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Title Page to Bulletin 137.

The Geology of the Fort Riley Military Reservation and Vicinity, Kansas

Bulletin 137

By Robert Hay

Department of the Interior, United States Geological Survey
Government Printing Office, Washington, D. C.

Note: The page numbers in the Contents and the Illustrations below do not correspond to the following documents as it has been reproduced. I am placing the original page numbers here so that you can refer to them for the original publication. Peggy B. Perazzo



Letter of transmittal 9
Topography 11
  Description of district 11
  River system 12
  Republican Valley 12
  Smoky Hill Valley 13
  Union of the valleys 13
  Creek valleys 13
  Ruggedness of the topography 14
  The Kansas-Neosho watershed 14
  Sink-holes 15
  Neosho Valley 16
  Typical character of the district 16
Geology 16
  Paleozoic 16
  Horizontal position of the strata 16
  Fort Riley section 17
  Description of strata 18
  The Main ledge 18
  The Quarry beds 19
  The Flint beds  19
  The mid-Shale bed 20
  The shales 20
  Gypsum 21
  Littoral and shallow-water conditions of deposition 21
  Pre-Quaternary erosions 22
  Continental uplifts 22
  Cretaceous 23
  Tertiary 24
  Quaternary 24
  Moraines 24
  Occasional bowlders 25
  Loess of two periods 26
  Description of sink-holes 26
  Late Tertiary and early Quaternary Contemporaneous 27
  Gumbo 27
  River alluvium; sand dunes 28
  Baselevels 28
Climatic changes 29
Correlation of different regions 30
Economic geology 30
  Soils 30
  Bottom soils 30
  Upland soils 31
  Building materials 31
  Brick clays 31
  Building stone 31
  Lime 32
  Cement 32
  Water supply 32
  Springs and wells 32
  Measurement of rivers 33
Paleontology 33



Plate I. General map of the Fort Riley Military Reservation and neighborhood, Kans. 11
II. Profile and geological section across the Smoky Hill Valley at Junction City, Kans. 16
III. The Main Ledge (limestone) in Wild Glen 18
IV. Stratified alluvium in river bank, Republican River, abutting against loess and gumbo 20
V. Quarries on the military reservation above the Main Ledge 22
VI. Bluffs in Wild Glen showing turret-like weathering of the Upper Flint beds 24
VII. Red bluffs (loess), Smoky Hill River, south by east from Fort Riley 28
VIII. Administration building, artillery post, Fort Riley, constructed of the magnesian limestone of the district 32
Fig. 1. Loess bluffs on the Republican River 14
2. Map showing the region of sink-holes in northern Morris County 15
3. Diagram of sink-hole 15
4. Section of the Lower Flint beds south of Parkersville, Morris County, showing the layers of flint in the limestone 20





Junction City, Kans., February 15, 1895.

Sir: I have the honor to transmit herewith, for publication as a bulletin of the United States Geological Survey, a report on the geology of the Fort Riley Military Reservation, Kans., and the country surrounding it. Most of the work of which this report is the result was done as early as 1889. Delay in printing has led to the recasting of parts of the paper, but in only two particulars are there any important changes, and these involve the introduction of new matter obtained as late as the spring of 1893, concerning the Cretaceous (Dakota) deposits and the glacial moraines not many miles east of the district described.

Acknowledgments are due for aid received in this survey to yourself and to Prof. W. J. McGee, as well as to Colonel (now General) Forsyth, commanding the post at Fort Riley; to Lieutenant (now Captain) Fuller, regimental quartermaster; and to Capt. George E. Pond, of the staff of the quartermaster-general.

Very respectfully,

Robert Hay,



Director United States Geological Survey.


The Geology of the Fort Riley Military Reservation.

