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Neogene Ostracodes

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Ostracode-bearing Strata

Pliocene Series

Laverne Formation--The Laverne Formation was described in an unpublished manuscript by V. V. Waite (Gould and Lonsdale, 1926) and named from a locality in Harper County, Oklahoma. In Meade County, Kansas, the formation generally consists of gray, fine to medium thin-bedded micaceous sandstone and gray to tan shale. A diagnostic unit in the Laverne is the tan-gray, friable, calcareous, silty fine sandstone locally used as building stone and named "sawrock" (Frye and Hibbard, 1941). The beds dip at angles as great as 15 degrees, which may indicate post-Laverne solution of underlying beds. The thickness exposed at the surface in Meade County does not exceed 80 feet, but in nearby Seward County, test holes (Byrne and McLaughlin, 1948) indicate greater thickness, which may be the result of basin filling during Early Pliocene time.

At locality 8 (Fig. 2), the ostracodes were recovered from a limonitic sandstone bed at the top of the Laverne Formation.

Ogallala Formation--No ostracodes were recovered.

Rexroad Formation--Smith (1940) named the Rexroad Formation for the exposures on the Clarence Rexroad ranch, Meade County, Kansas. The lower beds are sand and fine gravel; the intermediate beds are sandy silt and include layers of organic matter; and the upper beds are clay, sandy silt, and caliche. The upper caliche zone occurs as nodules or as a massive bed of caliche. The Rexroad Formation is judged to represent Late Pliocene time on the basis of the contained vertebrate fauna (Hibbard, 1950, 1953; Woodburne, 1961). In the Meade County area the thickness ranges from 8 to 80 feet.

At locality 9 (Fig. 2), ostracodes were collected at the top of the Rexroad Formation, from a limonitic sandstone cemented with calcium carbonate.

Pleistocene Series

Lower Pleistocene Subseries

The Meade Group as defined by the Pleistocene Conference held in Lawrence, Kansas, in June of 1956 (Foley, 1956) has been revised to include the Ballard and Crooked Creek Formations. The term Lower Pleistocene Subseries is used by the State Geological Survey (Jewett, 1959) for the sediments equivalent to the Meade Group.

Ballard Formation--Although ostracodes have not been recovered from the Ballard Formation, its stratigraphic position is important in the interpretation of overlying and underlying strata. The name Ballard Formation was proposed by Hibbard (1958) for the deposits that he had previously described as the Meade Formation (Hibbard, 1949b). In that earlier paper, Hibbard had restricted the Meade Formation to include Cragin's Meade gravels but to exclude the deposits at the section designated as type locality for the Meade Formation.

The basal part of the Ballard Formation contains stream-deposited arkosic (granitic) sand and gravel of Rocky Mountain source, which grades upward into sandy silt, clay, and caliche zones.

Crooked Creek Formation--Hibbard (1949b) applied the name Crooked Creek Formation to the sediments laid down during the cycle of deposition that followed deposition of the Ballard Formation, and as type section cited the same one previously designated by Frye and Hibbard (1941) as the type section of the Meade Formation. The basal member of the Crooked Creek Formation, the Stump Arroyo Member, consists of tan sand and gravel, which are distinguishable from the basal members of the Ballard, Rexroad, and Ogallala Formations in the Meade County area. The Stump Arroyo Member is dated by its contained vertebrate fossils (Hibbard, 1951).

The Atwater Member of the Crooked Creek Formation overlies the Stump Arroyo Member. It consists of sand, silt, and clay both above and below the included Pearlette Ash lentil.

Seven Crooked Creek localities in Meade County were examined but no ostracodes were found. Ostracodes have been identified by Staplin (1953) from above the Pearlette Ash at the Cudahy fauna locality. Ostracodes were collected from Lower Pleistocene deposits above the Pearlette Ash in Reno County, Kansas, at locality 10. Ostracodes have also been identified from deposits below the Pearlette Ash at locality 11 near Canyon, Texas.

Upper Pleistocene Subseries

In southwestern Kansas the Sanborn Group as proposed by the 1956 Pleistocene Conference includes the Kingsdown and Vanhem Formations. The term Upper Pleistocene Subseries is used by the State Geological Survey (Jewett, 1959) for sediments equivalent to the Sanborn Group. The Odee Formation (Smith, 1940) and some local basin fillings are judged to be Upper Pleistocene.

