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Geology in Relation to Ground Water
[Note: The terminology used in this paper is that of the State Geological Survey of Kansas and differs in some respects from that of the United State Geological Survey.]
The Smoky Hill Valley area is underlain in part by Permian shale, limestone, and gypsum and Cretaceous clay, shale, and sandstone, and in part by clay, silt, sand, and gravel representing slope, terrace, dune, and alluvial deposits of Tertiary to Recent age. Smoky Hill River and its major tributaries have cut deep valleys in the Permian bedrock and have later partly filled them with Pleistocene and Recent clay, silt, sand, and gravel. This report is concerned mainly with these alluvial deposits because they are the most important sources of ground water in the area. Rocks other than alluvium and certain terrace deposits were not studied in detail. A geologic map of the area and geologic sections are shown on Plate 1.
Permian Rocks
The upland surface on both sides of Smoky Hill Valley in Saline, Dickinson, and Geary Counties, except for the relatively small area of sand hills near Abilene and parts of northern and southern Saline County, is underlain by Permian rocks belonging to the upper part of the Wolfcampian Series and the lower part of the Leonardian Series (Pl. 1). Permian rocks are also found beneath the alluvial deposits everywhere in this area.
About 350 feet of rocks of the Wolfcampian Series, including all of the Chase group and the upper part of the Council Grove group, are exposed along the valley from Abilene eastward (Pl. 1). They consist of alternating beds of limestone and shale. The limestone beds are from a few inches to about 40 feet thick and the shale beds are from a few feet to about 50 feet thick. The thickest limestones are exposed in the eastern part of the area in the vicinity of Junction City. Hard flint-bearing limestones that form prominent benches and escarpments along their outcrop are the most conspicuous features of this series of rocks. The shale beds are poor sources of water supply, but some of the limestones, especially those which contain an abundance of flint, yield rather large supplies of water of good quality to shallow farm wells and springs (Moore, 1940, p. 43). During years of low precipitation many of these wells go dry or yield inadequate supplies of water for ordinary farm use. The chief water-bearing limestones are those of the Winfield formation, Fort Riley limestone, Florence flint, and Wreford limestone.
The Wellington formation of the Sumner group, Leonardian Series, underlies the alluvial deposits and forms the bluffs and upland surface in most of the area west of Abilene. It uncomformably underlies the Kiowa shale (Cretaceous) in parts of Saline County. The Wellington formation has a total thickness of about 700 feet and consists chiefly of gray shale, but it contains some red and green shale in the lower part. Discontinuous beds of gypsum and impure limestone are found at the outcrops, and thick beds of salt (Hutchinson salt member) occur near the middle of the formation in the subsurface. The Wellington is a poor water-bearing formation, for it consists largely of shale of low permeability. Shallow wells that tap the shale have small yields and are subject to failure during periods of drought. Somewhat larger yields are obtained from wells that penetrate the thin beds of limestone in the formation. Water in the Wellington formation generally is excessively hard and highly mineralized, owing to the large amount of soluble minerals in the formation. A former salt company obtained brine from three or four wells that tapped the Wellington formation west of Solomon.
Cretaceous Rocks
Kiowa Shale
Overlying the Wellington formation along parts of Smoky Hill Valley in Saline County are Cretaceous rocks belonging to the Kiowa shale (Comanchean Series). The Kiowa shale has a maximum thickness of about 200 feet in this area and consists of light to dark-gray and black clay and shale and thick lenticular beds of dark-brown iron-rich sandstone. Selenite is common in the shale and locally there are thin beds of limestone composed largely of fossil oyster shells. Owing to their greater resistance to erosion, the sandstone beds are the most conspicuous feature of the formation, even though shale is more abundant. Sandstone beds of the Kiowa shale cap all the high hills bordering Smoky Hill and Saline Valleys in Saline County.
