By M. N. Bramlette
The correlation presented in Plate VI is not so definite as could be desired, since cuttings from only widely separated wells were available for microscopic examination, and even the wells for which logs could be obtained in much of the area between Russell County and the eastern part of the state, where the various formations are more clearly identified, are too far apart to permit precise correlations. Correlation of the beds from Russell County northeastward to Osborn and Lincoln counties and thence southeastward to Ellsworth County is less definite than along the rest of the line, but the northerly wells were included because of the drilling activity in Lincoln County. The correctness of the correlation in the region to the north is checked by the evidence derived from the correlation of the beds between Russell County and Ellsworth County. The basis for some of the correlation lines that seem unjustified by the driller's logs will be found in the descriptions of the well cuttings. The several stratigraphic units discriminated are described below.
The attempt to make correlations from logs of wells, especially wells that are far apart, may lead to minor errors or even to complete misinterpretation. For areas where logs are numerous such misinterpretation may be avoided by tracing as far as possible thin individual beds that should be nearly equivalent stratigraphically; thicker beds or series of dominantly calcareous, arenaceous or argillaceous rock may be transgressing, and unless that fact is discovered serious errors may be made that can be corrected only by studies of collections of fossils. The surest way to avoid error in stratigraphic correlation is to preserve for examination numerous fossiliferous well cuttings, the supreme value of which should constantly be impressed upon the oil operator.
The first unit discriminated includes the formations above the Dakota sandstone. of the Russell County region. Individual formations cannot be separated and correlated from the drillers' logs, and are generally classed as brown, blue or grey shale, and an occasional thin bed of other lithologic type.
The Dakota sandstone is logged as a heterogeneous series of brown sands, blue shales, red rock and gray shales, the individual beds of which cannot be correlated definitely, though the uppermost red beds, in the upper part of the formation, seem to mark a fairly constant key horizon for correlation in the region near the original producing well of Russell County. The top of the Dakota sandstone is not easily recognized in the drillers' logs, and the line marking it in the cross section is based on information obtained in the field. Cuttings from this formation show that the sand is highly variable and poorly sorted, some of it very well rounded, some angular, at some places with an admixture of argillaceous material, at others with glauconite, and commonly with much pyrite. Some of the sand beds are water-bearing. The lower part of this series possibly belongs to the Comanche (Lower Cretaceous), but the Upper and Lower Cretaceous rocks are similar lithologically and cannot be separated with confidence in well records.
The top of the Permian "Red Beds," or Cimarron group, is a rather distinct horizon in Russell County, and though these beds cannot be subdivided into the units recognized at the outcrop in the southern part of the state, they include units that are of value for local correlation. One unit that is of especial value is the 50-foot bed of anhydrite that occurs about 330 feet below the top of the red series in the western part of Russell County. This bed, which is found throughout Russell County and in parts of adjoining counties, affords a valuable check on subsurface structure in the region. It is logged by the drillers as lime. Another bed, measuring something less than 50 feet, occurs in this series a little more than 100 feet below the base of the 50-foot bed of anhydrite. This is logged as brown or gray or blue shale by the drillers, and an examination of a few of the cuttings shows that it probably consists of anhydrite or gypsum and gray shale. The "Red Beds" generally consist of a red siltstone and some red, fine sandstones and red shales, with interbedded green-gray rock of the same lithologic character as the associated red rock. Finely granular gypsum occurs at irregular intervals through the "Red Beds." The Cimarron is more than 600 feet thick in western Russell County, but it becomes thinner eastward and northward and disappears altogether in McPherson County. The well-log cross section suggests that some of the beds in the thick series of gray shales above the salt in McPherson County may be gray equivalents of the red Cimarron.
Below the red strata there is about 100 feet of material, usually logged as blue shale, consisting of gray shale and anhydrite and probably belonging to the Wellington formation. This overlies the salt beds of the lower part of the Wellington formation. The bed of rock salt included in the Wellington is variable in thickness, ranging from less than 200 feet to more than 300 feet in Russell County and adj acent regions, but thinning toward the east, in McPherson County, and disappearing in eastern McPherson County and at the western edge of Harvey county. The salt is usually recognized by the drillers, but its exact upper and lower limits are often doubtful. In places it seems to be a bed of almost pure salt; at others it includes interbedded gray and red shale and anhydrite.
