The Pennsylvanian rocks of Kansas are divided into the following series, listed in descending order: Virgilian, Missourian, and Desmoinesian.
Major unconformities that resulted from widespread erosion and that display well-developed topographic features separate the series but there are innumerable minor unconformities within the groups and formations. The Pennsylvanian rocks of the central and eastern United States were deposited in very shallow and exceedingly fluctuating seas. Studies by Welter (1930) in Illinois, by Moore (1936), and others have demonstrated that the deposition of the Pennsylvanian rocks in Kansas and other states was cyclical and that the sequence of rocks may be divided into cyclothems representing deposits made during a single period of submergence. These cycles of deposition were the result of changes of sea level but differential regional deformation and in places differential local structural deformation accompanied many if not most of the cycles. Throughout the greater part of Pennsylvanian time the surface upon which each successive sheet of sediment was deposited was so nearly level that a lowering of the sea level of only a few feet resulted in the emergence of very large areas and a slight rise caused flooding of equally broad areas.
During the periods of emergence the degree and character of erosion were dependent upon the height of the surface above sea level and the length of time that elapsed before resubmergence. As the sea re-advanced upon the land, the first deposits were derived from the dissected surface of the land itself and were mainly silty shales and sandstones in which the remains of plant fossils were generally incorporated. Without discussing in detail the sequence of distinctive deposits that characterize a completed cyclothem (Moore, 1936, pp. 34-35), it may be stated that the initial deposits were followed by marine shales and by fosslliferous limestones as the water deepened and sources of sediment became more distant. During the completion of the cycle when the sea gradually became more shallow, similar sediments were repeated in reverse order and were concluded with a deposit of shale or sandstone. Local sources of clastic material were no longer available at the end of the cycle, so the material of the final phase of the cyclothem must have been derived from distant land areas and deposited in the shallowing sea by tides, waves, and currents.
The normal sequence of deposits of a cyclothem was often modified by local conditions, especially near the borders of the basin. Where clastic material from adjacent rapidly rising land areas was abundant, limestone deposition was inhibited in the offshore areas and the character of the cyclothems was altered. Toward land areas, therefore, limestones interfinger with shale and sand or grade laterally (in many places abruptly) into impure limestone, fossiliferous shale, and nonfossiliferous shale and sand. Near rising land, the abundance of clastic material that was being carried into the adjacent subsiding basin kept the surface of the basin almost continuously above sea level by the deposition of low alluvial fans reaching at times far into the basin.
All imaginable variations of cyclic deposition are probably represented in the interior basin of which the Salina basin formed a part. The variants include height of the surface and length of time of emergence, rapidity of advance and retreat of the sea, and depth and length of time of submergence. Although most cyclothems were completed, some were incomplete and a new cycle set in by re-advance of the sea before the surface was exposed. At the end of some cyclothems emergence was brief and there was little or no erosion. In many cases, however, exposure continued long enough to develop channels. Sometimes there was little or no dissection of the divides between the channels but sometimes mature topography of low relief developed. The several series of the Pennsylvanian System were separated by long periods of exposure during which the surface was deeply and maturely dissected. Also, channels more than 100 feet deep are known between the Pennsylvanian and Permian Systems.
As pointed out by Moore (1929, p. 479), many of the limestone and shale beds, although only a few feet thick, were evenly distributed across thousands of square miles. On the other hand there are many local and regional variations in thickness and distribution. Many of these deviations from regularity may be attributed to the effects of erosion between cycles of deposition. Where erosion cut down through part or all the deposits of the preceding cycle, the initial shale deposits of a new cycle occupy the position of the eroded parts of the deposits of the preceding cyclothem.
If mature dissection occurred during the emergerent phase of a cycle, and if subsidence at the beginning of the new cycle was so rapid that the initial shale deposits failed to level off the topographic relief, the middle or limestone phase of the new cycle might be deposited on a rolling or hummocky surface. The interval between the very persistent Haskell limestone and well-marked datum beds above and below shows so much local variation as to suggest that this limestone was deposited on such an uneven surface.
Some variations in thickness, however, seem to be the result of minor local warping of the surface during deposition of one or more cyclothems. It seems necessary to postulate local anticlinal warping of the surface during the period of deposition where all the phases of a single cyclothem or of several succeeding cyclothems are represented but are thinner in many places than the regional average. Local synclinal warping is similarly expressed by thickening of the cyclic phases. These relatively local differential structural movements in some cases affected the thickness of one or more cyclothems but generally were not perpetuated later. Cross sections along the outcrops of the Marmaton formations in southeastern Kansas by Jewett (1945) illustrate this phenomenon. In general, these movements resulted in greater local variations in the thickness of the formations than those due to erosion during intercyclical exposure. Even the most pronounced localized structural movements, however, were secondary to, and superimposed upon, the less striking but regionally greater movement of the sedimentary basin as a whole which in Kansas is reflected by the northerly and westerly thinning of the Pennsylvanian rocks and the southerly thickening toward the Ouachita basin. There were, however, differential structural movements of a subregional character, such as those resulting in the Central Kansas uplift, the Nemaha anticline, the Salina basin, and the Cherokee and Forest City basins that continued throughout Pennsylvanian time. These structural features will be discussed later in chapters on the regional structure.
