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Geologic Formations and their Water-bearing Properties, continued
Tertiary System
Pliocene Series
Laverne formation
The Laverne formation was named and described from a locality in Harper County, Oklahoma, by V.V. Waite in an unpublished manuscript which was quoted by Gould and Lonsdale (1926a). These beds were studied in 1889 by Cragin (1891) who correlated them with the "Loup Fork beds." Case (1894, pp. 143-147) visited the area in 1893 and made a collection of the flora. In 1902, Adams (1902, pp. 301-303) described similar rocks in the Cimarron Valley in southeastern Seward County and suggested that they were of Tertiary age and were equivalent to the beds described by Cragin. More recently the flora and fauna of the Laverne deposits in Beaver County, Oklahoma, were described by Chaney and Elias and by Hesse (Chaney and Elias, 1936, pp. 16-23 and 47-72). Smith (1940, pp. 37-39) measured a section of the Laverne formation in Seward County and tentatively assigned these beds to early Pliocene. More detailed studies of these beds have been made recently by Frye and Hibbard (1941), Frye (1942), and Byrne and McLaughlin (in press).
Character--Where the Laverne formation crops out in the Cimarron Valley in Meade and Seward Counties it consists primarily of shale, sand, and chalky sandstone containing caliche and thin-bedded limestone. Test holes drilled in that area, however, indicate that only a small part of the formation is exposed and that sand and gravel are the dominant constituents of the formation. The proportion of clay and shale seems to increase toward the west.
The sand and gravel are made up of materials derived from igneous rocks. The gravel consists principally of fragments of quartz and feldspar; the sand is primarily quartz but is in part feldspar. A few beds of sand contain abundant flakes of mica. The beds of sand generally are moderately well-sorted and are in places cross-bedded.
The clay and shale range from dark blue gray to light green, pink, and maroon but generally are gray. The clay is massive, blocky, and poorly bedded, whereas the shale is thinly bedded. The calcareous sandstone is soft, friable, poorly bedded, very porous, and is fine-grained to very fine-grained. It can be cut easily with a saw and has been quarried locally for building stone. These beds generally are cream-colored to buff but 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 the writer are given below and on page 116.
| Section of Laverne formation, sec. 25, T. 34 S., R. 31 W., Seward County | Thickness (feet) |
|
|---|---|---|
| Laverne formation | ||
 |
15. Sandstone, fine to coarse, light tan to buff | 2 |
|
14. Shale, gray, poorly bedded | 5 |
|
13. Caliche, sandy, very hard, white. Weathers to smooth round boulders | 0.5 |
|
12. Shale, thin-bedded, varicolored. Predominantly yellowish near base, gray in middle, and pink to maroon near top | 6.1 |
|
11. Sandstone, fine-grained, compact, hard. Forms prominent ledge. Weathers to large disc-shaped blocks having pitted surface. Top 4 inches contains caliche | 3 |
|
10. Alternating thin beds of gray, tan, and green shale and buff friable sandstone. Beds contain a few white limy zones. Abundant crystals of gypsum in upper part | 19.2 |
|
9. Shale, dark gray, containing lenses of thin buff sandstone | 1.3 |
|
8. Sandstone, medium-grained, white, containing thin partings of dark-gray shale | 0.6 |
|
7. Caliche, dense, hard, white | 0.3 |
|
6. Shale, massive, light, gray to blue gray | 3.6 |
|
5. Sand, fine to coarse, yellowish buff to rusty brown, and gravel, fine; unconsolidated to moderately well consolidated. Forms massive ledge where consolidated | 12 |
|
4. Silt, sandy, and clay | 12 |
|
3. Sandstone, fine-grained and very fine-grained, very porous, highly calcareous, even-bedded, cream-colored to light tan, containing silt and lesser amounts of medium sand and clay. In places it is case-hardened. Locally known as "saw rock." Contains abundant ostracodes | 21 |
|
2. Shale, silty, calcareous, diatomaceous, light buff to yellow tan, containing sand | 20-30 |
|
1. Clay, blue gray | 20 |
| Thickness of Laverne formation exposed | 126.6-136.6 | |
The lithology of the Laverne formation in Grant, Haskell, and Stevens Counties is known only from test-hole cuttings, and because of the lithologic similarity of the Laverne and overlying Tertiary and Quaternary formations it is not possible to recognize the upper limit of the Laverne with certainty. All the Tertiary and Qua-ternary deposits (except dune sand and alluvium), therefore, are shown as undifferentiated Pliocene and Pleistocene deposits on Plate 3. Inasmuch as the thickness of the Kingsdown, Meade, and Rexroad (?) formations probably is not over 350 or 400 feet, all Tertiary sediments more than 400 feet below land surface probably are a part of the Laverne formation. In Grant, Haskell, and Stevens Counties the Tertiary sediments that are more than 400 feet below land surface consist mainly of sand and gravel, although a few test holes (34, 37, 39, 40, and 45) encountered much silt and clay below that depth.
