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Cowley County Geology (1929)

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Stratigraphy, continued

Exposed Rocks, continued

Permian System

Council Grove Group

Varying but little from 150 feet in thickness, the lowermost group of strata in the Permian system, the Council Grove group, consists of alternate beds of shale and limestone. The well-known Cottonwood limestone occupies the lowermost 10 feet, and the succeeding 140 feet of the group is termed the Garrison shale. The limestone beds of the group are light gray to white on weathered surfaces; many are persistent across the county and form fairly conspicuous outcropping ledges. The shale beds range in color from gray or drab to tan, with a considerable proportion of maroon to chocolate-colored beds. In east-central Cowley County the Council Grove group crops out as a narrow band in the steeply sloping east face of the Flint Hills, its more prominent limestone beds forming blocky white ledges or shoulders in the slope. A bed of limestone near the middle of the Garrison shale forms a particularly prominent ledge that breaks down in rectangular blocks, which lie strewn along the line of outcrop. The Cottonwood limestone forms a pronounced shoulder or terrace in the slope, but rarely crops out as a ledge. In, the northeastern part of the county, in Tps. 30 and 31 S., Rs. 7 and 8 E., and in the southeastern part, in Tps. 34 and 35 S., R. 7 E., the overlying Wreford limestone of the Chase group has been much more thoroughly dissected and removed by erosion than farther north in Kansas, leaving the underlying Council Grove group occupying broad areas of the surface.

The Council Grove group is difficultly distinguished in most well logs, although its approximate position can generally be allocated by interpolation from the Wreford limestone above and the Foraker limestone some distance below. The rocks of the Council Grove group are commonly reported by drillers as mostly gray limestone with breaks of red shale.

This group was named in 1902 by Prosser from exposures in the bluffs of Neosho river, the uppermost part being exposed in the immediate vicinity of the town of Council Grove, Marion county, and the lower part about 6 miles downstream (Prosser, 1902, pp. 709-711). These localities are about 80 miles north of the northeast corner of Cowley County.

Cottonwood Limestone

One of the most striking limestone divisions in the entire stratigraphic succession of beds in northern Kansas is the Cottonwood limestone--striking because of its appearance at the outcrop as an unusually prominent ledge of yellowish-buff rock about 6 feet thick that is persistent with only minor variations in thickness and lithologic character throughout several counties in Kansas and into Nebraska (Prosser, 1895, pp. 697-705). When traced southward, however, it abruptly loses its distinguishing features, and from southern Chase and Lyon counties southward it appears merely as one of a number of grayish weathered limestone beds cropping out low in the eastward-facing slope of the Flint Hills. In Cowley County the Cottonwood limestone has a total thickness of about 10 feet, but commonly only the lowermost foot or two crops out, the upper part forming a gently sloping soil-covered surface receding from the outcropping ledge. Even more commonly the formation makes only a pronounced shoulder in the general slope formed by the Garrison shale above and the Eskridge shale below, as shown in Plate IV, which is a typical view of its outcrop in the Flint Hills slope. It is less conspicuous in its surface expression than anyone of a number of limestone divisions both above and below it--for example, the Crouse limestone member of the Garrison shale and the Wreford limestone above and the Neva, Red Eagle, and Foraker limestones below. In detail, however, the Cottonwood limestone has characteristics that distinguish it from other beds. The upper part is composed of fine-grained, rather soft limestone that weathers chalky white and which in most localities, although not all, contains some layers that are abundantly filled with small Fusulinas. In most localities this upper member weathers into irregularly shaped nodules that are 2 to 3 inches in diameter and extremely white and fine grained, and that lie strewn upon the surface of the grass-covered bench or terrace formed by the formation. The lowermost 2 feet or more of the formation is somewhat more siliceous at the outcrop than the upper part, is of darker gray color, and constitutes the ledge-forming part. It closely resembles weathered exposures of parts of the Neva limestone and one or two thin beds of limestone in the Garrison shale, in many localities being indistinguishable within itself from them. Immediately beneath the Cottonwood limestone is the abundantly fossiliferous shale in the upper part of the Eskridge shale. Abundant fossils were present at this horizon wherever it was seen exposed in the county; and associated with them are irregular tubelike calcareous concretions about 1 to 1 1/2 inches thick and ranging from a few inches to a foot or more in length. In most localities of its outcrop either this fossiliferous shaly zone beneath the Cottonwood limestone or the chalky white limestone containing Fusulina of the upper part. of the formation is present and serves to identify the formation. Because of poor exposures in a few localities, however, particularly parts of T. 35 S., R. 7 E., these criteria may not be sufficient for identification. In such localities it will be necessary to augment the study of the Cottonwood formation by measuring short stratigraphic sections of the lower partof the Garrison shale, which includes several limestone beds that are mappable locally. In short although the Cottonwood limestone forms a sufficiently distinctive outcrop in most of its exposed area in Cowley County to make possible its identification under the usual field procedure for reconnaissance geologic mapping, there are some areas in which it is distinguishable with difficulty, being decidedly inconspicuous as contrasted with its unusual prominence in northern Kansas.

Plate IV--Upper: Bench formed by Cottonwood limestone (see arrow) in sec. 16, T. 31 S., R. 8 E. Lower: Outcrop of limestone beds in the lowermost 6 feet of the Florence flint near southwest quarter comer of sec. 26, T. 33 S., R. 5 E.

Two black and white photos; top is of bench formed by Cottonwood limestone; bottom is of outcrop of limestone beds in the lowermost 6 feet of the Florence flint.

Probably the most complete exposure of the Cottonwood limestone seen in Cowley County is that on the county line near the northeast corner of the county, in the NE, sec. 5, T. 30 S., R. 8 E., where the following section was measured:

  Feet Inches
Garrison shale.    
Cottonwood limestone:    
Thin-bedded light-gray limestone; weathers white, and produces small irregularly shaped white nodules. Several beds are fossiliferous 6  
Light-buff limestone. Fairly large specimens of Fusulina abundant 6 to 10 inches above the base 1 8
Light-tan chert and gray siliceous limestone   5
Light-buff thick-bedded limestone; weathers gray 2 6
Total Cottonwood limestone 10 7
Eskridge shale:    
Fossiliferous calcareous shale, containing many irregularly shaped tubular masses of limy shale 1 to 1 1/2 inches thick and 4 to 10 inches long.    

The Cottonwood limestone was described by Prosser in 1894, more fully in 1895, and again in 1902, and was named by him from exposures on both sides of Cottonwood river near Cottonwood Falls and Strong City, Chase County, Kansas. [Prosser, 1894, p. 40; Prosser, 1895, p. 697-700; Prosser, 1902, p. 711, 712] In the latest of the three papers cited Prosser described the Cottonwood formation as "a massive light-gray to buff-colored foraminiferal limestone, frequently composed of 2 layers with a thickness of about 6 feet. It contains very few fossils, with the exception of Fusulina emaciata Beede, which is extremely abundant in its upper part and is called 'wild rice' by the quarrymen. It is the most important dimension stone in Kansas, and at various localities there are extensive quarries. Its constant lithologic character, with its line of outcrop frequently marked by a row of light-gray rectangular blocks filled with Fusulina, make it one of the most important stratigraphic horizons in the upper Paleozoic rocks for at least two-thirds of the distance across Kansas and into Nebraska."

Garrison Shale

The Garrison shale, consisting of 140 feet of interbedded shale and limestone, comprises all but the lowermost 10 feet of the total thick-ness of the Council Grove group. It is rarely well exposed with the exception of a few of its limestone beds, particularly one and in places two that are near the middle of the formation. The uppermost 15 to 20 feet of the formation is clearly exposed in a number of localities by virtue of its position beneath the resistant Wreford limestone of the overlying Chase group. In general, the lower half of the Garrison formation contains much more limestone and limy shale than the upper half. The shale beds are in part very limy and throughout are varied in color, ranging through gray, tan, green, maroon and chocolate-brown, the last two colors predominating. The most conspicuous division in the formation is a light-gray limestone known as the Crouse limestone member, about 6 feet thick, that occurs near the middle, 65 feet above the base. Another limestone, 15 to 25 feet below the Crouse, is prominently exposed in the northeastern part of the county.

A generalized section of the formation, from the base upward, shows mostly shale beds in part of chocolate color in the lowermost 15 to 20 feet, overlain by a bed of gray limestone 3 to 4 feet or more thick. Above this, occupying an interval of about 35 feet, is alternately bedded shale, in part red, and gray limestone; two thin beds of limestone in this division are exposed in many localities in the southern part of the county, one a little less than 10 feet above the base and the other a little less than 10 feet below the top. Next above is the Crouse limestone member, consisting of gray limestone 4 1/2 to 6 feet thick and constituting the most persistent and prominent limestone in the Garrison formation. It is prominently exposed 1 1/2 miles south of Hooser. The beds above the Crouse member consist mostly of shale with some shaly limestone and have a total thickness of 75 feet. No complete exposures of this uppermost unit were seen, and so its composition in detail is not known. A considerable part of its upper half is maroon clay shale, but the uppermost 5 to 15 feet is composed of gray shale and thin beds of fossiliferous limestone constituting strata of somewhat transitional character, grading upward into the limestone of the overlying formation. The maroon color of the shale approaches nearer the top of the Garrison formation in the southern part of the county than in the northern part. Only about 4 feet of limy shale and shaly limestone intervenes between the red shale and the Wreford limestone in the northwest corner of sec. 29, T. 34 S., R. 7 E., a mile east of Otto, and but 5 feet of green shale and shaly limestone crowded with fossils occupies this interval in the center of sec. 14, T. 34 S., R. 6 E., 1 1/2 miles northwest of Otto, in the southern part of the county. About 3 miles east of Burden, in the northeastern part of the county, near the northeast corner of sec. 31, T. 31 S., R. 7 E., the non-red rocks in the uppermost part of the Garrison have a total thickness of 14 1/2 feet, made up of gray to tan shale containing several beds of abundantly fossiliferous limestone from 1 to 4 inches thick. At this locality 11 feet of maroon shale is exposed below the non-red unit, and 6 feet beneath the red material and separated from it by a covered slope is a thin light-gray limestone.

