Rocks of Osage Age
Rocks of Osage age extend from the Appalachian Mountains to the Rockies. They are widely distributed in the Mississippi valley, both at and below the surface. They probably extended at one time across the region of the Ozark Mountains (Bridge, 1917, p. 558). West of Mississippi river, the Osage consists almost entirely of cherty limestones and dolomitic limestones, though some of the limestones included in it are free from chert or contain chert in very minor amounts. The name Osage was first applied to rocks in southeastern Iowa, where it consists only of Burlington and Keokuk limestones, together about 150 feet thick. The term was later expanded to include beds of Fern Glen age and some geologists include in it the Warsaw limestone, which is above the Keokuk limestone. The Osage rocks become thicker in the Joplin area, where, exclusive of the Warsaw limestone, they have a thickness of 285 feet, as shown in the preceding summary of formations in the Ballard Mine well, Cherokee county, Kansas, near the Mississippian outcrops. The cuttings of this well were analyzed by the insoluble-residue method by Mary Hundhauson in the laboratory of the Missouri Geological Survey.
|Summary of Formations from Residue Analyses of Cuttings from the Ballard Mine Well of St. Louis Smelting and Refining Company, Cherokee County, Kansas, sec. 10, T. 35 S., R. 24 E.||Thickness,
|Rocks of Chester age (20')|
|Rocks of Meramec age (90')|
|Rocks of Osage age (285')|
|Burlington and Keokuk limestones, undivided||130||300|
|Grand Falls chert of Missouri Geological Survey||45||345|
|Reeds Spring limestone of Fern Glen age (includes St. Joe limestone)||110||455|
Underground in Kansas, the Osage has a variable thickness, owing to overlap at the base and to unconformities at the top.
The Osage strata are composed almost entirely of limestone, cherty limestone, and cherty dolomitic limestone. Some geologists regard the Warsaw limestone as Osage in age and others regard it as Meramec in age. The rocks of Osage age, as defined in this report, include the greater part of the Boone formation of Missouri, Arkansas, and Oklahoma reports, but the Warsaw limestone, which is a part of the Boone formation, is excluded from the Osage on account of a pronounced disconformity at the base of the Warsaw, which will be discussed later. The lower formations of the Osage in southwestern Missouri consist of the St. Joe limestone and the overlying Reeds Spring limestone, which were correlated by Moore (1933, pp. 203-204) with the Fern Glen limestone of southeastern Missouri, The upper formations are the Burlington and Keokuk limestones.
St. Joe Limestone
The St. Joe is the lowest formation regarded a- of Osage age. It was first described by T. C. Hopkins (1893, pp. 253-349) in northern Arkansas where it is regarded as a member of the Boone formation. It is present in southwestern Missouri and is a partial equivalent of the Fern Glen limestone of southeastern Missouri, which it resembles lithologically. In the outcrops of Arkansas and Missouri, it has a thickness of 10 to 40 feet. In the outcrops it is a semigranular, crinoidal limestone, which in some places includes interstratified beds of greenish and reddish limy shale and pink and reddish limestone of no great thickness. It is generally noncherty though some outcrops show a little chert. In southwest Missouri and adjoining states this limestone is overlain by the cherty limestone and dolomite of the Reeds Spring. Laudon (1939, pp. 325-327) has described the St. Joe limestone in outcrops in Oklahoma where two phases of the formation are pointed out. One consists of thin-bedded gray to bluish-gray slabby limestone beds that are not markedly fossiliferous. The other consists of bioherms of exceptionally crinoidal limestone interbedded with greenish-gray and red very fossiliferous marls. These bioherms are reported to be a few feet to 2 miles long and as much as 80 feet thick. Laudon noted the presence of bioherms in correlatives of the St. Joe from Kentucky to New Mexico where they have a thickness exceeding 400 feet in one place.
Area of deposition in Kansas
The St. Joe limestone was deposited in southern Kansas along the Oklahoma border as far west as Barber county. In Clark county (Watchorn No. 2 Morrison well, sec. 20, T. 32 S., R. 21 W., well No. 7a, cross section F-F', pl. 7) it overlapped upon a surface underlain by pre-Chattanooga rock:" and seems not to have been deposited much farther west in Kansas. On the Missouri border it has not been identified north of Cherokee county. Toward the north it overlapped upon the very flat postKinderhook surface. As shown in plate 8 it has not been observed north of central Greenwood county east of the Nemaha ridge. It extends into northern Sedgwick county west of the Nemaha ridge.
