today.[41]
Elaphe E. nebraskensis Norden Bridge locality, Brown County, Nebraska.[41] Precaudal & anterior vertebrae.[41] A rat snake similar to E. vulpina in height of neural spine & size.
Eumeces E. minimus Egelhoff Quarry, Keya Paha County, Nebraska.[42] Crookston Bridge Member, lowermost part of the formation.[42] A frontal bone (MSU-VP 790).[42] A skink originally thought to be a species of Peltosaurus, may be a nomen dubium.[42]
cf. E. sp. Norden Bridge Quarry, Brown County, Nebraska.[40][39] Left dentary (MSUVP 966), 2 broken dentaries & a fragment of a maxilla (UNSM 61026).[40][39] A skink.
Geringophis G. depressus Norden Bridge Quarry, Brown County, Nebraska.[39] 1 trunk vertebra (MSUVP 893).[39] A boid.
Gerrhonotus G. sp. Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[40] An almost complete right dentary (UC 65857) & 3 vertebrae (UNSM 61027).[40] An alligator lizard.
Iguanidae Unidentified, form A Cherry County, Nebraska.[40] Fragment of a right dentary (UC 65856).[40] An iguanid lizard.
Unidentified, form B Norden Bridge Quarry, Brown County, Nebraska.[40] Fragment of a right dentary (UNSM 61025).[40] An iguanid lizard.
Lampropeltis L. similis Norden Bridge locality, Brown County, Nebraska.[41] Precaudal vertebrae.[41] A kingsnake.
Natricinae Gen. et. sp. indet. Norden Bridge locality, Brown County, Nebraska.[41] 2 vertebrae.[41] "A rather small natricine snake, but not one of the diminutive forms".[41]
Nebraskophis N. skinneri Norden Bridge Quarry, Brown County, Nebraska.[39] Trunk vertebra (UNSM 61037).[39] A colubrid snake.
Neonatrix N. elongata Norden Bridge Quarry, Brown County, Nebraska.[39] Trunk vertebra (MSUVP 967).[39] A colubrid snake.
N. magna Norden Bridge Quarry, Brown County, Nebraska.[39] Trunk vertebra (MSUVP 943).[39] A colubrid snake.
Paleoheterodon P. tiheni Norden Bridge locality, Brown County, Nebraska.[41] Precaudal vertebrae.[41] A colubrine closely related to Heterodon.
Peltosaurus P. minimus Egelhoff Quarry, Keya Paha County, Nebraska.[42][43] Crookston Bridge Member, lowermost part of the formation.[42][43] A frontal bone (MSU-VP 790).[42][43] Thought to be a glyptosaurine but reassigned to the skink genus Eumeces.[42]
Phrynosoma P. sp. Cherry County, Nebraska.[40] An almost complete jaw (UC 65855) & 2 less complete jaws.[40] A horned lizard.
Salvadora S. paleolineata Norden Bridge Quarry, Brown County, Nebraska.[39] Trunk vertebrae (MSUVP 892 & 968).[39] A patchnose snake.
Viperidae Indeterminate Norden Bridge Quarry, Brown County, Nebraska.[39] Trunk vertebra (MSUVP 889).[39] A viper.

Testudines
Testudines reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Chrysemys C. sp. Norden Bridge Quarry, Brown County, Nebraska.[40] A near complete hyoplastron.[40] An emydid turtle.
Emydoidea E. hutchisoni West Valentine Quarry, Cherry County, Nebraska.[44] Remains of at least 4 (probably more) individuals.[44] An emydid turtle.
Geochelone G. orthopygia Norden Bridge Quarry, Brown County, Nebraska.[40] Shell & limb elements.[40] A tortoise.
Glyptemys G. valentinensis Railway Quarry A, Cherry County, Nebraska.[45] Crookston Bridge Member.[45] Multiple carapace & bone specimens.[45] An emydid turtle.
Trionyx T. quinni Norden Bridge Quarry, Brown County, Nebraska.[39] Hyoplastrons & pleural bones.[39] A softshell turtle.
T. sp. Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[40] Multiple specimens.[40] A softshell turtle.