Distribution and thickness--The only known outcrops of the Laverne formation are in Meade and Seward Counties, Kansas, and in Beaver and Harper Counties, Oklahoma, but the subsurface extent of this formation probably is much greater than is implied by the limited areas of outcrop. The Laverne probably does not extend beyond Crooked Creek in Meade County where Permian rocks are at or near the surface and are overlain by the Ogallala formation. Similarly, these beds probably pinch out in Morton, Stanton, and Hamilton Counties where Cretaceous and older rocks are at or near the surface and are in many places overlain by the Ogallala formation. The Laverne probably underlies all of the Grant-Haskell-Stevens area except western Grant County, northwestern Stevens County, and northeastern Haskell County.
If it is assumed that the thickness of the overlying formations does not exceed 400 feet, then the greatest thickness of the Laverne formation encountered in test holes in this area would be approximately 300 feet in test hole 38 on the Stevens-Seward line. The Laverne probably thins westward and may be absent in the western part of the area. Test holes drilled in the area of outcrop of the Laverne indicate that the maximum thickness of the Laverne formation in that area may be as much as 485 feet. The thinnest section of Laverne encountered was about 350 feet.
Age and correlation--Many years ago, remains of fish, turtle, and plants were taken from a quarry in the Laverne formation on the Nieland ranch in sec. 24, T. 34 5., R. 31 W., in Seward County, but the specimens were not identified. Since that time no identifiable remains of vertebrates have been reported from these beds in Kansas. Many ostracodes have been found in the Laverne in the same locality (Frye and Hibbard, 1941, pp. 401, 402), but they were not sufficiently diagnostic to date the beds.
In 1940, S.W. Lohman collected material containing diatoms from the Laverne formation on the Nieland ranch. The diatoms were studied by K.E. Lohman of the U.S. Geological Survey, who recognized 34 species and varieties (listed in Frye and Hibbard, 1941, pp. 402, 403). The diatom flora contained many species that now live in saline lake waters, indicating that the diatomaceous marl was deposited under similar conditions. A molluscan fauna taken from beds above the diatomaceous marl, however, is believed by Leonard and Franzen (1944, p. 31) to have lived in fresh-water lakes. The best age determination that could be made from the flora was upper Miocene to lower Pleistocene. In a letter dated April 1, 1941 (Frye and Hibbard, 1941, p. 403), K.F. Lohman stated:
"This flora cannot be correlated with the diatom-bearing beds in Beaver, County, Oklahoma ... as only 12 percent of the present flora occurs in the Beaver County material. Eighteen percent of the present flora occurs in the Ogallala formation of Wallace County, Kansas ... but this again is too small a percentage for a comparison, particularly as it does not include the most significant species."
In the area of outcrop of the Laverne formation in Kansas, these beds are overlain by the post-Ogallala (?) Rexroad (?) formation. Inasmuch as the Laverne underlies Rexroad (?) and is lithologically dissimilar to the nearby middle Pliocene Ogallala formation, the Laverne formation probably is pre-Ogallala or lower Pliocene.
There is not sufficient fossil evidence at present to correlate the beds in Kansas with the Laverne formation in Oklahoma, but the similarity in lithology and structure of the beds in both areas indicate that they are equivalent. According to Hesse (Chaney and Elias, 1936, P. 68) the fauna from the beds in Oklahoma is most closely related to the Clarendon fauna of Texas and more distantly to the Esmeralda, Big Springs Canyon, Burge, and other faunas of lower Pliocene age.