The Kiowa shale is relatively impervious and is a poor source of water. The sandstone lenses, however, are good sources of water. Wells that penetrate them generally yield adequate supplies of water for stock and domestic use, and in some localities adequate water is available to supply the needs of small towns. The City of Gypsum, in southeastern Saline County, obtains its supply from wells that tap sandstone of the Kiowa shale. The wells are situated on the divide between Smoky Hill River and Gypsum Creek, about 6 miles southeast of Mentor. The City of Lindsborg, in northern McPherson County, prospected for a new water supply in these sandstones east of Lindsborg, but the quantity of water available was inadequate to supply the need.
Tertiary and Quaternary Slope Deposits
Relatively thin deposits of silt, sand, gravel, and conglomerate unconformably overlie the Permian rocks in places in the western part of the Smoky Hill Valley area. They are irregularly distributed on the upland surface in Dickinson and eastern Saline Counties and on the slopes that separate Smoky Hill Valley and the Cretaceous hills west of the valley in southern Saline County. In places in southern Saline County these deposits cap small hills or ridges along the west edge of the valley. The materials comprising these deposits are of local origin and probably represent slope deposits that were laid down by sheet wash and soil creep at and for a short distance beyond the base of the westward-retreating Cretaceous hills. Some of the material probably was deposited by small, short streams that headed in the Cretaceous hills or by larger streams that headed in areas of Cretaceous rocks farther away. In places, especially in the area south of Salina, some of this material seems to be the remnant of a once more extensive terrace deposit (see cross sections N-N' and O-O' on Pl. 1).
The lower part of these slope deposits and related terrace deposits generally consists of poorly sorted clayey sand and gravel composed of grains, pebbles, and cobbles of sandstone, ironstone, shale, and caliche nodules. The sand and gravel locally contains one or more irregular layers, ranging from a few inches to about 4 feet in thickness, which have been firmly cemented to form conglomerate. Gray and light-tan to brown sandy silt generally is found above the beds of sand and gravel. Pebbles and cobbles of sandstone, ironstone, shale, and caliche are irregularly distributed in the silt, especially in the lower part. Although they range in thickness from a few feet to about 40 feet, these deposits in most places are less than 10 feet thick.
In 1895, Prosser (p. 786) gave the name "Abilene conglomerate" to certain of these deposits in western Dickinson County and placed them in the Permian. Moore (1920, p. 63) later recognized the fallacy of this correlation and stated that the formation seemed to be a Tertiary deposit. Although no detailed study of the slope and terrace deposits was made during the course of the present investigation, available data indicate that they are of different ages in different places. The deposition of these sediments probably started in the Tertiary Period, when erosion of the Cretaceous rocks began, and has been more or less continuous to the present time.
The Tertiary and Quaternary slope deposits and related terrace deposits are unimportant as sources of water in the area studied. They are above the water table everywhere in this area. Because they are unimportant as a source of ground water and because of their irregular distribution and thinness, no attempt has been made to map these sediments.
Quaternary Deposits
Terrace Deposits
Stream-laid terrace deposits of Pleistocene age underlie the dune sand in the area north of Smoky Hill Valley between Solomon and Abilene. They unconformably overlie shale, limestone, and gypsum belonging to the Wellington formation and the upper part of the Wolfcampian Series of Permian age. The character of the terrace deposits is shown by logs 66-69, 71, 72, 89, and 90, and their relation to the underlying Permian rocks and to the alluvium in Smoky Hill Valley is shown by cross section E-E' on Plate 1. The materials making up the terrace deposits probably were deposited by Smoky Hill River at a time when it was flowing at a higher level than at present. The conditions that caused the river to swing widely to the north and deposit these materials are not known. The presence of the resistant Herington limestone in this area, the first limestone bed of any consequence encountered by the river, probably was partly responsible. The lowest part of the terrace deposits is 10 to 15 feet below the present flood plain of Smoky Hill River and the highest part is more than 100 feet above the flood plain.
