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History of study

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Benjamin Franklin Mudge

Complex facies (lithologic aspects)

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Long-running effort were made to stratigraphically define the Ogallala Formation,

If the agates are the top exposure, the "algal/pisolitic limestone is presumed to have weathered away or did not fully developed locally.

Top Ogallala - "caprock caliche" / "algal limestone" / "pisolitic limestone" (Kimbal)

"mammillary or colloform concretions" Ogallala Formation Silicified Rock

Top Ogallala - "moss agate" to "chert" (Kimball)

Benjamin Franklin Mudge


Top Ogallala - "Sidney gravel" (Kimball/Sidney)

Geologist attempted assigning the base of the Kimball formation to base of the "Sidney gravel".


Main Ogallala - "mortar beds" (Ash Hollow)


Main Ogallala - ash beds (Ash Hollow)


Main Ogallala - limestone lens (Ash Hollow)


Main Ogallala - dispersed gravel channels (Ash Hollow)


Bottom Ogallala - "opaline sandstone" / "green quartzite" / "opalized chalk" (Valentine)


Top Ogallala : "caprock caliche" / "algal limestone" / "pisolitic limestone" (Kimbal)

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In early literature on this High Plains Tertiary formation, the term "algal limestone" described the uppermost marker bed of the Ogallala Formation, a white to pink limestone up to 3 feet (1 meter) thick. Excluding particular ash beds, this "algal limestone" was considered the most consistent and potentially mappable bed of the Ogallala Formation. This feature is unique within the limey Neogene and Quarternary rocks of region, allowing for rapid identification this "algal"/"pisolitic" limestone when the bed is encountered.

More recently, the same bedding is mentioned or described as caliche or caprock, reflecting its appearance as thick caliche that formed on a stable surface and that it is commonly seen as a caprock because the material is rather resistant to weathering. While Ludvigson (2009) points out that any of a number of discontinuous resistant bed in the Ogallala can function as a limey caprock in lower bluffs, the usage "caprock" for this bed means that it is seen as the ultimate capping bed of the Ogallala. To be clear, "caprock" has different meaning when applied to this rock than when applied within the body of the Ogallala, that is, it means "caps the whole formation" rather than "caps bluffs" lower in the formation.

The curious diagnostic feature of this formation-capping "caprock" is thin red lines that commonly appear in parallel or concentric patterns, often in vertical tubular shapes. Even though this material is not formed of pisolites, it has been called "pisolitic limestone" because the rock has a pisolitic appearance when broken or cut across the vertical tubular patterns.

An original conjecture was that the reddish lines suggested that the bed was a limestone produced by algae in large, shallow, and continuous lakes. However, it has been concluded that this bed resulted from accumulation of calcite in a stable soil surface over millions of years.[1] Where this caliche is absent, it is presumed eroded away. Where it is present, sometimes with no other indication of typical Ogallala features (that is, no sand to speak of), it is suggestive of wider simultaneous soil development on a stable surface that followed the end of Ogallala sedimentation.

This "algal"/"pisolitic" limestone was generally included in the definition of the Ogallala. However, it is also found by itself froming miniature buttes on ridges of Cretaceous rock. In these situations, pieces of local Carlile and Greenhorn chalk can be found incrusted by the caliche, further demonstrating that the particular soil conditions were not limited to the Ogallala formation.

Further reading

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"algal limestone"