The Geology of the Fort Riley Military Reservation
And Vicinity, Kansas


By Robert Hay.1



Description of the district.-The military reservation at Fort Riley, Kans., occupies an area of about 20,000 acres, in Riley and Geary (formerly Davis) counties. The northern half of its boundary approximates an arc of a circle. The southern half may be roughly stated to be the Republican and Kansas rivers, which united at an obtuse angle near Junction City, through a small part of the reservation lies on the right bank of the Kansas River. The area of the reservation was originally larger than at present. The old boundary is indicated on the map (Pl. I) by a broken line which passes diagonally through the site of Junction City and incloses bottom lands between the Republican and Smoky Hill rivers. Very near the site of the military post these two rivers come together to form the Kaw or Kansas.2 The northern part of the reservation is in Riley County, but the post itself is in that part of it which belongs judicially to Geary County. The region described in the following pages which is outside the reservation includes the western half of Geary County and the panhandle comprising Milford Township, in its northwestern corner, with adjacent parts of Clay and Dickinson counties, to the ninety-seventh meridian. The thirty-ninth parallel passes about 6 miles south of the post.

The geology of the region, with the exception of that of the Quaternary deposits, is comparatively simple and is typically developed within the limits of the reservation, owing to the very striking features of the topography. With the assistance of the map (Pl. I) this topography will be easily described and readily understood.

River system.-The topographic feature which first strikes the eye on an inspection of the map is the great fluvial system of the region. The rivers ranking in size as third and fourth in the State of Kansas-the Republican and the Smoky Hill-here, by their confluence, form the Kansas River, the second river of the State. Geary County may appropriately be designated the County of the Three Rivers, for all the streams of the region belong to the Three River system.

Republican Valley.-The Republican River comes from the northwest through a broad valley in which its stream meanders at a depth of from 8 to 15 feet below the general level of the bottom. The bottom is bounded on both sides by steep bluffs that are in places precipitous. Where their abruptness is not softened by slopes of Quaternary deposits the bluffs show ledges of limestone definitely continuous for miles. These bluffs are mostly over 100 feet high, and are surmounted by slopes that reach back from the valley to double that height, or more. To the traveler coming into the region these bluffs constitute the most imposing feature of the topography. The fronts of the bluffs are broken by the outlets of ravines, which, often formed by the union of several others in the plateau immediately behind, ramify to such an extent as to produce a very broken country for several miles back from the river valley, the ravines and draws being separated by ridges, mounds, and promontories of a pronounced type. This feature is indicated by the contours of the map, which show that it belongs to the whole region as well as to the Republic Valley. The abruptness of the sides of the main valley is more pronounced on the left bank of the river, but diminishes on either side as we go toward the western limits of the district. This diminution of abruptness is due in nearly all cases to Quaternary deposits which are found buttressed against steep bluffs, making smooth upland at the heads of deep ravines. The river bottom north and northwest of Junction City, about 2 miles wide, is sandy and contains many true, wind-blown dunes. Most of these are now stationary, being covered with vegetation, and their regular arrangement testifies to the prevailingly southern direction of the winds during a long period.

Smoky Hill Valley.-The topography of the Smoky Hill Valley is similar to that of the Republican, with the distinction that it is the right side of the valley which has the steeper precipices and the more abrupt slopes. The resemblance is marked in the fact that abruptness on both sides sensibly diminishes westward within the limits of the district, and on the least abrupt banks of both rivers there is also a decided diminution at their lowest part, where easy slopes of Quaternary deposits may form a broad plain, as at the site of Junction City. The Smoky Hill has its bed mostly narrower but much deeper than that of the Republican, cutting into the Quaternary from 15 to 50 feet and in places reaching bed-rock.

Union of the valleys.-The meeting of the waters of these two streams is at a very narrow part of the valley, not more than 1 ¼ miles wide. The Republican, with long, sweeping reaches, has a general southwesterly direction, with the high wall of Sherman Heights to the north, which lower to a long promontory, and the coming of the Smoky Hill from the southwest has seemed to force the joint stream around another promontory, on which Fort Riley is situated, to the northeast. The Kansas, taking a northerly direction, lies in a valley of rather uniform width in this region, being hemmed in by abrupt hills that rise 150 feet directly from the valley, go 50 to 100 feet higher at very short distances back, and are broken into narrow ridges and long promontories by the valleys of the creeks and ravines immediately behind, as seen in Grant Cliff and Sheridan Bluffs. These ridges are at the same levels as well-defined plateaus seen in the distance beyond, and the most distant views show high prairie table-land nearly 400 feet above the level of the Kansas Valley. The sand dunes of the Kansas and Smoky Hill side of the mesopotamian region has dunes near the high prairie level.

