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Stratigraphic Paleontology

General Considerations

The guiding principles of stratigraphic paleontology have been well known for many years, but since they are not always borne in mind, even by those whose work is dependent upon them, a review of the most important considerations seems appropriate. (1) Fossils are useful in stratigraphic studies only when they occur in identifiable and characteristic faunal assemblages of limited vertical range; they thus become in essence a real part of the distinctive lithology of the rocks that contain them. (2) Distinctive assemblages of fossils must occur at many localities over a wide area if they are to be useful to the stratigrapher; otherwise the sites of occurrence, although perhaps interesting, become mere curiosities to the student of stratigraphy and without value for correlation of strata of rocks. (3) The principle of superposition applies to assemblages of fossils as well as to the rocks themselves, even though the vertical sequence of distinctive faunal assemblages may not be readily correlatable with stratigraphic schemes based on other criteria. And (4) it must be kept in mind that the validity of interpretations of past ecological conditions, based on the presence of organic remains in the rocks, is invariably dependent upon a knowledge of living representatives of the same or similar groups of organisms.

In the light of these principles, the groups of fossil organisms of stratigraphic significance in the Pleistocene rocks of Kansas become stringently limited. A few fossil seeds of grasses have been found at one or two exposures (SE sec. 20, T. 13 S., R. 11 W., Lincoln County) and pieces of well-preserved wood have been recovered from Kansas till (NW sec. 10, T. 6 S., R, 20 E., Atchison County) but these sporadic occurrences obviously have no practical importance in stratigraphic studies. The zygospore cases of some kind of alga resembling Chara are known to occur at several exposures in sediments of Nebraskan (SW sec. 22, T. 33 S., R. 29 W., Meade County) or late Kansan (NW sec. 36, T. 14 S., R. 11 W., Russell County; NW sec. 28, T. 13 S., R. 10 W., Lincoln County) age. These fossils have no stratigraphic consequence at the present because they are too poorly understood taxonomically, their areal distribution is too greatly restricted, and their vertical range is not known. Studies of fossil pollens have been carried on at a single locality in Kansas (NE sec. 16, T. 6 S., R. 17 E., Atchison County) where pollen of spruce and pine (R. L. McGregor, Department of Botany, University of Kansas, personal communication) have been isolated from sediments in a marsh deposit of late Wisconsinan age. Exploitation of fossil pollen in Pleistocene sediments in the State might prove to be profitable in stratigraphic studies. The fact is, however, that paleobotany has not yet contributed significantly to a knowledge of Pleistocene stratigraphy in Kansas.

The shells of ostracods are known to occur at a few places in sediments of Nebraskan (SW sec. 22, T. 33 S., R. 29 W., Meade County) and late Kansan (SW sec. 13, T. 30 S., R. 23 W., Clark County; SW sec. 35, T. 15 S., R. 2 E., Dickinson County; SE sec. 22, T. 14 S., R. 12 E., Wabaunsee County; and other localities) age but no systematically organized and intensive search for these minute fossils has ever been undertaken in the State. Exploitation of fossil ostracods for stratigraphic purposes in Pleistocene deposits in Kansas must await the acquisition of a knowledge of the living ostracod fauna of the region, which is at present almost entirely lacking. Studies of living and fossil ostracods, such as those currently in progress in Illinois (Kegling, 1951) might well prove to be profitable, especially where lacustrine sediments occur. Pending the development of a better knowledge of these organisms, fossil ostracods are virtually useless in studies of Pleistocene stratigraphy in Kansas.

In large measure, vertebrate fossils are also of limited utility for state-wide studies of stratigraphic correlation in the Pleistocene sediments under consideration. The early studies of Hay (1917; 1917a, 1924) and others were often conducted without critical attention to the stratigraphic occurrence of fossils, or identifications of the animals were based on inadequate or poorly preserved materials. Recent intensive studies of fossil vertebrates in sediments of Nebraskan and Kansan age (Hibbard, 1937; 1937a; 1937b; 1938; 1939; 1940; 1940a; 1941; 1941a; 1941b; 1941c; 1942; 1943; 1943a; 1944; 1948; 1949a; 1949b; 1950; 1951; 1951a; 1952a) in southwestern Kansas and at a few exposures in Kansan sediments in the central part of the State (Frye, Leonard, and Hibbard, 1943; Hibbard, 1952) have resulted in a highly detailed knowledge of Pleistocene vertebrates at a small number of exposures of limited areal distribution and restricted vertical range. While the value of these studies is fully recognized, the restricted areal and vertical distribution of the described assemblages of vertebrate fossils removes them from practical consideration in stratigraphic studies over the State. The vertebrate paleontology of Illinoian and Wisconsinan deposits in Kansas is essentially unknown, and since the reported occurrence of vertebrate fossils in sediments of these ages is sporadically and erratically distributed, remains of vertebrate animals contained in these portions of the Pleistocene rocks in Kansas have little practical utility in studies of stratigraphic correlation. That fossil vertebrates have been a valuable aid in studies directed toward elucidating the major subdivisions of Pleistocene rocks in the midcontinent region and intercontinental correlations of major subdivisions cannot be denied, but for reasons already stated, the field stratigrapher cannot feasibly utilize them in detailed correlation studies within Kansas.