The Desmoinesian Series has been divided into the Marmaton group above and the Cherokee shale below.
The beveled surface that resulted from the erosion of the warped and folded Mississippian rocks was subjected to renewed folding before the Pennsylvanian sea reached Kansas. The rejuvenated folding followed much the same pattern as at the end of Mississippian time but there was some modification of earlier folds and some structural features were not revived. When Pennsylvanian sedimentation began in Kansas the region east of the Nemaha anticline was already lower than the region to the west, and in consequence, the sea advancing from the south entered the Forest City and Cherokee basins east of the anticline before it submerged the Salina basin on the west. When the Pennsylvanian sea reached eastern Kansas, it is probable that the structural divide separating the Salina and Forest City basins was low and would have been covered at an earlier date if it had not continued to rise. The Pennsylvanian sea reached the Salina basin from the south during Cherokee time. The Burns dome on the crest of the Nemaha anticline in T. 23 S., R. 5 E. in northern Butler County was, however, not covered until the end of Cherokee time (Kellett, 1932). In southeastern Nebraska, the crest of the Nemaha anticline was not submerged until middle Kansas City time when the Drum limestone overlapped onto the crest of the fold (E. C. Reed, personal communication). The gradually rising crest of the anticline thus formed a southwesterly projecting peninsula of shrinking proportions that separated the Forest City and Salina basins at least until the close of Cherokee time. The greatest thickness of Cherokee rocks in the Forest City basin is 790 feet but the maximum known thickness of the Cherokee in the Salina basin is only 230 feet.
The Cherokee shale has not been divided into formations, although many beds--coal, sandstone, and limestone--which are widely distributed have been named (Moore, Frye, and Jewett, 1-1944, pp. 197-200). The Cherokee rocks in the outcrops in eastern Kansas and in the subsurface east of the Nemaha anticline in the Forest City and Cherokee basins consist mainly of clastic rocks. Light and dark shales predominate but there is much sandstone and sandy micaceous shale. A few thin limestones are present in some localities but the Ardmore limestone member, 65 to 135 feet below the top of the Cherokee, is the only limestone of general distribution. There are many coal seams but only a few are thick enough to mine.
The Cherokee rocks in the Salina basin consist mainly of gray silty shale interstratified with red shale. In the center of the basin two zones of red shale can be roughly correlated with each other. Toward the margin of the basin where the Cherokee overlapped. upon the differentially rising surface of the Central Kansas uplift, several relatively thin beds of red shale which do not extend far into the basin are commonly present. Each of these beds probably records a nearshore phase of a depositional cycle during which the normal marine phase was inhibited by outwash from the adjacent land areas. Some thin streaks of limestone are reported in some wells but on account of discontinuity or the lack of detail in the logs they cannot be traced from well to well. One limestone of some persistence, 135 to 145 feet below the top of the Cherokee in the center of the basin, is tentatively correlated with the Ardmore limestone.
The sandstone and coal beds, so characteristic of the Cherokee shale at the outcrops in southeastern Kansas, are not represented in the Salina basin. Streaks of black shale probably representing coal beds of the Cherokee basin are recognized in the samples of some wells,
The Pennsylvanian basal conglomerate is well developed in most wells. It reaches a thickness of 20 to 30 feet in many places but is not present everywhere. Extreme thicknesses exceeding 50 feet have been drilled. The occurrence of chert-bearing basal conglomerate is much more common in the Salina basin where most of the underlying rocks are cherty limestones than in the Forest City basin where the widely exposed sparsely cherty or noncherty limestones of Spergen, St. Louis, and Ste. Genevieve ages provided little material for a basal conglomerate.
In drillers logs and in many sample logs it is impossible to differentiate the Pennsylvanian basal cherty conglomerate from Mississippian chert that had been weathered in place. Currents and wave action during gradual submergence tend to remove residual debris from topographic crests and redistribute it in channels and basins. The top of the basal conglomerate, therefore, presents a more nearly level surface and consequently a more useful surface in the study of structural deformation than the actual, more irregular surface of the Mississippian. The thickness of the Mississippian and the thickness of the lower Pennsylvanian rocks have therefore been measured from the top of the chert-bearing beds (basal Pennsylvanian) rather than the top of the true Mississippian surface. This procedure, although not stratigraphically accurate, has the advantage of consistent application and it is to be understood that references to the thickness of the lower Pennsylvanian rocks exclude the cherty basal Pennsylvanian conglomerate.
In the drillers logs of old wells in which chert is consistently reported as sand, beds of "sand" in the position of the basal conglomerate have been assumed to represent chert in some wells. The elimination of these doubtful beds from the Cherokee and their inclusion in the Mississippian may have introduced some minor errors in the thickness maps.
The Cherokee shale is absent on the north end of the Nemaha anticline. It is 10 feet thick in sec. 32, T. 8 S., R. 9 E. and gradually increases in thickness toward the south although it is absent at places on structural and topographic highs. It is 55 feet thick in sec. 34, T. 17 S., R. 7 E. Along the axis of the Nemaha anticline, the thickness of the Cherokee varies with the height of the structural crest and with the topographic relief which was greater along the anticline than elsewhere.