Amphibians
Amphibians reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Ambystoma A. minshalli Brown (Norden Bridge Locality) & Cherry counties, Nebraska.[39][40][46] Multiple specimens.[39][40][46] A mole salamander.
Andrias A. matthewi Norden Bridge Locality, Brown County, Nebraska.[40] A maxilla & a fragment of a maxilla.[40] A giant salamander.
Bufo B. hibbardi Norden Bridge Quarry, Brown County, Nebraska.[39] Right ilium (MSUVP 1013).[39] A true toad.
B. cf. hibbardi Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[40] Multiple specimens.[40] A true toad.
B. kuhrei Norden Bridge Quarry, Brown County, Nebraska.[39] Proximal portion of a right tibiofibula (MSUVP 890).[39] A true toad.
B. valentinensis Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[40] Multiple specimens.[40] A true toad.
Cryptobranchus C. mccalli Norden Bridge Quarry, Brown County, Nebraska.[46] A complete right maxilla & the anterior portion of a left maxilla.[46] Synonymized with Andrias matthewi.[47]
Geophryne G. nordensis Brown (Norden Bridge Quarry), Keya Paha (Egelhoff Local Fauna) & Knox (Annie's Geese Cross Local Fauna) counties, Nebraska.[48] 4 ilia.[48] A hylid frog.
Pseudacris P. nordensis Brown (Norden Bridge Quarry), Keya Paha (Egelhoff Local Fauna) & Knox (Annie's Geese Cross Local Fauna) counties, Nebraska.[48] 4 ilia.[48] Reassigned to the genus Geophryne.
Rana R. sp. Brown (Norden Bridge quarry) & Cherry counties, Nebraska.[40] Multiple specimens.[40] A ranid frog.
Scaphiopus S. (Spea) cf. alexanderi Brown (Norden Bridge locality) & Cherry counties, Nebraska.[40] UNSM 61016 & 61017.[40] An American spadefoot toad.
S. (Scaphiopus) wardorum Norden Bridge Quarry, Brown County, Nebraska.[40] Multiple specimens.[40] An American spadefoot toad.

Fish
Fish reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Amia A. sp. Cherry County, Nebraska.[40] A broken left dentary (UC 65851) & a dorsal vertebra.[40] A bowfin.
Ictalurus I. sp. Cherry County, Nebraska.[40] A pectoral spine, dorsal spine, right dentary, & numerous fragments of spines and vertebrae.[40] A catfish.
Lepisosteus L. sp. Norden Bridge Locality, Brown County, Nebraska.[40] A scale.[40] A gar.
Lepomis L. cf. microlophus Norden Bridge Locality, Brown County, Nebraska.[40] A left dentary.[40] A sunfish.

Plants
Plants reported from the Valentine Formation
GenusSpeciesLocation Stratigraphic position MaterialNotesImages
Berriochloa B. communis [49] A grass also found in the Ash Hollow Formation.