Kingsdown Formation--The Kingsdown Formation was described by Cragin in 1896, but he did not designate a type section. Hibbard (1949b) thought that the type locality was on Bluff Creek in Clark County, Kansas. Cragin (1896, p. 54) stated:

". . . the Kingsdown Marl consisted of yellowish-brown lacustrine or slack water marls, containing variously shaped concretions of calcium carbonate and silicate of lime. They are very rarely fossiliferous."

Hibbard (1944) believed that Cragin's description applies to the lower beds but not to the overlying beds, which he removed to the Vanhem Formation.

The Kingsdown as restricted by Hibbard (1944) consists of a lower gravel member, composed of abraded caliche fragments and gravel, and an upper part composed of thick-bedded buff silt that grades upward into sandy silt and fine sand. The thickness of the (revised) Kingsdown Formation at the type section is 25 feet.

The ostracodes at locality 6 (Fig. 2) were collected from the upper part of the Kingsdown Formation silts at the Cragin Quarry located on Big Springs Ranch, Meade County, Kansas.

Vanhem Formation--The Vanhem Formation was named and described by Hibbard (1949b); the type section is the outcrop along the west bluff of a tributary of Bluff Creek in Clark County, Kansas. Smith (1940) regarded this section as the type section of Cragin's Kingsdown Formation.

The basal member of the Vanhem Formation consists of sand and gravel containing abundant calcareous pebbles and fragments of mortar-bed conglomerate, which were reworked from older formations. Contact with the middle silty layer, which contains small pebble layers, is indistinct. The upper member consists of silt which according to Hibbard (1949b) grades into loess at the top. The thickness of the Vanhem Formation at the type locality is 68 feet.

Ostracodes were recovered from the upper beds in the Jones Sink at locality 7 (Fig. 2), which Hibbard (1949b) judged to be Vanhem Formation on the basis of lithology and vertebrate fauna. We believe that the lower beds of the Jones Sink are Upper Pleistocene fluviatile deposits. A fossil soil is exposed 6 feet above the base of the section.

Odee Formation and local basin fillings--The formation was named by Smith (1940) from exposures in Odee Township in southern Meade County. It consists of beds that are all probably younger than the Crooked Creek Formation. Many of the Pleistocene deposits younger than the Crooked Creek Formation are lower topographically than the older formations. The sinkholes seem to be filled with locally derived material. The Odee Formation consists of red mudstone, sand, and silt. Ostracodes were found in all samples collected from the Odee Formation at localities 3 and 4 (Fig. 2). At locality 3 a thin layer of limonitic sandstone cemented with calcium carbonate might be described as an "ostracode coquina."

An ostracode-bearing clay at locality 5 (Fig. 2) is part of a sink-fill deposit that Hibbard (personal communication) believed to be approximately the same age as the upper beds of the Odee.

Ostracodes are abundant in samples from the Nye Sink in Beaver County, Oklahoma, locality 2. According to Hibbard (personal communication), the Nye Sink beds are equivalent to the lower part of the Odee Formation, and the deposits were called Odee Formation by Smith (1940). Ostracodes are extremely abundant in bed 15 of Smith's measured section (1940, p. 103). He described this bed as "Marl, diatomaceous to sandy, gray to white, contains fossils." All beds except those at the top of the section show signs of collapse during formation of the sink.

The Odee Formation is 104 feet thick at locality 3 and 55 feet thick at locality 4.

Smith attributed the reddish colors to reworked material eroded from Permian or Triassic redbeds. The sand deposits were possibly derived from reworked Ogallala sediments.

Quaternary sand--The ostracodes from locality 1 (Fig. 2) were collected alive from sands in a tributary of Crooked Creek that flows through Meade County State Park from an artesian spring. One species (Ilyocypris bradyi Sars) found at this locality was also represented by fossils in the Odee Formation (Pleistocene).

Water from this stream was used by Dr. Hibbard to wash his samples for microvertebrate fossils. Because of possible contamination of older ostracodes that were recovered with microvertebrates, it was necessary to know which ostracodes were indigenous to the stream.


Use as stratigraphic guide fossils--The ostracodes were examined in view of their potential use as stratigraphic indicators. Fossil fresh-water species of ostracodes are not well enough known to be used as stratigraphic indices for the subdivisions of the Pleistocene. Present knowledge indicates that the span of time since the beginning of the Pleistocene was inadequate for the selection and evolution of new forms. Hence the classic concept of appearance and extinction of species used to define a stratigraphic range may not be applicable in dividing the Pleistocene units. Changes in climate and corresponding geographic changes in environments and habitats of the ostracodes, however, have profound effect on the distribution of existing species. On the basis of comparison of modern distribution of ostracode species it is possible to distinguish some deposits associated with glacial stages as cold water in origin. No interglacial faunas were recognized.