The terrace deposits are 50 to 65 feet thick near the valley and thin to a featheredge at the north. They consist principally of unconsolidated silts, sands, and gravels that are poorly sorted. These materials form lenses that overlap one another irregularly. The finer materials, which consist of sandy silt and sand, are more common in the middle and upper parts. Sand is abundant in the lenses of silt or gravel but is uncommon in beds by itself. The coarser materials are composed of fine to very coarse gravel that generally contains much silt and sand. Lenses of sand and gravel, from a few inches to about 15 feet thick, occur throughout these deposits but are thickest and most common in the lower part. A thin bed composed of pebbles of ironstone and sandstone occurs at the base of the terrace deposits in most places. Test holes 66 and 69 encountered thin beds of conglomerate at or near the base of these deposits. The conglomerate is composed of lime-cemented sand and gravel containing pebbles of sandstone and ironstone.
The sands and gravels of the terrace deposits are the principal source of water in the sand-hills area and yield abundant supplies of water to stock and domestic wells. These deposits are also the source of the water that supplies Sand Springs. At present there are no large wells in this area. The test drilling indicates, however, that in some places the sands and gravels are sufficiently thick and coarse to supply several hundred gallons of water a minute to properly constructed wells. Furthermore, the cover of permeable dune sand affords excellent opportunity for a high rate of recharge from local precipitation. Analyses of samples of water from well 70 and spring 73 (Sand Springs) indicate that the water from the terrace deposits is softer and is less mineralized than any of the samples collected from the alluvium in the Smoky Hill Valley area. The samples from well 70 and spring 73 had, respectively, 239 and 265 parts per million of dissolved solids and hardness of 168 and 184 parts. Complete analyses for these samples are given in Table 9.
The material that forms the low terrace along the west side of Smoky Hill River south of Salina is mapped and described with the alluvium of Smoky Hill Valley.
Dune Sand
Dune sand underlies a large area north of Smoky Hill Valley between Solomon and Abilene and a smaller area near Detroit (Pl. 1). The material consists of tan to light-gray fine to medium quartz sand that locally contains considerable silt. The thickness of dune sand encountered by test holes in the Solomon-Abilene area ranges from 3 feet in test hole 90 to 20 feet in test hole 72. The thickness of the dune sand beneath the higher dunes probably exceeds 40 feet. The dune sand in the Detroit area is much thinner and probably is not more than 15 feet thick anywhere in the area.
The dune sand lies above the water table and so does not supply water to wells. Because the sand is loose and highly permeable, it provides excellent recharge facilities for the underlying water-bearing beds.
Alluvium
Alluvium of Pleistocene and Recent age occurs in Smoky Hill Valley and its tributary valleys in the area studied. The alluvium is the most important source of water in the Smoky Hill Valley area and furnishes water to stock, domestic, irrigation, industrial, and public-supply wells. All the large wells in the area derive water from alluvium. Most of the rest of this report describes the source, occurrence, availability, utilization, and chemical character of the ground water in these deposits.
The State Geological Survey drilled 93 test holes in Smoky Hill Valley and its tributary valleys to determine the character and thickness of the alluvium. In addition, the logs of 30 test holes and 23 wells were obtained from city officials and private drilling companies. These data are shown graphically by 14 cross sections, nine of which are of Smoky Hill Valley and one each of Republican, Solomon, Saline, Mulberry, and Dry Creek Valleys. The cross sections and locations of the cross sections are shown on Plate 1, and the logs of the test holes and wells are given at the end of this report.
The alluvium consists of stream-laid deposits of clay, silt, sand, and gravel, the character and proportions of which differ from one place to another. The finer materials of the alluvium commonly occur in the upper part and the coarser materials in the lower part. The thickness of the alluvium, as shown by the logs of test holes and wells, ranges from a few feet to more than 90 feet and averages about 55 feet. Water from the alluvium is hard to very hard and in some localities contains excessive iron or chloride.
The thickness and character of the alluvium are described by areas on the pages that follow.