In view of the present state of knowledge of the several kinds of organic remains preserved in Pleistocene deposits in Kansas, the shells of Mollusca are certainly the most widely useful fossils for purposes of stratigraphic correlation. The shells of mollusks occur in distinctive and recognizable assemblages of species, the assemblages are reasonably well distributed over much of the State (Fig. 5), there is a known vertical sequence of distinctive faunal assemblages characterizing each major cycle of Pleistocene deposition (Fig. 11), and in the case of Wisconsinan deposits, molluscan faunal aggregations even permit subdivisions of massive silts into zones corresponding to recognized lithologic units in the glaciated portion of the Mississippi Valley. Furthermore, since the ecological requirements of most mollusks are known, at least in their broad aspects, paleoecological interpretations of a conservative nature may be made with a reasonable expectation of accuracy. No claim for inerrancy in the use of these fossils can be made; distinctive assemblages are often lacking at critical exposures, the shells are highly susceptible to weathering and to destruction by abrasion in coarse fluviatile elastics, and identification of the kinds of mollusks, based on the shells alone, is often fraught with difficulty and a certain degree of inaccuracy. These admitted limitations are largely nullified by the ease with which shells are preserved in many sediments, notably silts, the widespread occurrence of shells where vertebrate fossils are rare or absent, the relatively high population density of most kinds of mollusks where they occur at all, and their sedentary habits as animals, from which it usually may be inferred that the shells were deposited in Pleistocene sediments not far from the places where the animals lived.

Figure 5--Maps of Kansas showing geographic distribution of Pleistocene molluscan faunas listed in this report.

Molluscan Faunal Assemblages in Nebraskan Deposits

A total of 34 kinds of fossil mollusks are known to be associated with deposits of Nebraskan age in Kansas; their occurrence and distribution at 11 localities are shown in Figure 6, and illustrations of a representative faunal assemblage are shown on Plate 14. At each of these localities, except one, shells of mollusks occur in fine silts and clays, or in sandy silts of lacustrine or fluviatile origin. Shells in sandy lentils in the uppermost 4 feet of the David City gravel (SE sec. 6, T. 2 S., R. 20 E., Doniphan County) were first discovered and collected by Raymond C. Moore; additional collections of shells from David City gravels and from lentils of sand or sandy silt in Nebraska till at the Iowa Point section were subsequently made by Frye, his students, and Leonard from time to time as excavation by the State Highway Department at this site exposed successive lentils of fossiliferous sand or silt.

Figure 6--Occurrence of fossil mollusks in Nebraskan deposits at 11 localities in Kansas. Asterisk in location info indicates collection from test hole samples. An Acrobat PDF version of this figure is available.

Molluscan species	Faunal localities
	SE sec. 6, T. 2 S., R. 20 E., Doniphan	SW sec. 12, T. 29 S., R. 8 W., Kingman	*SW sec. 31, T. 30 S., R. 26 W., Meade	*SW sec. 34, T. 30 S., R. 28 W., Meade	*SW sec. 33, T. 30 S., R. 29 W., Meade	*NW sec. 6, T. 31 S., R. 30 W., Meade	NW sec. 19, T. 32 S., R. 28 W., Meade	SW sec. 22, T. 33 S., R. 29 W., Meade	*NE sec. 33, T. 34 S., R. 29 W., Meade	SW sec. 35, T. 34 S., R. 30 W., Meade	SW sec. 36, T. 34 S., R. 31 W., Seward
Nebraskan or older to Recent
Cionella lubrica (Muller)
Ferrissia paralleIa (Haldemon)
Ferrissia rivularis (Say)
Gastrocopta holzingeri (Sterki)
Gastrocopta tappaniana (C. B. Adams)
Hawaiia minuscula (Binney)
Helicodiscus singleyanus (Pilsbry)
Helisoma antrosa (Conrad)
Lymnaea humilis modicella (Say)
Physa anatina Leo
Pisidium sp.
Pupoides albilabris (C. B. Adams)
Retinella electrina (Gould)
Sphaerium sp.
Strobilops cf. labryinthica
Succinea grosvenori Lea
VaIIonia gracilicosta Reinhardt
Vertigo milium Gould
Zonitoides arboreus (Say)
Nebraskan to Yarmouthian
Carychium perexiguum Baker
Deroceras aenigma Leonard
Strobilops sparsicosta Baker
Restricted to Nebraskan
Amnicola crybetes Leonard
Gastrocopta paracristata Franzen and Leonard
Gastrocopta rexroadensis Franzen and Leonord
Gyraulus enaulus Leonard
Lymnaea diminuta Leonard
Lymnaea macella Leonard
Lymnaea perexilis Leonard
Lymnaea turritella Leonard
Menetus kansasensis Baker
Polygyra mooreana (Binney)
Promenetus blancoensis Leonard
Vertigo hibbardi Baker