For distinguishing Pleistocene faunas from Pliocene, at least in southwestern Kansas, we believe that Eucandona nyensis n. sp. [sic., probably Candona nyensis n. sp.] is diagnostic. Its earliest appearance is in the Crooked Creek Formation (Lower Pleistocene), and it is conspicuously absent from Pliocene sediments (Table 1).

Table 1--Ostracode species from localities sampled. For description see Register of Localities.

Species Locality number
1 2 3 4 5 6 7 8 9 10 11 12 13
Cypricercus tuberculatus (Sharpe)                   X      
Cyprideis littoralis Brady   X X X X   X X X        
Cypridopsis vidua (O. F. Müller)   X   X X X       X      
Candona caudata Kaufmann   X                     X
Candona crogmaniana Turner               X   X      
Candona fluviatilis Hoff                   X   X  
Candona nyensis n. sp.   X X X X   X     X X   X
Candona renoensis n. sp.           X       X      
Eucypris meadensis n. sp. X                        
Ilyocypris bradyi Sars X X X             X      
Ilyocypris gibba (Ramdohr)                   X      
Limnocythere staplini n. sp.   X X X X   X ?   X      
Potamocypris smaragdina (Vávra)   X     X   X     X      
Age A,
D C B B A,
A, Upper Pleistocene; a, Recent; b, Wisconslnan; c. Early Wisconsinan;
d, Sangamonian; e, Illinoisan-Wisconsinan; f, Illinoisan;
B, Lower Pleistocene (Kansan);
C, Upper Pliocene (Rexroad Formation);
D, Lower Pliocene (Laverne Formation).

Use as ecologic indicators--Fresh-water ostracodes are found living in almost every modern stream, lake, pond, and spring. Generally ostracode species are geographically and seasonally distributed within the biomes or "life zones" affected by seasonal temperature changes and differences in latitude and altitude. Certain species, such as Cypricercus tuberculatus, are more common in warm-temperate or neotropical regions than in the colder near-artic or sub-alpine habitats. Nearctic forms adapted to cold waters are poorly known. Colder waters upwelling from artesian wells in Kansas contain what seem to be relic communities of microfaunas including Potamocypris smaragdina (Vávra) not found in surrounding warmer waters. The presence of southern or warm interglacial faunas and possible northern or near-glacial faunas in the same area but at different stratigraphic horizons may prove to be valuable in distinguishing sediments of interglacial from those of glacial stages.

Concerning more localized ecologic problems, Lohman (in Frye and Hibbard, 1941) stated that the diatoms found in the lower beds of the Laverne Formation suggest deposition under continental saline conditions. Leonard and Franzen (1944) postulated continental brackish-water conditions for these beds, citing the occurrence of spines on aqueous gastropods as well as the presence of the ostracode Cyprideis littoralis Brady identified by Tressler (in Frye and Hibbard, 1941, p. 401). They also pointed out that after deposition of the diatom-bearing marl, the water became fresh. Despite the postulated variety of these environments, C. littoralis Brady lived on the High Plains from Early Pliocene until Late Pleistocene time.

The occurrence of Cyprideis littoralis Brady, a common "brackish-water" form, in the Pleistocene sinkhole deposits of southwestern Kansas can be explained in two ways. (1) The sinkholes could have contained fresh water since the time of their origin; the implication is that C. littoralis Brady had to adapt itself to a fresh-water environment. (2) Some sinkholes contained fresh water while others contained brackish water, or some sinkholes contained brackish water at first but with the passage of time the water became fresh. The presence of Cyprideis littoralis Brady in multicycle sinks could not be cited as evidence for brackish water exclusively.

The sinkholes developed after the collapse of beds overlying Permian salt beds. Frye and Schoff (1942) show that the sinkholes are on the upthrown side of major faults. The evidence for a fresh-water environment is the abundant microvertebrate and gastropod fauna associated with the ostracodes in many sinkhole deposits. The other members of the fauna represent a fresh-water environment, therefore it is reasonable to assume that the ostracodes, including Cyprideis littoralis Brady, also lived in such a lake or pond environment during the Late Pliocene and Pleistocene. Klie (1938) mentioned the fresh-water occurrence of this species in Germany. It seems reasonable to assume that C. littoralis Brady is a euryhaline species capable of living successfully in various environments.