The thickness of the Cherokee increases rapidly east of the Nemaha anticline and its thickness in eastern Morris County only a few miles to the east of the crest exceeds 300 feet (Bass, 1936, pl. 1). On the northeastern flank of the Salina basin in sec. 10, T. 7 S., R. 4 E. the Cherokee is only 30 feet thick, but increases in thickness irregularly toward the center of the basin where, in sec. 2, T. 7 S., R. 11 W. near the deepest part of the basin it has a thickness of 230 feet, It thins southwestward from the center of the basin and wedges out on the pre-Pennsylvanian surface of the Central Kansas uplift.
The Cherokee is separated from the Mississippian limestones by a marked unconformity, but it is essentially conformable with the overlying Marmaton group.
The formations of the Marmaton group which are named in Table 7 in descending order have been differentiated in outcrops in southeastern Kansas (Jewett, 1945). The range and average thickness of each in southeastern Kansas has been reported by Moore, Frye, and Jewett (1944). The thicknesses in southeastern Nebraska are reported by Condra and Reed (1943).
Table 7--Sequence and thickness of formations of the Marmaton group.
|Range in thickness
|Memorial shale||0- 30||10||missing|
|Fort Scott limestone||24-35||33||36|
The formations of the Marmaton group that are referred to as limestones in the outcrops actually consist of conspicuous groupings of limestones which alternate with shale beds of varying thickness. The details of stratification in the subsurface can rarely be determined from drillers or sample logs because in the subsurface toward the northwest the shale beds become thinner than in the outcrop, and all the limestone members, which are not very hard, are seldom recorded. The upper limestone members of some formations were eroded during emergent phases of cyclothems shortly after deposition and some wedge out. The upper formations of the Marmaton down to the Bandera shale were removed from broad areas by pre-Missourian erosion. so that even in the outcrops the Marmaton sequence is not everywhere complete.
In the Salina basin the Marmaton group can be described only as a sequence of shale and thin limestones. The more persistent and thicker Fort Scott limestone at its base can generally be recognized. The sandstone members that provide reservoirs for oil and gas in the Forest City and Cherokee basins (the "Peru sand," of the Labette shale, the sandstone of the Bandera shale, and the "Wayside sand" of the Nowata shale) which are present only intermittently in eastern Kansas, are not represented at all in the Salina basin.
The formations composed dominantly of limestone include black shale and one or more streaks of coal. Some thin beds of red shale are interstratified with the limestones but they lack stratigraphic continuity and are of no help in identifying the several limestones. The upper members of the Altamont, Pawnee, and Fort Scott limestones in outcrops contain fusulines in abundance. The fusulines are the only features likely to be of assistance in differentiating the Marmaton formations in cuttings from wells, although the Fort Scott is generally recognized by its greater thickness and the Pawnee limestone by its brown color. It is probable that only the lower part of the Marmaton is represented in the Salina basin.
The Marmaton group is commonly about 200 feet thick in the Cherokee and Forest City basins but, so far as can be determined from the samples, the Marmaton in the Salina basin has a maximum thickness of only 130 to 140 feet. It thins markedly on the crest of the Nemaha anticline and probably to a lesser degree in other structurally positive areas. On the crest of the anticline in T. 17 S., R. 7 E. it ranges in thickness from 30 to 50 feet. In T. 9 S., R. 9 E. it is 45 feet thick. On the northern flank of the Salina basin in sec. 1, T. 1 S., R. 2 E. it is 65 feet thick. On the southwestern side of the Salina basin it becomes gradually thinner and individual formations overlap on the pre-Pennsylvanian surface of the rising Central Kansas uplift.
The Missourian Series is separated from the Desmoinesian Series by an unconformity and by a faunal break. The unconformity was accompanied by erosion of the upper Marmaton beds and by the development of channels later filled by sandstone deposits. The subordination of the Bronson rocks to a subgroup of the Kansas City group was agreed upon at a four-state nomenclature conference of the state geologists of Kansas, Nebraska, Iowa, and Missouri held in Lawrence May 5, 1947. The term Bourbon shale was abandoned in favor of the older equivalent term, Pleasanton group.
The Missourian Series has been divided into the following groups listed in descending order: Pedee, Lansing, Kansas City (Zarah, Linn, and Bronson subgroups), and Pleasanton.
Four formations of the Pleasanton group, named in descending order in Table 8, have been differentiated in outcrops in southeastern Kansas. The average thicknesses of the formations have been reported by Moore, Frye, and Jewett (1944).
Table 8--Sequence and thickess of formations of the Pleasanton group.
in eastern Kansas,
|Knobtown sandstone and shale||30|
(southeastern Kansas only)
The Hepler sandstone was deposited in channels and basins eroded in the upper formations of the Marmaton group. On account of the unconformity, the Hepler sandstone and the overlying shale are of variable thickness and character in eastern Kansas. The Knobtown sandstone of Linn and Bourbon counties is replaced toward the south by thin beds of dense blue limestene alternating with thin beds of black shale (Moore, Frye, and Jewett, 1944, p. 195). Sandstone can be traced westward across the Nemaha anticline on the line of cross section X-X' (Pl. 13) to T. 5 E. (well 44). Westward from this point it is replaced by red shale and gray silty shale in part finely micaceous. Some black shales and dark shales are locally interbedded with lighter-colored shales. The red shales were probably deposited during submergence after periods of weathering and exposure.