Below the rock salt lie about 400 feet of alternating gray shale, gray anhydrite, impure dolomite and red beds, without limestone and with only a few fossils in its lower part. This series might well be classed as a part. of the Wellington, though in the area to the east the base of the salt is considered the base of the Wellington. Whether these beds represent a formation that has no stratigraphic equivalent in the area to the east, or whether they are a much thicker development of the gypsiferous Pearl shale member of the Marion formation, or the nonmarine equivalents of some of the fossiliferous marine upper Permian in the region of its outcrop, has not been determined. The cross section suggests the relation last mentioned, and indicates that these anhydrite, shale and dolomite beds may be equivalents of the Marion formation and part of the Chase formation of the region to the east. The beds of anhydrite and dolomite are logged by the driller as limestones. In a few of the wells, such as the Denmark well in Lincoln County (sec. 9, T. 11 S., R. 8 W.), some thin fossiliferous limestones are interbedded with the lower part of this series, and some anhydrite occurs below. the first very fossiliferous cherty limestone of the underlying unit, showing that there was an alternation of conditions in some regions.
The first distinctly fossiliferous marine limestone occurs at a depth of 1,915 feet in the original producing well in Russell County, the Valerius Oil and Gas Company's C. C. Oswald No. 1. The upper part of this limestone, containing crinoids, ostracods, bryozoa, a small foraminifer, and other fossils, is somewhat cherty, and at a depth of 1,950-1,970 feet the limestone is more cherty. This unit cannot be exactly correlated with the outcropping marine Permian until more cuttings from intermediate wells have been examined, but a similar cherty, fossiliferous limestone containing an unusually large number of bryozoa occurs at apparently the same horizon in the Denmark well (sec. 9, T. 11 S., R. 8 W.), Lincoln County; in the Sheridan well (sec. 21, T. 15 S., R. 6 W.), Ellsworth County; in the Allison well (sec. 28, T. 19 S., R. 3 W.), McPherson County; and at a depth of about 260 feet in the Batt well (sec. 9, T. 19 S., R. 4 E.), Marion County. This horizon in the Batt well is apparently that of the Wreford, according to correlations made by the Kansas Geological Survey in Marion County. This cherty, very fossiliferous unit of the western region may possibly be correlated with beds that lie at a higher horizon farther east, such as the Fort Riley limestone or the Florence flint; but its relation to adjacent beds, its lithologic character, and its fossils--though all the species of Bryozoa are not identical--make its correlation with the Wreford of Marion County seem the most probable.
Below unit 6 in the original producing well there are about 400 feet of shales, limestones and red beds, and below these lie 450 feet of blue shale and thin layers of limestone and sand. Individual beds in this thick series cannot be certainly correlated with units recognized farther east, but the entire series would seem to be equivalent to formations extending downward from the Council Grove (Permian) through the Wabaunsee and part of the Shawnee to the Topeka limestone. Individual red beds of this series correlate well through Ellsworth, Saline and McPherson counties and check the general correlation shown on the cross section. In Marion and McPherson counties the lower part of this series, including the Scranton and Severy shale members of the Shawnee formation, is distinctly arenaceous.
Below unit 7, at a depth of 2,753 feet in the original producing well, the Valerius Oil and Gas Company's C. C. Oswald No. 1, begins a series of limestones and thinner beds of shale and sand that extend downward for 284 feet to the bottom of the well. These limestones are light gray to yellow brown, fossiliferous (many Fusulina), somewhat cherty, and at certain horizons oolitic, notably at a depth of 3,010-3,014 feet. The whole group seem to correlate with the Shawnee from the top of the Topeka limestone and the Douglas to the base of the Oread limestone. The cuttings from the oil-producing rocks are limestone and a little dark gray shale and chert, but no sand, and would seem to correlate with the Oread limestone of eastern Kansas.
In wells drilled below this limestone series in Ellsworth County and to the east there is an aggregate of beds of shale, sandstone and limestone 200 or 300 feet thick, which is classed as Douglas below the Oread, including the thick Lawrence shale, and there is a very considerable amount of sand in the upper part of this series corresponding to the sandy facies of the Lawrence shale at many of its outcrops. These sands are at many places water-bearing. Some beds of red shale occur in this series in Ellsworth, Saline and Russell counties, but they do not seem to persist at any definite horizon.