Plate 14--A representative assemblage of mollusks from Nebraskan deposits in Kansas. All figures enlarged approximately 5 times natural size. An Acrobat PDF version of this plate is available that shows more detail.

Shells illustrated in figures d, e, h, i, o, q, r, s, t, u, v, and x are restricted to Nebraskan deposits in Kansas. All are extinct except fig. v (Polygyra mooreana) which seem identical with a species still living in southern Texas. Shells represented by figures c, g, and j are common in Nebraskan deposits, but they appear also in faunal assemblages in Kansan sediments. Other species illustrated are typical of Nebraskan faunal assemblages, but they range into Wisconsinan or Recent time (Fig. 11).

Cionella lubrica (Müller) Pupoides albilabris (C. B. Adams) Deroceras aenigma Leonard Vertigo hibbardi Baker Gastrocopta rexroadensis Franzen and Leonard Vallonia gracilicosta Reinhardt Strobilops sparsicosta Baker Amnicola crybetes Leonard Gastrocopta paracristata Franzen and Leonard Carychium perexiguum Baker Gastrocopto tappaniana (C. B. Adams) Retinella electrina (Gould) Hawaiia minuscula (Binney) Ferrisia parallela (Haldeman) Promenetus blancoensis Leonard Zonitoides arboreus (Say) Lymnaea macella Leonard Lymnaea turritella Leonard Lymnaea diminuta Leonard Gyraulus kansasensis Baker Gyraulus enaulus Leonard Polygyra mooreana (Binney) Helisoma antrosa (Conrad) Lymnaea perexilis Leonard Succinea grosvenori Lea Physa anatina Lea

Known occurrences of fossiliferous sediments of Nebraskan age in Kansas are limited in number, but the incidence of distinctive molluscan faunules in such deposits in Seward and Meade counties in the southwest, in Kingman County in the south-central, and in Doniphan County in the northeastern part of the State gives these characteristic molluscan assemblages a statewide, if sparse, distribution. The occurrence in each of these areas of groups of molluscan species that are known to be restricted to sediments of Nebraskan age does, however, make these faunal assemblages of significant value in studies of stratigraphic correlation.

The assignment of a Nebraskan age to the fossil mollusks discussed here is based on several considerations, among the most important of which is the direct relation of this distinctive faunal assemblage to glacial till of unquestioned Nebraskan age, and the positive establishment of its stratigraphic position with respect to Pearlette volcanic ash and its associated characteristic Kansan fauna. Twelve species among the 34 are not known to occur in older or in younger sediments, and of these restricted species, five of them (Amnicola crybetes, Lymnaea diminuta, L. perexilis, Menetus kansasensis, and Promenetus blancoensis) occur in David City gravel and Nebraska till in Doniphan County where the stratigraphic relations are known clearly. At the Kingman County locality (Fig. 6) these same five species occur with several others (Lymnaea macella, L. turritella, and Vertigo hibbardi) which are of limited vertical range (A. B. Leonard, 1952a). Furthermore, the Kingman County exposure lies topographically below adjacent widespread deposits known to be of late Kansan age, and the degree of weathering and amount of caliche accumulation in the sediments associated with the molluscan faunule is further indication of Nebraskan age; In southwestern Kansas, the five restricted species known from David City gravel and Nebraska till are associated with seven others (Gastrocopta paracristata, G. rexroadensis, Gyraulus enaulus, Lymnaea macella, L. turritella, Polygyra mooreana, and Vertigo hihbardi) also known to be restricted in vertical range. Here the relation of the fossiliferous sediments to Afton soil is not always entirely clear, but the faunal assemblages are stratigraphically below, and readily separable on a faunal basis from the molluscan assemblages associated with the Pearlette volcanic ash and related silts, previously shown to be of late Kansan age (Frye, Swineford, and Leonard, 1948). Three species of mollusks (Carychium perexiguum, Deroceras aenigma, and Strobilops sparsicosta) occur in assemblages associated with deposits of Kansan age as well as in the assemblages under discussion, but in Kansan sediments these three species are associated with a distinctively different aggregation of molluscan species.

