Silicified rock was found to occur at many stratigraphic positions within the Ogallala formation. As noted by Elias (1931, p. 136) chert occurs in Wallace County, Kansas, a few feet below the "Algal limestone," which is presumed to mark the top of the formation, and rock that is believed to be equivalent to this limestone was found to be partly silicified near Lamesa, Texas. At many localities in Kansas (Graham, Ness, Norton, Phillips, and Rawlins Counties) quartzite is in direct contact with Cretaceous strata or only a few feet above the base of the Ogallala. Even though silicified zones occur high within the Ogallala, the available evidence indicates that the lithology here referred to as quartzite is restricted to the lower part of the formation.
Detailed stratigraphic subdivision of the Ogallala has been made only in Nebraska, where it has been considered by Lugn (1939, pp. 1258-1264) as a group composed of the following formations in ascending order: Valentine, Ash Hollow, Sidney, and Kimball. Elsewhere within the Great Plains the Ogallala has been classed as a formation and has not been subdivided into named stratigraphic units. Elias (1942) has described fossil seeds from these beds in Kansas and Nebraska and established floral zones. He designated the lowest such zone within the formation as the Stipidium commune zone and considered it to include most of the Valentine of Nebraska classification. His Krynitzkia coroniformis zone occurs next higher and is believed to include the upper Valentine and lower Ash Hollow beds. Elias' Biorbia fossilia zone includes all but the lowermost part of the Ash Hollow. The Kimball formation is generally barren of fossil seeds.
Although detailed regional stratigraphic studies on the Kansas Ogallala have yet to be made, the available data seem to indicate that the lowest beds included in the formation near the Nebraska line (Stipidium zone and possibly the Krynitzkia zone) are early Pliocene in age (Hibbard, 1942; Elias, 1942; Hibbard and Phillis, 1945), and that equivalents are absent in southwestern Kansas and Oklahoma or may be in part represented by the Laverne formation (Frye and Hibbard, 1941). Thus the stratigraphic position of the extensive quartzite deposits of north-central Kansas is lower than any part of the Ogallala formation in southwestern Kansas. Southward in Kansas younger Ogallala overlaps older Ogallala deposits.
In contrast to this north to south overlap of the Kansas Ogallala, the lower part of the formation seems to be relatively continuous in any one latitude eastward from the Colorado line, whereas the upper part has been largely removed by erosion in the eastern part of the outcrop area. Study of the stratigraphy of the Ogallala formation in Wallace County, Kansas, by Elias (1931) indicates that the formation there attains a maximum thickness of 210 feet (p. 134) and contains Biorbia in the upper 80 to 90 feet. On the basis of test hole samples, Frye (1945, p. 66) states that the Ogallala attains a maximum thickness of 266 feet in Thomas County, Kansas. Still farther east, near Lenora in southwestern Norton County, Kansas. exposures have yielded fossil seeds identified by M. K. Elias as Biorbia fossilia (Berry) from beds 115 to 135 feet below the top of the local Ogallala section and an unknown distance above the Cretaceous contact. In northeastern Norton County this same species occurs only 40 feet below the top of the local section (Swineford and Frye, 1946, p. 10) and more than 100 feet above the Cretaceous contact. At this same locality Krynitzkia coroniformis was collected 45 feet below the beds that yielded Biorbia. Meager fossil data, obtained at one locality only, suggest that the quartzite occurs in the zone of Stipidium commune or the lower part of the zone of Krynitzkia coroniformis. Available information indicates that the Ogallala does not thin markedly eastward across the region of prominent quartzite exposures, and points to removal of the upper part of the formation by erosion during post-Ogallala time and to a restricted occurrence of the quartzite in the lower part of the formation.
Inasmuch as the presence of lenticular deposits of volcanic ash is believed to be related to the origin of the quartzite, it is important to establish the relative stratigraphic positions of ash beds and quartzite. Swineford and Frye (1946, pp. 9-11) have discussed the stratigraphy of the Ogallala volcanic ash deposits in Norton County, and in a measured section south of Almena report the occurrence of this ash 66 to 79 feet above the base of the formation. They place the ash at the top of Elias' Krynitzkia coroniformis zone and below his Biorbia fossilia zone, but present evidence indicating that some ash may belong in the lower part of the Biorbia fossilia zone. Thus, the horizon of the Ogallala volcanic ash occurs stratigraphically above the zone of the prominent quartzite lentils.