In the southern half of its outcropping area in Cowley County the red-shale unit in the upper part of the Garrison contains a lenticular body of sandstone in its upper part. Although the distribution of the sandstone was not studied in detail it was noted in several localities cropping out as a thick bed that thinned abruptly laterally. These characteristics suggest that the sandstone may be at least in part of stream-channel type--that is, formed by the filling of a stream channel in upper Garrison time. Inasmuch as the outcrops of the sandstone occur in most localities as ledges jutting out from sod-covered slopes, its unusually great thickness in scattered localities might satisfactorily be explained by lateral variation in the hardness of the bed, the portions that crop out in a thick bed being the harder parts that have better resisted the agencies of weathering, the softer parts having been more readily disintegrated at the surface and now remaining concealed from view by a mantle of soil. However, a channel-filling mode of origin is suggested in an exposure that was made in grading for the highway in the NE SE, sec. 13, T. 34 S., R. 6 E., 6 miles due south of Dexter, where the sandstone and adjacent red clay have been cut through, revealing the body of sand abutting laterally abruptly against red clay. The sandstone here exposed is relatively fine-grained of light-tan color, weathering rusty brown, intricately cross-bedded, and about 10 feet thick where exposed 25 feet from its contact with the red clay. The sandstone crops out also near the northeast corner of sec. 36, T. 34 S., R. 6 E., where it is 10 to 12 feet thick and intricately crossbedded; it thins southward within a few hundred yards to a thickness of 1 1/2 feet. The bed is unusually thick in an outcrop just south of the center of sec. 12, T. 35 S, R. 6 E. Logs of wells drilled in the area immediately west of the region of outcrop of this sandstone do not record sand at its horizon, indicating that it is not widespread.

The Garrison shale is defined at the base and top by relatively abrupt changes in lithology. The rocks of the lowermost and uppermost few feet of the formation are composed of shaly limestone and shale with a sufficiently large shale content to give them a quite different character from the underlying Cottonwood limestone and the overlying Wreford limestone. These differences in lithologic character, however, are not sufficiently marked to be detected in wells drilled with churn drills. Much of the material that is called limy shale on a weathered outcrop is commonly recorded as limestone in well logs. The beds of red shale in the formation are readily detected in drill cuttings, and so in most logs the formation is recorded as alternately bedded limestone and red shale. The formation is usually allocated in a log by the position of the Wreford limestone, which overlies it, and the Foraker limestone, which lies below, although separated from it by other beds.

The following section of the Garrison shale was measured by hand level about 2 miles south of Hooser, in the NW, sec. 12, T. 34 S., R. 7 E. It is only partly exposed but represents one of the better-exposed sections in the county:

  Feet Inches
Wreford limestone.    
Garrison shale:    
Steep grass-covered slope 28  
Weathered blocks of rusty-brown micaceous sandstone, not sure to be in place 3  
Covered grassed slope 44  
Crouse limestone member:    
Gray weathered limestone, light buff on freshly broken surface. Forms prominent ledge. Upper surface smooth except for vertical cylindrical pits about the size of automobile-engine cylinders. A few fragments of rod-shaped fossils etched upon the surface in places crops out as a single bed and in other places is split into two or three layers 3 4
Shaly fossiliferous limestone. Weathers more readily and so undercuts the bed above 1  
Covered slope 8 6
Weathered brown limestone, composed almost entirely of fragments of fossils 1  
Red clay 5 6
Covered grass slope 11  
Blue-gray limestone; weathers gray-white; only partly exposed   4
Covered slope 9  
Blue-gray thick-bedded limestone; weathers gray-white; forms slight shoulder in the slope 3 6
Covered slope. Some green and chocolate-colored shale exposed 17 6
Total of Garrison shale 135 8
Cottonwood limestone.    

A section of the formation measured in the railroad cut 1 1/2 miles northeast of Grand Summit station, in the SE, sec. 4, T. 31 S., R. 8 E., follows:

  Feet Inches
Wreford limestone.    
Garrison shale:    
Covered slope 75  
Crouse limestone member: Gray limestone; forms ledge; weathers with a fairly smooth surface. Upper 2 feet breaks into large rectangular blocks 5 6
Covered slope. Some red shale exposed in the upper part, and some shaly limestone in the lowest part 33  
Gray limestone 2 6
Covered slope; some reddish shale exposed in the lower part 13  
Gray shale, in part limy 6  
Total Garrison shale 135  
Cottonwood limestone.    

The Garrison shale occupies a considerable part of the surface of Tps. 32 to 35 S., R. 7 E., and Tps. 30 to 31 S., Rs. 7 and 8 E., but its entire thickness was nowhere seen exposed. In the following localities the total thickness of the formation occupies the surfacer but only parts of the strata are exposed: In sec. 11, T. 34 S., R. 7 E., 2 miles south of Hooser; along the east face of the Flint Hills in the E2, sec. 36, T. 32 S., R. 7 E.; near the west sides of secs. 7 and 18, T. 33 S., R. 8 E.; and in the railroad cut 1 1/2 miles northeast of Grand Summit.

The formation was named by Prosser from exposures in the valley of Big Blue river south of Garrison, Riley County, Kansas (Prosser, 1902, p. 712, 713). Prosser described it as consisting of two parts in this northern region a lower yellowish fossiliferous shale ranging from 2 to 13 feet in thickness, which he had earlier designated the Cottonwood shales and later named the Florena shales, and an upper unit of alternately bedded gray limestone and variegated shale to which he applied the name Neosho, the formation having a total thickness of 140 to 145 feet.

The following fossils were collected in Cowley County from the lower part of the Garrison shale and identified by G. H. Girty:

U.S.G.S. No. 6161. Collected on Winfield-Dexter highway
in NW, sec, 12, T. 33 S., R. 6 E.:
Derbya multistriata
Deltopecten occidentalis
Aclisina sp.

Crouse limestone member. One of the most conspicuously exposed limestone divisions cropping out in the eastern part of Cowley County is the Crouse member of the Garrison shale. It forms a prominent ledge of large white blocks about a third of the way below the crest of the slope extending west of the highway for 1 1/2 miles southward from Hooser. At this locality the member consists of a lowermost division, 1 foot thick, of abundantly fossiliferous shaly limestone that has been eroded away more rapidly than the overlying beds and so forms a notch undercutting the main ledge-forming part of the member, which is 3 feet 4 inches thick. This upper part of the member consists of massive to indistinctly bedded limestone that is light buff on freshly broken surfaces, but weathers to a very light gray. The most characteristic feature of the member in the southern part of Cowley County is the presence of vertical or nearly vertical cylindrical pits ranging in diameter between 1/2 inch and 10 inches, but most commonly about 4 inches. The walls of the pits are vertical or nearly so, do not taper inward like the pits so abundant in the Wreford limestone, and are commonly lined with material that appears to be largely silica. The pits are spaced from a few inches to a foot or more apart and in general resemble cylinders in an automobile engine. They are present in all exposures of the member seen in the southern third of the county and southward for many miles into Oklahoma, but are absent at most localities in the northeastern part of the county where the member was examined. The northernmost exposure seen to contain the pits is about 2 miles east of Cambridge, in the NE, sec. 35, T. 31 S., R. 7 E.

Although in the southern part of Cowley County the Crouse limestone member is readily recognizable because of its greater prominence of outcrop where contrasted with that of other limestone divisions of the Garrison formation and because of the presence of the cylindrical pits, in the northern part of the county it is not so easily determined. There are two limestone divisions, separated by an interval of about 20 feet, near the middle of the Garrison formation, that form prominent ledges in the northeastern part of the county, being particularly well exposed in the region about Cambridge. From the facts that a few cylindrical pits occur in the upper of these divisions and that its stratigraphic position corresponds closely to that of the Crouse member in southern Cowley County, it is believed that the upper division is the Crouse member, but its positive identification could not be made without more detailed tracing. The two limestone divisions, the lower one about 6 feet thick and the upper 5 to 8 feet thick, form the capping ledges of the Flint Hills from a point a short distance north of Grand Summit southward for several miles. Because of their regular thickness and abundant exposure, these beds in the northern part of the county and the Crouse member in the southern part of the county constitute excellent key beds for structural mapping.

Chase Group

Alternately bedded limestone, in part cherty, and shale, with a total thickness varying slightly from 275 feet, constitute the Chase group in Cowley County. The two types of rock form about equal parts of the group. The limestone beds present light-buff, light-gray or white weathered surfaces, and the interbedded shale strata are drab, gray, chocolate-brown and maroon. The abundant chert, found chiefly in the lowermost and middle limestone formations, is probably the most characteristic feature of the group. The lowermost formation of the group is the cherty Wreford limestone, and the topmost formation is the Winfield limestone. These two formations are two of the best ledge formers and consequently most prominently exposed strata in Cowley County. The middle fifth of the group is composed of limestone that is divided into two formations-the Fort Riley limestone above and the Florence flint below. As indicated by the names the upper formation contains practically no chert and the lower formation, which is the thinner of the two, is abundantly cherty. The strata between the Wreford limestone and the Florence flint consist of gray limy shale, maroon clay, and relatively thin beds of gray limestone collectively known as the Matfield shale. The beds between the Fort Riley and Winfield limestones, known as the Doyle shale, are composed of material similar to that of the Matfield shale except that there is much less limestone. The limestone and cherty limestone beds of the group are widely exposed and sufficiently persistent in their chief characteristics to afford excellent horizons for mapping. In drill records the precise boundaries of the group cannot be readily determined, but its approximate position can be recognized by the red shale bands in the Matfield shale and by the Wreford limestone and Florence flint, which are usually reported as sandy limestone or sandstone carrying water.

The Chase group occupies about half of the surface of Cowley County, extending from the rim of the Flint Hills, in the eastern part, westward to the bluffs bordering the west side of the Walnut river bottoms in the western part, constituting a zone about 25 miles wide extending a little east of north across the county. The area is characterized by expansive but somewhat dissected uplands floored by the resistant limestone and cherty limestone divisions of the group. The uplands are terminated laterally by steep slopes formed by the softer shale beds. Isolated flat-topped buttes capped by the Wreford limestone are present in the eastern part of the county, and similar buttes capped by the Winfield limestone occur in the western half of the county, constituting surface forms that are typical of the region occupied by the Chase group.

The Chase group as a whole and its several divisions were described in detail by Prosser in 1895 from field studies in Chase and Marion counties and contiguous areas (Prosser, 1895, p. 771-786). It is interesting to compare Prosser's compiled section of the group, derived from exposures in Marion, Chase, Morris, and Geary counties, with the compiled section in southern Cowley County. The two sections are shown diagrammatically in Figure 5. They indicate a striking continuity in thickness and lithologic character of individual beds, although separated by a distance greater than 50 miles.

Figure 5--Sections of Chase group.

Sections of Chase group.