Beneath this clastic series for about 300 feet the strata, which consist largely of limestone, but include a few thin beds of shale and sand, seem to correlate with the thick Lansing and Kansas City calcareous formations of eastern Kansas. OOlitic limestone is common and is often logged by drillers as sand, as is some of the cherty limestone in these formations. Fusulina is seldom found in this series, and is usually represented by a small species, such as is found in this part of the Pennsylvanian section in eastern Kansas.
The series of shales, sandstones, red shales and thin limestones under the limestones of the Lansing and Kansas City formations may be correlated with the Marmaton and Cherokee formations. The red shales usually encountered in the lowest part of this group are much thicker than any encountered in eastern Kansas.
Below the Cherokee shale at many places lies a bed of cherty limestone that is considered of Mississippian age. It is generally water-bearing and in a few wells it gives showings of oil. Beneath this bed lies a series of beds of limestone, shale, dolomite and sand, the lower part of which is undoubtedly Ordovician. In the Urschell No.4 well, in T. 21 S., R. 5 E., Marion County, the formation immediately under the Cherokee shale is a cherty dolomite and is probably Ordovician, indicating that the Mississippian has been eroded from this region, though the typical chert is found in the Batt well, in T. 19 S., R. 4 E. Well cuttings from these pre-Pennsylvanian rocks have been very commonly preserved, especially in eastern Kansas, and a stratigraphic study based on these cuttings may yield some very definite results.
After this correlation was completed, some paleontologic work was done on the faunas obtained from the cuttings. In general this work corroborated the conclusions reached by the lithologic and well-log correlation, but it developed one important difference. A very fossiliferous sample taken from a depth of 3,500 feet in the Sheridan well, in sec. 21, T. 15 S., R. 6 W., Ellsworth County, proved to be of Pennsylvanian age. If this sample is representative of the formation at 3,500 feet, it disproves the conclusion as to age arrived at in the correlation, and the very cherty horizon classed as Mississippian chert in this region would be of Pennsylvanian age. As this particular sample is very different both in lithology and in its abundant fossils from the samples above and below, and as such a horizon has not been found in this part of the section elsewhere, it seems possible that it may be a caved sample and so of no significance. All other evidence seems to favor the Mississippian age of this cherty horizon, and the writer believes that the sample is not representative. However, its value must remain an open question until more paleontologic evidence from the chert zone or from the underlying shales is obtained. Since this is an important question, any such evidence, if found, should be made known.
Some samples received from the M. M. Valerius Oil and Gas Company's Phillips well, sec. 3, T. 13 S., R. 13 W., Russell County, after the completion of this study, show that there is a series of limestones and some shales, with Fusulina, down to a depth of 3,135 feet that is certainly of Pennsylvanian age, and the limestone from 3,000 feet to about 3,150 feet are tentatively considered to be representative of the dominantly calcareous Lansing and Kansas City formations of eastern Kansas. A fossiliferous horizon at 3,160 feet was examined by P. V. Roundy, of the United States Geological Survey, and found to contain Glyptopleura sp., Bairdia sp., Fusulinella sp., Cytherella sp., Endothyra? sp., Meekospira? sp., and Natacopsis (immature) sp. He considers this fauna of early Pennsylvanian age. In this well the Pennsylvanian rocks below the main producing horizon of Russell County are thus about 200 feet thick. This is much less than the thickness of the equivalent beds in eastern Kansas which contain more coarse clastic material. No cherty horizon like that classed as Mississippian in the region to the east is present here.
The shales, red rock and thin limestones between 3,200 feet and 3,300 feet may be basal Pennsylvanian, Mississippian or Ordovician, as samples were not available for examination. Red rock of Ordovician age occurs at 3,400 feet in this well, and there is red rock in the basal Pennsylvanian east of Russell County. The red rock between 3,220 feet and 3,285 feet may represent residual or weathered material formed between Ordovician and Pennsylvanian times.
Fossils definitely of Ordovician age have been found in this well at a depth of 3,335 feet. A few samples were examined from depths of 3,465 feet to 3,554 feet that were a brown crystalline, cherty, sandy dolomite identical lithologically with the material classed as Ordovician dolomite in the region to the east.
Kansas Geological Survey, Geology
Placed on web March 17, 2014; originally published 1925.
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