Further evidence of the Nebraskan age of the molluscan families considered here is the absence in them of a number of genera (Aplexa, Discus, Euconulus, Hendersonia, Oxyloma, Planorbula, Pomatiopsis, Stenotrema, and Valvata) which are of common occurrence in sediments of Kansan age. In addition, a number of genera that occur in both horizons are represented by different species at the two levels. The following incomplete list serves to emphasize this observation.

Nebraskan species	Kansan species
Amnicola crybetes	Amnicola limosa parva
Gastrocopta paracristata	Gastrocopta cristata
Gastrocopta rexroadensis	Gastrocopta proarmifera
Gyraulus enaulus	Gyraulus pattersoni
Lymnaea perexilis	Lymnaea reflexa
Lymnaea diminuta	Lymnaea parva
Menetus kansasensis	Menetus pearlettei
Polygyra mooreana	Polygyra texasiana
Promenetus blancoensis	Promenetus umbilicatellus
Vertigo hibbardi	Vertigo ovata

It is usual in Pleistocene sediments, except eolian silts, to find shells of terrestrial species of mollusks mingled with the shells of species known to live in or near water, and the safe assumption is that shells of terrestrial species are washed into ponds and streams from surrounding slopes. Drift lines of modern lakes and ponds often contain, along with miscellaneous organic and other detritus cast up by wave action, the shells of both aquatic and terrestrial species of mollusks. The aggregate molluscan fauna from Nebraskan sediments in the State reflects this tendency for the shells of mollusks from various habitats to be deposited together. Slightly more than half (19) of the total number of species represented are those of terrestrial habit; 15 species are typically aquatic in habit. Among the several exposures of Nebraskan sediments from which molluscan faunules have been obtained, all contained some mixture of terrestrial and aquatic species, except the Iowa Point exposures in Doniphan County, where, thus far, none but aquatic species have been collected.

Among the aquatic species, Amnicola crybetes represents the branchiate or gill-bearing snails, which are limited in habitat to permanent and relatively silt-free waters, since they are dependent upon water for respiration. Such snails cannot survive more than brief periods of drying. Species of Menetus, Promenetus, Gyraulus, and Ferrissia, while not branchiate snails, are susceptible to drying, and die after extended exposure to dessication. Some of the living species of Physa, Lymnaea, and Helisoma, on the other hand, are able to survive extended periods without the presence of open water, although they require a relatively high humidity for long survival. Even Sphaerium, a lamellibranch mollusk, is able to survive the lack of open water for considerable periods of time by taking advantage of the relatively high humidity found in cracks in the bottoms of drying ponds and streams, or in the burrows of worms and crayfish.

At the Iowa Point section, the molluscan faunule although not rich in species, is sufficient to indicate a terrain characterized by the presence of permanent ponds and streams. Even though the genera Physa, Helisoma, and Sphaerium are represented there, from the presence of the branchiate snail, Amnicola crybetes, and such aquatic pulmonates as Menetus kansasensis and Promenetus blancoensis which presumably were dependent upon permanent bodies of water, the conclusion may safely be drawn that such permanent ponds and streams were prevalent in the area at the time of the approach of the Nebraskan glacier. No safe inference can be drawn relative to prevailing mean temperatures in the area, although the climate may have been somewhat cooler than at present for some time previous to the actual approach of the moving Nebraskan ice. Many species of Amnicola, Menetus, and Promenetus now live at higher latitudes than Kansas, but there are many exceptions to this generalization; a species of Menetus survives in ponds in the artesian basin in Meade County, and many species of Amnicola are to be found in the humid but warm southeastern part of the United States. Amnicola seems not to be represented in the living molluscan fauna of Kansas; there is a record of a single living animal of this genus from a lake in Douglas County, where it may have been artifically introduced. In southeastern Kansas, Amnicola is relatively common as a fossil in post-Bradyan Wisconsinan stream terraces.

Since there are no terrestrial species known from Nebraskan sediments in the Iowa Point area, there is no evidence from which inferences can be drawn relative to the nature of the floral cover prevalent there in Nebraskan time.

In the Kingman County deposits, the molluscan faunule likewise indicates the presence of permanent bodies of water, for Amnicola crybetes, Ferrissia rivularis, Menetus kansasensis, and Promenetus blancoensis occur there, as well as several species of Lymnaea whose water requirements are not surely known. In this same assemblage are several terrestrial species, including Gastrocopta tappaniana, Helicodiscus singleyanus, Retinella electrina, and Zonitoides arboreus, which are known to inhabit woodlands or woodland border areas. Of these species, Retinella electrina is most dependent upon woodlands, and it does not occur as far west as Kingman County at the present time. Thus the terrestrial aspect of the molluscan faunule from Nebraskan deposits in Kingman County points to woodlands such as might be found along streams, but there is no indication of extensive forests. The typical forest-inhabiting genera, such as Anguispira, Mesodon, Mesomphix, Polygyra, and others that live in woodlands in eastern and southeastern Kansas, are not known from the Nebraskan sediments in Kingman County.