The thickness of the Pleasanton group is controlled in part by the erosional relief at its base, but in large part also by regional warping of the pre-Pleasanton surface. The Pleasanton thins northward from an average thickness of about 100 feet in areas of outcrop in eastern Kansas to 18 feet in southeastern Nebraska where until the recent reclassification it was regarded as the basal formation of the Bronson group (Condra and Reed, 1943, p. 53). The Pleasanton group is 60 feet thick in central Chase County and continues to thin westward to McPherson County where it is 20 to 40 feet thick. In the center of the Salina basin it increases to a thickness of 50 or 60 feet; on the northeastern flank of the Salina basin in sec. 10, T. 4 S., R. 7 E., it thins to 20 feet; and in sec. 1, T. 1 S., R. 2 E. to 25 feet. It thins also on the southwestern flank of the Salina basin where it overlaps upon the pre-Pennsylvanian surface of the rising Central Kansas uplift. On the crest of the Nemaha anticline it is thin or absent. The thickness of the Pleasanton group, although controlled locally by movements such as the Nemaha anticline, the Salina basin, and the Central Kansas uplift, increases regionally toward the southeast and shows a definite relation to the regional deformation of the Ouachita basin.
Kansas City and Lansing Groups
The Kansas City and Lansing groups, which consist of alternating shale and thick limestone, were deposited in sequence above the Pleasanton group with only cyclical interruptions. The cyclical periods of exposure, during which minor channeling and erosion occurred, were not infrequent and each exposure reduced in varying degree the thickness of the limestone and shale members of the preceding cyclothem. The loss of limestones by dissection was in general compensated by an increase in thickness of initial shale deposits of the succeeding cycle. The net result of such cyclical erosion and filling tended to restore the level surface of the vast basin before the limestones of the new cyclothem were deposited.
The Kansas City and Lansing groups are composed dominantly of limestone in Kansas but southward the formations and members composed of shale become thicker and the limestone beds in general grade into contemporaneously deposited shale and sandstone. Some of the limestones extend into northern Oklahoma, others fade out in southern Kansas. Many of the formations are convenient lithological groupings of beds without regard to the cyclothems involved.
Most of the formations referred to as limestones include shale members of varying thicknesses, some of which have characteristics recognizable in outcrops throughout extraordinarily broad areas. In the outcrops the limestones display faunal, lithological, and weathering characteristics by which they are commonly recognized. Most of the distinctive features of color, weathering, jointing, and faunal content and texture, however, cannot be determined in the cuttings taken from wells. The identification of formations is in consequence dependent upon the sequence of limestone beds and upon the thickness of shale between them, confirmed by the fusulines, oolites, and cherts of some limestones, and by the regular occurrence of black, red, olive-colored, and sandy shale units having the rank of members and formations. Unfortunately none of these characteristics can be relied upon with certainty over very broad areas. Both oolites and chert are variable. Algal limestones include oolites in some areas but fail to do so in others. Chert is a more or less constant constituent of some limestones in certain areas but chert is absent from ordinarily cherty beds in many wells and on the other hand, has been found in nearly all the limestones at some place in the subsurface. Fusulines are widely distributed but because of their frequency, are not very useful as lithologic features. A report on the zoning of fusulines in the Pennsylvanian and Permian rocks in Kansas, in preparation by M. L. Thompson, will provide an important means of identifying many formations. The detailed sequence of the members, many of which are thin, is seldom fully revealed by well cuttings or by the most careful logs, but the thickness and position of the group as a whole can generally be determined from good sets of well samples in areas where the shale units that are formations are well. developed. In parts of the Salina basin, however, such shale units are so thin that even the groups are doubtfully differentiated in some wells.
Kansas City Group
The several formations of the Kansas City group listed in descending order in Table 9 have been differentiated in outcrops in southeastern Kansas. The range and average thickness at outcrops of each formation have been reported by Moore, Frye, and Jewett (1944, pp. 187-193). The thicknesses of the formations in southeastern Nebraska have been reported by Condra and Reed (1943, pp. 51-53).
Table 9--Sequence and thickness of the formations of the Kansas City group.
|Range of thickness
|Kansas City group|
|Bonner Springs shale||0-60||20||6-8|
|Quivira shale member||3-11||7||6-14|
|Westerville limestone mbr.||1-16||8||17-18|
|Wea shale member||15-35||25|
|Block limestone member||3-8||4||14-30|
|Fontana shale member||5-25||15|
|Total thickness in Salina basin, 255 feet|
Bronson subgroup--The lower member of the Hertha is partly algal in the outcrops and it becomes oolitic in places in the subsurface in the Salina basin.
The Swope limestone is commonly oolitic in outcrops but not everywhere oolitic in the subsurface. The Hushpuckney black fissile shale member in the lower part of the Swope is generally recognized in the samples and is useful in identifying the Swope limestone.
The Dennis limestone also includes a useful black fissile shale (Stark shale member). The upper member of the Dennis, the Winterset limestone, is cherty and oolitic in outcrops. The chert is widespread but is not everywhere recognized in the subsurface. The oolitic facies of the Winterset is not dependable in the subsurface.
