Geologic Formations and Their Water-bearing Properties
The Laverne formation was named and described from a locality in Harper County, Oklahoma, by V. V. Waite in an unpublished manuscript which was quoted by Gould and Lonsdale (1926). These beds were studied in 1889 by Cragin (1891) who correlated them with the "Loup Fork beds." Case (1894) made a collection of the flora of these beds in 1893. Adams (1902) described similar rocks in Cimarron Valley in southeastern Seward County and suggested that they were of Tertiary age and that they were equivalent to the beds previously described by Cragin in Oklahoma. The flora and fauna of the Laverne formation in Beaver County, Oklahoma, were described more recently by Chancy and Elias (1936, pp. 16-23). Detailed studies of the Laverne formation in Kansas have been made recently by Frye and Hibbard (1941), Frye (1942), and McLaughlin (1945).
Character--The Laverne formation exposed in Cimarron Valley in Meade and Seward Counties consists primarily of steeply dipping beds of shale, chalky sandstone, sand, and gravel containing caliche and thin-bedded limestone. Test holes drilled in that area indicate that the lower part of the formation consists principally of sand and gravel containing interbedded clay or shale (Pls. 7 and 8).
The sand and gravel is made up of materials derived from igneous rocks and consists principally of quartz and feldspar although mica is abundant at some horizons. The beds of sand and gravel where exposed generally are moderately well sorted, in part cross-bedded, and in places cemented with calcium carbonate to form "mortar beds."
The clay and shale generally are light gray to dark blue gray but locally may be light green, pink, or maroon. The clay in many places contains fine quartz sand and mica. The shale is thinly bedded and the clay generally is massive, blocky, and poorly bedded.
The calcareous or chalky sandstone is soft, friable, poorly bedded, very porous, and is fine-grained to very fine-grained. These beds are known locally as "sawrock" inasmuch as they can be cut easily with a saw and have been quarried locally for building stone (P1. 9B). These beds generally are cream-colored to buff but they weather to brown, dark gray, and nearly black. They contain abundant ostracodes and some remains of fish. Sections of the Laverne formation measured by Claude W. Hibbard and Thad G. McLaughlin are given below and on page 74.
Distribution and thickness--The Laverne formation crops out in Meade and Seward Counties, Kansas, and in Beaver and Harper Counties, Oklahoma, but the subsurface extent of the formation probably is much greater than is indicated by the limited areas of outcrop. These beds probably underlie much of Seward, Haskell, Stevens, and Grant Counties, Kansas, as well as large areas in Oklahoma. They are absent in part of Morton, Stanton, and Hamilton Counties where the Cretaceous or older bedrock crops out or is overlain by the Ogallala formation. Similarly, they probably do not extend east of Crooked Creek in Meade County where the Permian redbeds are exposed or are overlain by the Ogallala formation. The northern and southern limits of these deposits are not known.
The thickness of the Laverne formation is not known inasmuch as the base of the formation is nowhere exposed. About 80 feet of these beds have been measured near the mouth of Wolf Canyon in sec. 7, T. 35 S., R. 30 W., Meade County, and about 135 feet have been measured in sec. 25, T. 34 S., R. 31 W., Seward County. Test holes in Meade and Seward Counties (16, 18, and 20) that were begun on Laverne strata penetrated from 301 to 464 feet of material before entering the Permian redbeds. All of this material is believed to be a part of the Laverne formation. The test hole that penetrated 464 feet of material (20) was begun on a ledge of "saw-rock" (bed 4 in measured section on page 75); hence, the total thickness of these beds may exceed 500 feet.
Water supply--Relatively few wells in Seward County obtain all their water from the Laverne formation because adequate quantities of water generally can be obtained in the overlying Rexroad (?) formation. Many of the deep wells that obtain most of their water from the Rexroad (?) formation may also obtain some water from the Laverne. Some of the municipal wells at Liberal, for example, penetrate all water-bearing materials that lie above the Permian redbeds.
Test holes drilled in this area indicate that in many places the Laverne formation contains thick deposits of sand and gravel and therefore is an important potential source of large quantities of ground water.
The Ogallala formation does not crop out in Seward County and whether or not it is present in the subsurface cannot be determined at present. Where the Cimarron Valley has been cut below the base of the Rexroad formation in southeastern Seward County and southwestern Meade County, it has been found that the Rexroad beds overlie the Laverne formation and that the Ogallala formation is absent. The absence of the Ogallala in these places can be explained in two ways: 1. The more resistant beds of the Laverne formation formed "high" areas over which the Ogallala sediments were not deposited. 2. The post-Ogallala erosion removed much or all of the Ogallala formation in this area before the Rexroad sediments were laid down.
The beds in the upper part of the Laverne formation are, in general, more resistant than those of the other Cenozoic formations of this area. On the Nieland Ranch, for example, the tilted Laverne beds formed a "high" during most of Rexroad time and are overlain only by the uppermost beds of the Rexroad. This indicates that the upper beds of the Laverne formation in this area are sufficiently resistant to have remained above the level of deposition during Ogallala time.
The principal evidence that much or all of the Ogallala formation was removed from this area during the interval of erosion between Ogallala time and Rexroad time is that all beds that are known to be Rexroad and those believed to be Rexroad lie at an elevation below that of a line projected from the base of the Ogallala in Morton County to the base of the Ogallala along Crooked Creek in Meade County. The position of the Rexroad beds in relation to that of the Ogallala beds could be accounted for in parts of the Meade Basin by faulting and by subsidence but there is no evidence of either faulting or subsidence between southeastern Seward County and Point of Rocks in Morton County.