Water supply--Few wells in Grant, Haskell, and Stevens Counties obtain water from the Laverne formation, because adequate quantities of water generally can be obtained from the overlying beds. A few of the deeper irrigation wells may obtain some water from the Laverne, but most of the irrigation wells are in western Grant County where the Laverne is very thin or absent. Some of the deep wells that were used to supply water for drilling gas wells probably obtained part of their water from beds in the Laverne formation.
The Laverne formation contains thick beds of sand and gravel in its lower part in much of the Grant-Haskell-Stevens area and therefore is a potential source of large quantities of ground water.
Ogallala formation
(See note by R. C. Moore on page 33.)
The Ogallala formation of middle Pliocene age does not crop out in Grant, Haskell, or Stevens Counties, but it may be present in the subsurface. The nearest known outcrops of the Ogallala formation are in southern Hamilton County, in the vicinity of Point of Rocks in the Cimarron Valley in Morton County, along Crooked Creek in Meade County, and along the Beaver River in Texas County, Oklahoma. It is doubtful if the Ogallala in any of these areas extends into the Grant-Haskell-Stevens area except perhaps in southern Stevens County. The Ogallala does not crop out in Stevens County and cannot be identified from drill cuttings.
Rexroad (?) formation
(See note by R. C. Moore on page 33.)
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, these beds were designated the Rexroad member (upper Pliocene) of the Ogallala formation by Frye and Hibbard (1941, p. 407) for the following reasons:
"(1) ... on the basis of both surface and subsurface data, it seems evident that in parts of the basin there was continuous sedimentation from middle Pliocene through upper Pliocene time, and in these localities no break is distinguishable; (2) the deposits were trapped in a local basin, and, although there are deposits of equivalent age outside this general area, they are not stratigraphically continuous with the deposits of the Rexroad type locality, and are not genetically related to them; and (3), as Smith (1940, pp. 95-97) has pointed out, the lithology of the Rexroad beds for the most part is indistinguishable from the middle Pliocene part of the Ogallala formation. For these reasons the Rexroad beds do not constitute a mappable unit, except partially in the vicinity of the type locality, where the upper contact, but not the lower, can be mapped."
Various studies indicate that the Rexroad deposits occur stratigraphically above the "Algal limestone" which represents the top of the Ogallala formation. In a recent paper (Elias, 1945) by members of the geological surveys and the museums of vertebrate paleontology at the Universities of Kansas and Nebraska it was proposed:
"that Blancan be used to serve as a provincial time zone for beds and faunas in the Great Plains region younger than the 'Algal limestone' and older than beds of undoubted Pleistocene age."
The Rexroad deposits, therefore, appropriately may be considered as a distinct stratigraphic unit.
Much additional work was done on the beds of the Rexroad in the summers of 1943 and 1944 by Claude W. Hubbard and the writer who measured sections of these beds in Meade County and on Rexroad (?) in areas farther west. We concluded from these studies that sedimentation seemingly was discontinuous from middle Pliocene through upper Pliocene time inasmuch as the Rexroad or Rexroad (?) is nowhere known to lie on Ogallala. Where the base of the Rexroad (?) appears, it is underlain by the Laverne formation. The lower part of the Rexroad (?) formation comprises sand and gravel channeled deeply into the underlying beds. We also concluded that the deposits are widespread, inasmuch as typical Rexroad beds crop out in the Cimarron Valley of Meade County, Rexroad (?) beds occur westward to Morton County, and all these have distinctive lithology.
For these reasons, the Rexroad - plus Rexroad (?) - is judged to be a mappable unit and in this report and a forthcoming one on Seward County (Byrne and McLaughlin, 1946) it will be classed as a formation.
Character--The Rexroad (?) formation comprises sand and gravel in the lower part, sand and silt containing nodules and thin stringers of caliche in the middle, and silt and clay in the upper part.
The sand and gravel are mostly grains and pebbles of igneous rocks which probably were derived from the Rocky Mountains. They range from fine to coarse but generally are not as coarse as the sand and gravel in the overlying Meade formation. In most places the sand and gravel are in part cemented by calcium carbonate to form "mortar beds" which crop out as prominent ledges in parts of the Cimarron Valley. "Mortar beds" of the Rexroad (?) differ in general from similar beds of the Ogallala formation in that they contain less calcium carbonate, are coarser grained, consist mainly of materials derived from igneous rocks, and, in addition, their weathered surface is smoother. The "mortar beds" of the Rexroad (?) resemble more closely those in the sand and gravel of the Meade formation, although the "mortar beds" of the Meade generally are much coarser grained.