The widespread occurrence of Amnicola crybetes and other strictly aquatic species in sediments of Nebraskan age in southwestern Kansas is indicative of the presence of permanent ponds and lakes there in late Nebraskan time. It might be inferred that rainfall was considerably higher than now, or more equitably distributed throughout the year, or both, but since the fossiliferous deposits in question lie on the downthrown side of the Crooked Creek fault, permanent ponding of water might have been largely the result of poor drainage conditions rather than the result of any significant increase in rainfall. The availability of water from artesian sources is also a contributing factor, all of which adds to the difficulty of making sound judgment concerning rainfall conditions in the area in late Nebraskan time. The climate may have been somewhat cooler than at present, and perhaps lacked summer extremes of high temperature coupled with low humidity such as characterize the Great Plains today, but no indication of boreal climate may be inferred from the molluscan fauna. In fact, nothing more than cool temperate climate may be inferred from the molluscan assemblage at any of the Nebraskan localities, including the Iowa Point section, where it is obvious that the shells were incorporated in glacial outwash and till itself. This may be interpreted to suggest that the ice advanced rapidly, or that the presumed zone of boreal climate along the advancing ice front was a very narrow one at the latitude of northern Kansas.

A considerable number of terrestrial species of mollusks occurs among the several exposures of Nebraskan sediments in southwestern Kansas. Cionella lubrica, Strobilops sparsicosta, Retinella electrina, Zonitoides arboreus, and Polygyra mooreana comprise the component of the molluscan assemblage which may be thought of as being most dependent upon woodland habitats. Such species as Gastrocopta holzingeri, G. paracristata, G. rexroadensis, Helicodiscus singleyanus, Pupoides albilabris, Vallonia gracilicosta, and possibly Deroceras aenigma, although capable of thriving in woodlands, are also known (with reservations as far as the extinct species are concerned) to inhabit woodland borders or even open grasslands. Hawaiia minuscula and Pupoides albilabris are common although not abundant on the semi-arid prairies of western Kansas today. From these considerations it may be judged that a varied terrain characterized the local areas surrounding the ponds and streams in which the aquatic species of mollusks lived. Floral types ranged from open prairie to woodland border to woodland, but there is no indication of extensive areas of forest. Pollen studies might throw additional light on local vegetative types, but such studies have not been made, and most Nebraskan sediments known are presumed to have been unsuitable for the preservation of pollen.

Molluscan Faunal Assemblages in Kansan Deposits

Deposits of Kansan age in the State have yielded an abundant and distinctive molluscan fauna; a total of 64 species is known, of which 12 are extinct kinds known only from this Pleistocene stage, and a number of others, although living elsewhere in North America today, are for practical purposes, indices to Kansan sediments in the State. The occurrence and distribution of fossil mollusks at 26 localities in the State are shown on Figure 7, where the total assemblage is divided into a number of categories based on the relative usefulness of the fossils for stratigraphic purposes; a representative faunal assemblage is illustrated on Plate 15. The molluscan fauna associated with Kansan deposits has been previously treated by Frye, Swineford, and Leonard (1948) and by A. B. Leonard (1950) who described and illustrated the faunal assemblages in detail.

Figure 7--Occurrence of fossil mollusks in Kansan deposits at 26 localities in Kansas. Asterisk in location info indicates collection from test hole samples. An Acrobat PDF version of this figure is available.