Creek valleys.-The topography of the creek valleys is similar to that along the three rivers. There are abrupt bluffs on one side, and nearly level bottoms from a quarter to half a mile wide and smooth Quaternary slopes on the other side. The horizontal limestone ledges show in the steep cliffs like rows of giant teeth or mural defenses of cyclopean dwellers, and on the opposite side they crop out occasionally through the later sediments to attest their presence. On Lyons Creek and on Clark Creek the principal Quaternary deposits are on the west side of the valley, making long, smooth slopes to the western upland. In important tributaries of these streams-Otter Creek, Dry Creek, and Humboldt Creek-the eastern side is the smoother slope, though there are exceptional localities. The meandering of the creeks in their Quaternary beds is as marked as that of the most tortuous of the three rivers, which a reference to the map shows at once is the Smoky Hill. Where the circumvolutions are not so close as in other places, a straight line from the railway station at Junction City to the station at Fort Riley, a distance but slightly over 3 miles, would cross the Smoky Hill River three times and the Kansas River once. A similar line from the Fort Riley railway station to the northwest corner of Junction City would cross the Republican twice, the Smoky Hill once, and the Kansas once. A straight line can be laid that in 10 miles will cross the Smoky Hill thirteen times.

Ruggedness of the topography.-The ruggedness of the district is nowhere more conspicuous than on the military reservation, where the headwaters of Three Mile, One Mile, and Four Mile creeks, deep Dale, and Wild Glen begin in long draws in the upland, creating the phenomena of a rolling prairie, and then below a certain limestone horizon drop suddenly into deep ravines 75 to 150 feet deep, separated by the ridges and promontories previously described, many not more than a few hundred feet across. This ruggedness is perhaps due to erosion of greater activity than now exists anywhere in the region of the Great Plains. The evidence is here decided that this configuration represents a period of time preceding the great Ice age. Some things appear to suggest that this time was immediately pre-Glacial, but one or two facts seem to indicate positively that it was before the mid-Tertiary epoch. But the discussion of these phenomena may properly be deferred to the geological part of this report, with the observation that the ruggedness is still much modified by Quaternary deposits, which would appear to have once smoothed it over entirely. (See fig. 1.)

Fig. 1. Loess bluffs on the Republican River.
Fig. 1. Loess bluffs on the Republican River.

The Kansas Neosho watershed.-In seeking to make this report as permanently useful as possible, it seemed desirable to go beyond the limit indicated by the map, so as to connect the stratigraphy of the Kansas Valley with that of the Neosho, that correlation might be made of the horizons which yield the so-called magnesian limestones for building purposes all across the State of Kansas. A rapid survey of the region of northern Morris County was therefore necessary, and the topography needs some description. Being at the headwaters of the principal creeks of Geary County, this region has rolling, high prairie surface, which is formed largely of Quaternary deposits and presents the phenomena known as sink-holes. The highest watershed separating Kansas River waters from the tributaries of the Neosho is here over 1,500 feet above tide, and broad depressions are formed where these phenomena exist.

Fig. 2. Map showing the region of sinkholes in northern Morris County.
Fig. 2. Map showing the region of sinkholes in northern Morris County.


Sink-holes.-Parts of the divide are as much as 4 miles south of the Geary-Morris boundary line, but toward the east the distance diminishes. In sec. 9, T. 14, R. 7 E., the sink-holes are very numerous, and in the northern half of the section to the south (sec. 16) they are as numerous in proportion to the area. In section 9-that is, in 1 square mile-forty-two were counted, and the exploration of that section was not such as to make it sure that all had been seen. A single example is also found in section 30 in the same township-i.e., 3 miles south and 2 west. The subsoil of the high prairie is loess, or a modification of it, and owing to long-continued vegetation the humus is several feet deep. It is in these that the sink-holes exist, sometimes showing a ledge of bed-rock in their sides, and almost uniformly loose stones from 20 or 30 pounds to 100 or 200 pounds in weight are in the center of the depression.

Fig. 3 Diagram of sink-hole.
Fig. 3 Diagram of sink-hole.