Smoky Hill Valley--The character and thickness of the alluvium in Smoky Hill Valley in Saline, Dickinson, and Geary Counties are indicated by the logs of 93 test holes and wells, including 56 logs of test holes drilled by the State Geological Survey. The thickness of the alluvium in Smoky Hill Valley ranges from less than 30 feet to more than 90 feet. The maximum thickness encountered was 94 feet in test hole 223, 1 mile southeast of Mentor. The thickness of the alluvium and shape of the bedrock floor at nine places in the valley are shown by cross sections on Plate 1. The maximum and average thickness of the alluvium and width of the valley at each cross section are given in Table 1. It is not possible to predict at what point along a given line across the valley the greatest thickness of alluvium will be found. There seems to be no definite relationship between the position of the present stream channel and the greatest depth to bedrock, where the alluvium is thickest. In some places (cross sections N-N' and O-O') the channel of the river nearly coincides with the deepest place in the bedrock floor. In other places the deepest part of the bedrock floor is on the opposite side of the valley from the present stream channel (cross section E-E'). At Enterprise the river is at the south edge of the valley, whereas the deepest part of the bedrock floor is near the middle of the valley (cross section D-D').
Table 1--Maximum and average thickness of the alluvium and width of the valley for nine cross sections in Smoky Hill Valley
| Cross section |
Location | Number of test holes |
Width of valley, miles |
Thickness of alluvium, feet |
|
|---|---|---|---|---|---|
| Maximum | Average | ||||
| B-B' | 3 mi. above Junction City | 5 | 1.7 | 61 | 50 |
| C-C' | At Chapman | 4 | 1.5 | 64 | 43 |
| D-D' | At Enterprise | 7 | 2.0 | 68 | 50 |
| E-E' | 3 mi. above Abilene | 5 | 2.8 | 65 | 53 |
| G-G' | 3 mi. below Salina | 9 | 4.0 | 69 | 61 |
| K-K' | South edge of Salina | 10 | 3.2 | 76 | 55 |
| L-L' | 3 mi. above Salina | 9 | 3.5 | 72 | 53 |
| N-N' | 1 mi. above Mentor | 6 | 2.4 | 94 | 64 |
| O-O' | 2 mi. above Assaria | 5 | 1.8 | 90 | 75 |
In some places the alluvium has a relatively uniform thickness across the valley (cross sections D-D' and G-G') , but elsewhere it varies considerably. South of Junction City, at cross section B-B', the alluvium is thickest in the middle of the valley and thins toward the edges of the valley. At Chapman (cross section C-C'), the thickest alluvium is found near the north edge of the valley and it gradually thins to the south. Three miles above Abilene (cross section E-E') the alluvium is thickest near the south edge of the valley and gradually thins to the north.
The upper 8 to 45 feet of material in the alluvium in Smoky Hill Valley consists of silt, sandy silt, and fine sand. This finer material is underlain by coarse sand and gravel that ranges in thickness from less than 5 feet to about 70 feet. The sand and gravel in most places is poorly sorted and contains thin lenses of silt and sandy silt. Locally derived cobbles of sandstone, ironstone, and limestone which measure as much as 10 inches in their greatest dimension, are commonly found in coarse gravel at or near the base of the alluvium. The sand and gravel are made up principally of rounded and subrounded grains of quartz, feldspar, and other material derived from igneous rocks. Where small tributaries enter Smoky Hill Valley the alluvium may be composed almost entirely of clay, silt, and sand. This is true south of Salina where the alluvium along the west edge of the valley consists mostly of fine material deposited by Dry Creek (see cross sections K-K' and L-L'). The fine material in the alluvium at the south edge of the valley 3 miles below Salina probably was brought in by the unnamed tributary that enters the valley at that point (cross section G-G').
Republican Valley--The character and thickness of the alluvium in the lower part of Republican Valley are indicated by cross section A-A' on Plate 1 and by the logs of 19 test holes and wells (logs 5-15, 18-24). The alluvium here is similar in character to the alluvium in Smoky Hill Valley. Its thickness ranges from less than 30 feet to 82 feet and averages about 45 feet. The greatest thicknesses of alluvium were encountered along the northeast side of the valley. The upper 3 to 40 feet consists of silt, sandy silt, and sand. From 17 to 57 feet of water-bearing sand and gravel occurs below the finer material.
