The placement of the beds originally described as Ogallala within the Neogene of the standard time scale is based entirely on the contained vertebrate fossils. Vertebrate fossils also are the primary evidence used in the controversial question of Miocene vs. Pliocene age for all or part of the Valentine member. However, only four known localities in northwestern Kansas yield assemblages of fossil vertebrates that can be used for regional stratigraphic purposes. One locality in Yuma County, Colorado, is near enough to our area to be stratigraphically significant in this study. The four local faunas in Kansas are not well distributed over the area under study, as two are in Wallace County, another in adjacent Sherman County, and the fourth in Phillips County. Other collections are too poorly known or too fragmentary to be of use.
No significant studies of vertebrate fossils from the Ogallala formation in northwestern Kansas have been made in the 20 years from 1935 to 1955. It is our judgment, based on field observations made over a period of 15 years, that further detailed collecting of vertebrate fossils in Ogallala sediments in northwestern Kansas would be profitable, and might contribute greatly to a knowledge of detailed stratigraphy of the formation. In general, bones in Ogallala sediments are silicified, and hence well preserved.
We are indebted to Robert W. Wilson, vertebrate paleontologist in the Museum of Natural History, The University of Kansas, for the following lists of vertebrates represented in local assemblages in the Ogallala formation of northwestern Kansas and nearby Colorado. Wilson has searched the literature for all available records, and has brought the names of the several species up to date as far as possible, but we, of course, assume full responsibility for any errors that may be present.
Wray local fauna
Ogallala formation, Hemphillian, Yuma County, Colorado (Cook, 1922, 1922a, 1927, 1930; Cook and Cook, 1933; Stirton, 1936, 1944; Frick, 1937; Wood and others, 1941; Simpson, 1933). A tentative faunal list based on the above citations follows:
|Osteoborus pugnator||?Peraceras ponderis|
|Machairodus coloradensis||Aphelops longinaris|
|Amebelodon hicksi||Prosthennops sp.|
|Amebelodon paladentatus||Megatylopus cf. M. gigas|
|Neohipparion occidentale||?Alticamelus sp.|
|Pliohippus, sp. indet.||Sphenophalos? figginsi|
|Teleoceras [Paraphelops] yumensis||Pediomeryx|
As nearly as can be determined from all the evidence available, the Wray local fauna occurs in lower Ash Hollow deposits.
Edson local fauna
Ogallala formation, Hemphillian, sec. 25 T. 10 S., R. 38 W., Sherman County, Kansas (Hibbard, 1939; Simpson, 1933; Stirton, 1936; Wilmarth, 1938; Wood and others, 1941).
|Plioambystoma kansensis||Peromyscus martinii
[Onychomys martinii acc. Hoffmeister, 1945]
|Scaphiopus pliobatrachus||Oryzomys? pliocoenicus|
|Bufo arenarius||Osteoborus cynoides|
|Bufo hibbardi||Leptocyon shermanensis
[Vulpes? acc. to Stirton]
|Chelydra sp.||Martinogale alveodens|
|Testudo sp.||Plesiogulo marshalli|
|Grus nannoides||Adelphailurus kansensis
[Pseudaelurus acc. to Simpson]
|Colymbus nigricollus||Machairodus cf. M. catacopis|
|Scolopacidae, sp.||Pliohippus interpolatus|
|Corvidae, sp.||Nannippus nr. N. lenticulare|
|Talpidae, sp.||Aphelops mutilus|
|Mylagaulus monodon||Prosthennops serus|
|Kansasimys dubius||Megatylopus gigas|
|Sciurus sp.||Pliauchenia sp.|
|Perognathus dunklei||Procamelus sp.|
Stratigraphically the position of the Edson local fauna is clearly in the upper part of the Ash Hollow member. The Kimball-Ash Hollow contact was not observed at this locality; it may be only a few feet above the position of the fauna.
Rhinoceras Hill local fauna
Ogallala formation, Hemphillian; SE NE sec. 11, T. 11 S., R. 38 W., Sherman County, Kansas (Hesse, 1935; Stirton, 1936; Wilmarth, 1938; Wood and others, 1941).
|Osteoborus nr. O. cyitoides||Aphelops mutilus|
|Machairodus catacopis||Teleoceras fossiger|
|Amebelodon fricki||Megatylopus? sp.|
|Pliohippus interpolatus||Pliauchenia? sp.|
|Neohipparion sp.||Cervidae sp.|
|Nannippus? sp.||Capromeryx altidens|
On the basis of all evidence available, the Rhinoceras Hill local fauna occurs in the middle of the Ash Hollow member.