The sink-holes are mostly oval in form, but a few are nearly circular. One of these measured 30 feet one way and 28 feet transversely; others were nearly 50 feet by 30 to 35 feet. Some show no stones, owing to the falling in of the sides, but a stick inserted down the middle meets with stony obstruction about 2 feet below the visible bottom. The bottom material of all of them is loose in arrangement, and two of them have low trees growing in them. The depth is remarkably uniform, none less than 8 feet, none over 10 feet. Some of them are single, but usually there are more than one in a large depression-five in one instance, three and two commonly. A few small areas otherwise resembling sink-holes have standing water in them. They apparently are sink-holes in which the mud has become a clay puddle, checking subterranean drainage. The sink-holes proper carry away underground all the water that runs into them.

Noesho Valley.-The main valley of the Noesho becomes rapidly deeper at the same horizon which marks that phenomenon in the Three Rivers region, but the ruggedness of the confluent valleys is not nearly so pronounced as in the more northern district.

Typical character of the district.-The ruggedness of the Fort Riley district is typical of a much more extended area stretching across Riley, Pottawatomie, and Wabaunsee counties, and far to the north. It may be attributed to pre-Glacial erosion, the modification of which may as certainly be attributed everywhere to Glacial and post-Glacial deposits. It was because of this typical character that some details of the topography have been dealt with somewhat more minutely than would be necessary for the treatment of a larger district, and the same is true of the descriptive geology that follows:



Horizontal Position of the Strata.

We have said that the geology is simple, corresponding with the topography. A prominent feature is the increase in number of deposits westward, new formations coming in above, giving increment of elevation in that direction. Its strongest feature, however, is the almost horizontal position of the strata. There is some variation of the dip, but the general dip for the whole region is west-northwest. In parts, however, it is to the southwest, and small folds show a westerly uplift. There seems to be evidence of slight depression toward the stream valleys, indicating small synclines as the basis of the original drainage.

Plate II. Profile and Geological Section Across the Smoky Hill, Valley, East and West at Junction City, by Robert Hay, F.G.S.A.
Plate II. Profile and Geological Section Across the Smoky Hill,
Valley, East and West at Junction City, by Robert Hay, F.G.S.A.


West of Chapman Creek, in Dickinson County, and up the Republican in Clay County, the flint beds again crop out, showing that there is a north-and-south trough of a syncline of considerable extent and of some depth, but the details have not been made out. The average west by north to northwest dip is probably not more than from 10 to 15 feet to the mile, or 0° 10', but local variations are as much as 3 ½ in 600, or 0° 25'. One of these to the south and west of One Mile Creek which gives easterly dip is conspicuous in the railway cutting on the river bank at Fort Riley. This brings into view some of the lowest strata in the district, so that on the military reservation may be seen the outcrop of three-fourths of the more than 300 feet of deposits which come to the surface in this region. It is therefore appropriate to name this series the Fort Riley section. It is as follows:

Fort Riley section3
No. Strata Fossils Thick-ness
Permian 14 Impure limestones,4 with some flints and numerous geodes. A univalve 10
13 Light-colored shales, with lavender flag beds. Athyris, Pecten, Pleurophorus 50-60
12 Bluff limestones, with shale partings, changing to shales with limestone ledges. Pecten, Nautiloids, Athyris, Meekella, Hemipronites, Martinia, Fenestella, Synocladia, Schizodus. 30-40
11 The Fort Rile Main ledge; a buff magnesian limestone in one thick ledge, with a thinner ledge resting on it; in places the layers are continuos into the layers of 12. Pecten, Allorisma, Martinia, Athyris, Retzia, Hemipronites, Synocladia, Fenestella. 6
Permo-Carboniferous 10 Shales, light-colored and laminated Product, Allorisma, Chonetes. 15
9 The Upper Flint beds: limestones containing numerous flint nodules and separated by definite layers of flints. Producti, Chonetes, Allorisma, Martinia. 25-30
8 Shales, alternate colors, gray, greenish, maroon, brown. No fossils 30
7 Limestone: the mid-Shale bed, varying from a laminated flaggy layer to a solid building stone. Planorbis and another univalve, Allorisma, Meekella, Myalina, Hemipronites, Producti, etc. 6
6 Shales, alternate colors, as No. 8. No fossils 16
5 The Wreford limestone,5 the Lower Flint beds: flints as in No. 9; parts of the beds are silicified in localities as if by infiltration. Crinoids, Syntrilasma, Athyris, Retzia, Pinna, Meckella, Producti, cup-corals. 25
4 Shales, bands of maroon and greenish-gray, with a seam of coal on Humboldt Creek. No fossils 16
3 Limestone, in cuboidal or rhomboidal blocks; in places oolitic; a seam of coal under it on Humboldt Creek. ----- 4
2 Shales and buffy "slate." ----- 10
1 "Slate," bluish and hard Occasional Discina 10
  These outcrops are beyond the east border of the district. Shales, blue and lavender, with gypsum. ----- 30
White limestone Many fossils 5


Description of Strata.