Wreford Limestone

The lowermost formation of the Chase group, the Wreford limestone, is one of those rock divisions that exert a pronounced influence on the surface features of the state, for it forms the backbone of the Flint Hills throughout much of their extent, particularly in Cowley County. Its striking characteristics are its abundance of chert and its weathered light-gray to white, vertically pitted beds of limestone. In Cowley County the formation varies little from 33 feet in thickness and is composed almost entirely of beds of limestone and chert. The chert occurs most abundantly in regular layers interbedded with the limestone, but also as small, irregular masses or nodules unsystematically arranged within the limestone beds, The limestone occurs in beds that range from a few inches to 3 feet in thickness, is buff on freshly broken surfaces, and for the most part weathers to a very light gray or white, but the lowermost few feet weathers tan or light brown. The massive beds occur in the middle and uppermost parts of the member. The interbedded chert and thin-bedded limestone occupy a zone about 6 feet thick, occurring about a third of the way above the base of the formation, and another zone of about the same thickness 5 feet below the top. The greater part of the chert that occurs in irregular nodules within the limestone beds is in the lowermost 8 feet of the formation. The nodules are of irregular shape and range from 1 to 3 inches in diameter; the smaller ones are the more abundant. The bedded chert occurs in layers as much as 10 inches thick; it is light tan on its outer surfaces and blue and steel-gray on freshly broken surfaces. In many of the chert layers the individual nodules are separated by limestone, although continuous beds with wavy upper and lower surfaces, such as that shown in Plate V, are of more common occurrence.

Plate V--Upper: Deeply pitted limestone bed in uppermost part of Wreford limestone in western part of sec. 19, T. 32 S., R. 8 E. Lower: Interbedded limestone and chert in the Wreford limestone about 1 1/2 miles east of Burden.

Two black and white photos; upper is limestone bed in uppermost part of Wreford limestone; lower is limestone and chert in the Wreford limestone.

The Wreford limestone is rather sharply defined lithologically at its base and top. It is true that the limestone in the lowermost few feet of the formation is somewhat shaly and transitional, characteristics that are accentuated by weathering, but in the uppermost part of the underlying Garrison shale the rocks are predominantly shale with thin beds of very fossiliferous limestone. The upper boundary of the Wreford is exposed in few places, because the uppermost bed of limestone is relatively soft and is readily eroded away. A few clean exposures, however, show that the rocks change in character abruptly from the buffish-white massive bed of limestone of the Wreford to clay shale, commonly maroon, of the succeeding formation. A compiled section of the Wreford limestone measured in a series of closely spaced exposures in recent cuts along the right of way of the Atchison, Topeka & Santa Fe Railway from 1 1/2 to 2 miles east of Burden follows:

  Feet Inches
Matfield shale.    
Wreford limestone:    
Massive light-buff limestone; weathers white and deeply pitted 4  
Interbedded limestone and chert; limestone weathers light gray and chert light tan. Limestone beds average about 4 inches thick and chert beds 4 to 8 inches. Uppermost limestone bed is 1 foot thick overlain by a layer of chert 3 inches thick 6 6
Covered 5  
Massive light-buff to light-gray limestone; weathered surface is roughly pitted. Inconspicuous amount of chert in unsystematically arranged nodules through the limestone 3 6
Buff limestone, weathering gray, in beds 6 to 8 inches thick interbedded with chert, gray and blue on freshly broken surfaces and light tan on weathered surfaces, in beds 2 to 8 inches thick. Some chert irregularly distributed within the limestone 4 1
Grayish-buff limestone. At base is the uppermost distinct layer of chert, about 2 inches thick, and 5 inches above the chert bed is a layer of flattish, siliceous nodules that weather brown and are commonly 6 to 8 inches thick and 1 to 2 feet long parallel with the bedding, although several are as much as 10 inches thick and 3 feet long. These nodules have a concentric banding that closely resembles the graining in wood. Many of the banded nodules contain smaller nodules of light-tan chert, similar to that which occurs in layers in other parts of the member, cutting cleanly across the banded structure 1 9
Dull-buff limestone with irregularly spaced nodules of chert 1 inch in diameter 4 1
Dingy-buff limestone   4
Tan limy shale   4
Dingy-buff limestone. containing silicified fossils; lower-most 8 inches shaly; small irregularly spaced nodules of chert in middle third 3 2
Total Wreford limestone 32 9
Garrison shale.    

Another section measured near the north quarter corner of sec. 10, T. 34 S., R. 6 E., 3 miles northwest of Otto, is as follows:

  Feet Inches
Matfield shale (covered slope).    
Wreford limestone:    
Massive, deeply pitted dingy-white weathered limestone capping a covered slope 5 6
Massive, deeply pitted light-gray limestone with abundant rodlike fossil fragments (Bryozoa (1) and spines) etched upon the surface, capping a grassed slope strewn with abundant fragments of brown chert 6  
Massive light-gray limestone weathered to a relatively smooth surface, capping a covered grassed slope 5  
Thick-bedded light gray limestone with no chert capping the bluff on the south side of the gulch 5 6
Interbedded light-buff limestone and tan chert 9  
Weathered light-brown limestone with no chert 2  
Total Wreford limestone 33  
Garrison shale.    

Several of the massive beds of limestone in the Wreford weather with deeply pitted surfaces, but a bed near the middle develops especially striking vertical pits, as shown in Plate V. This bed is conspicuously exposed on the south side of the highway about 1 1/2 miles northwest of Dexter, in the NW, sec. 12, T. 33 S., R. 6 E.

The Wreford limestone forms the rim of the Flint Hills in much of their extent in Cowley County and far northeastward in Kansas, although erosion has removed it in much of the southern third and northeastern part of Cowley County. The broad dip slope of the Wreford, terminated abruptly on the east by a steep slope descending eastward, is typically developed in Tps. 32 and 33 S., R. 7 E.; in the south-central part of T. 30 S., R. 8 E., 3 miles northeast of Grand Summit; and in T. 34 S., R. 7 E., for 2 miles south of Hooser. Only the lowermost 10 to 15 feet of the formation commonly forms the immediate rim in these localities, the upper beds being concealed beneath a very gently inclined grass-covered slope. The relatively thin but persistent and resistant brown concretionary bed that occurs about 10 feet above the base of the formation appears to produce, more than any other single bed, the prominent surface features of the formation, although the chert beds, because of their relatively great resistance to the agencies of weathering, contribute materially to a like result. Most of the isolated flat-topped buttes that are so numerous in the northeastern part of the county and a number of the long, narrow prongs that extend out from the main Wreford plateau in the east-central and southern part (see Pl. 1) are capped by fragments of this bed of brown-banded concretionary chert, that lie upon the surface in sharp-edged blocks, ranging from a few inches to a foot or more in width and from 6 to 8 inches in thickness.

Aside from the two localities of the detailed sections above described, strata of the Wreford are clearly exposed on the west side of Grouse creek, west of the road just south of the Glenwood schoolhouse in the SW, sec. 28, T. 33 S., R. 6 E., and in the SW, sec. 3, T. 34 S., R. 6 E. The lowermost 20 feet of the formation is well exposed in the road cut in the steep hill just east of Dexter on the Dexter-Hooser highway.

Matfield Shale

The Matfield shale consists of varicolored shale interbedded with gray limestone ranging in total thickness from 58 to 65 feet. In general it contains maroon and gray clay shale in the lowermost 10 feet, overlain by fossiliferous gray limestone about 6 feet thick; another gray fossiliferous limestone that is slightly thinner occurs a little below the middle of the formation, and the two are separated by gray shale, in part limy. These two limestone beds are remarkably persistent throughout Cowley County and presumably for many miles to the north, as a section measured by Prossers near Matfield Green, in southern Chase County, shows two beds of fossiliferous, gray limestone at the same horizons (Prosser and Beede, 1904). In southern Cowley County more than 30 feet of shale, containing a few thin beds of limestone, the lower part of the shale of a maroon color, occupies the uppermost part of the formation. The maroon clay shale of this upper part is covered in the exposures of the formation seen in the northern part of the county, and the thickness of this upper division is somewhat reduced there. A bed of limestone about 3 to 4 feet thick is present 5 feet below the top of the formation throughout the northern part of the county, but was not seen in exposures in the southern, part. Fossils occur abundantly in the two lower beds of limestone, in parts of the shale separating them, and in the shale and limestone beds in the upper 10 to 20 feet of the formation. The Matfield is usually reported in well logs as a series of interbedded limestone and red shale.

The upper boundary of the Matfield shale is placed below the lowest chert-bearing limestone bed of the Florence flint. The uppermost few feet consists of transition beds from limy shale to limestone, and grades into the limestone of the Florence flint, with no abrupt lithologic change except the appearance of chert. The base of the Matfield shale is more sharply defined, being rather abruptly terminated by the massive bed of white limestone constituting the top bed of the Wreford.

The total thickness of the Matfield formation decreases slightly northward in Cowley County. No definite statement as to the nature of this convergence can be made, but data disclosed by sections of the formation studied at three localities in the county suggest that it is accomplished by a transgression downward of the chert of the overlying Florence flint, which thickens northward.

The following section of the Matfield shale was measured about 2 miles south of Silverdale, near the north quarter corner of sec. 17, T. 35 S., R. 5 E.:

  Feet Inches
Florence flint.    
Matfield shale:    
Very limy shale, fossiliferous 3 4
Limestone, grayish tan 2  
Clay shale, gray to drab; small part covered 9  
Maroon clay 12  
In part covered; part is limy shale 6 8
Hard gray limestone; small fossils and fossil fragments abundant. Makes prominent ledge. (In near-by exposure is 11 feet thick) 4 6
Gray limy shale, particularly limy in upper part 8  
Gray hard limestone; large fossils abundant 6  
Gray limy clay 2 10
Maroon clay; base concealed 6  
Covered 1 6
Total Matfield shale 65  
Wreford limestone.    

Another section measured about 1 1/2 miles east of Burden, near the north quarter corner of sec. 36, T. 31 S., R. 6 E., follows:

  Feet Inches
Florence flint.    
Matfield shale:    
Buff limy shale, with a few thin beds of fossiliferous limestone, two near the middle fairly prominent 5 6
Light-buff limestone, upper part massive, lower part thin bedded. Lowermost 10 inches abundantly fossiliferous. A conspicuous bed throughout the northern part of Cowley County 3  
Grayish-tan shale, upper part abundantly fossiliferous 3  
Covered 11  
Dull-buff limestone; soft and fossiliferous in upper 1 to 1 1/2 feet. Lower part more massive. Rarely makes a showing in weathered slopes 3  
Greenish-tan to gray clay shale 7 6
Gray limestone   4
Covered 10  
Light-buff limestone. Uppermost 10 inches thin bedded; next lower 1 foot 6 inches is massive bed; and lower 3 feet 3 inches is massive bed. Forms a prominent ledge of thick blocks in this vicinity. Lowermost 6 to 8 inches is abundantly fossiliferous 5 6
Buff limy shale, in part fossiliferous. A 3-inch bed of limestone occurs 3 inches above base 1 9
Buff limestone with abundant fossils   9
Light-buff clay; lowermost few inches is in part of chocolate color 7 2
Total Matfield shale 58 6
Wreford limestone.    

The Matfield shale occupies a relatively narrow band of the surface of Cowley County, in most places forming a fairly steep, grassed slope capped by the lowermost limestone beds of the Florence flint and terminated below by the Wreford limestone ledges. Its most extensive exposures in the county are along Grouse, Silver and Timber creeks.