It will be noted that the thickness of the shale units that are formations in the table decreases toward the north more rapidly than that of the limestones. The average thickness of the formations of the Bronson subgroup that are mainly limestone is 79 feet in outcrops in eastern Kansas and 61 feet in southeastern Nebraska. Part of the thinning of the formations that are mainly limestone is probably due to the thinning of the shale members within the predominantly limestone formations. In the same areas the thickness of the shales of formation rank decreases from 55 feet to 13 feet. The average thickness of the Bronson subgroup as a whole in Kansas outcrops is 134 feet. The average thickness of the Bronson in seven wells in the subsurface on the line of cross section X-X' (Pl. 13) is approximately 100 feet. The decrease in thickness toward the northwest is almost entirely due to loss of shale,
Linn and Zarah subgroups--The nomenclature conference of state geologists May 5, 1947, restored to accepted usage in Kansas the term Cherryvale shale as the designation of a formation to include the Quivira shale, Westerville limestone, Wea shale, Block limestone, and Fontana shale as members.
The Block limestone has not been identified in outcrops south of Linn County and it thins northward. In southeastern Nebraska, a limestone 7 inches thick in the base of the Cherryvale shale may represent the Block, if the Fontana is absent. The Block is either absent or indistinguishable in the Salina basin where the Wea and Fontana shales in some places unite.
The Westerville limestone is cherty and oolitic in outcrops. The chert is not conspicuous in the Salina basin and the oolite is not well developed. The Westerville seems to be somewhat thicker in some wells than in outcrops, but it is not clearly distinguishable throughout the Salina basin.
The Quivira shale in the outcrop includes black shale which may occur also in the subsurface of the Salina basin.
The Drum limestone is oolitic in outcrops but oolites are not common in it in the Salina basin.
The Chanute shale was identified by Betty Kellet (1932) as far west as McPherson and Rice counties but it has not been identified farther west and has not been recognized in the Salina basin, where, if present, it forms a thin parting between the Drum and the Iola.
The Iola limestone in outcrops includes the black fissile Muncie Creek shale member, a good datum in the subsurface.
The Lane shale, although thin, is a persistent formation and is recognized in many but not all wells in the Salina basin.
The upper member of the Wyandotte limestone is oolitic in the outcrops. It is also generally oolitic in the subsurface, but is not everywhere recognized in logs. The lower part of the Wyandotte includes the black fissile Quindaro shale member which is recognized in some wells.
The Bonner Springs shale, although much reduced in thickness, is recognized in most of the wells of the Salina basin. The thickness and distribution of the Bonner Springs shale illustrate the effects of the erosion that sometimes occurred between cyclothems. The Kellett cross section (1932) shows that westward from Woodson County the thickness of the Bonner Springs shale increases at the expense of the underlying rocks.
A comparison of the thickness of the formations of the Linn and Zarah subgroups in different areas shows that the total average thickness of formations composed mainly of limestones in the outcrops of east-central Kansas decreases northward toward southeastern Nebraska from 81 feet to 64 feet and the shales that are formations decrease from 190 feet to 71 feet. The total average thickness of the two subgroups in outcrops in east-central Kansas is 275 feet and in the Salina basin only 155 feet. The exact amount of decrease of the thickness of the shale cannot be determined from the sample logs but it is plain that much if not all the decrease to the northwest is due to thinning and wedging out of shale. The sample logs in the Salina basin seem to consist almost entirely of limestone but Schlumberger logs reveal the presence of many shale beds not recognized from the samples. The thickness of the Kansas City group as a whole decreases from an average of 409 feet in eastern Kansas outcrops to 203 feet in southeastern Nebraska.
The sequence of formations of the Lansing group, listed in descending order in Table 10, has been established in outcrops in eastern Kansas. The range and average thickness at outcrops are reported by Moore, Frye, and Jewett (1944, pp. 186-187). Thicknesses in southeastern Nebraska are reported by Condra and Reed (1943, pp. 50-51).
Table 10--Sequence and thickness of the formations of the Lansing group.
|Range of thickness
Southward along the outcrops the Plattsburg limestone thins and disappears near the Oklahoma border bringing the Vilas shale in contact with the Bonner Springs shale, so that in southeastern Kansas near the Oklahoma border almost the entire section from the base of the Stanton to the top of the Drum limestone is shale. The Stanton limestone is more persistent than the Plattsburg and continues southward across Kansas but near the Oklahoma, line it interfingers with shale and becomes difficult to trace (Moore, 1936, fig. 4A, p. 36; Moore, Frye, and Jewett, 1944, p. 186). The Stanton and the Plattsburg extend westward into the Salina basin with unbroken continuity.
The Plattsburg in the outcrops is generally oolitic but is not consistently oolitic in the subsurface of the Salina basin. On the other hand, chert is not conspicuous at the outcrops but is generally present in the Plattsburg in the Salina basin. The black Hickory Creek shale member in the outcrops of the Plattsburg is recognized in some wells in the Salina basin.