The Main Ledge.-The most conspicuous feature of the topography is the district is the outcrop of the massive limestone we have numbered 11 and named the Main Ledge. Its topographical importance was remarked by Dr. Hayden nearly forty years ago. It is a buff, soft, magnesian limestone, yielding easily to the tools of the mason, but hardening on its exposed surfaces. While not conspicuously fossiliferous, except in certain localities, it has in the aggregate many fossils, and it also contains small cavities, now partially filled with calcite, which are apparently due to the former presence of fossils. These form imperfections in this rock as a building stone, but its durable quality and the thickness of its bed-5 to 7 feet- have caused it to be used where large blocks are required. The east wing of the capitol at Topeka was built from quarries at Junction City in this ledge, it being the first limestone in the State that was observed to yield large blocks. Grant Cliff and Sheridan Bluffs, on the Kansas, and Sherman Heights, on the Republican, show this ledge conspicuously, the exposure last named being several miles in length. The limestone may be seen on both sides of the Smoky Hill and toward the head of all the creeks to the south. Its conspicuous position in the topography suggests the use of its name in the geological nomenclature of the region, for we may divide the deposits generally into two groups-those above and those below the Main ledge of limestone, the Main ledge itself belonging to the upper group. It is the Main ledge which we mentioned as the certain horizon, below which the topography is more rugged. It follows, then, that, though the lower group of strata is thicker than those developed above it, the areal exposure of the higher group is greater than that of the loser-its slopes are gentler, its valleys less profound. In going westward the increment of the formations upward is most marked in the great valleys, but each formation is found farther east at some distance back from the streams.

The Main Ledge (Limestone) in Wild Glen
The Main Ledge (Limestone) in Wild Glen.

The first appearance of the Main ledge in the Sheridan Bluffs in the Kansas Valley is just below the old town-site of Pawnee. Plate III is a view of a typical exposure, showing also the stratum next above it. The view of Sherman Heights shows its position in the Republican Valley with 100 feet of other strata resting on it (see Pl. IV). It has very little areal exposure anywhere in the region, the largest areas being farther east and south of the river. Besides being conspicuous in the topography and stratigraphy of the region, the Main ledge seems to have paleontologic importance. It appears to be the upper limit of the Productidæ. On the south line of Geary County we have found specimens of Productus semireticulatus lying loose on the Main ledge, but in no other place have we found Producti above the shaly material at the base of that stratum. The specimen referred to might have been transported from a horizon only a few feet lower geologically and at a decidedly greater altitude only a few miles away.

It will be convenient to speak of this as the Main ledge, while its identity for comparison with other work in the State will be best established by its number (11) in the Fort Riley section.

The Quarry beds.-The beds immediately above the Main ledge may be spoken of as the Quarry beds. Throughout all the region they yield good building stone, easy to work and of soft, warm tint, in layers from 6 to 18 inches thick, of jointed structure, which give masses 6 to 12 feet long and 3 to 5 feet wide. The shale partings thicken in places to shale beds several feet thick, and the stone changes to shaly flags with rhomboidal fracture, passing upward sometimes into a lavender shale of the hard kind, locally called slate, or into massive beds with hydraulic properties, as at Milford. These beds may be altogether 50 feet thick, above which shales predominate, with occasional ledges of stone, of which only the highest is numbered, and which attains the thickness assigned to it in the section only west of the ninety-seventh meridian, somewhat beyond the limits of the district. The geodes in this bed (No. 14), which is developed in force on Chapman Creek (11 miles west of Junction City), and also south of the Smoky Hill at the same meridian, are accompanied by cherty nodules, which are the source of the flinty (cherty) gravels occasionally found above the Main ledge.