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  • Maxim K. Elias (1931). "The Geology of Wallace County, Kansas". Kansas Geological Survey Bulletin (18). Kansas Geological Survey: Stratigraphy, continued, Tertiary, Ogallala Formation. Retrieved 2024-07-25. The pink concentrically banded limestone usually does not outcrop as a solid ledge, but is broken into irregularly oval or angular and somewhat flattened cobbles a few inches to a foot or more in horizontal diameter. The texture of the bed may be called irregularly pisolitic, the limestone being traversed by a very fine more or less concentric rhythmic banding. The fine banding presents an alternation of creamy, light-brown, brick red, and otherwise shaded reddish-brown irregularly concentric bands, the cores of which and the matrix between the irregularly oval "ovulites" are usually colored in nearly uniform light creamy or pinkish shades. The rock is usually full of scattered grains of colorless quartz and pink feldspar, the size of which ranges from tens of microns to a few millimeters. Very rarely much larger pebbles of quartz are observed in the rock. Some of the sand grains are found in the center of the smaller and more regular pisolitic "ovulites," but the vast majority of these grains have no relation to the banding at all and are scattered uniformly through the rock. Many of the larger loops of banding embrace groups of smaller concentric structures. A few fragments, also, with nearly parallel banding have an enveloping crust of fine concentric banding. This and other examples of interrupted and resumed growth are fairly frequent. The thin section reveals a cryptocrystalline structure, the banding of which is due to the zonal arrangement of nearly opaque calcium carbonate, a little more crystallized and more transparent buff-colored bands of the same substance and occasionally still more transparent layers of the same carbonate with a faint radial (transverse) structure. The first two kinds of bands are not sharply separated, the nearly opaque substance presenting lobate and digitate outgrowths into the lighter bands. Locally there are much thinner and closer spaced brick-red bands of iron oxide and buff-colored calcium carbonate. In the broader bands may be noticed a few small spherical bodies with a comparatively thin outer zone made of a mosaic of comparatively coarse-grained colorless calcite, much like the walls of the hollow spheres representing the individual cells of Chlorellopsis coloniata Reis, the microscopic alga of the Green River Formation reefs. Some of the spherical bodies from the Ogallala rock are hollow also. The more important difference between the spheres from the limestones of the two formations is the smaller diameter of the spheres from the Ogallala.
  • Alvin Leonard Lugn, University of Nebraska - Lincoln (1938). "The Nebraska State Geological Survey and the "Valentine Problem"". American Journal of Science. 36 (213). University of Nebraska - Lincoln: 220. Bibcode:1938AmJS...36..220L. doi:10.2475/ajs.s5-36.213.220. S2CID 129509059. [p. 223] The Valentine formation occurs under the typical Ogallala "mortar beds." The "cap rock bed," a field term mentioned by Johnson,14 is the lowest part of the "mortar beds" division of the Ogallala group. It, the "cap rock bed," is also almost exactly the equivalent of the Krynitzkia fossil seed zone of Elias.15 .... The "mortar beds" division of the Ogallala group, which in the main is the only part exposed in the "type locality" (?) near Ogallala, Nebraska, as defined by Elias," is now to be known as the Ash Hollow formation, 100 to 250 feet thick. It contains the "cap rock bed" of the Krynitskia coronoformis fossil seed zone, ... [p. 224] The third formation of the Ogallala group is now known as the Sidney gravel formation from occurrences at Sidney, Nebraska. It ranges in thickness from 15 to 50 feet; and it is widespread in southwestern Nebraska, northeastern Colorado, and in parts of western Kansas. ... A fourth and uppermost formation of the Ogallala group is to be known as the Kimball formation from its typical occurrence at the highest remnant levels of the High Plains in Kim- ball County, Nebraska. The thickness of the Kimball formation ranges from 30 to 40 feet when present in its full development; and it consists of silt, clay, fine sand more or less cemented with caliche, with one or two algal limestone beds at the very top. It is pinkish to reddish in color. ... The most striking feature of this formation is the occurrence at the very top of an algal limestone (Chlorellopsis bradleyi Elias). ... The old Ogallala formation, as indicated in the above discus- sion, is now to be redefined as a group consisting of four definite and mappable formations. The formational names: Valentine, Ash Hollow, Sidney, and Kimball were not the choice of the present writer alone, nor of any one individual. These names were agreed upon first in conference early in March 1936 in the State Geologist's office at Lincoln, Nebraska, by the following: Dr. G. E. Condra, State Geologist of Nebraska; Dr. R. C. Moore, State Geologist of Kansas; Mr. Maxim K. Elias, Kansas State Geological Survey, and the writer [Alvin Leonard Lugn]. Agreement on Ogallala nomenclature also had been reached with Mr. C. Bertrand Schultz, Assistant Director (in charge), Nebraska State Museum. The Ogallala formations. now have been mapped areally in detail by the Nebraska State Geological Survey; and a bulletin will be published soon which will contain these maps and a general and somewhat detailed survey of the stratigraphy of all of the Tertiary system in Nebraska. The acceptable stratigraphic nomenclature will be described. All names used have now been approved by the United States Geological Survey.
  • F. M. Van Tuyl, W. S. Levings (1949). "Pliocene Ogallala Algal Limestone in Union County, New Mexico". AAPG Bulletin. 33 (8). American Association of Petroleum Geologists. Retrieved 2024-08-11. In recent years much interest has arisen in regard to the origin and distribu- tion of the capping limestone member of the Ogallala (Pliocene) formation in southwestern Nebraska, eastern Colorado, western Kansas, the panhandle of Oklahoma, and on the Llano Estacado Plateau of western Texas and southeastern New Mexico. Increasing evidence indicates that the distribution of this impor- tant stratigraphic unit is more extensive than heretofore supposed.
    Reconnaissance field studies by the present writers, in Union County, north- eastern New Mexico, during the summer of 1948 revealed the presence of rather extensive, though disconnected and in some places unmapped, areas of typical Ogallala stream deposits locally overlain by previously unreported algal limestone. The most prominent and distinct exposures of this member are in T. 28 N., R. 31, 32, and 33 E. Here it is as much as 5 feet thick and caps low hills and ridges of the Ogallala which overlies the Dakota sandstone.
    Cursory examination of the limestone capping about 138 feet of Ogallala gravels, sands, and silts about 1 mile east and 1 1⁄2 miles north of the town of Grenville, disclosed the presence of conspicuous, pinkish, concentric and wavy bands associated with pisolitic or nodular structure. These distinctive features, together with the massive, resistant character of the rock and its stratigraphic position, were regarded by the writers as significant in indicating the presence of the cap rock of the Ogallala which M. K. Elias and others have shown to be the only reliable geologic and physiographic datum in the Pliocene deposits over a wide area of the High Plains.