Sand and gravel of the Rexroad (?) formation grade upward into fine sand and silt containing a small amount of clay. In the zone of transition the clay and silt bind the pebbles of sand and gravel to form a moderately well-consolidated bed which weathers to a nearly vertical ledge. The material in this zone is poorly sorted and "dirty," whereas the underlying beds are more uniform, well sorted, and "clean."
The middle part of the formation generally consists of reddish silt and sand which in many places contain clay. These beds are poorly sorted, moderately well consolidated, and contain many nodules and thin stringers of caliche which give them a red and white mottled appearance. The caliche nodules usually are relatively soft but in places they are hard and are more resistant to erosion than the surrounding rock material, causing the accumulation of caliche rubble on eroded surfaces.
The upper part of the formation consists of better sorted and finer grained material, and generally contains one or more beds of brown to gray-green clay and one or more beds of caliche ranging in thickness from a few inches to about 2 feet. One 2-foot bed of caliche near the top of the formation is cherty and is extremely hard, and weathers to characteristically irregular, rough, pitted boulders. In many places this bed has been removed by the deep channeling of the overlying Meade formation (Pl. 9).
Except for the two small outcrops in Grant and Stevens Counties, lithology of the Rexroad (?) formation in the Grant-Haskell-Stevens area is known only from well cuttings. Where these beds crop out in this area they underlie the basal sand and gravel of the Meade formation and consist of brown blocky clay and buff-red silty sand containing nodules and stringers of caliche. The lithology of these deposits is characteristic of part of the middle and upper parts of the Rexroad (?) formation. Well cuttings indicate that the lower part of the formation in this area consists primarily of sand and gravel.
Several sections of the Rexroad (?) formation as measured by Claude W. Hibbard and the writer 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 some upper beds seem to have been removed by channeling of the overlying Meade formation {Pls. 9 and 11).
| Section of Rexroad (?) and Laverne formations in sec. 7, T. 35 S., R. 30 W., Meade County | Thickness (feet) |
|
|---|---|---|
| Rexroad (?) formation | ||
|
19. Sand and gravel; coarse; locally cemented with calcium carbonate to form mortar beds | 11 |
| Rexroad (?) formation | ||
|
18. Silt, fine sandy, buff red, containing caliche | 13.5 |
|
17. Silt, sandy, light, brown to red, containing caliche. The caliche near the top is nodular and cherty | 14 |
|
16. Silt, fine sandy, buff red to red, containing caliche. Material near the middle cemented with calcium carbonate | 14 |
|
15. Caliche, siliceous, massive, very hard, white | 2 |
|
14. Sand, fine to coarse, tan to buff red, containing irregular nodules and bands of caliche and much silt. Becomes finer toward top. Most of the silt and caliche are in the upper part | 20 |
|
13. Sand and gravel; coarse; moderately well sorted; cross-bedded. The pebbles are predominantly igneous rocks but some are abraded fragments of caliche. The upper two-thirds of the bed is cemented with calcium carbonate to form "mortar beds." The "mortar beds" form prominent ledges and cap several low mesas and have been eroded into long rectangular blocks | 22.5 |
| Laverne formation | ||
|
12. Clay, brown, containing lenses of rust-stained quartz sand. Weathers to gray green. Contains fragments of fossil camel | 17 |
|
11. Sand, fine to medium, gray to yellow, cemented with calcium carbonate to form "mortar beds." Bed dips eastward | 15 |
|
10. Sand and gravel; unconsolidated; yellow to rusty | 5.5 |
|
9. Clay, silty. blocky, tan, sandy at top | 2.5 |
|
8. "Mortar hods." thin, crinkly, containing fine to medium sand | 0.2 |
|
7. Sand, fine, and silt; pinkish | 1 |
|
6. Sand, fine to medium, yellowish tan, containing a few pebbles of coarse sand and gravel. Upper part cemented with calcium carbonate to form "mortar beds." Dips west-southwestward | 5 |
|
5. Clay, gray | 8 |
|
4. Sandstone, massive, soft, friable, highly calcareous, very porous, tan to buff, containing very fine sand, silt, and a few grains of medium sand. Contains abundant remains of ostracodes. Locally known as "saw rock" | 21 |
|
3. Clay and silt; containing fine sand | 2 |
|
2. Sand, fine to coarse, yellow to rusty | 2 |