Although it has not been possible everywhere to define the stratigraphic position of the quartzite lentils within the Ogallala section precisely and conclusively, at many places the exposures are adequate to permit determination of their approximate horizon by means of fossil seeds or stratigraphic methods. The Ogallala strata adjacent to the quartzite are best exposed in the area lying south of North Solomon River and west of Glade. In this area zones of quartzite occur at several horizons throughout the lower 80 feet of the formation. The following section measured south of Speed shows the repetition of quartzite lentils in this part of the formation. Exposures in near-by gullies clearly indicate the contact of the Ogallala with the Niobrara chalk is not more than 30 feet below the base of the section.
|Measured section south of Speed, SW sec. 13, T. 5 S., R. 19 W. Phillips County, Kansas (Measured by John C. Frey, Ada Swineford, and A. R. Leonard)||Thickness,
|12.||Silt and sand, tan||8.0|
|11.||Quartzite, fine-grained, dense, green||1.5|
|10.||Sand, massive, green and red; contains fragmentary Mastodon tooth||5.0|
|9.||Quartzite, fine-grained, fairly well cemented, green||1.0|
|8.||Sand and silt, massive, green; spotted and streaked with white calcium carbonate||3.0|
|7.||Silt and sand, massive, partly silicified, hard, light gray||1.5|
|6.||Sand, silty, massive, tightly cemented with calcium carbonate; weathers to a deeply etched surface of vertical columns and horizontal sheets||1.0|
|5.||Sand, fine, and silt, green; speckled with calcium carbonate||2.5|
|4.||Quartzite, fine-grained, lenticular, light green; lenses out along road ditch||1.5|
|3.||Silt and fine sand, partly covered, light greenish gray, weathers to ash gray; contains a few nodules of calcium carbonate||2.5|
|2.||Sand. fine, and silt, indistinct bedding, very light greenish gray, weathers to platy and nodular surface; loosely cemented throughout with calcium carbonate; forms indistinct bench along near-by canyon side||4.5|
|1.||Silt, sandy, calcareous; contains calcium carbonate in irregular nodules and stringers; upper part more clayey, darker gray, contains less carbonate||6.0|
West of this measured section,, fossil seeds of Stipidium commune Elias were collected from 12 feet below a thin bed of quartzite in sec. 17, T. 5 S., R. 20 W., Phillips County. Although the beds below the Stipidium-bearing strata are mostly covered, partly silicified sand and gravel is exposed approximately 75 feet below the upper quartzite.
Exposures of the lower part of the Ogallala formation were studied in the area immediately west of Sugar Loaf Mound in Rooks County. Well-silicified quartzite was not found in the immediate area of the measured section given below, but a lower zone is partly silicified and the horizon of the upper quartzite was approximately established within the section by hand level from its occurrence in the prominent mound less than one-half mile to the east. In the immediate vicinity of Sugar Loaf Mound, three lenticular zones of quartzite, the upper two of which are visible in Plate 2B, occur in the interval included in the measured section.All other quartzite deposits of the North Solomon and Bow Creek Valleys area, except for one exposure in the NE sec. 18, T. 5 S., R. 19 W., occur in the lower 25 to 30 feet of the Ogallala (Pl. 3B). This is also true of the quartzite deposits in Rawlins, Graham, and Ness Counties, The exposure in Ness County is of particular interest because three zones of silicification--Niobrara chalk immediately below the base of the Ogallala, conglomeratic green quartzite, and white to gray chert--occur in a vertical interval of 40 feet.
|Measured section west of Sugar Loaf Mound, SE sec. 8, T. 6 S., R. 19 W, Rooks County, Kansas.||Thickness,
|7.||Sand, loose, partly covered; contains carbonate nodules. This interval is approximately at the same horizon as the lenticular quartzite forming the caprock of Sugar Loaf Mound||5.0|
|6.||Sand, loose, green; contains calcium carbonate nodules in lower part; cemented in upper part to a bench-forming ledge; contains root molds||4.5|
|5.||Sand, silty, green; poorly cemented with calcium carbonate in lower part; upper 2 feet well cemented to a bench-forming ledge; contains Celtis willistoni (Cockerell) Berry||11.0|
|3.||Sandstone, cemented with calcium carbonate, silty in upper part, grains of lower part stained green; lower 2 feet green and partly silicified in SE NE sec. 8, T. 6 S., R. 19 W.||10.0|
|1.||Chalky shale, blue gray|
An appreciable vertical range in the stratigraphic position of the quartzite lentils of the Ogallala in other regions is indicated by the presence of two such beds separated by an interval of 40 feet in South Dakota (Todd, 1889). Data are not adequate for accurate correlation of the quartzite in west-central Texas with the Kansas Ogallala section. The position of these lentils in the local Texas section and their distance below the "Algal limestone" horizon suggest that they are not younger than mid-Ogallala.
Chert deposits have been observed at many stratigraphic positions within the Ogallala from the "Algal limestone" at the top to near the base; however, chert has not been observed in the basal few feet of the formation or below the lower zone of quartzite.
Kansas Geological Survey, Geology
Placed on web Aug. 20, 2007; originally published July 1946.
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