Inasmuch as the Ogallala formation does not crop out in Seward County and as there is strong evidence that erosion removed much or all of the Ogallala beds in this area, the Ogallala formation is herein considered absent in Seward County.
Rexroad (?) Formation
The Rexroad formation was named by Smith (1940, pp. 95-99) from exposures along tributaries of Crooked Creek on the Rexroad Ranch in sec. 22, T. 33 S., R. 29 W., Meade County, Kansas. In 1941 Frye and Hibbard (1941, p. 407) designated these beds the Rexroad member (upper Pliocene) of the Ogallala formation. Subsequently these beds have been classified as the Rexroad formation. In this report the term Rexroad (?) is used for those deposits in Seward County that are believed by us to correlate with the Rexroad formation in Meade County.
Character--The Rexroad (?) formation consists of sand and gravel in the lower part, silt to coarse gravel containing nodules and stringers of caliche in the middle, and silt and clay containing caliche in the upper part (P1. 7).
The basal sand and gravel deposit lies in channels in the underlying deposits. For this reason there is wide variation in its thickness. In at least one place the sand and gravel deposit is absent (NW 1/4 sec. 24, T. 34 S., R. 31 W.). At this place the Laverne formation lies about 15 feet below the base of the Meade formation. The tilted Laverne strata were high erosional remnants that were not covered until near the close of Rexroad (?) deposition.
The sand and gravel consist of materials derived from igneous rocks. The gravel consists of fragments of feldspar, quartz, and some chalcedony, and the sand is made up principally of quartz. In most places at least part of this deposit has been cemented with calcium carbonate to form "mortar beds" which form prominent ledges in some places along Cimarron Valley. The "mortar beds" in the Rexroad (?) formation differ markedly from those in the Ogallala formation in adjacent areas. They are coarser-grained, contain less calcium carbonate, and weather to a smoother surface. The "mortar beds" of the Rexroad (?) resemble more closely those of the Meade formation. Those in the Med7de formation generally are coarser-grained but this cannot be used as a criterion for distinguishing them.
The middle part of the Rexroad (?) formation represents a transition from the coarse sand and gravel in the lower part to the fine sand, silt, and clay in the upper part. The middle part consists of an admixture of reddish clay, silt, sand, and gravel containing, in many places, abundant nodules and stringers of caliche giving the rock a mottled red and white appearance. The top and bottom of this part of the formation is not sharply defined inasmuch as it grades into the upper and lower parts. The middle part is very poorly sorted and is moderately well indurated.
The upper part of the formation generally consists primarily of silt, fine sand, and clay containing a few beds of caliche. Near the top of the formation is a 2-foot bed of hard cherty caliche that weathers to irregular, rough, pitted boulders. In most places, this bed has been removed by the deep-channeling preceding the deposition of the overlying Meade formation. The upper part of the formation generally is brown and gray in various shades. A thick bed of dark-brown blocky clay has been found at most places where the Rexroad (?) formation crops out.
Several sections of the Rexroad (?) formation that were measured by Claude W. Hibbard and Thad G. McLaughlin are listed below. The first was measured in one of the very few places where both the top and bottom of the Rexroad (?) formation are exposed, although in this section a few of the upper beds appear to have been removed by channeling.
Distribution and thickness--The Rexroad (?) formation crops out in many places in the Cimarron Valley between central Seward County and southwestern Meade County and along tributaries of Crooked Creek in west-central Meade County. It crops out also in Cimarron Valley in the NW 1/4 sec. 35, T. 30 S., R. 37 W., Grant County, in secs. 20 and 29, T. 31 S., R. 38 W., Stevens County, and in sec. 35, T. 32 S., R. 40 W., in Morton County.
Between central Seward County and northwestern Stevens County the channel of Cimarron River has been cut to approximately the level of the contact between the Rexroad (?) formation and the overlying Meade formation. Where the sand and gravel of the Meade formation are thick, the contact is below the stream level and where they are thin it is above stream level. Recent pediment-like deposits cover much of the valley slopes and mask the bedrock except in a few places where such deposits have been removed by the widening channel of Cimarron River or by the deepening channels of some of its tributaries.
The Rexroad (?) formation underlies much of Grant, Haskell, Stevens, and Seward Counties and parts of Meade, Morton, and Stanton Counties. It is absent east of Crooked Creek in Meade County and north and west of Point of Rocks in Morton County. It extends southward into Beaver County, Oklahoma, but its northern and southern limits are not known. The thickness of the Rexroad (?) formation is shown in the measured sections listed in the preceding pages.
Water Supply--The Rexroad (?) is the principal water-bearing formation in Seward County. These beds supply all or part of the water to most of the wells in the county. The coarse sand and gravel at the base of the formation, where adequately thick, is capable of yielding large quantities of water to wells. The middle part of the formation consists of poorly sorted materials and the upper part consists of fine-grained materials; hence they will not yield large quantities of water to wells but may yield sufficient water for domestic and stock uses. Water from the Rexroad (?) formation generally is moderately hard but is suitable for most uses.
Kansas Geological Survey, Seward County Geohydrology|
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Web version Sept. 2001. Original publication date March. 1948.