Molluscan species	Faunal localities
	SW sec. 13, T. 30 S., R. 23 W., Clark	SW sec. 35, T. 15 S., R. 2 E., Dickinson	SE sec. 6, T. 2 S., R. 20 E., Doniphan	SW sec. 21, T. 13 S., R. 26 W., Gove	SW sec. 33, T. 1 S., R. 9 W., Jewell	NW sec. 28, T. 13 S., R. 10 W., Lincoln	SW sec. 34, T. 30 S., R. 26 W., Meade	*SW sec. 31, T. 30 S., R. 26 W., Meade	SE sec. 2, T. 31 S., R. 28 W., Meade	*SW sec. 34, T. 30 S., R. 28 W., Meade	SE sec. 35, T. 31 S., R. 28 W., Meade	NE sec. 26, T. 32 S., R. 28 W., Meade	*SW sec. 33, T. 30 S., R. 29 W,, Meade	*NE sec. 33, T. 30 S., R. 29 W., Meade	*NE sec. 33, T. 34 S., R. 29 W , Meade	*NW sec. 6, T. 31 S., R. 30 W., Meade	SW sec. 19, T. 5 S., R. 22 W., Norton	NW sec. 11, T. 6 S., R. 13 W., Osborne	NW sec. 29, T. 10 S., R. 5 W., Ottawa	NE sec. 1, T. 25 S., R. 7 W., Reno	SW sec. 36, T. 24 S., R. 7 W., Reno	NW sec. 36, T. 14 S., R. 11 W., Russell	NW sec. 35, T. 33 S., R. 32 W., Seword	SE sec. 28, T. 14 S., R. 21 W., Trego	NE sec. 33, T. 14 S., R. 21 W., Trego	SE sec. 22, T. 14 S., R. 12 E., Wabaunsee
Kansan or older to Recent
Amnicola limosa parva Lea
Aplexa hypnorum (Linne)
Cionella lubrica (Muller)
Discus cronkhitei (Newcomb)
Euconulus fulvus (Muller)
Gastrocopta armifera (Say)
Gastrocopta contracta (Say)
Gyraulus similaris (Baker)
Helicodiscus parallelus (Say)
Helisoma trivolvis (Say)
Helisoma wisconsinensis Winslow
Hendersonia occulta (Say)
Lymnaea bulimoides Lea
Lymnaea caperata (Say)
Lymnaea palustris (Muller)
Lymnaea reflexa Say
Physa elliptica Lea
Pisidium compressum Prime
Polygyra texasiana (Moricond)
Pomatiopsis cincinnatiensis (Lea)
Promenetus umbilicatellus (Cockerell)
Pupilla blandi Morse
Pupilla muscorum (Linne)
Sphaerium sp.
Stenotrema leai leai (Binney)
Succinea avara Say
Succinea ovalis Say
Vallonia pulchella (Muller)
Valvata lewisi Currier
Valvata tricarinata (Say)
Vertigo gouldi (Binney)
Vertigo modesta (Say)
Vertigo tridentata Wolf
Zonitoides arboreus (Say)
Restricted to Kansan
Gastrocopta falcis Leonard
Gastrocopta proarmifera Leonard
Gastrocopta tridentata (Leonard)
Gyraulus labiatus Leonard
Gyraulus pattersoni Baker
Menetus pearlettei Leonard
Oxyloma navarrei Leonard
Physa sp.
Planorbula nebraskensis Leonard
Planorbula vulcanata occidentalis Leonard
Planorbula vulcanata vulcanata Leonard
Pupilla muscorum sinistra Franzen
Nebraskan to Kansan
Carychium perexiguum Baker
Deroceras aenigma Leonard
Strobilops sparsicosta Baker
Nebraskan or older to Recent
Ferrissia parallela (Haldeman)
Gastrocopta cristata Pilsbry & Vanatta
Gastrocopta holzingeri (Sterki)
Gastrocopta procera (Gould)
Gastrocopta tappaniana (C. B. Adams)
Hawaiia minuscula (Binney)
Helisoma antrosa (Conrad)
Lymnaea parva Lea
Physa anatina Lea
Pupoides albilabris (C. B. Adams)
Retinella electrina (Gould)
Succinea grosvenori Lea
Vallonia gracilicosta Reinhardt
Vertigo milium (Gould)
Vertigo ovata Say

Plate 15--A representative assemblage of mollusks from Kansan deposits in Kansas. All figures enlarged approximately 5 times natural size. An Acrobat PDF version of this plate is available that shows more detail.

Shells represented by figures g, h, i, l, o, r, t, u, v, and ee are restricted to Kansan faunal assemblages in Kansas. All are extinct in the Great Plains, but species represented by figures o, t, and u are living elsewhere in North America. Species represented by figures d, m, and z make their last appearance in the geologic column in Kansan sediments, while those represented by figures c, i, o, p, q, and u make their first appearance in these deposits.

a. Gastrocopta contracta (Say) b. Vertigo ovata Say c. Pupilla muscorum (Linne) d. Deroceras aenigma Leonard e. Zonitoides arboreus (Say) f. Helicodiscus parallelus (Say) g. Gyraulus pattersoni Baker h. Gastrocopta proarmifera Leonard i. Pupilla muscorum sinistra Franzen j. Hawaiia minuscula (Binney) k. Pisidium compressum Prime l. Menetus pearlettei Leonard m. Strobilops sparsicosta Baker n. Euconulus fulvus (Muller) o. Pomatiopsis cincinnatiensis (Lea) p. Hendersonia occulta (Say) q. Discus cronkhitei (Newcomb) r. Planorbula vulcanata occidentalis Leonard s. Gyraulus similaris Baker t. Amnicola limosa parva Lea u. Valvata tricarinata (Say) v. Gyraulus labiatus Leonard w. Cionella lubrica (Muller) x. Vallonia gracilicosta Beinhardt y. Helisoma antrosa (Conrad) z. Carychium perexiguum Baker aa. Physa elliptica Lea bb. Lymnaea parva Lea cc. Lymnaea palustris (Muller) dd. Succinea grosvenori Lea ee. Oxyloma navarrei Leonard