The cities of Milford and Junction City, the Cavalry Replacement Training Center at Fort Riley, and Fort Riley obtain water supplies from wells (1, 14, 15, 16-19, 21-24) that tap the alluvium in Republican Valley. The yields of these wells range from 150 to 1,200 gallons a minute.
Solomon Valley--Nine test holes drilled by the State Geological Survey in the Solomon Valley in Saline County penetrated 44 to 65 feet of alluvium (logs 102-107, 109, 112, and 113). Peat, clay, silt, sandy silt, and sand constitute the upper 20 to 40 feet and coarse water-bearing sand and gravel comprises the lower 15 to 25 feet. In general, the proportion of coarse material to fine material is lower here than in Smoky Hill Valley and more silt and clay are mixed with the sand and gravel. There are no large wells in this part of Solomon Valley. In some places the water from the alluvium in Solomon Valley has such a high concentration of chloride that it is unfit for ordinary uses.
Saline Valley--Six test holes were drilled in a line across Saline Valley just above its confluence with Smoky Hill Valley, and a cross section (H-H') was prepared. The width of the valley at this point is 3.2 miles. The alluvium in these test holes ranged from 20 to 92 feet in thickness and averaged about 64 feet. Test hole 129, at the southwest edge of the valley, did not encounter any sand or gravel, but it penetrated 20 feet of silt and clay above the bedrock. The other test holes encountered 14.5 to 42 feet of sand and gravel in the lower part of the alluvium at depths ranging from 23 to 76 feet. The sand and gravel is overlain by clay and silt that contains small lenses of peat. It is poorly sorted and ranges in texture from fine sand to very coarse gravel. Limestone, sandstone, and shale fragments are abundant in the coarse gravels.
The recovery of ground water from the alluvium in Saline Valley is limited at present to small farm wells, although larger-yielding wells could be developed in this valley. Analyses indicate that the water is hard to very hard and locally is high in chloride and iron.
Mulberry Creek Valley--The character and thickness of the alluvium in Mulberry Creek Valley near its confluence with Smoky Hill Valley are shown by cross section J-J' and the logs of test holes 148-152, which were used to prepare this cross section. The valley is 2 miles wide at the location of the cross section. The five test holes encountered 36 to 66 feet of alluvium here. Clay and silt comprise the upper 20 to 38 feet, and fine sand to coarse gravel comprises the lower 10 to 28 feet. The materials of the alluvium in Mulberry Creek Valley were derived locally from Cretaceous rocks to the west. The coarser materials are composed of fragments of sandstone and ironstone from the Kiowa shale and Dakota formation.
There are no large wells in this part of Mulberry Creek Valley. Two samples of water from farm wells in this area contained 846 and 1,499 parts of total solids and had a hardness of 487 and 838 parts respectively (see analyses 146 and 147).
Dry Creek Valley--Test holes 209 and 211-218 were drilled in Dry Creek Valley to determine the character and thickness of the alluvium in that area. The results of the test drilling are shown graphically by cross sections M-M' and N-N'. The alluvium in Dry Creek Valley is 17 to 53.5 feet thick and is composed principally of material derived locally from Cretaceous and Permian rocks. It consists chiefly of silt and clay but contains some sand and gravel which occurs in lenses from a few inches to 10 feet thick. The sand and gravel is poorly sorted and generally is intermixed with much silt and clay. The gravels are composed entirely of fragments and pebbles of shale, sandstone, ironstone, and "mortar beds."
The lenses of sand and gravel in the alluvium of Dry Creek Valley yield small supplies of water to farm wells for domestic and stock use. A sample of water collected from well 210 in this area was very hard and contained 380 parts per million of chloride (see analysis 210).
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Kansas Geological Survey, Geology
Placed on web Nov. 13, 2013; originally published October 1949.
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