|
1. Sand, fine, tan | 1 |
| Thickness of Rexroad (?) formation | 86 | |
| Thickness of Laverne formation | 80.2 | |
| Section of Rexroad (?) formation in sec. 1.9, T. 34 S., R. 30 E., Meade County, (mild sec. 2.4, T. 34 S., R. 31 W., Seward County | Thickness (feet) |
|
|---|---|---|
| Rexroad (?) formation | ||
|
8. Caliche, cherty, very hard, white. Forms prominent bench | 2 |
|
7. Unexposed. Covered by caliche rubble from above. Gentle slope indicates silt or clay | 10 |
|
6. Clay, silty and fine sandy, gray brown to huff, containing thin impersistent layers of caliche | 21 |
|
5. Clay arid silt; fine sandy; buff to pink; containing nodules and thin stringers of caliche | 16.5 |
|
4. Sand and gravel; containing abraded pebbles of caliche and small lenses of clay | 75 |
|
3. Clay, light brown | 2 |
|
2. Clay, blue gray, containing caliche. Weathers to rusty brown | 2 |
|
1. Sand and gravel; coarse. Pebbles are predominantly igneous rocks but some are abraded caliche. Base not exposed | 9-25 |
| Thickness of Rexroad (?) formation exposed | 70-86 | |
| Section of Rexroad (?) formation in SE 1/4 sec. 35 and SW 1/4 sec. 30, T. 32 S., R. 33 W., Seward County | Thickness (feet) |
||
|---|---|---|---|
| Terrace deposits | |||
|
8. Sand and gravel; coarse; containing cobbles as large as 5 inches in diameter Meade formation | ||
|
7. Sand and gravel; coarse; cemented near base with calcium carbonate to form "mortar beds" | 20 | |
|
Rexroad (?) formation | ||
|
6. Clay, blocky, gray green and brown. Grades upward into fine-grained micaceous sand. The sand is cemented in some places to form a 4-inch "mortar bed | 3.8 | |
|
5. Shale, calcareous, thin-bedded, white, containing fine sand and remains of ostracodes | 0-0.5 | |
|
4. Silt, fine sandy, tan at base to green at top. Varies from massive at base to blocky in middle to thin-bedded at top. Top part grades laterally into a varved diatomaceous marl | 4 | |
|
3. Clay, blocky, in part sandy, brown to gray | 4 | |
|
2. Sand, fine, and silt; poorly sorted; consolidated; tan to reddish brown; containing nodules of caliche. Lower 5 feet is mostly fine sand containing clay as a binder. Middle 4 feet mostly tan to brown silt. containing irregular nodules of caliche which give the rock a mottled appearance. Upper 4 feet predominantly massive fine-grained poorly consolidated tan to red-brown sand | 13 | |
|
1. Sand and gravel; coarse | 15 | |
| Thickness of Rexroad (?) formation exposed | 40.3 | ||
| Section of Rexroad (?) formation near Ulysses bridge along south bluff of Cimarron River in NW 1/4 sec. 35, T. 30 S., R. 37 W., Grant County | Thickness (feet) |
|
|---|---|---|
| Meade formation | ||
|
5. "Mortar beds," gray, containing sand and fine gravel at base and coarse gravel in upper part | 17 |
| Rexroad (?) formation | ||
|
4. Clay, dark gray to brown, containing pebbles of caliche | 1.5 |
|
3. Sand, fine, consolidated, gray, containing silt and clay | 3 |
|
2. Clay, blocky, grayish brown, containing several thin bands of caliche | 10.5 |
|
1. Sand, fine, reddish brown, containing silt, clay, and a small amount of caliche. Weathers to massive ledge | 5 |
| Thickness of Rexroad (?) formation exposed | 20 | |
| Section of Rexroad (?) formation in road cut near Rolla bridge in SE 1/4 NW 1/4 sec. 35, T. 32 S., R. 40 W., Morton County | Thickness (feet) |
|
|---|---|---|
| Terrace deposits | ||
|
3. Gravel, coarse, consisting of pebbles of both igneous and sedimentary rocks. Contains a few pieces of scoriaceous basalt | 3 |
|
Rexroad (?) formation | |
|
2. Clay, brown, blocky, weathers to grayish brown. Contains a gray calcareous zone about 5 feet from base | 8 |
|
1. Sand, fine, and silt; reddish tan; contains caliche at base | 7 |
| Thickness of Rexroad (?) formation exposed | 15 | |
Distribution and thickness--Rexroad (?) deposits crop 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. Outcrops occur also in the banks of the Cimarron River in secs. 35 and 36, T. 32 S., R. 33 W., Seward County, in NW 1/4 sec. 35, T. 30 S., R. 37 W., Grant County (Pl. 9), in secs. 20 and 29, T. 31 5., R. 38 W., Stevens County, and in sec. 35, T. 32 S., R. 40 W., Morton County (Pl. 9). The Rexroad (?) appears in nearly vertical bluffs in Grant and Stevens Counties but is not. shown on Plate 1 because the outcrops are very small. The Rexroad (?) was unrecognized in Grant and Stevens Counties and in Morton County (McLaughlin, 1942) until 1944 after field work for the Grant-Haskell-Stevens area had been completed.