The Matfield shale was named by Prosser from exposures in Matfield township, Chase County, Kansas, in which the town Matfield Green is situated (Prosser, 1902, p. 704 (diagram), 714). Prosser described the beds that make up the formation in 1895 in terms that aptly apply to its general characteristics in Cowley County (Prosser, 1895, p, 773). His section compiled from observations taken at a number of exposures in Chase County and the near-by region is quoted below:

  Feet
Florence flint.  
Matfield shale:  
Yellowish, chocolate-colored, and greenish shales 31
Light-gray limestone, containing an abundance of small Lamellibranchia
Shales, not well exposed 12±
Shaly, buff limestones, containing large brachiopods, sometimes a massive limestone 10±
Shale, not well exposed 15±

The following fossils collected in Cowley County were identified by G. H. Girty:

U.S.G.S. No. 6165. Collected 1 mile southeast of Silverdale,
in the SE, sec. 5, T. 35 S., R. 5 E.:
Derbya multistriata
Pustula nebraskensis
Composita subtilita

Florence Flint

Thick-bedded limestone interbedded with chert, ranging in total thickness between 11 feet at the state line to 35 feet in the northern part of the county, constitutes the Florence flint of the Chase group in Cowley County. The limestone beds are relatively soft, massive, rather coarse grained, light buff on freshly broken surfaces, and light gray to white on weathered surfaces; they are very fossiliferous, some of the beds, particularly in the lower part of the formation, being composed almost entirely of fossils, and are for the most part within themselves indistinguishable from the limestone beds of the Fort Riley limestone, the next overlying formation, although in most localities they lack the minute spotting so common in the lower part of the Fort Riley beds. The chert of the Florence flint, which constitutes its most striking characteristic, occurs in abundance throughout the formation interbedded with the limestone except in the lowermost 5 to 6 feet, which is largely limestone. (See Pl. IV.) The relation of the chert and limestone beds is shown in Plate VI. The chert is distinctly nodular, although in some layers the nodules are commonly joined, so that the layer of chert is continuous. In other layers, representing the more common occurrence, the chert nodules are separated, and the intervening spaces are filled with limestone. The characteristic mode of occurrence of the chert is in layers interstratified with the limestone, the nodules ranging in thickness from 1 inch to 5 inches, but in some localities relatively small nodules of chert are irregularly distributed within the beds of limestone. The broken faces of a chert nodule are steel-gray and blue; the slightly weathered outer surface is tan and on further weathering becomes dark tan and rusty brown. As a general rule the chert is unfossiliferous. The chert beds are relatively more numerous in the middle part of the formation, where they occur in layers 4 to 10 inches apart. In the lower part the chert beds are typically separated by beds of limestone 6 to 18 inches thick, and in the uppermost part the intervening beds of limestone are about 1 foot thick. Near the south quarter corner of sec. 26, T. 33 S., R. 5 E., the Florence flint is exposed beneath a massive bed of weathered light-gray limestone 2 1/2 feet thick, which forms the basal bed of the Fort Riley limestone. The uppermost 4 feet of the Florence flint is composed here of light-gray limestone containing a layer of chert nodules, separated by spaces averaging about a foot each; the next lower 7 feet contains chert bands about 6 inches apart and parallel with the bedding; below this are beds of light-gray to white weathered limestone 1 to 2 feet thick interbedded with a small amount of chert; and the lowermost foot. of the formation is composed of somewhat shaly limestone and chert. The Florence flint has a total thickness of 18 feet at this locality.

Plate VI--Upper: A part of the Florence flint in a cut about a mile east of Burden. Lower: Close-up view taken at point marked X in upper, to show nature of chert nodules in the limestone.

Two black and white photos; upper is Florence flint in railroad cut; lower is closeup of chert nodules in the limestone.

The formation thins southward in Cowley County at a comparatively rapid rate; it is 35 feet thick a mile and a half northeast of Floral, near the northwest corner, in sec. 16, T. 31 S., R. 5 E.; 33 feet thick half a mile south of Floral; 18 feet thick near the south quarter corner of sec. 26, T. 33 S.,.R 5 E.; and 11 feet thick on the Kansas-Oklahoma line in sec. 18, T. 35 S., R. 5 E. Fath gives its maximum thickness in the El Dorado district, 20 miles north of Cowley County, as 35 feet, and the total thickness exposed in the quarry face at Florence, Marion county, as 27 feet (Fath, 1920, p. 47). The percentage of chert also appears to decrease southward, there being relatively little chert in the exposure in sec. 18, T. 35 S., R. 5 E., and almost none in a railroad cut on the state line in sec. 18, T. 35 S., R. 6 E., 6 miles farther east.

The upper part of the formation, including all but the lowermost 4 to 6 feet, breaks down more readily than the remainder and forms gentle slopes strewn with weathered sharp-edged fragments of chert averaging about 2 inches in diameter. The beds in the lowermost 4 to 6 feet weather to a white, somewhat rough surface and commonly form a low ledge like that shown in Plate IV, or crop out as two or three steps or rock terraces capping relatively steep slopes of the underlying Matfield shale. These lower beds form more continuous outcrops than any other part of the formation and are so widely exposed that they can be traversed almost continuously across Cowley County.

The contact of the Florence flint with the Fort Riley limestone :is drawn at the top of the uppermost chert-bearing bed. The base is drawn at the base of the chert-bearing limestone, which coincides in general with a lithologic change from limestone containing only a minor amount of shale to shaly limestone and shale. Weathered outcrops of the Florence flint resemble somewhat those of the Wreford and Foraker limestones, but it has several features that distinguish it from these other formations. In general its chert nodules are smaller than those in the Wreford, although this characteristic cannot be relied upon, as each formation varies widely in this respect; the Florence flint does not contain beds of limestone that weather in such distinctive vertically pitted white surfaces as are present in the Wreford; its chert nodules lack the fossil Fusulina so abundant and omnipresent in the Foraker chert; and except in the southernmost part of the county chert is much more abundant in the Florence flint than in the Foraker. On the whole the limestone beds of these two formations are quite similar in general appearance. Viewed in its relation to an extensive stratigraphic section the Florence flint is readily distinguished by its position, for it is the highest formation, stratigraphically, that contains chert in abundance, although some chert is present in the Herington limestone, and farther north in Kansas chert occurs near the top of the Doyle shale and in the Winfield limestone (Prosser, 1902, p. 715-716).

The formation is reported in many well logs as sandstone or sandy limestone and in others as limestone not separated from the overlying Fort Riley beds. The Florence commonly produces water in wells, and springs are numerous along its outcrops.

The Florence flint exerts a marked influence on the surface features in Cowley County, as well as farther north in Kansas. It forms a broad upland surfaced by weathered chert and inclined Westward at a low angle conforming to the regional dip of the strata. This upland surface is particularly well developed in northern Cowley County in Tps. 30 and 31 S., and Rs. 6 and 7 E., and thence northward across Butler County. It can be seen along the highway east from Rosalia, Butler County, to the rim of the Flint Hills west of Sallyards, and again for miles northeast of El Dorado on the Cassoday and Matfield Green highway.

Exposures of the lowermost 5 to 8 feet of the formation are comparatively common in Cowley County, but complete exposures of the formation are rare. The lower beds are extensively exposed along Timber creek in the northern part of the county, bordering Grouse creek on the west nearly the north-to-south length of the county, and on both sides of Silver creek throughout most of its course. About half of the total thickness of the formation is well exposed in a railroad cut about a mile east of Burden. The entire formation and its contact with the Fort Riley limestone above and with the Matfield shale below can be seen in a series of partial exposures along a gulch near the south quarter corner of sec. 26, T. 33 S., R. 5 E., just north of the road.

The Florence flint was named by Prosser from its excellent exposures in the quarries about a mile northeast of Florence, Marion county, Kansas, on the McPherson branch of the Atchison, Topeka & Santa Fe Railway (Prosser, 1895, p. 773; Prosser, 1902, p. 714). Prosser describes it as being 20 to 22 feet thick, but Fath states that it is 27 feet thick in the quarry face half a mile northeast of Florence (Fath, 1920, p. 47).

Fort Riley Limestone

The Fort Riley limestone is well known throughout Kansas and northern Oklahoma because of its extensive use as building stone. The typical rock of the formation is a very light buff limestone of granular texture, relatively soft and occurring in beds as much as 3 feet or even more in thickness. In Cowley County the formation has a total thickness of 45 to 55 feet, but the thick-bedded character of its individual strata does not continue throughout this thickness; in general the lowermost 15 to 20 feet is made up of thick beds, and the remaining upper part is composed of thin-bedded and somewhat shaly limestone alternating with thicker beds which in many localities form a series of low ledges or steps in the slopes. The granular appearance so characteristic of the thick-bedded part of the formation is produced by the occurrence of small white globular masses that are so abundant as to constitute nearly the whole of the rock. Numerous zones within the shaly parts of the formation, as well as a few zones within the thick-bedded portion, are abundantly fossiliferous. The lithologic change between the uppermost beds of the Fort Riley and the lower part of the overlying Doyle shale is not abrupt, but an upward gradation from limestone through a zone of shaly limestone to shale; consequently, the boundary between the two formations cannot be drawn with precision throughout much of the county. In the north half of the county a bed of limestone 2 to 3 feet thick that weathers very white and vesicular and characteristically forms shallow sink holes, like that shown in Plate III, constitutes the uppermost bed of the formation and forms a sharply defined upper boundary. This bed is particularly well exposed in the northern part of T. 30 S., R. 5 E., where there are numerous sink holes in the west half of section 6, north of the center of section 5, and west of the center of section 12.

This porous limestone bed does not persist in typical phase throughout Cowley County, however, but does extend far northward into Butler County. In central and southern Cowley County the upper boundary of the Fort Riley formation is drawn at the uppermost blocky bed of limestone of the interbedded limestone and limy shale zone. A section of the formation measured in T. 30 S., R. 6 E., in the northern part of the county, by Mr. Hudson, of the Empire Gas and Fuel Company, shows a total thickness of 45 feet. Matching this section, drawn up in graphic form, with others obtained in the southern part of the county, suggests that the bed of white porous limestone forming the top of the formation in northern Cowley County may be the limestone bed that occurs about 10 feet below the top (Nos. 7 and 8 of detailed section measured in sec. 6, T. 35 S., R. 5 E., given below) in the southern part of the county, the limy character of the uppermost 10 feet of the formation decreasing northward and merging into lithology typical of the Doyle shale. The meager information available from the reconnaissance study of the area merely suggests this correlation, and more detailed work such as the tracing of beds and the measuring of numerous stratigraphic sections distributed through the county would be necessary to establish the true relation of the individual beds in the zone adjacent to the Doyle-Fort Riley contact. The base of the Fort Riley limestone is more sharply defined; it is drawn above the uppermost limestone bed that contains chert in the Florence flint. The limestone of the Fort Riley is strikingly similar to that of the Florence flint, the absence of chert in appreciable quantity being the only distinguishing feature. The contact between the two formations is not clearly exposed in many localities, but its approximate position is determined by the upper limit of the residual chert fragments from the Florence flint that remain on weathered slopes.