Lost Quarry local fauna
Ogallala formation, Hemphillian; NW sec. 1, T. 15 S., R. 38 W., Wallace County, Kansas (Hibbard, 1934; Stirton, 1936).
|Osteoborus cynoides||Pratifelis martini|
|?Aelurodon haydeni||?Pliohippus interpolatus|
|Agriotherium sp.||Nannippus sp.|
The stratigraphic position of this local assemblage is not well known, but seemingly it is in the upper part of the Ash Hollow member.
Long Island Quarry
Ogallala formation, Hemphillian?; Overton Farm, south of Long Island, Phillips County, Kansas. This quarry has yielded few fossils other than Teleoceras fossiger, but on the bases of its topographic position and of the occurrence of fossil plants in nearby localities it is judged that this quarry is situated in the lower to middle part of the Ash Hollow member.
Plate 5--Details of fossils in Ogallala rocks. A. Hulls of Stipidium as they appear in matrix; NW NE sec. 34, T. 1 S., R. 27 W., Decatur County, Kansas. B. Natural casts of Lymnaea lavernensis and Helisoma valens from soft diatomaceous limestone; center W line, sec. 3, T. 12 S., R. 20 W., Ellis County, Kansas.
The occurrence of these local fossil vertebrate faunas in the Ash Hollow member of the Ogallala formation not only firmly establishes the Pliocene age of this member in northwestern Kansas but allows firm correlation with the Ogallala formation (group, according to Nebraska classification) in Nebraska, where fossil vertebrates from rocks of this age are said to be better known. It is obvious, however, that detailed stratigraphic correlations cannot be made on the basis of these meager and poorly distributed assemblages of fossil vertebrates. As a matter of fact, we did not find it possible to utilize these faunas in local correlations.
The question of delineation of the Pliocene-Miocene boundary line in the Great Plains region is not within the province of this report. This is a problem involving the correlation of vertebrate faunas from this region with fossil assemblages in Europe, and the further correlation in Europe of the beds containing fossil vertebrates with the typical marine units originally defined as Pliocene and Miocene. The term Neogene, which is used generally in Europe to include both of these units, is therefore used as a general age designation for the Ogallala formation, as it comprises a sedimentary and lithologic unit.
Fossil molluscan assemblages have been used extensively for stratigraphic purposes in the Pleistocene of the Great Plains region, but hitherto have not been used for stratigraphic correlation of nonmarine Pliocene or Miocene beds in interior North America. They have proved useful to us, however, in stratigraphic studies of the Ogallala formation in this region.
Determination of the kinds of mollusks in the Ogallala formation has been attended by unusual difficulties, because except for a single locality in Wallace County (center North line sec. 29, T. 12 S., R. 42 W.) where a few entire shells are preserved in silty clay or in silicious nodules, mollusks in the Ogallala sediments are represented only by more or less imperfect external molds of the shells that were entombed in soft, diatomaceous limestone. Thus, for the most part, species have been determined by comparison of known species from older or younger rocks with casts made from these molds of shells. This method has been generally satisfactory, but not entirely so, and a few species remain undetermined.
Casts of gastropods were made by the following method. Large pieces of limestone, selected in the field because molds (cavities) were obvious on a weathered surface, were sawed into slabs about 3/4 inch thick, and carefully dried in an oven. "Ward's Bioplastic" was heated to 140° F. after the addition of the catalyst; heating reduces the viscosity of the syrupy plastic and increases the penetrability of the plastic into the rock. Slabs of limestone were placed in the warmed plastic contained in dishes of convenient size and these were evacuated and maintained at a pressure of approximately one-fifth atmosphere for 30 minutes. This treatment drew the air from the porous rock and allowed the plastic to penetrate the molds. After the catalyzed plastic had congealed, the blocks of limestone encased in plastic were sanded on all free surfaces to expose the rock. These were etched in hot dilute hydrochloric acid, which removed all the denser parts of the rock not infiltrated by plastic. The residue after acid treatment is a reticulum of plastic, duplicating the former pore spaces of the limestone, within which the casts of gastropod molds may be found. Many satisfactory casts were obtained by this tedious method, but several difficulties were encountered. Secondary deposits of calcite or other minerals in some molds prevented satisfactory casting, and in a few slabs the limestone was too dense to allow satisfactory penetration of the viscous plastic to the molds. The elapsed time during which the slabs of rocks are in plastic under reduced pressure is critical; too short a period does not allow proper penetration of the molds by the plastic. If possible, it is best to allow the limestone to remain under reduced pressure until the plastic has congealed.
At one locality (center West line sec. 3, T. 12 S., R. 20 W., Ellis County) almost perfect natural casts, especially of large species of gastropods, were found in diatomaceous limestone lentils. Many of these casts could be removed merely by breaking the rock. Natural casts of Lymnaea lavernensis and Helisonia valens are shown on Plate 5B.
