Looser sand of the Valentine Formation sloping back from its contact with the Rosebud Formation on the Niobrara River at the Valentine, Nebraska, type location. Water from the Ogallala Aquifer seeps from the base of the Valentine down the face of the Rosebud.[1]
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 Miocene epoch of the Neogeneperiod and is particularly noted for Canid fossils.[2][3] This unit consists of loosely-consolidated sandstone that crumbles easily. These sands carry the water of the Ogallala Aquifer and is the source of much of the water in the Niobrara River.[1] 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. Although 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 name to any mappable lithology beyond the type location have been abandoned. Even so, opaline sandstone[4] has been used to refer to this green-gray opalized conglomerate sandstone that is widely found in the lower Ogallala Formation.
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[5] 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.[6][4] 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.
The Valentine Formation presents white, buff, 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,[7]
particularly Niobrara chalk cobbles and chalk sand.[8] Thin, localized beds of caliche are abundant. A specific index stone for the Valentine is the lenticular beds of grey-green opaline sandstone. Locally thick beds of volcanic ash are associated with the underlying opaline sandstone
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.[9][10]
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[12]). 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.
^ ab"Geologic Formations". Niobrara National Scenic River. National Park Service. Retrieved 2024-02-24. Valentine Formation -- Beneath the Ash Hollow is the Valentine Formation. This loosely-consolidated sandstone crumbles easily, but holds the primary source of the Niobrara River in this area: the Ogallala, or High Plains, aquifer. About 70% of the water in the river comes directly from groundwater.
^"Geologic Unit: Valentine". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved 2020-06-05.
^ abJohn 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).
^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, ...
^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 ...
^ abcdefgCzaplewski, Nicholas J. (1991). "Miocene Bats from the Lower Valentine Formation of Northeastern Nebraska". Journal of Mammalogy. 72 (4): 715–722. doi:10.2307/1381832. ISSN0022-2372. JSTOR1381832.
^ abcdefghijklmnopqrstuvwWang, Xiaoming; Tedford, Richard H.; Taylor, Beryl E. (1999). "Phylogenetic systematics of the Borophaginae (Carnivora, Canidae)". Bulletin of the American Museum of Natural History (243). hdl:2246/1588.
^ abWerdelin, 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.
^ abcdefghijklmnoVoorhies, 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. ISSN0272-4634. JSTOR4523860.
^ abcBarnosky, Anthony D. (1986). "New Species of the Miocene Rodent Cupidinimus (Heteromyidae) and Some Evolutionary Relationships within the Genus". Journal of Vertebrate Paleontology. 6 (1): 46–64. doi:10.1080/02724634.1986.10011598. ISSN0272-4634. JSTOR4523073.
^ abcKorth, William W. (2007). "The Skull of Nothodipoides (Castoridae, Rodentia) and the Occurrence of Fossorial Adaptations in Beavers". Journal of Paleontology. 81 (6): 1533–1537. doi:10.1666/05-110.1. ISSN0022-3360. JSTOR4541271. S2CID129875541.
^ abcBreyer, John A. (1983). "The Biostratigraphic Utility of Camel Metapodials". Journal of Paleontology. 57 (2): 302–307. ISSN0022-3360. JSTOR1304654.
^ abcHolman, J. Alan (1976). "A New Peltosaurus (Reptilia, Sauria, Anguidae) from the Upper Miocene of Nebraska". Journal of Herpetology. 10 (1): 41–44. doi:10.2307/1562926. ISSN0022-1511. JSTOR1562926.
^ abHolman, J. Alan (1995). "A New Species of Emydoidea (Reptilia: Testudines) from the Late Barstovian (Medial Miocene) of Cherry County, Nebraska". Journal of Herpetology. 29 (4): 548–553. doi:10.2307/1564737. ISSN0022-1511. JSTOR1564737.
^Meszoely, Charles (1966). "North American Fossil Cryptobranchid Salamanders". The American Midland Naturalist. 75 (2): 495–515. doi:10.2307/2423407. ISSN0003-0031. JSTOR2423407.
^Gabel, Mark L.; Backlund, Douglas C.; Haffner, Jacob (1998). "The Miocene Macroflora of the Northern Ogallala Group, Northern Nebraska and Southern South Dakota". Journal of Paleontology. 72 (2): 388–397. doi:10.1017/S0022336000036362. ISSN0022-3360. JSTOR1306723. S2CID130146978.