Fossiliferous Kansan deposits are rather well distributed over the State (Fig. 5); they occur in the southwest in Clark, Meade, and Seward counties, in the northwest in Norton County, in the northeastern part of the State in Doniphan County, in the Flint Hills in Wabaunsee County, and many exposures occur in the central part of Kansas. Fossiliferous Kansan deposits are, however, entirely unknown in southeastern Kansas east of the Flint Hills, where deposits known to be of this age are almost entirely limited to terraces of chert gravel, in which shells are not preserved.

Assignment of a late Kansan age to the molluscan faunas under present consideration is based on (1) their direct relation to lentils of Pearlette volcanic ash contained in the Sappa silt member, Meade formation, (2) direct association of a segment of the distinctive elements of the faunal assemblage with Kansas till where stratigraphic relations are firmly established, (3) relation of the fossiliferous silts to Yarmouth soil, and (4) distinctive features of the faunal assemblage which clearly distinguish it from older and from younger molluscan faunas in the Pleistocene.

A significant attribute of the Pearlette volcanic ash is that it has been shown to be petrographically uniform and distinct from other volcanic ashes in the midcontinent region (Swineford and Frye, 1946). A natural corollary of this is the assumption that the numerous lentils of this material were deposited in a period of brief temporal magnitude. The relation of Pearlette volcanic ash to Kansas till, and the topographic and stratigraphic relations of the ash and associated Sappa silts, discussed elsewhere in this report, confirm its late Kansan age. Wherever molluscan faunules are associated with Pearlette ash, the relation is an intimate one; while fossils are only infrequently found in the ash itself, they are situated in the silts with which the ash is interstratified, either immediately below or above the ash, but more frequently the former. The lack of weathering in the upper part of ash lentils where they are covered by a significant thickness of Sappa silt and the fact that molluscan faunules are identical in composition when they occur both above and below the ash (for example, SW sec. 35, T. 15 S., R. 2 E., Dickinson County) conclusively demonstrate that no geologically significant interval of time elapsed during the deposition of the silts in which the ash and the shells are incorporated.

At the Iowa Point section in Doniphan County, a small series of species of mollusks has been recovered from lentils of sand in the lower few inches of the Kansas till, which here lies above Nebraska till which contains in its top a mature Afton soil profile. Only five kinds of mollusks have been obtained from Kansas till here, but at least two of them, Gyraulus labiatus and Planorbula nebraskensis, are restricted to the Kansan faunal assemblage.

At a number of localities (SE sec. 2, T. 31 S., R. 28 W., Meade County; SW sec. 33, T. 1 S., R. 9 W., Jewell County; and others) fossiliferous silts bearing the distinctive late Kansan molluscan fauna occur below truncated Yarmouth soil. At the Meade County locality cited above, weathering has penetrated to the upper portion of Pearlette volcanic ash, and no fossils are found above the ash although they are abundant below; at the Jewell County exposure, fossil shells occur even in the lower portions of the Yarmouth soil which at this place is a poorly drained profile.

In all, 12 species among the total Kansan assemblage are extinct kinds thus far found only in Kansan sediments. The shells of the majority of these mollusks are of common occurrence in the Kansan Stage and often are abundantly represented where they occur. This is particularly true of Gyroulus labiatus, Gyraulus pattersoni, Gastrocopta proarmifera, Menetus pearlettei, and the several kinds of Planorbula, all of which are easily recognized in the field. Pupilla muscorum sinistra and Oxyloma navarrei are also easily recognized mollusks, but they are not so widespread in occurrence as those mentiond above. Gastrocopta falcis and G. tridentata, while distinctive enough in appearance, are so limited in areal distribution that they have little practical value. Deroceras aenigma, Carychium perexiguum, and Strobilops sparsicosta are not limited to Kansan sediments but they form a characteristic element of the fauna, and all except the first mentioned are numerously represented and conspicuous in most faunules. A number of additional species, although not extinct in the strict sense of the word, are not now living in this region, nor do they occur at other stratigraphic positions within the Pleistocene in Kansas. These species, including Valvata tricarinata, Lymnaea palustris, Promenetus umbilicatellus, Gyraulus similaris, Amnicola limosa parva, Polygyra texasiana, Aplexa hypnorum, Physa elliptica, Pomatiopsis cincinnatiensis, Valvata lewisi, and Lymnaea reflexa, may be thought of as distinctive of Kansan deposits, at least in the State, and all are useful in recognition of sediments at field exposures. Thus nearly half of the total molluscan assemblage of species in Kansan sediments is practically useful for stratigraphic purposes. It follows, of course, that many species in this assemblage are of little value for purposes of stratigraphic interpretation, especially those which range from Nebraskan to Recent deposits, but even these species provide a basis for interpreting past ecological conditions. In fact such species are superior for this purpose, because their ecological tolerances are well known in most cases.