The Vilas shale contains sandy beds and some sandstone in outcrops along the Kansas River but westward in the subsurface the Vilas is thin and contains no sand although it is locally silty. Red shale is present in the Vilas in some wells. In the Salina basin, the thickness of the Vilas does not exceed 10 feet. The Vilas shale occurs locally in McPherson County and in structurally subsiding areas in the center of the basin, but it is generally absent or obscure in the subsurface of the Salina basin.
The Stanton limestone in outcrops is a sequence of three limestone alternating with two shale members. Neither chert nor oolites are reported in the outcrops although the lowest limestone member is siliceous. In the subsurface of the Salina basin, however, the Stanton is generally either cherty or oolitic, but neither chert nor oolite is present in all wells. The lower shale member of the Stanton, the black fissile Eudora shale, is a good datum in eastern Kansas both in the outcrops and in the subsurface. In the Salina basin it has been identified in the samples of some wells.
In northeastern and southeastern Kansas the Lansing group is commonly overlain conformably by the Weston shale of the Pedee group, but later erosion, which in many places removed the Weston and the upper members of the Stanton, introduced local irregularities in the thickness of the Stanton. The Weston shale is probably absent in the Salina basin. Irregularities in the thickness of the Stanton, where the Weston shale has been eroded, are probably due mainly to the post-Pedee unconformity. In some places in the Salina basin as in the White Eagle No. 1 Ucker well, sec. 12, T. 17 S., R. 2 E. (well 43, cross section X-X', Pl. 13), a limestone bed younger than the Stanton of near-by areas occurs at the top of the Lansing. Because of topographic relief so general on its upper surface, the top of the Stanton, although easily recognized, is not a dependable datum for close contouring.
As in other groups of the Missourian Series, the Lansing group thins northward from an average of 85 feet in outcrops in eastern Kansas to an average of 53 feet in southeastern Nebraska. Part of the thinning occurs in the Vilas shale and in shale members of the Plattsburg but part of the thinning occurs also in the limestone members of both the Plattsburg and the Stanton. No thinning of the Lansing group as a whole is noted in the Salina basin where the average thickness is about 95 feet.
The formations of the Pedee groud recognized in outcrops in northeastern and southeastern Kansas are listed in descending sequence in Table 11. The range of thickness of the formations in Kansas is reported by Moore, Frye and Jewett (1944). The range of thickness in southeastern Nebraska is reported by Condra and Reed (1943).
Table 11--Sequence and thickness of formations of the Peedee group.
|Range of thickness
in outcrops in
|Range of thickness
The Weston shale, which overlies the Stanton limestone in probable conformity, consists of dark-bluish to bluish-gray shale in contrast to the generally yellowish sandy shale of the overlying unconformable Douglas group. At least 200 feet of Weston shale occurs at outcrops in southeastern Kansas and about 100 feet in northeastern Kansas but in Douglas and Leavenworth counties and elsewhere the Weston shale was eroded during the hiatus between the Missourian and Virgilian Series. The occurrence of the Iatan limestone is even more restricted. It has not been recognized in the subsurface far from its outcrops in northeastern and southeastern Kansas.
The Weston shale is reported in the subsurface of Woodson and Greenwood counties by Kellett (1932). It may be represented in wells 44, 45, and 46 of cross section X-X' (Pl. 13) by the shale below the sandstone of the Douglas group but in any case it thins westward from the outcrops and is probably absent throughout the Salina basin.
During the hiatus between the Missourian and Virgilian Series there was widespread and deep erosion which in many areas exposed the Stanton limestone without, however, cutting very deeply into it. The regional topographic relief of the pre-Virgilian surface between southeastern Kansas where 200 feet of Pedee rocks survived and areas in which the Stanton was exposed was not less than 200 feet.
The Virgilian Series is divided into the following groups, listed in descending sequence: Wabaunsee, Shawnee, and Douglas.
The hiatus that separates the Missourian and Virgilian rocks was accompanied by low regional warping with regional subsidence toward the southeast as indicated by a westward and northward convergence of the interval between the Stanton limestone and the base of the Oread limestone. No perceptible thinning of this interval occurs, however, on the axis of the Nemaha anticline on the line of cross section X-X' of Plate 13.
The formations of the Douglas group, represented in outcrops in eastern Kansas, are listed in descending order in Table 12. The range of thickness in outcrops in eastern Kansas is reported by Moore, Frye, and Jewett (1944); in southeastern Nebraska by Condra and Reed (1943).
Table 12--Sequence and thickness of formations of the Douglas group.
|Range of thickness
in outcrops in
|Range of thickness
The Stranger formation in the outcrops consists of yellowish-gray shale and sandstone with one or two limestone members in the upper part. The thickest areas of the Stranger formation occur in places where the Pedee was deeply eroded or entirely removed. The lower part includes the Tonganoxie sandstone member, which is irregular in distribution and character. The Tonganoxie sandstone is absent in some places and in others has a thickness of as much as 90 feet. The Haskell limestone member in the upper part of the Stranger formation is in places as much as 10 feet thick but it is generally thinner. The Haskell limestone is very persistent, but the interval between this limestone and the base of the Shawnee above is so variable that it seems to have been deposited on an uneven surface. The Haskell limestone, in consequence, is unsuitable for detailed contouring.