Inasmuch as the upper part of the Fort Riley is composed in part of relatively soft rock that breaks down readily, the formation is rarely exposed in its entirety at any locality. Probably the best exposure seen is that near the old quarry in the SW, sec. 6, T. 35 S., R. 5 E., in the bluff formed by Arkansas river, where the following section was measured:

  Feet Inches
Doyle shale.    
Fort Riley limestone:    
10. Relatively thin-bedded gray-white limestone. Caps the slope and floors the bench above. The uppermost 1 1/2 feet of this bed weathers in a blocky ledge in many exposures 3  
9. Covered slope 7 6
8. Gray-white limestone; weathers in white nodules 1  
7. Light-buff to gray limestone; weathers to a soil-covered slope below No. 8 2 6
6. In part covered. Uppermost foot is thin-bedded limestone, and lowermost foot is limy shale 3  
5. Thick-bedded buff granular limestone. Lower 3 feet soft and in most exposures forms covered slope. Upper 3 feet forms ledge 6  
4. Covered slope 7 6
3. Massive buff, granular limestone 5  
2. Shaly limestone; breaks down readily 3  
1. Buff granular limestone in massive beds 3 to 6 feet thick 17 6
Total Fort Riley limestone 56  
Florence flint.    

The Fort Riley limestone together with the Florence flint (not differentiated on the geologic map, Plate I) occupy a greater part of the surface of Cowley County than any other formation, being present throughout a broad band that extends from north to south through the central part of the county, containing most of Rs. 4, 5 and 6 E. and the northern part of R. 7 E. The Fort Riley is particularly well exposed in the bluffs immediately east of Arkansas river in T. 35 S., R. 5 E., in bluffs on the east side of Walnut river and on both sides of Silver creek in Ts. 33 and 34 S., R. 5 E.; in bluffs on the east side of Walnut river in T. 33 S., R. 4 E.; and on the south side of Timber creek in T. 31 S., Rs. 5 and 6 E. It is extensively exposed far beyond the limits of Cowley County northward across Kansas and southward 70 miles into Oklahoma (Miser, 1926).

The type locality of the Fort Riley limestone is Fort Riley, Geary county, Kansas. The name was first applied by Swallow to a series of thick beds of limestone constituting a thickness of 8 to 10 feet that form a prominent ledge in the vicinity of Fort Riley and Junction City (Swallow, 1866). These strata were later correlated by Prosser with those exposed on Cottonwood river near Florence, and the term Fort Riley limestone was expanded to include not only the thick-bedded limestone that occurs a few feet above the Florence flint, but also the beds of shaly limestone that immediately overlie and underlie the thick beds, making a total thickness there of a little more than 40 feet (Prosser, 1902, p. 714-715). Prosser had previously designated the thick-bedded portion as the Florence limestone in the following section taken from exposures near Florence and Fort Riley (Prosser, 1895, p. 773):

  Feet Inches
Buff shaly limestone 22  
Massive buff limestone. Florence limestone 5+  
Buff shaly limestone 15  

A comparison of the Cowley County section with Prosser's description of these strata on Cottonwood and Kansas rivers farther north in Kansas indicates that the principal features of the formation persist southward to Cowley County. Prosser describes the Fort Riley limestone as "a series of massive buff limestone, changing to thin-bedded and shaly strata in the upper part of the formation, which have a total thickness of 40 feet or more." (Prosser, 1902, p. 714) Fath describes the formation in Butler County, adjacent to Cowley County on the north, as having a threefold character, being composed of thick-bedded limestone in the lower and upper thirds and thin-bedded limestone in the middle third (Fath, 1921, p, 48-49).

The following fossils collected from the Fort Riley limestone, in sec. 1, T. 35 S., R. 5 E., were identified by G. H. Girty, of the United States Geological Survey:

U.S.G.S. No. 6154a:
Fusulina sp. Productus semireticulatus
Echinocrinus sp. Composita subtilita
Derbya multistriata? Deltopecten occidentalis
Meekella striaticostata Deltopecten mccoyi

Doyle Shale

The steep slopes so persistently present below the Winfield limestone and the gently rolling bench land into which they merge below are formed by a relatively thick body of soft rocks known as the Doyle shale. This formation is composed of green, maroon, varicolored, greenish-gray, and tan clay shale, a minor part being limy, and a few thin beds of limestone. In general the limy part of the formation is confined to the lowermost 25 to 30 feet and the uppermost 10 feet; the remaining middle part is composed mostly of clay shale. The most conspicuous limestone unit occurs in the lower part of the formation, from 25 to 30 feet above the base, and is prominently developed only in the southern part of the county, some of the best exposures being near Silverdale, specifically in the W2, sec. 6, T. 35 S., R. 5 E. Throughout the county, however, a limy zone occurs in the approximate stratigraphic position of this limestone unit, 20 to 35 feet above the base of the formation. This zone is slightly harder than the overlying and underlying beds, so that it forms a slight shoulder in the slope. Prosser mentions the presence of a thin grayish limestone about 20 feet above the base of the Doyle shale in central Kansas (Prosser, 1902, p. 715), and Fath describes a limestone which he called the Towanda limestone bed as being 35 feet above the base of the Doyle in the El Dorado district in Butler County (Fath, 1920, p. 54). In Cowley County the lowermost 20 to 35 feet of the Doyle shale is composed of tan clay shales, in part limy, and thinly laminated shaly limestone.

The uppermost few feet of the formation consists of argillaceous limestone and limy shale containing abundant small concretions ranging between one-eighth and one-half inch in diameter. These concretions are present at every locality where this part of the formation was seen exposed and constitutes a diagnostic feature of this part of the section. The upper part of the Doyle formation is extremely limy in the northwestern part of the county, a few exposures showing beds of limestone 2 to 4 feet thick interbedded with shale in the uppermost 20 feet. Elsewhere in the county, however, this division of the formation is composed largely of shale containing a few thin beds of limestone. A detailed section of the upper part of the Doyle shale measured near the southwest corner of sec. 35, T. 33 S., R. 4 E., follows. The uppermost part of this section is shown in Plate VII:

  Feet Inches
Winfield limestone.    
Doyle shale:    
Shaly limestone, containing concretions one-eighth to one-half inch in diameter and small fossils; weathered light tan 1 4
Limy shale, containing an abundance of small concretions, weathered light tan 1 4
Thin-bedded shaly limestone and limy shale. The uppermost 8 inches contains abundant small lime concretions 4  
Limy shale with a few thin layers of shaly limestone, weathered light tan 3  
Green clay grading upward into gray and light-tan shale 6 6
Maroon clay containing a thin bed of green clay 3 1/2 feet beneath the top 7 6
Base concealed.    

The following section of the entire Doyle formation was measured with a hand level near the east quarter corner of sec. 1, T. 35 S., R. 4 E.:

  Feet Inches
Winfield limestone.    
Doyle shale:    
Grayish-tan limy weathered shale, greenish in lower part, and thin-bedded shaly limestone; increases in lime content upward. Contains fossils and abundant lime concretions one-eighth to one-half inch in diameter in uppermost 4 feet 11  
Maroon clay, mottled with green in lowermost part 27  
Green clay, largely noncalcareous. A bed of dark limestone 1 inch thick, made up almost entirely of shells, occurs 4 feet above base 19  
Covered gentle slope, probably mostly shale 10  
Light-buff to light-gray cherty limestone. Contains abundant fossils that appear to be of one species. Locally forms a ledge; weathers to a fairly rough surface 2  
Sod-covered slope 23  
Total Doyle shale 92  
Fort Riley limestone.    

The total thickness of the Doyle shale shown here is slightly greater than that measured elsewhere in the county. A section measured by hand level in the NW NE, sec. 30, T. 33 S., R. 5 E., shows a thickness of 83 feet; another measured near the south quarter corner of sec. 26, T. 33 S., R. 4 E., shows 83 feet, and still another measured in the NE, sec. 23, T. 33 S., R. 4 E., shows it to be 78 feet thick. Considerable variation in thickness at relatively closely spaced localities within Cowley County has been noted also by geologists of the Roxana Petroleum Corporation (E. L. Jones, personal communication). The thickness of the formation was not measured in northern Cowley County, but Fath gives a total thickness ranging between 90 and 105 feet in the El Dorado district, 20 to 25 miles north of the northern boundary of Cowley County (Fath, 1921, p. 54-56). Prosser shows this formation as being 62 feet thick in Chase County, but if we add the 17 feet of beds that he included in the Winfield below the thick-bedded upper limestone believed to be alone the correlative of the Winfield limestone of Cowley County, the total thickness of the Doyle shale in Chase County is 79 feet (Prosser, 1895, p. 772, 773).

Clean exposures of the entire formation at one locality were not seen, and in general exposures are poor except for the uppermost 10 to 15 feet, which is extensively exposed because of its position immediately beneath the ledge forming Winfield limestone. The middle part of the formation is rarely exposed, probably the best exposure seen being that lying below a southward-projecting prong capped by the Winfield limestone near the east quarter corner of sec. 1, T. 35 S., R. 4 E. The limestone unit 25 to 30 feet above the base of the formation is exposed rather widely in the southernmost part of the county, but elsewhere forms only a slight shoulder in the grassed slope. The only exposure of the lowermost beds of the formation seen in the county is near the south quarter corner of sec. 26, T. 33 S., R. 4 E., back of the buildings on the George Howard farm.