The known faunule in Kansan deposits at the Iowa Point section is too small to be of much value in paleoecological interpretations. It is perhaps worthy of note that Planorbula nebraskensis has been reported by A. B. Leonard (1950) from Kansan deposits from western and northwestern Iowa and from extreme northern Nebraska. The known distribution of this aquatic pulmonate might thus suggest that a cooler climate than now existed in Doniphan County in Kansan time, but this is little contribution, since the shells are found in glacial till. Moreover, since the species is known only from a few localities, and because it is extinct and its ecological tolerances hence unknown, interpretations of ecological conditions based on this one species seem hardly worth while.

The widespread occurrence of a number of branchiate snails, including Valvata tricarinata, V. lewisi, Amnicola limosa parva, and Pomatiopsis cincinnatiensis, most certainly indicates that permanent, clear ponds and lakes and streams containing little silt were common in late Kansan time. These species, as well as the aquatic pulmonates Gyraulus similaris and Aplexa hypnorum, are in general distributed in more northern latitudes than Kansas (the former occurs in montane lakes in Colorado) which may point to slightly cooler climate at the time these snails lived in Kansas, but no suggestion of boreal conditions may be inferred from the total molluscan assemblage.

That ecological conditions over the State were conducive to good floral cover is attested by the number and variety of snails of terrestrial habitat which occur in the assemblage. These snails live at the bases of plants, in leaf mold, under the bark of dead trees, or in the upper parts of the soil where humus is abundant. Many terrestrial snails feed on decaying organic matter or upon the fungus which grows where organic matter such as dead leaves and grass forms a thick mat. Moisture is not only necessary for the growth of the fungus, but terrestrial snails are dependent upon such conditions for proper development of their eggs and young. Slightly more than half of the species represented in the Kansan assemblage are terrestrial in habit: they range from kinds known to be tolerant of a wide variety of ecological conditions to those more or less restricted to some special ecological situation, such as prairie, woodland border, or woodlands. The occurrence of Cionella lubrica, Zonitoides arboreus, Hendersonia occulta, Stenotrema leai, Retinella electrina, and Polygyra texasiana is indicative of woodland habitats or perhaps woodland border situations, or both. Zonitoides arboreus, Retinella electrina, Cionella lubrica, Stenotrema leai, and Polygyra texasiana live in woodlands under bark or in leaf mold near fallen tree trunks. Hendersonia occulta occurs in shrubs, especially near streams on flood plains. However, there is nothing in the molluscan assemblage to suggest extensive forests, and none of the genera so common in the forested areas of eastern parts of the Missouri River Valley are known to be present in the Kansan faunal assemblage. Other terrestrial species, such as Pupilla muscorum, Discus cronkhitei, Succinea grosvenori, and the several species of Vallonia, Vertigo, and Gastrocopta prefer relatively open situations, such as woodland borders or even dense growth of herbs in meadows or near streams. Vallonia frequently occurs in dense growth of grass on open prairies, as does Hawaiia minuscula, Pupoides albilabris, and Gastrocopta armifera. Possibly G. proarmrfera had similar ecological requirements.

In summary, a reconstruction of ecological conditions in most parts of the State in late Kansan time would include the presence of permanent ponds and lakes together with relatively silt-free streams indicating more abundant rainfall, or better distribution of rainfall throughout the year as compared with present rainfall; a slightly lower mean temperature lacking the extremes of summer high temperature and low humidity; and more luxuriant floral cover than at present, especially in the western part of the State, and representing all prevailing types such as prairie, meadow, woodland border, and woodland, but without extensive forests.

It is difficult to compare ecological conditions in the State in Nebraskan time with those in Kansan time. The greater abundance and variety of both branchiate aquatic snails and terrestrial species seems to point to even better rainfall and floral conditions in late Kansan time than in earlier Pleistocene time, but the relatively restricted number of Nebraskan deposits and their more limited areal distribution make direct comparisons difficult and uncertain. It is our judgment, based on available data, that ecological conditions were not significantly different in Nebraskan and Kansan time in most parts of Kansas, at least in the closing phases of these Pleistocene stages.

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Kansas Geological Survey, Pleistocene Geology
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Web version August 2005. Original publication date Nov. 1952.
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