Outcrops of the Lawrence shale consist chiefly of blue-gray and yellowish shale with a thin discontinuous limestone member (Amazonia limestone) near the top and the tan-colored Ireland sandstone member of irregular thickness and distribution at its base. An unconformity of considerable erosional relief occurs between the Stranger formation and the Lawrence shale. The thickest deposits of Ireland sandstone lie in deeply eroded areas of the Stranger formation and, in some places, the base of the Ireland lies below the Haskell limestone. A very persistent bed of red shale near the top of the Lawrence shale is widely distributed in outcrops in eastern Kansas and southeastern Nebraska. In the subsurface it extends into western Kansas where it persists after all other parts of the Lawrence shale have wedged out. It seems to be the initial deposit of a cyclothem below the Oread limestone, the first formation of the Shawnee group.
Westward the Douglas group becomes progressively thinner. The Tonganoxie sandstone thins out in the region east of the Nemaha anticline. In the Salina basin the Tonganoxie sandstone is seldom encountered. In McPherson and Marion counties on the southeastern margin of the Salina basin the Ireland sandstone is more than 150 feet thick and makes up the greater part of the Lawrence shale (Kellett, 1932). The Ireland sandstone thins westward and is represented in the Salina basin by lenticular sandstone bodies.
The Douglas group combined with remnants of the Weston shale thins northwestward from 270 feet in sec. 31, T. 20 S., R. 10 E. (well 46, cross section X-X', Pl. 13) to 225 feet in sec. 15, T. 20 S., R. 7 E (well 45) on the crest of the Nemaha anticline. It is 200 feet thick in sec. 23, T. 18 S., R. 5 E. (well 44) and thins gradually northwestward to 45 feet in well 38 at the nortbwestern end of the cross section. The regularity in the westward thinning of the Douglas-Pedee sequence on and across the crest of the Nemaha anticline implies that little or no local movement of the Nemaha anticline took place during Douglas-Pedee time.
The formations of the Shawnee group are listed in Table 13 in descending sequence. The thicknesses of the formations at outcrops in eastern Kansas are reported by Moore, Frye, and Jewett (1944, pp. 177-182). The thicknesses in southeastern Nebraska were reported by Condra and Reed (1943, pp. 46-49).
Table 13--Sequence and thickness of formations of the Shawnee group.
|Range of thickness
in outcrops in
in outcrops in
|Thickness in outcrops
|Calhoun shale||10-60||30||2 1/2|
|Deer Creek limestone||20-80||40||29-32|
The formations referred to as limestones are convenient groupings of limestone beds separated by thin shales without regard to division into cyclothems. The thicknesses of the limestone and shale members of the formations vary considerably but abnormally thin limestones in local areas are generally overlain by thick shales. The thickness of the formations, all of which have been traced in outcrops across the State from Nebraska to Oklahoma, also varies considerably.
Well samples of the limestones present no distinguishing lithologic characteristics. Each limestone of formation rank includes one or more algal members, some of which are oolitic in outcrops, although oolites are uncommon in the subsurface. Also, each limestone of formation rank includes a bed of black shale. Parts of the Oread and Topeka limestones are cherty in the outcrops but all the limestones are cherty at some point in the subsurface. All the limestones include one or several members containing fusulines but the range of the species is not yet well enough kdown to identify specific formations.
All the shale units that are formations include sandstone and sandy shale at the outcrops. In the subsurface, sandstones and sandy shale occur intermittently in the Calhoun, Tecumseh, and Kanwaka shales as far west as T. 1 W. Farther west none of the shale units of formation rank is more than 10 feet thick and in some wells they cannot be recognized in the samples, although thin shale beds are revealed by electric logs. In the absence of recognizable shale units it is dimcult or impossible to differentiate the limestones.
A comparison of the average thicknesses of the formations of limestone and shale of the Shawnee group in outcrops in eastern Kansas and southeastern Nebraska (Table 13) reveals that with two exceptions all the formations thin northward although the limestones thin much less than the shales. The Tecumseh and Calhoun shales are the exceptions to northward thinning. The maximum thickness of both these shales is reported in outcrops in the Kansas River Valley where the Tecumseh is 65 feet thick and the Calhoun is 60 feet thick. The outcrops of both are thinner north and south of this area (Moore, Frye, and Jewett, 1944, pp. 178-179). Probably the thickening of these shales in the same general area is due to more or less local and temporary synclinal warping of the strata prior to the deposition of the shales. The general northward thinning of the Shawnee group as a whole is the result of thinning of the shales of the group and only in minor degree to the thinning of the limestones.
The overall thickness of the Shawnee group in the subsurface also decreases gradually from southeast to northwest. It is 370 feet thick east of the Nemaha anticline in well 46 of cross section X-X' (Pl. 13); 335 feet in well 18; and 200 feet in well 38. No material thinning of the Shawnee occurs on the crest of the Nemaha anticline in well 45, from which it is concluded that this structural feature was quiescent at this locality during Shawnee time.
The formations of the Wabaunsee group, listed in Table 14 in descending sequence, have been differentiated in the outcrops in eastern Kansas and southeastern Nebraska. The thicknesses in Kansas are reported by Moore, Frye, and Jewett (1944, pp. 172-176) and those in southeastern Nebraska by Condra and Reed (1943, pp. 41-46).