Prosser described the strata composing the Doyle shale as "yellowish, chocolate, and greenish shales with occasional layers of thin limestone" and designated the unit as "No. 17" of the stratigraphic section given in his early report (Prosser, 1895, p, 772-773), but later applied to it the name Doyle shale, from exposures "at various places in the Doyle creek valley to the southwest of Florence," in southern Marion County." (Prosser, 1902, p. 715)

The following fossils, collected from the Doyle shale in Cowley County, were identified by G. H. Girty:

U.S.G.S. No. 6145b. Collected near the east quarter corner of sec. 1, T. 35 S., R. 4 E.,
from the limestone bed 28 feet above the base of the formation:
Pleurophorus subcostatus?
U.S.G.S. No. 6154. Same locality as above.
Collected 53 feet below the top of the formation:
Myalina perattenuata?
U.S.G.S. No. 6150. Collected in railway cut in SE, sec. 19, T. 32 S, R. 4 E., from uppermost few inches of formation:
Spirorbis sp. Schizodus sp.
Derbya multistriata Deltopecten occidentalis
Allerisma terminale Pleurophorus sp.
U.S.G.S. No. 6151. Collected in road cut a little way south of the north quarter corner of sec. 32, T. 31 S., R. 4 E., from a thin limestone bed 2 feet beneath top of formation:
Derbya multistriata Composita subtilita

Winfield Limestone

The uppermost formation of the Chase group, the Winfield limestone, forms probably the most conspicuous outcrop of all the limestone units exposed in Cowley County. It consists of 10 to 11 feet of massive limestone, generally occurring in two beds, that is light buff on freshly broken surfaces and light to dirty gray on weathered surfaces. The unweathered rock is coarse and has a granular texture, constituting a distinctive characteristic in core-drilled specimens. It characteristically weathers to a somewhat siliceous, sharply rough pitted surface. The roughened surface is covered by an abundance of silicified fragments of fossils that have been etched into relief by the weathering away of the surrounding limestone substance. A myriad of fine rod-shaped fragments and small spines, fragments of lace-like Bryozoa, and a few spiny-backed bivalve shells about 1 1/2 inches in diameter occur on the surface of weathered exposures of the rock. In most exposures showing the entire thickness of the formation the pitted character of the rock has its greatest development about 3 or 4 feet below the top of the formation. In this zone, which ranges from 1 inch to 1% feet in thickness, the greater part of the rock is dissolved and removed, leaving only a course honeycomb or network to support the upper bed; and in a cliff where the rock has been somewhat weathered this porous zone everywhere makes a deep indentation in the cliff face. The formation is thus split into two beds, which in many places crop out as two ledges; in much of the area of its outcrop, however, the upper bed is not exposed, the outcropping ledge of the Winfield being formed by the lower bed alone.

According to Prosser the Winfield limestone is characterized in east-central Kansas by large irregular brown-weathering concretions (Prosser, 1895, p. 772), and Fath described the concretionary character of the Winfield as being locally developed in the vicinity of El Dorado, in Butler County (Fath, 1921, p. 59). The only locality in Cowley County where concretions were seen in the Winfield is 4 miles due north of Winfield, in the SW SE, sec. 33, T. 31 S., R. 4 E., which is probably the locality referred to by Prosser as containing concretions typical of those in the Winfield limestone of east-central Kansas (Prosser, 1897, p. 64). At the locality 4 miles north of Winfield the concretions are of flatfish, irregular shapes, commonly 3 to 5 inches thick and 6 to 18 inches wide, composed of limestone made up almost entirely of fossil fragments. The concretions are embedded in the massive limestone of only the upper bed of the Winfield and weather a deep rusty-brown color, in sharp contrast with the gray of the surrounding rock. They are more resistant than the surrounding limestone and so remain scattered upon the soil-covered slopes that recede from the ledge formed by the lower bed of the Winfield. An abundance of dull-brown weathered slabs 2 to 4 inches thick and 6 to 10 inches wide lie scattered upon the sloping surface below the Winfield limestone outcrop in the northern part of T. 32 S., R. 5 E.; these slabs are probably weathered out of the Winfield, but none were seen in place. Throughout most of Cowley County, however, the Winfield limestone is typically lacking in concretions, and the examples described above are of only local occurrence and constitute exceptions to the usual characteristics of the formation in this region.

The Winfield limestone is clearly exposed in the road cut and quarry immediately west of the Walnut river bridge on West Ninth street west of Winfield, where the following section was measured:

  Feet Inches
Luta limestone (lower part):    
White or very light gray, somewhat argillaceous limestone, in beds 1/2 inch to 3 inches thick 8  
Winfield limestone:
Massive. dull-gray limestone; surface made rasp-like by abundant silicified fossil fragments, fine rods, spines, and an occasional spiny-backed shell. A few small weathered pits are present in an irregular horizontal band near middle 3  
Honeycombed siliceous limestone with abundant deep pits partly filled with residual red-brown clay; forms a deep notch in cliff face 1 6
Massive limestone, dull gray; surface has a rasp-like roughness as a result of a mosaic of silicified fossil fragments of slender rods and spines and an occasional spiny-backed bivalve shell that have been weathered out in relief. The uppermost 2 feet contains relatively abundant weathered pits from 1/2 inch to 1 1/2 inches in diameter and depth. There are likewise a few pits in the surface of the lower part of the bed, but they are shallower and do not produce so roughened a surface. Forms ledge 5 6
Total Winfield limestone 10  
Doyle shale.    

This formation is well exposed also about half a mile northwest of the above-described locality, in the face of an old quarry and in a cut made by the Atchison, Topeka & Santa Fe Railway Company a few hundred yards west of Winfield Junction, in the SW, sec. 20, T. 32 S., R. 4 E. The section measured there is similar to that described for the Ninth street locality, except that the contact of the Winfield and Doyle and the uppermost few feet of the Doyle shale is clearly exposed. Argillaceous limestone containing abundant small concretions half an inch in maximum diameter, those measuring about a quarter of an inch being the most numerous, forms the uppermost 2 feet of the Doyle shale and constitutes transition beds between a clay shale below and the massive Winfield limestone above. In recently cut exposures the upper half of the concretionary bed appears as a well-consolidated limestone not greatly dissimilar to the overlying beds. Such an exposure naturally raises the question as to the proper position for the Winfield-Doyle contact. In records of churn-drilled wells the Luta (?) limestone, about 25 feet thick, the 10 to 11 feet of massive limestone (Winfield), and the argillaceous limy beds below are all logged as one unit of limestone. In exposures where the 10-foot bed of massive limestone (Winfield) and the underlying argillaceous limestone (Doyle) have been subjected to a considerable amount of weathering the division between the two is sharply defined. The argillaceous limestone breaks down and weathers more readily than the overlying massive bed, which thus forms an overhanging ledge. The concretionary character of the lower rocks is also accentuated by weathering, because the concretions are more resistant than the matrix that contains them and so weather out upon the surface in abundance. Because of this marked lithologic difference manifest by weathering the Winfield limestone is here identified as the massive cliff-forming limestone, and the underlying concretionary argillaceous limestone and limy shale are allocated to the Doyle shale.

The contact of the Winfield limestone and Doyle shale is exposed at many places in the western part of Cowley County, but only a few of them will be mentioned-namely, near the center of sec. 29, T. 31 S., R. 4 E., on the Winfield-Augusta highway; and on the boundary between secs. 4 and 5, T. 30 S., R. 4 E., on the same highway north of Rock. In the southern part of the county it is exposed in a comparatively recent road cut (and the rocks are consequently not so greatly weathered) in the Big Hill about 5 miles east of Arkansas City on the Arkansas City-Joplin highway-specifically near the west quarter corner of sec. 36, T. 34 S., R. 4 E. A view taken at this locality is shown in Plate VII, the lower picture showing the contact as it is exposed in the road cut in the SW, sec. 35, T. 33 S., R. 4 E., where the rocks have been subjected to weathering for a long time. The head of the hammer shown in both views marks the contact of the two formations. In the latter locality weathering has accentuated the lithologic differences between the massive thick beds and the underlying more argillaceous beds. The view is typical of the contrast between the two formations in weathered exposures.

Plate VII--Upper: Wreford limestone and uppermost part of Doyle shale. Hammer head marks the contact of the two formations. View taken at the big hill 5 miles east of Arkansas City on the Joplin highway. Lower: Lower part of the Winfield limestone and uppermost part of Doyle shale in SW, sec. 35, T. 33 S., R. 4 E. Hammer head marks the contact of the two formations.

Two black and white photos; upper is Wreford limestone and uppermost part of Doyle shale; lower is lower part of the Winfield limestone and uppermost part of Doyle shale.

Although the contact of the Winfield and Luta limestones is rarely well exposed, it is sharply defined by an abrupt change from the massive granular dull-gray rock of the Winfield to a thin-bedded fine-grained white to bluish-white, somewhat argillaceous limestone of the Luta.

The Winfield limestone is well exposed throughout most of its outcrop in the western part of Cowley County, as shown on Plate I. Because of its excellent exposures it has been extensively used as a key bed in the structural mapping done by the operating oil companies, so that detailed maps of most of its outcrop were available and were used, supplemented by rather thorough review in the field, in compiling the geologic map (Pl. I); the boundaries of this formation as shown are consequently believed to be fairly accurately drawn. The formation owes its excellent exposures to its stratigraphic situation between two relatively thick, soft shale units--the Enterprise shale above and the Doyle shale below; it is resistant compared with the shales and as a result forms a prominent ledge capping the steep slopes formed by the Doyle shale. Its outcropping edges have been intricately dissected, so that its outcrop line presents a very irregular pattern characterized by numerous isolated patches, which represent flat-topped buttes, rising 75 feet or more above the surrounding region; these buttes are particularly abundant in the vicinity of Winfield, both northeast and southeast of the town, and in the eastern part of the town proper; the old reservoir, Richardson Hall of Southwestern College, and the State Hospital for the Feeble-Minded are built on buttes capped by the Winfield. The formation makes a prominent escarpment skirting the Walnut river bottoms on the west throughout the river's course across Cowley County; it is prominently exposed east of the Winfield-Augusta highway that trends north from Winfield from a point 2 miles north of Winfield northward nearly to Rock and again north of Rock. It the southern part of the county its outcrops are particularly conspicuous throughout much of T. 34 S., R. 4 K, and the western part of R. 5 E. Typical outcrops occur north of the Arkansas City-Joplin highway 2 to 7 miles east of Arkansas City. One outcrop of the Winfield in the northwestern part of the county and another a short distance west of the county boundary are of interest because of their structural significance. In the E2, sec. 14, T. 30 S., R. 3 E., the formation dips westward at a low angle beneath the overlying beds, but it reappears in the N2, sec. 10, where it has been elevated by a small dome-shaped fold. The other outcrop is on the Churchill anticline, about in sec. 26, T. 31 S., R. 2 E., just west of Arkansas river and the Churchill pool, where the Winfield limestone lies several feet above the river bed and crops out in the bluff west of the railroad track. This exposure is about 5 miles west of the westernmost outcrop of the formation in Cowley County.

On a much-weathered surface where the outcrop of the formation is represented by limestone fragments projecting out of the soil the Winfield resembles the Foraker limestone of the Wabaunsee group and certain beds of the Fort Riley limestone. The beds of each of these formations weather to very light gray, irregularly shaped, more or less flat nodular forms containing pit holes through the rock. Such outcrops of the Winfield can be distinguished from the Foraker by the absence of small sharp-edged fragments of tan-colored chert strewn upon the surface and containing large Fusulina in abundance, which are always present upon a weathered surface of the Foraker; the Winfield has a little grayer color, which distinguishes it from the white weathered surface of the Fort Riley; and its etched fossil fragments of slender rods and spines are most distinctive. The abundant small concretions that occur in the uppermost part of the Doyle shale, immediately beneath the Winfield limestone, constitute the most certain criterion for its identification, because they are present at all exposures seen throughout the county and were not found elsewhere in the section.