The evidence for changing environment is presented by the Meade Salt Sink (Merriam and Mann, 1957). This sinkhole, formed in Meade County in 1879, was first filled with saline water but now is almost filled with sediment. In periods of ample rainfall it contains fresh water, whereas during years of drought it remains dry. Perhaps this sequence was common during the Pleistocene, and many sinkholes that are now filled with sediment had such a history.

In San Antonio Bay, Texas, Swain (1955) found Cyprideis littoralis Brady in the brackish midbay subfacies of the river and prodelta facies, whereas Candona caudata Kaufmann and Potamocypris smaragdina (Vávra) were found in the brackish river and prodelta facies. These three species were found together in the Pleistocene sinkhole deposits of southwestern Kansas. Swain found that some fresh-water species are capable of living in brackish water at mouths of rivers, and that they do not necessarily represent a fresh-water environment.

In addition to the above conclusions, the authors of this report would stress the potential usefulness of ostracodes in the study of Pleistocene history but would also emphasize the need for further study of distribution and ecology of Recent forms. The living faunas of ostracodes in North America are inadequately known. Many species have been described from only one or two localities. Additional information about tropical, temperate, and arctic species living today will increase the significance of the fossil forms for interpreting past climates and environments.

One of the environmental parameters controlling distribution of most aquatic organisms is water temperature. Changes in temperature with changes in season, and differences in temperature due to differences in climate, altitude, latitude, depth, or other factors, presumably affect the distribution of fresh-water ostracodes, but the effects are almost totally unknown. Hoff (1942, p. 25) found that in his field experience in Illinois the small temperature range there had little effect on the distribution of ostracodes other than possibly on seasonal occurrence. Swain (1961, p. Q 211), in quoting Hoff, implied that temperature of water generally has little or no effect on distribution of ostracode species. In view of the lack of experimental or field data and our present knowledge of the effects of temperature on other organisms, perhaps Swain's conclusion is too strongly stated. The complex interrelationship of the several environmental factors depending ultimately on changes in temperature and their effect on ostracode distribution needs to be studied further.

Register of Localities

(Shown on locality map, Fig. 2)

1. Recent--Artesian spring, well, and drainage, wayside park in Meade County State Park, NW SW sec. 14, T. 33 S., R. 29 W., Meade County, Kansas.

2. Pleistocene (Illinoisan-Wisconsinan)--Nye Sink deposits, NW SW sec. 15, T. 6 N., R. 25 E. C. M., Beaver County, Oklahoma. Measured section (Smith, 1940, p. 103).

3. Pleistocene (Illinoisan-Wisconsinan)--Odee Formation, NE sec. 35, T. 34 S., R. 29 W., Meade County, Kansas. Measured section (Smith, 1940, p. 101).

4. Pleistocene (Illinoisan-Wisconsinan)--Odee Formation, NW SE sec. 1, T. 34 S., R. 29 W., Meade County, Kansas. Measured section (Frye, 1942, p. 107).

5. Pleistocene (Sangamonian or Early Wisconsinan)--1/8 mile downstream from Hibbard's Dire Wolf locality, SW sec. 33, T. 34 S., R. 29 W., Meade County, Kansas.

6. Pleistocene (Sangamonian)--Cragin Quarry locality, Big Springs Ranch, SW sec. 17, T. 32 S., R. 28 W., Meade County, Kansas.

7. Upper Pleistocene (Wisconsinan)--Jones Ranch beds, NW NE sec. 8, T. 33 S., R. 27 W., Meade County, Kansas.

8. Lower Pliocene--Laverne Formation, W2 sec. 29, T. 34 S., R. 30 W., Meade County, Kansas.

9. Upper Pliocene--Rexroad Formation, NW sec. 3, T. 33 S., R. 29 W., Meade County, Kansas.

Localities Outside Meade County Area
(Not shown on locality map, Fig. 2)

10. Lower Pleistocene (Late Kansan or Early Yarmouthian)--Above Pearlette Ash, SE NE sec. 1, T. 25 S., R. 7 W., Reno County, Kansas.

11. Pleistocene (Kansan)--Below Pearlette Ash, Canyon on U. S. Highway 87 just north of underpass, on east side of road before one reaches C. S. Highway 60 at Canyon, Texas. Collected by Jack Hughes.