Table 14--Sequence and thickness of formations of the Wabaunsee group.
|Range of thickness
in outcrops in
in outcrops in
|Range of thickness
|Pony Creek shale||5-20||14||5|
|French Creek shale||30||30||8|
|Jim Creek limestone||1/4-2||1||1|
|Langdon shale||5-50||30||not reported
|Maple Hill limestone||1-5||3|
|Soldier Creek shale||12-18||15||12-14|
|Silver Lake shale||25||25||10-12|
|Happy Hollow limestone||1-8||4||6-8|
|White Cloud shale||30-80||50||80|
The Wabaunsee group comprises a sequence of alternating limestones and shales. Most of the limestones are relatively thin but nearly all extend in outcrops from southeastern Nebraska to Oklahoma. On the outcrop, the Howard limestone in places is 30 feet thick, the Wakarusa reaches 18 feet, the Reading 15 feet, and the Dover 20 feet. In most places, however, these limestones are less than 10 feet thick. Few of the other limestones exceed 5 feet in thickness and in many places do not exceed 2 or 3 feet in thickness.
The total average thickness of all the limestones of the Wabaunsee group, in the outcrops in Kansas, including the shale members of formations comprised mainly of limestones, is only 104 feet or about 20 percent of the average total thickness of the group. In outcrops, the shale units of formation rank include, without exception, sandy shales and many include beds of sandstone. Streaks of coal, some of which are thick enough to have been mined near the outcrop, occur in nearly all the shales. The cuttings of coal beds, because they float away, are seldom recognized in washed samples. Thin discontinuous limestones are not uncommon in the shales of formation rank, and in some wells, thin limestones that probably appear as unnamed calcareous marine shale in outcrops toward the source of clastic sediments are noted. On the other hand, some limestones reported in drillers logs are probably indurated shales. Some of the widely distributed limestones are only occasionally recognized and reported in logs because they are thin and argillaceous. As a result there is considerable confusion and uncertainty in the identification of individual formations in the logs of many wells that penetrate the Wabaunsee group.
The Howard limestone is generally recognized in logs as a prominent limestone about 50 feet above the top of the Topeka limestone. In the subsurface, the Happy Hollow limestone is generally noted but the Rulo limestone seems to be lenticular and erratic in distribution. The coal or black shale that occurs between the Happy Hollow and Rulo limestones in outcrops has been noted in the subsurface in some wells. In some areas in the subsurface a streak of red shale occurs between them and is useful in local correlations.
The Burlingame limestone seems to be missing in many wells in the Salina basin. The Wakarusa, Reading, and Elmont limestones, in areas where the intervening shales become thin, draw closer together and in some logs are recorded as a single limestone. A red shale between the Reading and the Wakarusa is helpful in some areas in identifying these limestones.
The Tarkio limestone is characterized by an abundance of exceptionally large fusulines. The Maple Hill limestone is thin and doubtfully present in the Salina basin. The Dover limestone, on the other hand, is persistent and well developed in the Salina basin. Westward in the subsurface the interval between the Dover and the Tarkio becomes markedly thinner.
The formations of the Wabaunsee group that lie above the Dover limestone were in many places eroded during the hiatus between the deposition of Pennsylvanian and Permian rocks. Most of the formations designated as limestones above the Dover in the outcrops are thin or are in reality sequences of thin limestones separated by shale members. Inasmuch as they display no marked lithologic peculiarities, they are doubtfully identified in the subsurface.
The thickness of the Wabaunsee group ranges from 420 feet to 210 feet. Much of the variation in thickness is due to the unconformity at its top, into which erosion cut channels as much as 120 feet deep in some places. Harned and Chelikowsky (1945) report the relief of the pre-Permian surface to be 250 feet in Pottawatomie County, Kansas, where Permian beds, lying on an irregular surface, rest on Pennsylvanian beds as much as 150 feet below the Dover limestone. In well 46 of cross section X-X' (Pl. 13) east of the Nemaha anticline, the thickness of the Wabaunsee below the Brownville limestone is 390 feet. In well 45, the same interval measures 380 feet. It is concluded, therefore, that little or no movement of the Nemaha anticline occurred at the location of this well during Wabaunsee time. In well 44 where some Pennsylvanian beds above the Brownville were preserved from erosion, the thickness of the Wabaunsee is 420 feet, but in well 42 where erosion cut below the Tarkio the thickness is only 210 feet.
The amount of northeastward convergence across the Salina basin during Wabaunsee time is difficult to determine because of the erosion of the upper part of the Wabaunsee, but there is definite convergence of the limestones in this direction. The average thickness of the Wabaunsee group from the Brownville limestone to the Topeka limestone at outcrops in eastern Kansas is 514 feet. A composite section of the same sequence, 390 feet thick, was measured in southeastern Nebraska by Condra and Reed (1943). Measurements of the Wabaunsee from the base of the Brownville to the top of the Topeka in the eastern part of the Salina basin average about 385 feet. The pattern of relative subsidence toward the southeast therefore continued through Wabaunsee time.
Kansas Geological Survey, Geology
Placed on web Dec. 28, 2007; originally published Nov. 1948.
Comments to email@example.com
The URL for this page is http://www.kgs.ku.edu/Publications/Bulletins/74/03_strat3.html