Prosser described and named the Winfield limestone in 1897 from its exposures in the bluffs of Walnut river west of Winfield (Prosser, 1897, p. 64) and definitely correlated it with a limestone which he had previously described and called "Marion concretionary limestone," from its exposures near Marion, Marion county, Kansas (Prosser, 1895, p. 772). In [1902] Prosser again described this limestone and definitely substituted the name Winfield formation for "Marion flint and concretionary limestone," stating that the formation consisted of "a cherty limestone at the base with a massive concretionary one at the top, the two separated by yellowish shales," with a total "thickness of about 25 feet." (Prosser, 1902, p. 715, 716) It appears probable from a correlation of Prosser's central Kansas section of the Chase group and a section of the same group as exposed in Cowley County that the Winfield limestone as described herein corresponds to the "massive concretionary" limestone that Prosser described as being about 10 feet thick and occurring at the top of his Winfield formation. The lower part of his Winfield formation may then correspond to the uppermost part of the Doyle shale as described herein, the lower cherty limestone being absent in southern Kansas.

The following fossils collected from Reservoir Hill, in the eastern part of the town of Winfield, were identified by G. H. Girty:

U.S.G.S. No. 6149:
Echinocrinus aff. E. cratis Rhombopora lepidodendroides
Spirorbis sp. Derbya multistriata?
Stenopora sp. Composita subtilita

Sumner Group

All strata lying between the top of the Winfield limestone and the "Red Beds" are here included in the Sumner group. This group includes, from the base upward, the Luta limestone, the Enterprise shale, the Herington limestone, and the Wellington formation. As thus defined the terms "Marion formation," "Pearl shale," and Abilene conglomerate of former Kansas Geological Survey reports are not used (Moore and Haynes, 1917; Moore, 1920). Only the lower part of the Sumner group--the beds up to and including a little less than 100 feet of the Wellington--is exposed in Cowley County, but the entire unit underlies the region several miles west of the county. The group is characterized by a large percentage of soft shale, with minor amounts of limestone, decreasing in abundance upward; beds of gypsum are abundant in parts of the group, and in central Kansas it includes thick beds of salt.

Luta Limestone

Overlying the Winfield limestone and composing the basal formation of the Sumner group is 20 to 25 feet of thin-bedded light-blue limestone that weathers chalky white and occupies the stratigraphic position of the Luta limestone, described by Beede as intervening between the Enterprise and Winfield formations in the vicinity of Marion, Marion county, Kansas, about 50 miles north of Cowley County (Beede, 1909). Inasmuch as this limestone is exposed in only a few localities in Cowley County and does not constitute a mappable unit it is not separated from the overlying Enterprise shale on the geologic map (Pl. I), where it is for convenience treated as a member of the Enterprise shale. It is in part abundantly fossiliferous, particularly about 3 and 5 feet above the base; the uppermost 5 feet is shaly and becomes less limy upward, grading into greenish shale above. A short distance west of the west boundary of Cowley County, just west of Arkansas river and the Churchill oil pool, about in sec. 26, T. 31 S., R. 2 E., the Winfield limestone, Enterprise shale, and Herington limestone are exposed; there the thin-bedded Luta limestone is 25 feet thick, although in the uppermost 10 feet limestone is alternately bedded with shale, and the limestone beds are increasingly shaly upward. The entire thickness of the formation is rarely exposed, but exposures of the beds occupying the lowermost few feet were seen in road-drainage ditches and excavations at a number of localities in the county.

The following fossils collected from the Luta limestone were identified by G. H. Girty:

Fucoid Productus semirecticulatus
Delocrinus sp. Composita subtilita
Fenestella sp. Parallelodon tenuistriatus?
Rhombopora Lepidodendroides? Myalina sp.
Derbya multistriata Pseudomonotis sp.
Echinocrinus aff. E. cratis Pleurophorus? sp.
Septopora sp. Bellerophon? sp.

Enterprise Shale

The Enterprise shale is composed largely of greenish and blue shale beds occurring between the Luta and Herington limestones. Two thin but persistent beds of limestone separated by 3 to 4 feet of shale occur in the upper part of the Enterprise throughout its outcrop in the southern part of Cowley County. The upper one, which weathers light tan, is 8 to 10 inches thick and lies between 6 and 9 feet beneath the top of the formation. The lower part of this limestone bed and the shale immediately below it are crowded with fossil brachiopods. The lower limestone bed is 1 to 2 feet thick and weathers into a chippy ledge containing abundant specimens of a flattish circular form about the size of a half dollar. These specimens are probably masses of fossil calcareous algae covering shells. The fossil forms associated with these limestone beds, particularly those of the lower bed, serve excellently to identify them in several partial exposures in the southern part of the county.

Because of the relative abundance of soft, easily decomposed rocks the Enterprise shale forms long, gently graded slopes, making the determination of its total thickness difficult to obtain. The few sections measured indicate that it varies considerably in thickness within the county; two measured sections in the southwestern part. of the county, one about a mile southeast of Arkansas City, in the SW, sec. 5, T. 35 S., R. 4 E., and the other about a mile northeast of Arkansas City, near the center of sec. 18, T. 34 S., R. 4 E., show a thickness of about 52 feet, but a core-drill record of the Roxana Petroleum Corporation shows a thickness of 36 1/2 feet in the north-central part of T. 34 S., R. 3 E. A hand-level section measured in the northwestern part of the county, in sec. 3, T. 30 S., R. 3 E., shows a total thickness of 60 feet for the Enterprise shale and Luta limestone. A variation in thickness of the part of the formation above the thin limestone beds in the upper part and the appearance of a number of cores from borings made in this region by the Roxana Petroleum Corporations suggest the presence of an unconformity, probably of slight relief and perhaps local extent, between the Enterprise shale and the Herington limestone (E. L. Jones, personal communication).

The base of the Enterprise shale in Cowley County is indefinitely marked by a gradational change downward from shale beds through limy shale to the soft, thin-bedded limestone of the Luta. At the top the change from the soft shale beds of the uppermost part of the Enterprise to the thick-bedded limestone of the Herington is a rather definite boundary.

Throughout most of the area of their outcrop in Cowley County the Enterprise shale and Luta limestone occupy a gently graded soil-covered slope between the ledge below formed by the Winfield limestone and one above formed by the Herington limestone. The ledge-forming ability of the Herington is not so pronounced as that of the Winfield, and in parts of the county the Herington forms not the slightest interruption in the general lay of the surface. The outcrop of the Enterprise and Luta forms a relatively narrow band in the eastward-facing slope on the west side of Walnut river from the northern boundary of the county southward to Arkansas City and continues south of Arkansas river, occupying an even narrower strip of the surface. In sec. 10, T. 30 S., R. 3 E., and near Arkansas City, both north and south of Arkansas river, the slopes are exceptionally steep, and parts of the Enterprise are clearly exposed, although throughout most of the area occupied at the surface by this formation the beds are entirely concealed beneath a mantle of soil. Parts of the formation are exposed southwest of Winfield, in the northwestern part of the Country Club's grounds. The most complete exposure seen is that in the steep slope below the east end of the municipal golf course north of Arkansas City, near the center of sec. 18, T. 34 S., R. 4 E., where the following section was measured by hand level:

  Feet Inches
Herington limestone, capping the slope.    
Enterprise shale:    
Buff limy shale; a very shaly limestone 4 inches thick about 3 feet above the base 5-9  
Compact limestone; weathers buff. Abundant brachiopods (Composita subtilita) in its lower part   10
Buff weathered shale, limy; abundant brachiopods in uppermost few inches 3  
Limestone; weathers to very light buff and breaks down into small chips, with numerous forms that are flattish circular and about the size of a half dollar, covered with fossil algae, and constituting its most striking characteristic 1  
Light-tan weathered shale 1 4
Greenish-gray shale 7  
Purplish-gray shale 2  
Greenish-gray shale 8  
Bluish-gray shale 3  
Limy shale; weathers into white chips 1  
Greenish and bluish-gray shale grading into weathered buff shale in lower part 16 6
Total Enterprise shale 52 8
Luta limestone:    
Covered slope 7 6    
Thin-bedded chalky-white weathered limestone 1  
Covered but known from near-by exposures to be thin-bedded bluish-gray limestone, in part very fossiliferous 9  
Winfield limestone, 10 feet thick, exposed in the railroad cut at the base of the slope.    

The Roxana Petroleum Corporation, through E. L. Jones, courteously furnished the following record of a core-drill hole bored in the northern part of T. 34 S., R. 3 E.:

  Feet Inches
Herington limestone:    
16. Limestone, porous in upper part and fossiliferous below 10  
Enterprise shale:    
15. Blue shale 1
14. Green shale 8  
13. Blue shale 3  
12. Limy shale 3  
11. Limestone 2  
10. Blue shale 2  
9. Limy shale and limestone 2  
8. Blue shale 6 6
7. Limestone 2  
6. Green shale 7  
Total Enterprise shale 36 6
Luta limestone:    
5. Banded limy shale 5 6
4. Limy shale and limestone 3  
3. Limestone with some shale 8  
Winfield limestone:    
2. Granular limestone 9 6
Doyle shale:    
1. Limestone containing abundant small concretions; referred to as "birdseye maple" limestone 5  
>

The Enterprise shale was named by Beede from exposures near Enterprise, Dickinson County, Kansas (Beede, 1909, p. 253).

The following fossils collected from the Enterprise (Nos. 11 and 13 of section quoted above) were identified by G. H. Girty:

U.S.G.S. Nos. 6152 and 6152b. Collected in the NW, sec. 32, T. 31 S., R. 4 E.:
Spirorbis sp. Composita subtilita
Septopora biserialis Deltopecten occidentalis
Derbya multistriata Calcareous algae (?) embedding
various fossils
.