The channel of the Cimarron River has been cut to approximately the level of contact between the Meade and Rexroad (?) formations from western Stevens County to central Seward County. Where the gravel and sand of the Meade are thin, a few feet of Rexroad (?) may be exposed; but where the Meade has channeled deeply into the Rexroad (?), only sand and gravel of the Meade are exposed along the channel. In addition, recent pediment-like deposits cover much of the valley floor and mask the bedrock except in a few places where the surficial deposits have been removed by widening of the channel of the Cimarron River. Additional widening of the channel may expose other beds of the Rexroad (?).
The Rexroad (?) formation probably underlies all or most of Grant, Haskell, and Stevens Counties. The outcrops of this formation in many places in the Cimarron Valley between Morton County and Meade County imply widespread distribution. The Rexroad (?) probably pinches out in northwestern Grant or southeastern Hamilton County on the flank of the Syracuse anticline. True Rexroad probably does not extend east of Crooked Creek in Meade County and Rexroad (?) beds end between the Rolla and Elkhart bridges in the Cimarron Valley in Morton County. On the south side of the Cimarron River, however, the Rexroad (?) may extend much farther to the south and west. In a gravel pit 5 miles north and 1 mile east of Elkhart in Morton County, terrace deposits overlie "mortar beds" of the Meade formation which are channeled into a brown clay that resembles closely upper beds of the Rexroad (?) formation. North of the Cimarron River in that vicinity, however, the Ogallala formation is at or near the surface.
The top and base of the Rexroad (?) formation could not be determined by study of cuttings from test holes in Grant, Haskell, and Stevens Counties; hence the thickness of the formation in this area is not known. Greatest measured thickness of the Rexroad (?) is 86 feet in Meade and Seward Counties (note the first two sections given above, but at only one place are the top and bottom of the formation exposed. The thickness of the upper part of the formation is moderately uniform, whereas the thickness of the basal sand and gravel is highly variable. Where the base of the Rexroad (?) is exposed there has been relatively little or no channeling into the underlying Laverne formation. Hence the basal sand and gravel and therefore the entire Rexroad (?) formation are relatively thin.
Test holes drilled near the areas of outcrop of the Rexroad in Meade County and of the Rexroad (?) in Seward County indicate that these deposits may be as much as 170 feet thick. Test holes that penetrated thick sections of Rexroad (?) encountered thick deposits (50 to 100 feet) of sand and gravel in the lower part.
The thinnest exposed section of the Rexroad (?) beds is in southeastern Seward County where there is less than 15 feet of the Rexroad (?) between basal sand and gravel of the Meade formation and the Laverne formation. This outcrop is less than 1 mile from one of the places where the measured thickness of the Rexroad (?) is 86 feet.
Age and correlation--The age of the Rexroad (?) formation is not definitely known. The formation is younger than the Ogallala formation because much or all of the Ogallala between east-central Morton County and Crooked Creek in Meade County, in the view of the author, was removed by erosion before the Rexroad was laid down. The Rexroad is separated from the overlying Pleistocene Meade formation by a prominent disconformity.