The Flint beds.-The two series of Flint beds, Nos. 5 and 9 of the section, form a quite important part of the stratigraphy of the region and of much of the country to the east and south. The name flint is used designedly. The material appears to be much more siliceous than the chert of southeastern Kansas and Missouri. It appears undistinguishable from the flints of the Cretaceous formations of England. The greater part of the beds consists of limestone, through which the flint is scattered in globular, ellipsoidal, and irregular nodules, with one or two bands of black and white near their surfaces. Besides the irregularly disposed nodules, there are flint layers 3 to 12 inches thick between the limestone layers. Fig. 4 is a section on the Neosho in Morris County, which shows a little more than the average amount of flint farther north.

Fig. 4. Section of the Lower Flint beds south of Parkersville, Morris County, showing the layers of flint in the limestone.
Fig. 4. Section of the Lower Flint beds south of Parkersville, Morris County,
showing the layers of flint in the limestone.


The presence of the flint serves to give a hardness to these beds, which, however, does not hinder their disintegration; for, under the influence of frost the flints themselves split into many fragments, with conchoidal, splintery, and smooth fracture; but under certain conditions of exposure the broken flints acquire a vitreous surface and case to break, and so form surfaces that slowly acquire a sedentary soil. Both series of flint beds, and also the Main ledge, frequently form vertical exposures, while through the wearing away of the shales beneath they overhang and topple over in large masses. On some faces there is a turret-like weathering which is peculiar (see Pl. V).

The mid-Shale bed.-The bed No. 7 in the section is very variable in structure. In some places it is only a laminated shale with vertical fracture, in others it is a flaggy shale with one or two layers of real flags, and again it becomes a compact limestone suitable for building purposes and massive through its whole thickness. In Eagle Ravine, southwest from Junction City, this bed-there 3 feet thick-is occasionally oolitic.

The Shales.-The colored shales, Nos. 6 and 8, are not variegated, but are beds of different colors alternately. Some are purplish-brown, others green, and some red-brown., each color varying on exposure. The bands are from 3 inches to 2 feet in thickness, and the gray-greens exceed that. One of the red bands seems to be of the texture for mineral paint. There are conspicuous outcrops, vertical exposures, of parts of these beds at the water-mill on the Smoky Hill, at Fort Riley railway cut, and at other places. Shales that occur below these beds are mostly lavender or greenish, and those above the Main ledge are with few exceptions the same. Where the shales have areal development they form a cold, intractable subsoil, which, however, has by long-continued growth of vegetation become in places a fertile humus.

The strata thus briefly described belong to the later part of the Carboniferous epoch. They are nearly at the top of Kansas Paleozoics. They have a facies, in the limestone, that is not found east of Manhattan in the Kansas Valley, but which appears at corresponding positions farther north and south. This may be called the Permian facies. The limestones of the Coal Measures to the east are harder and rougher, and rarely have the milky or buff hue that prevails here. With the possible exception already mentioned, the Producti are not found in the higher beds. But without reference to the paleontology, there is a lithological reason for distinguishing these from the Coal Measures horizons which outcrop to the east. And yet Coal Measures characteristics come up into these beds. On Humboldt Creek, just at the eastern limit of the district, in lower shales, is a seam of coal 12 inches thick, and a few miles away is another at a slightly higher horizon in the west. The blue slate, No. 1 of the section, is similar to beds at much lower horizons, and contains occasional Discinæ. The term Permo-Carboniferous, though cumbrous, seems fully justified for the series below the Main ledge, while Nos. 11 to 14 might properly be called Permian. There is no break in the succession of the strata from the Coal Measures below.

Plate IV. Stratified alluvium in River Bank, Republican River, abutting against loess and gumbo
Plate IV. Stratified alluvium in River Bank, Republican River,
abutting against loess and gumbo.

Gypsum.-Below the beds of this section, in shales which preceded them, there is a gypsiferous horizon, revealed in wells. It is found on Clarks Creek, in Junction City, and on the military reservation. The gypsum occurs as satin-spar from half an inch to 2 inches thick, and in thicker, semitransluscent, crystalline masses. The exact horizon of the gypsum has not been made out, but there may be more than one, or it may be distributed all through a thick bed of shale-the miner's soapstone. At a still greater depth strong salt brine was reached some years ago in a deep well at Junction City.

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