  • Dorothy R. Hill and Jessie M. Tompkin (1953). "General and Engineering Geology of the Wray Area, Colorado and Nebraska" (PDF). Geological Survey Bulletin (1001). Washington, DC: United States Government Printing Office: 12–15, 19–21. Retrieved 2024-07-28. The bulk of the Ogallala formation consists of sand and silt cemented with calcium carbonate; the degree of cementation varies laterally and vertically. The formation crops out as a succession of alternating ledges and slopes called "mortar beds"; none of the beds can be traced more than a few hundred feet. The only marker bed in the formation is the capping layer of algal limestone. ... Portions of the section of the Ogallala formation are exposed in various places; some exposures include the basal conglomerate and some include the capping algal limestone, but no single complete section including both capping and basal beds was found [in the Wray area]. ... A pinkish, banded, pisolitic limestone, which Lugn believes to be identical to the "algal limestone" described by Elias (op. cit., 1931), is the uppermost bed of this formation. ... the Kimball formation can be distinguished only in the few places where the capping algal limestone crops out. ... A marker bed of banded, pisolitic algal limestone is the capping layer of the formation. ... This capping layer, which averages about 2 feet thick, is the only marker bed in the formation. A similar bed at the top of the Ogallala formation was found by Elias (1931, pp. 131-163) in Wallace County, Kans. ... Elias has named the alga Chlorellopsis bradleyi. In megascopic appearance, the grayish-orange (10 YR 7 /4), concentrically banded limestone at the top of the Ogallala formation in the Wray area is almost identical with that of the algal limestone described by Elias. Thin sections of the Wray area limestone show the same concentric banding as that in the limestone described by Elias. The limestone capping the Ogallala formation in the Wray area has been identified by Elias (personal communication, March, 1950) as Chlorellopsis bradleyi. In Nebraska, the algal limestone is at or near the top of the Ogallala formation and was described by Lugn (1939) as part of the Kimball formation.
  • Thad G. McLaughlin (1954). "Geology and Ground-Water Resources of Baca County, Colorado". Geological Survey Water-Supply Paper (1256). United States Department of the Interior: 126, 128. Retrieved 2024-08-04. (p. 126) The formation is generally capped by the algal limestone. (p. 128 ) Along Dry Creek ... there is an 8-foot bed of caliche containing angular blocks of the Dakota sandstone as large as 1 foot in diameter. The caliche is capped by a 5-inch bed of algal limestone which marks the top of the Ogallala formation. The uppermost bed of caliche in the Ogallala formation is the thickest and most persistent in Baca County. It generally is at least 5 feet thick and locally may be 20 to 25 feet thick. The bed is capped by a 2- to 6-inch layer of algal limestone and is quarried extensively in the eastern part of the county for use as road metal. The hardest and most persistent bed in the Ogallala is the capping limestone. It is 2 to 6 inches thick and marks the top of the formation. The limestone is hard and dense and contains scattered grains of quartz ranging in size from very fine sand to fine gravel. In some places the sand consists in part of magnetite. The lime- stone generally is compact but may contain a few small fractures and pores. It generally is so hard that many of the grains of quartz break when the limestone is fractured. The color may be uniformly cream to light tan but in most places the rock is banded. The bands are various shades of brown, tan, and pink and may be straight or curved. Locally the limestone displays the typical algal structure so common throughout the central High Plains. The uniform and banded limestone weathers into rectangular slabs, whereas the algal limestone has irregular vertical joints and weathers into rounded biscuit like cobbles having an irregular surface and displaying the typical tan and pink concentric bands characteristic of algal structure (fig. 49). The capping limestone in many parts of the county forms a prominent low bench which can be traced for a considerable distance in the field and is conspicuous on aerial photographs.
One of two reports cited later as definitively covering the soil origin of the "algal" limestone.
One of two reports cited later as definitively covering the soil origin of the "algal" limestone.
  • John M. Jewett and Daniel F. Merriam (1959). "Geologic framework of Kansas--a review for geophysicists". Kansas Geological Survey Bulletin (137). Kansas Geological Survey: Geologic Formations in Relation to Ground Water. Retrieved 2024-08-04.
    >>An interesting layer of rock marks the top of the Ogallala formation. This is a pisolitic limestone that some authors call the "Algal limestone." According to Swineford, Leonard, and Frye (1958) it is thought to have developed by soil-forming processes acting on sands and silts of the uppermost part of the Ogallala formation. The absence of definite fossils; anomalous distribution of detrital grains with respect to oolites, pisolites, and bulbous structures; inverted orientation of bulbous structures themselves; and physiographic and climatic considerations all argue against algal origin of the rock. The so-called "Algal limestone" is a convenient datum plane; it is the uppermost part of the Ogallala formation, and except where there is local Pleistocene cover, it marks the High Plains surface and the top of the great mass of debris washed from the mountains.
