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Table of Contents

Abstract

Introduction

Geography

General Geology

Ground Water

Geologic Formations

Well Records

Well Logs

References

Plates

Table 4

System	Series	Subdivision	Thickness (feet)	Physical character	Water supply
Quaternary	Recent	Alluvium	0-75 (?)	Coarse sand and gravel containing silt and clay	Yields adequate supplies of relatively hard water to domestic and stock wells
		unconformable on older formations
		Dune sand	0-60 +/-	Medium-grained sand containing fine-grained sand and silt	Does not yield water to wells in this area, but assists in recharge of underlying formations
	unconformable on older formations
	Recent and Pleiocene	Terrace deposits	0-10 (?)	Coarse sand and gravel	Do not yield water to wells in this area
		unconformable on older formations
		Kingsdown silt	0-40 +/-	Silt and fine sand containing nodules of caliche
	disconformity
	Pleistocene	Meade formation	50-150 (?)	Sand and gravel at base; sand, silt, clay, and caliche in upper part. Locally contains volcanic ash	Yield abundant supplies of moderately hard water to domestic, stock, irrigation, and public-supply wells
unconformable on older formations
Tertiary	Pliocene	Rexroad (?) formation*	100-200 (?)	Sand and gravel at base; sand, silt, clay, and caliche in upper part. Sand and gravel in part cemented with calcium carbonate
		unconformable on older formations
		Laverne formation	0-300 (?)	Sand and gravel in lower part; micaceous sand, calcareous sandstone, silt, clay, caliche, and limestone in upper part	Yields water to very few wells in this area because of its relatively great depth below land surface. An important potential source of ground water
unconformable on older formations
Cretaceous	Gulfian**	Graneros shale	0-30 +/-	Dark-gray to black fissile shale	Yields little or no water to wells in this area
		Dakota formation	0-150	Brown, yellowish-brown, reddish-brown, buff, and tan fine-grained sandstone and varicolored clay	Locally is a potential source of ground water, but is practically unexploited in this area because of its great depth
	Comanchean	Kiowa shale	0-135	Dark gray to black shale. Locally contains lenses of sandstone	Yields little or no water to wells in this area
		local disconformity
		Cheyenne sandstone	0-100 +/-	Gray and white fine-grained to coarse-grained sandstone	Locally is a potential source of ground water, but is practically unexploited in this area because of its great depth
disconformity
Permian	Leonardian and Guadalupian**	Undifferentiated redbeds	1,500 +/-	Brick-red sandstone and siltstone containing salt, gypsum, anhydrite, and dolomite	Locally is a potential source of ground water, but is practically unexploited in this area because of its great depth and its generally high mineral content

* Note by R.C. Moore--The deposits designated as Rexroad (?) formation in this publication were called Rexroad formation [without query] in McLaughlin's manuscript of the report, and with acquiescence of supervisory officials of the Federal and State Geological Surveys this manuscript usage was set in print prior to my return from military service. Inasmuch as employment of Rexroad formation in the area here treated involves both a change in stratigraphic classification previously adopted by the Kansas Geological Survey (Frye and Hibbard, 1941; Frye, 1942; Moore, Frye, and Jewett, 1944, Kansas Geol. Survey, Bull. 62, p. 149) and extension in recognition of these deposits beyond Meade County, Kansas, it was desirable to review published and unpublished available data bearing on these changes. All pertinent publications were examined and an unpublished manuscript by Byrne and McLaughlin on Seward County was read. Conferences were held with Dr. J.C. Frye, who has studied Cenozoic deposits in southwestern Kansas extensively, with Dr. C.W. Hibbard, who has collected and studied vertebrate remains from virtually all known southwestern Kansas fossil-bearing localities, and with Dr. A.B. Leonard, who for some years has been investigating fossil molluscan faunas from Cenozoic deposits in western Kansas.

Classification of the Rexroad deposits as a member of the Ogallala formation previously has been judged appropriate on the grounds that (1) known occurrence of these fossil-bearing beds is geographically restricted to parts of Meade County, Kansas, (2) the lower boundary of the Rexroad deposits is poorly defined, (3) lithologic distinction between Rexroad and pre-Rexroad Ogallala deposits is slight or lacking, and (4) there is great difficulty generally in mapping Rexroad as a separate stratigraphic unit. Although a disconformity indicating break in sedimentation is inferred to exist in parts of Meade County at the base of the Rexroad, elsewhere in this region sedimentation of Rexroad on Ogallala was presumed to be conformable (Frye and Hibbard, 1941). Definition of the stratigraphic span of the Ogallala formation in southwestern Kansas properly is not based solely or even primarily on time concepts, in such fashion that it is presumed to exclude deposits interpreted to be younger than the so-called "Algal limestone" of northern Kansas-despite the fact that this limestone marks the top of the Ogallala in the north. Thus, it has seemed proper to apply the name Ogallala in a broadly inclusive manner to Tertiary terrestrial deposits of the western Kansas region in which neither lithologic nor structural grounds for significant subdivision in mapping is afforded. Inasmuch as the Rexroad (?) deposits of Seward County and areas farther west, which are reported to rest unconformably on Laverne deposits, are not established as true Rexroad, evidence is not yet available to show that an important break in sedimentation occurs at the base of the Rexroad; also, satisfactory grounds for recognizing Rexroad deposits outside of Meade County, Kansas, seem not yet to have been brought forward. Nevertheless, paleontological evidence emphasizes the lesser age of the Rexroad beds (very late Pliocene or early Pleistocene) as compared with pre-Rexroad Ogallala deposits elsewhere (early to late Pliocene). All things considered, it is judged desirable to revert to the original usage of Smith (1940) in which Rexroad deposits are treated as a distinct formation.

The question of recognizing Rexroad formation in Seward, Grant, Haskell, Stevens, and Morton counties is quite distinct from that of classifying these deposits as a formation or as a member. Evidence that Cenozoic deposits older than the Meade formation of this region belong to the Rexroad rather than the Ogallala seems not yet to have been obtained. Vertebrate remains from southeastern Seward County studied by Hibbard (1944, 1944a, and personal communication, June 14, 1946) indicate middle Pliocene age or at least a distinctly greater antiquity than the type Rexroad fauna; this refers to Hibbard's Saw Rock Canyon locality and vicinity. Leonard reports that fossil mollusk assemblages associated with the Saw Rock Canyon vertebrates are clearly differentiated from those of the type Rexroad. Rhinoceros remains found by Smith (1940, p. 74) near Arkalon in Seward County assuredly denote pre-Rexroad Ogallala, though mapped as Rexroad (Byrne, F.S., and McLaughlin, T.G., unpublished report). Accordingly, I judge that no secure grounds have yet been adduced for recognition of Rexroad outside of areas in Meade County, and it seems probable that all of the Rexroad (?) formation of this report comprises Ogallala deposits of pre-Rexroad age. Changes have been made in proof to indicate the questionable identification of Rexroad in Grant, Haskell, Stevens, Morton, and Seward Counties.

The outcrop areas of Rexroad (?) formation (probably Ogallala) have been omitted from the geologic map (Pl. 1); although small (see p. 118), these areas are not differentiated from the Meade formation.

** - The classification is that in use by the State Geological Survey of Kansas but not by the U.S. Geological Survey.