Herington Limestone

Above the Enterprise shale is a unit of light-buff limestone and dolomite about 30 feet thick known as the Herington limestone. Only the lowermost 3 to 6 feet, composed of fossiliferous limestone, crops out in most localities, commonly forming a ledge in the slope. The upper two-thirds of the formation has the appearance of fine-grained tan sandstone that is rarely exposed; in one locality seen it is cross-bedded, the laminae being very thin and deviating at a low angle from the true bedding planes; tests of outcrop samples and a core sample from a drill hole showed that this upper part of the formation is dolomite. Observations at a few exposures indicate that the separation of the limestone and dolomite is not a sharply defined boundary but a zone of gradation from limestone below to dolomite above. The dolomite is relatively soft and is rarely exposed, but the limestone constitutes the ledge-forming part of the formation. Numerous geodes of calcite 1 to 6 inches in diameter, the larger ones ellipsoidal and the smaller ones spherical, are distributed through beds of dolomite, where they are exposed beside the road on the line between the SW, sec. 26, and the NW, sec. 35, T. 34 S., R. 3 E. The geodes have walls only one-fourth to one-half inch thick composed of calcite crystals, and are embedded in sugary-textured, relatively soft dolomite that gives no visible reaction with cold hydrochloric acid. The exposure here reveals a total thickness of 20 feet of dolomite beds; the lower 12 feet is thin bedded and contains most of the geodes; the upper 8 feet is thick bedded. Spherical and irregularly shaped small nodules of white, drusy chert characterize weathered exposures of the Herington; the chert nodules are commonly 2 to 3 inches in diameter and have crenulated outer surfaces closely resembling heads of cauliflower. Nodules were not seen in place within the formation, but they lie everywhere strewn upon the surface formed by the upper part of the Herington. The similarity of shape and size between the calcite geodes seen in the dolomite beds and the chert nodules suggests that the chert may represent replacement of the calcite. Inasmuch as no chert nodules of similar shape and appearance occur in this region in other strata of the exposed stratigraphic succession, these nodules served excellently to identify the Herington in areas of poor exposures.

The Herington limestone constitutes one of the most important stratigraphic units in this part of Kansas, because it is the "key bed" through which hundreds of cored holes have been drilled to obtain information concerning the attitude of the strata throughout an extensive region west of the outcrop of the formation. Common practice is to drill down within a few feet of the Herington with a fishtail bit, which does not preserve a core, and then drill through the Herington with a bit equipped for coring.

The Herington limestone was named by Beede from exposures in and near Herington, Dickinson County, and correlated with exposures near Winfield and Arkansas City, Cowley County, and other exposures in Noble County, Oklahoma (Beede, 1909, p. 253, 254). Beede describes the formation as being composed of a lower resistant fossiliferous limestone, with softer flaggy beds containing geodes above.

The following fossils collected near the center of sec. 18, T. 34 S., R. 4 E., from the ledge-forming limestone beds were identified by G. H. Girty:

U.S.G.S. Nos. 6148 and 6148b:
Septopora biserialis Pleurophorus calhouni
Crania modesta Pleurotomaria sp.
Composita subtilita Myalina wyomingensis?
Deltopecten occidentalis? Pseudomonotis equistriata

Wellington Formation (redefined)

Strata with an aggregate exposed thickness of about 80 feet occur above the Herington limestone in the western part of Cowley County; almost this total thickness is occupied by soft clay shale. Although the unit contains a few beds of limestone there is no individual bed or group of beds that can be readily distinguished at the surface throughout any but exceedingly local areas. In short, this group of beds does not lend itself to separation into smaller units in Cowley County. Consequently the name "Pearl shale," which was applied by Beede in Dickinson County to the 70 feet of beds succeeding the Herington limestone, is not used in Cowley County, but the Wellington formation is redefined so as to include the rocks above the Herington limestone (Beede, 1909, p. 225; named from Pearl, Dickinson County).

Because of their softness these beds are rarely exposed. The few partial exposures seen, one of the best a short distance east of Geuda Springs along the river highway and another in the NE, sec. 21, T. 34 S., R. 3 E., indicate that they are composed of varicolored banded beds of clay shale, in minor parts limy. Coarsely honeycombed beds of gypsiferous limestone occur about 50 feet above the base of the formation and locally form conspicuous outcrops. A bed of limestone about 3 feet thick, that weathers similarly to these, crops out in a prominent ledge across secs. 7, 17 and 20, T. 33 S., R. 3 E., in the Rainbow Bend oil field. The exact stratigraphic position of this bed was not determined, but it is probably the bed mentioned in many core-drill records of this region as a bed of limestone and gypsum 4 to 8 feet thick about 50 feet above the base of the Wellington formation.

It is apparent that because of lack of good exposures, which in turn is the result of the composition of the strata, little detail as to the nature of the rocks in the Wellington formation can be gained from a surface examination. Because of this dearth of exposures of mappable surface beds throughout the extensive area occupied by the Wellington formation several of the oil companies operating in the region have resorted to drilling a large number of shallow holes, extracting cores from parts of the rocks drilled through, in order to obtain definite altitudes on some recognizable key bed for the determination of the attitude of the rocks. Throughout a broad area west of the outcrop of the Herington limestone the holes are drilled to the base of the Herington, as it serves admirably as a key bed. As a byproduct of such procedure the operators have gained an extensive and detailed knowledge of the strata that make up the Wellington shale. E. L. Jones, of the Roxana Petroleum Corporation, kindly supplied a few logs typical of the region and called attention to those beds that are particularly persistent throughout extensive areas and to the fact that beds of salt, so characteristic of the Wellington formation in the vicinity of Hutchinson and elsewhere in central Kansas, change laterally southward and eastward to interbedded salt and gypsum and finally to beds of gypsum. The log of a core-drilled hole that penetrated the lowermost 400 feet of the Wellington formation in southeastern Sumner County, adjacent to Cowley County on the west, is reproduced in Figure 6, but only the lowermost 80 feet or less of the beds shown in the Wellington are present in Cowley County. The lowermost 25 feet of the. Wellington is recorded as interbedded blue and green shale, in part limy and gypsiferous and containing several thin beds of limestone and gypsum. About 25 feet above the base of the formation is a bed of shale only 2 to 4 feet thick that is in part green but contains some-red and brown shale which according to Jones is persistent from central Harvey County, Kansas, southward across Sedgwick County, eastern Sumner County and western Cowley County into Oklahoma (E. L. Jones, personal communication). In many localities this varicolored shale bed is underlain by a thin bed of gypsum. Above it is 20 to 25 feet of alternately bedded green and blue clay shale containing several thin beds of gypsum. Succeeding these beds, about 50 feet above the base of the formation, is a bed of limestone and gypsum 4 to 8 feet thick that is recorded in nearly all core-drill logs throughout this part of the state. This may be the bed that crops out and forms a porous ledge in the western part of the Rainbow Bend oil field. Overlying this limestone-gypsum bed is a little more than 20 feet of green and blue clay shale succeeded by a series of interbedded gypsum and green and blue clay shale with two or three thin reddish layers that occupies the interval from about 80 to 290 feet above the base of the formation. The lowermost part of this unit is commonly occupied by a bed of gypsum about 10 feet thick, and 35 feet above it is another of similar thickness; both beds are widespread in their occurrence and recognizable in shallow drill holes. Logs of core-drill holes farther north in the state indicate that the uppermost part of this unit, which is occupied by gypsum and gypsiferous shale in Sumner County, contains the thick salt bed mined at Hutchinson and Lyons (E. L. Jones, personal communication). Two units, one about 50 feet and the other about 70 feet beneath the main Hutchinson salt bed, shown by core drilling to contain salt beds throughout an extensive region north-northwest of Sumner County, are occupied by beds of gypsum, each 5 to 8 feet thick, in southern Sumner County. The 130 feet of beds next above the Hutchinson salt horizon recorded in Figure 6 consist of blue clay shale with less green and an increasing number of red beds.

Figure 6--Section of lower part of Wellington formation as recorded in core-drill hole in southeastern Sumner County. (Figures represent interval in feet from base of Wellington formation.)

Section of lower part of Wellington formation.

The section recorded in Figure 6 includes only the lowermost 420 feet of the Wellington formation, although it attains a thickness greater than 800 feet a little farther west in Kansas. As reported in well logs that penetrate the entire formation it may in general be divided into three units--an upper one of blue clay shale 200 to 450 feet thick, a middle one containing thick beds of salt and thin beds of blue clay shale with a maximum thickness of about 400 feet, and a lower one of interbedded shale and gypsum. The lower boundary of the formation is difficult to determine in well logs, because the gypsum beds beneath the main salt are commonly recorded as limestone, and consequently the log shows no lithologic difference between the rocks of the lower part of the Wellington formation and those of the formation below it. There is but little doubt involved in determining the position of the upper boundary of the formation in well logs; it is placed at the horizon of change from the great thickness of red beds of the upper part of the Permian series to the blue clay shale of the upper division of the Wellington formation, a horizon that is rarely missed by the drillers. The location of the outcrop of the top of the Wellington formation is quite another matter, however. Because of the softness of the strata that make up the Wellington formation and the overlying "Red Beds," the contact between the two, which lies many miles west of Cowley County, is thickly mantled by soil and cannot be traced from surface observations, except in a very general way. The Herington limestone, although concealed in places along its eastern margin, is sufficiently well exposed throughout much of its outcrop to permit the mapping of the lower boundary of the Wellington formation with a fair degree of accuracy. It is fairly well exposed in Cowley County except throughout the region west of Hackney.

The Wellington formation occupies the westernmost tier of townships in Cowley County, much of the surface of Sumner, Sedgwick, and Harvey counties, and the western part of Butler County and thence narrows northward into northern Dickinson County. The area underlain by it is characterized by broad plains practically devoid of outcropping rocks, forming a strikingly featureless surface when contrasted with the surface of the remainder of the state lying to the east and formed by the alternately bedded resistant limestone and shale in the lower part of the Permian and the upper part of the Pennsylvanian series.

The Wellington formation was named by Cragin from exposures and the record of a boring near Wellington, Sumner County, Kansas (Cragin, 1896, p. 17). Cragin applied the name to only those beds that lie above the principal salt beds and below the "Red Beds" and described them as constituting a body of clay shale of blue-gray, drab, slate, buff, and various shades of blue and brownish-red colors 250 to 450 feet thick. Some beds of shaly limestone, calcareous shale, gypsiferous shale, gypsum, and dolomite are present in the upper half of the formation where it crops out in the type locality, according to Cragin; he described the lower half as greenish and blue with some reddish clay shale as recorded in a well drilled at Wellington. Moore and Haynes (Moore and Haynes, 1917, p. 115, 116) extended the lower boundary of the Wellington formation to include the salt beds and all beds above the Abilene conglomerate, which was described as being about 70 feet above the Herington limestone (Prosser, 1895, p. 786). Named from Abilene, Dickinson County, Kansas). The Abilene conglomerate was later described by Moore as being of Tertiary age and therefore excluded from the Permian series (Moore, 1920, p. 63, footnote). Inasmuch as the rocks that occupy the entire interval between the Herington limestone and the horizon of the principal salt beds are essentially similar to the beds that are interbedded with the salt and occupy the interval above the salt and beneath the "Red Beds," the whole is herein included in the Wellington formation; that is, the entire interval between the Herington limestone below and the "Red Beds" above. It is true that the bed of gypsiferous limestone that occurs about 50 feet above the Herington limestone, the salt beds, and some beds of gypsum are widespread in this part of the state as recorded in well logs and on the basis of well records might serve to separate the formation into several divisions, The surface expression of these beds is so weak, however, that the positions of their outcrops are not mappable except in areas of local extent, and on the basis of the present information it is not deemed expedient to subdivide the Wellington.


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Kansas Geological Survey, Geology
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