Bioplastic casts made by this infiltration technique are almost as useful as the actual shells for identification of species. The shape and dimensions of the shell, the number and relative convexity of the whorls, the shape and size of the aperture, and even the details of surface sculpture of the original shell are more or less perfectly reproduced in a cast. Inasmuch as most of the molluscan species in Ogallala rocks may also be represented by well-preserved shells in older or younger rocks, comparison of the casts with shells of known species made firm identifications relatively easy. The apertural lamellae of pupillid gastropods are not, of course, reproduced in plastic casts, but generally speaking, other characters can be used for identification; several gastropods thought to represent species of pupillids still remain unidentified, however, because of the failure to cast all details of their tiny shells.
Fourteen species of mollusks have been identified with certainty from Ogallala sediments in northwestern Kansas; the occurrence of these fossils at eight localities is shown on Figure 3. Molds of mollusks have been observed in soft diatomaceous limestone lenses at other localities, but inasmuch as the labor involved in preparing, removing, and cleaning satisfactory casts is considerable, only those localities judged to be stratigraphically significant are considered here. The details of the chalky-white casts are difficult to photograph, so shells from other sources have been used to illustrate the faunas, shown on Plates 6 and 7.
Plate 6--Fossil mollusks from Ogallala formation. a. Physa hawni Lea; b. Physa anatina Lea; c. Calipyrgula hibbardi Leonard and Franzen; d. Calipyrgula senta Leonard and Franzen; e. Lymnaea lavernensis Leonard and Franzen; f. Lymnaea macella Leonard. All figures X 7.6, except e, X 4.6 [images enlarged for web viewing].
Plate 7--Fossil mollusks from Ogallala formation. g. Promenetus blancoensis Leonard; h. Helisoma goodrichi Leonard and Franzen; i. Helisoma parallelum Leonard and Franzen; j. Pseudosuccinea columella (Say); k., l. Plastic casts of Promenetus blancoensis Leonard; m. Vertigo ovata Say; n. Immature example of Lymnaea macella Leonard; o. Plastic cast of immature example of Lymnaea macella Leonard; p. Helisoma antrosum (Conrad); q. Pupoides albilabris (C. B. Adams); r. Helisoma valens Leonard and Franzen. All figures X 6 [images enlarged for web viewing].
Generally speaking, the molluscan fauna preserved in the Ogallala formation in northwestern Kansas is characterized by species of planorbid snails; these animals are pulmonate (air-breathing) aquatic gastropods, generally capable of living in temporary pools subject to complete drying from time to time; the two species of Physa have similar environmental tolerances. The ecological requirements of Lymnaea macella are not known, but judging from its faunal associations, it lived in permanent bodies of water. Lymnaea lavernensis is an extinct animal, but it is best known from lake-bed deposits in northwestern Oklahoma (Leonard and Franzen, 1944) where it is associated with large populations of branchiate (gill-breathing) gastropods, from which it may be concluded that it thrives best in permanent bodies of water. Pseudosuceinea is often found out of water, but in regions where it survives today, it frequents permanent bodies of water more often than not. The two species of Calipyrgula are branchiate gastropods present in enormous populations in lacustrine deposits of northwestern Oklahoma, from which it may be concluded that their occurrence is limited to permanent lakes or ponds. They are associated there with a species of Viviparus, also a branchiate gastropod.
Figure 3--Check list of fossil mollusks. The symbols V, AH, and K indicate the occurrence of mollusks in the Valentine, Ash Hollow, and Kimball members in the Almena section.
|C N line sec. 5, T. 1 S., R. 14 W., Smith Co.||NW NE sec. 30, T. 1 S., R. 19 W., Phillips Co.||W2 sec. 16, T. 2 S., R. 21 W., Norton Co. (Almena section)||NW NW sec. 2, T. 4 S., R. 24 W., Norton Co.||C N line sec. 34, T. 5 S., R. 25 W., Norton Co. (New Almelo section||C W line sec. 3, T. 12 S., R. 20 W., Ellis Co.||SW sec. 7, T. 11 S., R. 37 W., Logan Co.||C N line sec. 29, T. 12 S., R. 42 W., Wallace Co.|
|Total Number of species||5||6||7||6||5||6||5||8||6||9|
Terrestrial snails are poorly represented in Ogallala sediments, as far as known; only two species have been identified with certainty, Pupoides albilabris and Vertigo ovata. Both are known from the Laverne of northwestern Oklahoma and from sediments of early Pleistocene age in southwestern Kansas; both are living in western Kansas. Pupoides albilabris frequents the grasslands of the plains; its ability to survive long periods of aridity and high temperature is well known. Vertigo ovata is limited in distribution in western Kansas to a marsh habitat in the Meade Artesian Basin. It is likely, judging from the usual associates of Pupoides albilabris and of Vertigo ovata, that other genera and species of pupillid gastropods occur in Ogallala sediments, especially as a diversity of such mollusks occur either in older or in younger rocks in the plains region. Perhaps their small size, which may preclude or render difficult long preservation of the molds of their shells in soft limestone, accounts for their seeming absence. The absence of shells of large forest-dwelling gastropods, such as Polygyra and Anguispira, conforms to the general picture of a prevalent grassland habitat in northwestern Kansas during the deposition of Ogallala rocks, a picture firmly drawn from the widespread remains of grasses and forbs, and the almost complete absence of remains of trees (fruits of the hackberry, Celtis willistoni, being a notable exception) in Ogallala sediments.