    >>The present attitude of the "Algal limestone" (Fig. 15) is essentially an eastward-dipping homocline modified by minor irregularities superposed on the major structure (Merriam and Frye, 1954). The surface is gently inclined eastward from an altitude of about 4,000 feet on the Kansas-Colorado line to about 1,600 feet in eastern Mitchell and Lincoln Counties in central Kansas. If more detailed control were available, the map probably would reveal minor noses and re-entrants in addition to those shown.
  • Warren G. Hodson and Kenneth D. Wahl (1960). "Geology and Ground-water Resources of Gove County, Kansas". Kansas Geological Survey Bulletin (145). Kansas Geological Survey. Retrieved 2024-08-04. A thin discontinuous bed of pisolitic limestone, commonly 1 to 3 feet thick, forms the top of the Ogallala ... in Gove County.
  • Hubert E. Risser (1960). "Kansas Building Stone". Kansas Geological Survey Bulletin (142, pt 2). Kansas Geological Survey: Geologic Formations in Relation to Ground Water. Retrieved 2024-08-04.
    >>At the top of the upper (Kimball) member of the Ogallala, a dense, hard, nodular, pisolitic limestone occurs locally (Swineford, Leonard, and Frye, 1958). This limestone has been used to some extent for buildings in Norton County and other counties of north-central Kansas. A church in New Almelo was constructed from this material, reportedly quarried in Graham County (Byrne, Beck, and Bearman, 1949, p. 15).
    >>Pisolitic Ogallala limestone can be worked, but it is dense and nodular and contains abundant quartz grains. Ranging from grayish white to pink when freshly broken, it turns dark gray when exposed to the weather. It resists weather reasonably well in a dry climate.
  • Daniel F. Merriam (1963). "The Geologic History of Kansas". Kansas Geological Survey Bulletin (162). Kansas Geological Survey: Appendix A--Known "Algal Limestone" Occurrences in Kansas. Retrieved 2024-07-25.
  • Warren G. Hodson (1965). "Geology and Ground-Water Resources of Trego County, Kansas". Kansas Geological Survey Bulletin (174). Kansas Geological Survey: Geologic Formations in Relation to Ground Water. Retrieved 2024-08-04. A thin, discontinuous pisolitic limestone, 1 to 3 feet thick, commonly occurs as the topmost bed of the Ogallala ... in Trego County,
  • Charles K. Bayne, Paul C. Franks, and William Ives, Jr. (1971). "Geology and Ground-water Resources of Ellsworth County, Central Kansas". Kansas Geological Survey Bulletin (201). Kansas Geological Survey. Retrieved 2024-08-08.
    The upper surface of the Kimball is marked by the widespread occurrence of a distinctive bed called the "algal limestone." The name "algal limestone" was introduced by Elias (1931, p. 138) in the belief that the structures in the limestone were the work of algae, but Swineford and others (1958) present evidence that the bed resulted from soil-forming processes.
    In Ellsworth County only the uppermost bed, the "algal limestone," is present. About 40 localities were visited during this investigation where the so-called algal limestone crops out. These outcrops occur in small knobs or ridges occupying the highest topographic positions in the general area of the outcrop. The thickness ranges from a few inches to about 3.5 feet. The "algal limestone" deposits in Ellsworth County do not represent clastic deposits but rather are the remnants of a widespread soil formed in this area during late Pliocene and possibly into early Pleistocene time. The deposits occur only in divide areas and serve as marker horizons, which have been relatively stable since the close of the Pliocene Epoch. Figure 16 shows contours on top of the "algal limestone" in and adjacent to part of Ellsworth County. The contours indicate a general slope toward the east and also show topographic highs near the present drainage divides between the Saline and the Smoky Hill Rivers and between the Smoky Hill and Arkansas Rivers. There is some indication that a drainage channel existed in or near the Smoky Hill Valley and the abandoned Wilson valley.    {{cite journal}}: CS1 maint: multiple names: authors list (link)
  • Roy W. Foster, Richard M. Frentress Walter C. Riese (1972). "Subsurface Geology of East-Central New Mexico" (PDF). New Mexico Geological Society (4). Kansas Geological Survey: 2. Retrieved 2024-08-04. Deposits of caliche are widespread and range from the indurated caprock of the Llano Estacado, Las Vegas Plateau, and various buttes and mesas to the more recent material found in the alluvial deposits. The hard, banded, pisolitic caliche of the caprock has been considered by many geologists as the youngest unit of the Ogallala Formation. Baldwin and Muehlberger (1959) suggested that the caliche should be considered a separate lithologic unit because it does not everywhere overlie the Ogallala but may be developed on basalt flows or pre-Ogallala sediments. It is not known just when the caliche formed but it post-dates the post-Ogallala surface and predates all but the initial stage of dissection of this surface. Thus the time of formation of the caliche must be latest Pliocene or earliest Pleistocene.
  • Jesse M. McNellis (1973). "Geology and Ground-Water Resources of Rush County, Central Kansas". Kansas Geological Survey Bulletin (207). Kansas Geological Survey: Geology and Water Supply of Rock Units. Retrieved 2024-08-08.