12. Pleistocene (Wisconsinan)--Terrace deposit, SE SW sec. 8, T. 52 N., R. 36 W., Platte County, Missouri. Collected by A. B. Leonard.

13. Pleistocene (Illinoisan)--Doby Springs glacial fauna, SW sec. 10, T. 27 N., R. 24 W., Harper County, Oklahoma. Collected by C. W. Hibbard.

Taxonomic Problems

Basis of Classification

All of the genera of this report are represented by previously described living species. At least two of the new species found in older Neogene strata are still living today. The existing generic and specific classifications of the living fresh-water ostracodes based on appendages are used in this report for most of the Pleistocene and older forms. Most ostracode neontologists do not regard variation in the features of the carapace as important in morphologic studies. The carapaces of living species and even of fossil species have not been sufficiently studied to justify a revised classification based on carapace morphology comparable to the one based on appendages. Both morphologic features are fundamental parts of the animal, hence separate classifications should be avoided if possible. Eventually the living species, which have been described and delineated on soft parts, should be re-evaluated in terms of present knowledge of carapace morphology to correlate with their fossil predecessors.

Significant Features of Carapace

Carapace features generally used by paleontologists to classify fossil fresh-water ostracodes include size and shape, adductor and mandibular muscle-scar patterns, normal pore canals, configuration of the duplicature, and ornamentation. The type of hinge is generally taxonomically significant in more advanced forms of Ostracoda, but the hinge of most forms of Cypridacea is adont, and differences are subtle and obscure. All members of the Cypridacea have some sort of bar and groove arrangement or are completely without a groove. The more complex merodont hinge, characteristic of a large group of predominantly brackish-water and marine Cytheracea is found only in Cyprideis among fresh-water inhabitants. The intermediate lophodont hinge is known from species of Limnocythere and perhaps from those of Ilyocypris.

The general shape, outline, and relative size of the valves are useful characters for delineation of some ostracode species and genera. Most species of the genus Candona are much larger and more reniform than those of the genus Eucypris, although within the genus Candona adults of the species range from 1 mm (Candona renoensis n. sp.) to 1.3 mm (Candona nyensis n. sp.) in length and from subreniform to subtrapezoidal. Much experience is needed to recognize the consistent difference in shape in these forms.

The muscle-scar pattern within the central area of the carapace is the most complex morphologic structure visible in many an otherwise simple cyprid carapace. Variation in shape and arrangement of the discrete scars that compose the mandibular and adductor muscle-scar patterns seems to be significant on the generic and even on the species level. For example, a rosette of five smaller scars and one elongate scar located dorsally tends to be distinctive of the genus Candona. The genus Eucypris can be recognized by its muscle-scar pattern of a subparallel group of five elongate scars whose long axes are oriented at an angle of about 45° with a tangent to the ventral margin.

The presence of sulci and lobes distinguishes a few genera from most of the unornamented fresh-water ostracode genera. The genus Ilyocypris is readily distinguishable from the genus Limnocythere by its more pronounced dorsolateral sulci. Although these forms belong to two different and widely separate families, on many specimens the diagnostic muscle-scar patterns cannot be seen.

The development of the marginal area and its associated structures (e.g., selvage, flange, vestibule, duplicature, list) is usually regarded as a generic character, although many genera have similar marginal areas. The genera Cypridopsis and Eucypris have similar marginal areas, but can be differentiated by size, shape, and muscle-scar pattern.

Character of minor ornamentation (e.g., nodes, reticulations, protrusions, and tuberculae) is generally used for distinguishing species. Ilyocypris gibba (Ramdohr) is distinguished from I. bradyi Sars by the presence of lateral protrusions and nodes on the former.

Sexual dimorphism is notable in some species of fresh-water ostracodes. The males of Candona nyensis n. sp. have a more arched dorsum and are more sinuate in lateral outline than are the females. Generally, the male eucandonids are larger and broader in the posterior region than are the females, which is quite the contrary of many species of marine ostracodes, in which the females are consistently broader. In some fresh-water species the males are absent, and some taxonomists have used presence or absence of males to distinguish genera. This criterion is difficult to impossible to apply to fossil forms unless all other species can be identified to the exclusion of a single maleless species.

The examination of normal pore canals, radial pore canals, and the marginal features is necessary for completeness in morphologic studies, but their taxonomic significance at the generic or specific level has not yet been demonstrated.

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Kansas Geological Survey, Geology
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