The known molluscan fauna from the oldest Ogallala deposits in northwestern Kansas is composed of species characteristic of the Laverne faunal assemblages known from northwestern Oklahoma, and that from the youngest Ogallala rocks mostly of species represented in Pleistocene (Nebraskan) rocks in southwestern Kansas. This trend is best seen in the faunules collected from three horizons at the Almena section (W2 sec. 16, T. 2 S., R. 21 W., Norton County) where mollusks occur in Valentine, Ash Hollow, and Kimball members. The Valentine assemblage is preserved as imperfect molds of gastropods in soft limestone, but the known species are characteristic of the Laverne fauna; Lymnaea lavernensis, Helisoma valens, and two species of Calipyrgula are common here, and there is evidence of the occurrence of a species of Viviparus, but identifiable casts of this gastropod were not obtained. In Ash Hollow rocks at this locality Lymnaea lavernensis does not occur, nor does either of the two species of Calipyrgula, but a few Laverne species, such as Pseudosuccinea columella, persist into this member. The Kimball assemblage, represented by numerous well-preserved molds in limestone near the top of the section, lacks all diagnostic Laverne species, and the complexion of the assemblage, is essentially similar to that of earliest Pleistocene faunas (Frye and Leonard, 1952, pl. 14, fig. 6, and p. 148-155). Both the Ash Hollow and the Kimball assemblages are predominantly composed of planorbid species, which fact suggests that the ponds in which the mollusks lived were not necessarily permanent. The limestones in the Ogallala formation in which molds of fossil mollusks occur in northwestern Kansas are without exception richly diatomaceous. Unfortunately, the contained diatom floras have not been studied, and therefore are not reported here.
The faunal assemblages of mollusks in the Ogallala formation undergo a typological evolution (and perhaps some organic evolution as well) in which there is an orderly but gradual change in the complexion of the assemblages from Valentine to Kimball. Therefore in terms of stratigraphic utility the assemblages present a different aspect than that of the molluscan assemblages in the overlying Pleistocene formations, in which wide-scale extinctions, migrations, and other changes in faunas come with dramatic suddenness. Instead of the abrupt faunal discordances present in Pleistocene deposits in northwestern Kansas, Ogallala sediments in the same region show unmistakable change of the molluscan faunas by gradual transitions throughout Ogallala time. More than 75 percent of the mollusks in the Valentine assemblage at the Almena section (Frye and Leonard, 1952, pl. 6, 7; fig. 4) consist of diagnostic Laverne species; less than 50 percent of the mollusks in Ash Hollow deposits at this locality and others are diagnostic Laverne species, and less than 10 percent of the Kimball fauna at the Almena section are typical Laverne mollusks. In summary, it is possible to place molluscan faunas of the Ogallala formation in stratigraphic sequence in any section in which there is a reasonably good assemblage of mollusks, but the unusual precision of stratigraphic placement possible in the Pleistocene in this region is not feasible in the Ogallala. In at least one locality, for example, local conditions seem to have been favorable for the survival of certain Laverne species into the lower Ash Hollow; in the sequence of Ogallala sediments exposed in a road cut in the center of the West line of sec. 3, T. 12 S., R. 20 W., Ellis County, Lymnaea lavernensis, Helisoma valens, and other Laverne species occur in strata that seem to be lower Ash Hollow beds. The stratigraphic placement of this fossiliferous limestone lentil, however, is not conclusively shown, because plant fossils have not been found in close stratigraphic proximity to the molluscan remains. If our judgment of this local situation is correct, it may be assumed that although certain species characterize Valentine strata, they are not limited to beds of Valentine age. Generally speaking, however, Valentine, Ash Hollow, and Kimball molluscan assemblages are so distinctly characterized that confusion among them is extremely unlikely.
Kansas Geological Survey, Geology
Placed on web Aug. 4, 2011; originally published March 1956.
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