    The dominant types of lithology of the Ogallala in Rush County are (1) arkosic sand and gravel with associated clay balls that are sometimes poorly cemented with calcium carbonate, clay and silt beds, and some bentonite, (2) a quartzitic-appearing green conglomerate with an opaline cement matrix, and (3) a distinctive, discontinuous, very hard and dense white to pink limestone commonly referred to as "algal limestone." A study by Swineford, Leonard, and Frye (1958) indicates that development of the limestone was by soil-forming processes rather than by algae, and that pisolitic limestone is an accurate descriptive term for the bed. Common conversational usage is "algal limestone," which is used in this report. The "algal limestone" marks the stratigraphic top of the Ogallala Formation and the Kimball Member.
  • George O. Bachman (1973). "Surficial Features and Late Cenozoic History in Southeastern New Mexico" (PDF). Open File Report (USGS-4339-8). United States Department of the Interior: 9-13. Retrieved 2024-08-04.
    >>The Ogallala Formation consists of lenticular beds of medium- to yellowish-gray conglomeratic sandstone and fine to medium-grained well sorted sandstone. These deposits are overlain by distinctive beds of light-gray sandy, pisolitic limestone--the caliche "caprock" of the High Plains.
    >>Ogallala deposition ceased before the end of Pliocene time. The pisolitic limestone that caps the Ogallala over much of the High Plains is generally regarded as being part of a pedocal soil profile (the Ogallala-Climax soil) that developed over the region near the close of Pliocene time ... It ranges in thickness from about 5 feet to as much as 60 feet in southeastern New Mexico.. The top of the Ogallala Formation, where not extensively eroded, is a constructional physiographic surface that has been called the High Plains, or Llano Estacada.
  • Joseph R. Thomasson (1979). "Late Cenozoic Grasses and Other Angiosperms from Kansas, Nebraska, and Colorado: Biostratigraphy and Relationships to Living Taxa". Kansas Geological Survey Bulletin (218). Kansas Geological Survey: Geology. Retrieved 2024-08-04.
    >>"Algal" (psiolitic) limestone was noted at seventeen localities in Ellis County. At some localities the characteristic pink concentric structural nature (see Swineford, Leonard, and Frye, 1958) of the limestone was brilliantly developed while at other sites it was only faintly noticeable. This unit is now considered by most workers to be an edaphic structure formed as a result of climatic events of the Quaternary (Frye et al., 1974; Boellstorff, personal communication, 1975). For a review of the various early hypotheses regarding its origin, consult Bretz and Horberg (1949) or Swineford, Leonard, and Frye (1958).
Graphic Sections of the Ogallala Fomation, Ellis, Rooks Counties, Kansas
  • William C. Johnson (1993). "Surficial geology and stratigraphy of Philips County, Kansas, with emphasis on the Quarternary Period" (PDF). Kansas Geological Survey Technical Series (TS1). Retrieved 2024-07-25. [p. 12] The Ogallala is capped locally by a hard pisolitic limestone or by a dence caliche, which is apparently isochronous, that is, a unique time-stratigraphic unit. [p. 15] A dense pink to white pisolitic nodular caliche (calcrete), 3 ft (0.9M) or less in thickness, caps the [Kimball] member. Because of the discovery of an alga Chlorellopsis bradleyi, that required a perennial body of water, Elias(1931) believed that the pisolitic layer was an algal limestone originating from a terminal Ogallala lacustrine environment. Darton originally thought that the Kimball was a secondary deposit, and subsequent studies by Frye et al. (1956) and Swineford demonstrated that the layer is primarily a product of pedogenesis.
Also pages on the colloidal opaline sandstone.
  • Rex Buchanan (revised by) from the 1986 edition by Laura Lu Tolsted and Ada Swineford (1998). "Kansas Rocks and Minerals". Kansas Geological Survey Educational Series (2). Kansas Geological Survey: Kansas rocks. Retrieved 2024-08-04. Caliche--Caliche is a type of calcite-cemented sandstone that forms in the soils of dry regions. ... The pisolitic limestone near the surface of the High Plains in western Kansas is such a bed. This dense limestone (formerly called "algal") has a distinctive structure and can be recognized by its pinkish color, banded appearance, and concentric areas. It was formed after the close of Tertiary time when the climate was drier than it is now.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  • Greg A. Ludvigson, Robert S. Sawin1, Evan K. Franseen, W. Lynn Watney, Ronald R. West, and Jon J. Smith. "A Review of the Stratigraphy of the Ogallala Formation and Revision of Neogene ("Tertiary") Nomenclature in Kansas". Kansas Geological Survey, Current Research in Earth Sciences (256, part 2). Kansas Geological Survey: Stratigraphy of Subsurface Rocks. Retrieved 2024-08-04. The member names for the Ogallala Formation (including the Valentine, Ash Hollow, and Kimball) in Kansas of Zeller (1968) are abandoned.' The Ogallala Formation in Kansas includes strata of Miocene and earliest Pliocene age, revising earlier correlation to the Pliocene only (Zeller, 1968). The Kansas Geological Survey is abandoning use of the term "Tertiary," to be replaced by the term "Neogene." International stage boundaries for the Neogene have not been established in Kansas.
    >>Attempts have been made to revive the term Tertiary, most recently by Salvador (2006a, b) and Head et al. (2008). Head et al. (2008) point out that 'it [Tertiary] has never been officially eliminated by the IUGS.'     {{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)