See also

References
  1. Robert L. Evander, Emanuel County Junior College (1986). "Carnivores of the Railway and Quarries Local Fauna". Transactions of the Nebraska Academy of Sciences and Affiliated Societies Nebraska Academy of Sciences. University of Nebraska - Lincoln.
  2. "Geologic Unit: Valentine". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved 2020-06-05.
  3. John C. Frye; A. Byron Leonard; Ada Swineford (1956). Stratigraphy of the Ogallala Formation (Neogene) of Northern Kansas, Bulletin 118. University of Kansas Publications, State Geological Survey of Kansas. p. Methods of Correlation. ... and the configuration of the lower surface indicates location of preexisting valleys and the most likely locale of earliest sedimentation. ... Therefore, it is expectable that the lowest, hence oldest, members be present in low areas of the bedrock, ... The relation of the configuration of the erosional surface at the base of the Ogallala to the stratigraphy of the formation has been fully recognized only recently (Merriam and Frye, 1954).
  4. Alvin Leonard Lugn, University of Nebraska - Lincoln (1938). "The Nebraska State Geological Survey and the "Valentine Problem"". American Journal of Science. University of Nebraska - Lincoln. 36 (213): 220. Bibcode:1938AmJS...36..220L. doi:10.2475/ajs.s5-36.213.220. S2CID 129509059.
  5. Alvin R. Leonard; Delmar W. Berry (1961). Geology and Ground-water Resources of Southern Ellis County and Parts of Trego and Rush Counties, Kansas, Bulletin 149. University of Kansas Publications, State Geological Survey of Kansas. p. Geomorphology / Stream Development. At the close of Pliocene time, the area from the Rocky Mountains to the Flint Hills was a nearly featureless aggradational plain crossed by streams flowing toward the east. During the formation of this [Ogallala] plain in central Kansas the Cretaceous [Niobrara] rocks were buried under a mantle of debris, ...
  6. "Ogallala Group". USGS.
  7. John C. Frye; A. Byron Leonard; Ada Swineford (1956). Stratigraphy of the Ogallala Formation (Neogene) of Northern Kansas, Bulletin 118. University of Kansas Publications, State Geological Survey of Kansas. p. Measured Sections.
  8. Warren G. Hodson (1965). "Geology and Ground-Water Resources of Trego County, Kansas". State Geological Survey of Kansas Bulletin 149. University of Kansas. Retrieved 2021-06-13. Silica also is present as a cementing material in beds of opaline sandstone ...
  9. Jesse M. McNellis (1973). "Geology and Ground-Water Resources of Rush County, Central Kansas". State Geological Survey of Kansas Bulletin 207. University of Kansas. Retrieved 2021-06-13. (2) a quartzitic-appearing green conglomerate with an opaline cement matrix, ...
  10. Glenn Scott (1969). "General and Engineering Geology of the Northern Part of Pueblo, Colorado" (PDF). Geological Survey Bulletin. United States Department of the Interior (1262): 112. Retrieved 2021-06-13.
  11. "Sherman Dam: Constructed 1959-1962". United States. Bureau of Reclamation. 1964. p. 25.
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  13. Wang, Xiaoming; Tedford, Richard H.; Taylor, Beryl E. (1999). "Phylogenetic systematics of the Borophaginae (Carnivora, Canidae). Bulletin of the AMNH ; no. 243". hdl:2246/1588. {{cite journal}}: Cite journal requires |journal= (help)
  14. Rothwell, Tom (2003). "Phylogenetic systematics of North American Pseudaelurus (Carnivora, Felidae)". American Museum Novitates (3403): 1–64. doi:10.1206/0003-0082(2003)403<0001:PSONAP>2.0.CO;2. hdl:2246/2829. S2CID 67753626.
  15. Hunt, Robert (1998-01-01). "Amphicyonidae". Mammalogy Papers: University of Nebraska State Museum.
  16. Tedford, Richard H.; Wang, Xiaoming; Taylor, Beryl E. (2009). Phylogenetic systematics of the North American fossil Caninae (Carnivora, Canidae). (Bulletin of the American Museum of Natural History, no. 325). [New York] : American Museum of Natural History. hdl:2246/5999.
  17. Werdelin, Lars; Yamaguchi, Nobuyuki; Johnson, W. E.; O'Brien, S. J. (January 2010). "Phylogeny and evolution of cats (Felidae)". Biology and Conservation of Wild Felids: 59–82.
  18. Voorhies, M. R.; Timperley, C. L. (1997). "A New Pronotolagus (Lagomorpha: Leporidae) and Other Leporids from the Valentine Railway Quarries (Barstovian, Nebraska), and the Archaeolagine-Leporine Transition". Journal of Vertebrate Paleontology. 17 (4): 725–737. doi:10.1080/02724634.1997.10011020. ISSN 0272-4634. JSTOR 4523860.
  19. Barbour, E. H. (1916). "A new longirostral mastodon from Nebraska, Tetrabelodon osborni sp. nov". American Journal of Science. 41 (246): 522–529. Bibcode:1916AmJS...41..522B. doi:10.2475/AJS.S4-41.246.522. S2CID 130158099.
  20. Korth, William W.; Emry, Robert J. (1997). "The Skull of Anchitheriomys and a New Subfamily of Beavers (Castoridae, Rodentia)". Journal of Paleontology. 71 (2): 343–347. doi:10.1017/S0022336000039251. ISSN 0022-3360. JSTOR 1306468. S2CID 86110621.
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