Fossils from the Rexroad formation (type) in Meade County have been described by Hibbard (1938a, 1939, 1941, 1941a, 1941b), Baker (1938), Taylor (1941 and 1941), and Wetmore (1944). Hibbard's interpretation of the Rexroad fauna is as follows (Frye and Hibbard, 1941, p. 410):
"On the basis of the fossil mammals the Rexroad, Blanco, Benson, and Hagerman faunas are believed to be of approximately the same age. The differences between the faunas are thought to be of only geographical significance. The Rexroad fauna shows a closer relationship to the Blanco and Benson faunas than to the Hagerman fauna. Although the fauna as a whole shows relationships with forms now found in Mexico and Central America rather than with the recent forms now found in southwestern Kansas, a few fossil forms possess boreal affinities.
The fauna indicates that meadow flats and timbered areas existed at least along parts of the late Pliocene stream valleys, and that the climatic conditions then were not drier nor colder than those at present. There is some indication, moreover, that the climate of late Pliocene time lacked extremely cold winters or severely hot summers, accordingly being more equable than the present climate, and that there was a somewhat greater degree of humidity than exists now in this region.
The environment during Rexroad time as interpreted by Wetmore (1944, p. 91) from his study of the remains of birds is as follows:
"Of the identified specimens, more than one-half belong to aquatic species that live in and around marshes, streams, and ponds. Remains of turkeys represent birds of wooded areas, while parrots, pigeons, and quail are species of forests, or regions where thickets and groves grow amid plains, prairies, or savannas. The passeriform birds may have lived in prairie land, in thickets, or in forests."
McGrew (1944, pp. 33-42) has correlated the Rexroad and Blanco faunas with the Sand Draw and Broadwater faunas of Nebraska, which he considers to be Pleistocene (Aftonian). He states that:
"Geologically, there seems to be little reason to assign the Rexroad to the late Pliocene. Some rather significant geologic changes--the faulting, the development of sink holes, and erosion--took place between the Pliocene beds beneath and the Rexroad proper."
Similarly, there was movement along the major faults (Frye, 1942, p. 26), continued solution and collapse, and widespread erosion after the deposition of the Rexroad formation and before the accumulation of the Meade formation. It does not seem to be possible at present, therefore, to date the Rexroad formation accurately on the basis of geologic history or stratigraphic position.
Vertebrate paleontologists of Kansas and Nebraska are in agreement that the Rexroad fauna of Kansas is equivalent in age to the Broadwater fauna of western Nebraska and the Blanco fauna of northwestern Texas and that the deposits from which these faunas were taken occur stratigraphically above the horizon of the "Algal limestone" (top of the Ogallala) and below the horizon of beds of undoubted Pleistocene age (such as the Meade formation).
In a recent paper by Elias (1945), the geologists and vertebrate paleontologists of the Nebraska and Kansas geological surveys proposed that:
"the placement of the Blancan in either the late Pliocene or in the early Pleistocene of the standard time scale be held in abeyance until there is more general agreement among paleontologists as to age; and that Blancan be used to serve as a provincial time zone for beds and faunas in the Great Plains region younger than the 'Algal limestone' and older than the beds of undoubted Pleistocene age."
Water supply--The Rexroad (?) formation probably yields water to many deep wells in Grant, Haskell, and Stevens Counties. Deep irrigation wells in areas of shallow water probably obtain part of their water from the Rexroad (?). Where the depth to water is 150 to 200 feet or more below land surface (Pl. 2) almost all wells get all or part of their water from the Rexroad (?). Where the water table is at or below the top of the Rexroad (?) beds, as in east-central Grant County and in central and west-central Haskell County (note the water table near the top of a persistent zone of silt and clay, Pl. 3), wells generally must be drilled through the upper part of the Rexroad (?) into basal sand and gravel to obtain sufficient water. At the site of the former town of Santa Fe, near the center of Haskell County, the municipal wells failed to encounter an adequate supply of water in the silt and clay just below the water table, although nearby dug wells obtained water sufficient for most domestic and stock uses. The municipal wells, however, were deepened to the underlying sand and gravel in order to obtain an adequate supply of water. Where Rexroad (?) deposits are present in Grant, Haskell, and Stevens Counties, supplies of water adequate for most uses probably can be obtained from the basal sand and gravel. Water from the Rexroad (?) deposits generally is moderately hard but is suitable for most uses.
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Kansas Geological Survey, Geohydrology
Web version May 2002. Original publication date July 1946.
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