Top Ogallala "moss agate" to "chert" (Kimball)

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Graphic Sections of the Ogallala Fomation, Ellis, Rooks Counties, Kansas

Top Ogallala "Sidney gravel" (Kimball/Sidney)

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Geologist attempted assigning the base of the Kimball formation to base of the "Sidney gravel".


Bottom Ogallala "opaline sandstone" / "green quartzite" (Valentine)

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References

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  1. ^ William C. Johnson (1993). "Surficial geology and stratigraphy of Philips County, Kansas, with emphasis on the Quarternary Period" (PDF). Kansas Geological Survey Technical Series (TS1). Retrieved 2024-07-25. [p. 12] The Ogallala is capped locally by a hard pisolitic limestone or by a dence caliche, which is apparently isochronous, that is, a unique time-stratigraphic unit. [p. 15] A dense pink to white pisolitic nodular caliche (calcrete), 3 ft (0.9M) or less in thickness, caps the [Kimball] member. Because of the discovery of an alga Chlorellopsis bradleyi, that required a perennial body of water, Elias(1931) believed that the pisolitic layer was an algal limestone originating from a terminal Ogallala lacustrine environment. Darton originally thought that the Kimball was a secondary deposit, and subsequent studies by Frye et al. (1956) and Swineford demonstrated that the layer is primarily a product of pedogenesis.
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