Subsurface character in Kansas
The limestone correlated with the St. Joe in the subsurface of Kansas has the same stratigraphic relations and lithologic character as at the surface outcrops. It is for the most part semigranular in texture and is composed of crystalline fragments imbedded in a firm limestone matrix. In some places. and especially near the base, the limestone is partly fine-textured and does not contain the crystalline fragments that are probably composed chiefly of broken fossils. Where the formation is thick the upper part is more or less crinoidal. The formation is distinguished in the cuttings by the small amount or complete absence of chert in contrast to the usually very cherty overlying rocks of the Reeds Spring or rocks of late Fern Glen age. Much of the chert in the insoluble residues seems to have been abraded from the higher rocks during drilling operations. Neither glauconite nor oolitic limestone was observed in any of the St. Joe samples from Kansas wells, although both are reported in some outcrops in northeastern Oklahoma.
Shale of the St. Joe formation
East of Cowley county the St. Joe formation is only 5 to 20 feet thick, although somewhat thicker sections occur locally. West and north of Cowley county where the St. Joe borders the central Kansas uplift, the formation thickens greatly and the lower part includes considerable dark greenish argillaceous shale. The upper part of the formation is not very shaly, although a few flakes of shale appear in some of the cuttings. Some of the limestone is semiopaque and greenish and the residues in most places show paper-thin flakes of greenish or gray shale.
No red shale or red limestone, such as distinguishes the St. Joe in Missouri and Arkansas, was noted in the cuttings of wells east of Cowley county, except in one well in Montgomery county (Lynn No. 1 well, sec. 10, T. 33 S., R. 17 E.) where some pink limestone was present 20 feet above the base of the formation, which in this well is thicker than usual for the area. In many wells in Cowley and Sedgwick counties considerable red shale and pink and reddish limestone are interstratified with crinoidal limestone. These red rocks occur in a zone 30 to 50 feet thick that lies above the lower shaly part of the section. In some wells, the red shale is 5 feet or more thick, but in most wells it seems to be present as partings between limestone beds, some of which are faintly colored by ferruginous impurities. The red shales are lenticular and in some places seem to grade laterally into green shales. The reddish limestones are erratic in distribution and have a greater vertical range than the red shale.
The wells in which red rocks were found in the St. Joe are indicated on the map (pl. 8). Red rocks seem not to be present in all wells in the localized area of occurrence. The absence of red shale in the samples may be due in part to excessive washing of the cuttings, but is probably due mainly to the erratic distribution of the ferruginous material. The red shales are probably somewhat more widely distributed, however, than is indicated on the map,
The grayish-green and dark-green shale near the base of the formation is much more widely distributed than the red shale. It is a common constituent of the St. Joe from Cowley county westward to Barber county. The shale is argillaceous and is unlike the shale of the Northview, which is predominantly silty over wide areas. In parts of Barber county (Sinclair-Prairie No. 1 Gentry well, sec. 1, T. 33 S., R. 15 W., and Skelly No. 1 Temple well, sec. 13, T. 34 S., R. 15 W.) the calcareous green shale member, which is not a sharply defined unit, is 50 feet thick and occurs 40 to 60 feet above the base of the formation. As shown in cores of the Sinclair Prairie-Gentry well the shale contains thin sheets and streaks or crinoidal limestone. The underlying limestone, which includes some shale, contains semi translucent chert, which, although scarce, is more abundant than in the St. Joe farther east. In Cowley and adjoining counties the prominent shale member near the base is only 10 to 20 feet thick and occurs 10 to 35 feet above the base of the formation.
Limestone of the St. Joe formation
In some localities, limestones that have the lithologic characteristics of the St. Joe attain considerable thickness, especially in a belt extending along the southern margins of Sedgwick and Butler counties. In south-central Sedgwick county (Alco Royalty et al. No. 1 Schulte well, NE SE NW sec. 18, T. 28 S., R. 1 W.), a total thickness of 210 feet of noncherty limestone rests on Chattanooga shale. The lower 45 feet consists of dark limy shales and fine-textured limestone typical of the lower St. Joe in the area, but the upper 160 feet is an unbroken sequence of noncherty crinoidal gray and greenish-gray limestone. Pink limestone and some greenish shaly dolomite occur in some of the samples from this interval. One mile to the south in the nearest well (Murphy and Western Kansas No. 1 Thone well, SW NW sec. 19, T. 28 S., R. 1 W.) from which samples are available, limestone of Fern Glen age with typical chert is present from 75 to 120 feet above the Chattanooga. The overlying rocks consist of chert characteristic of the Burlington and Keokuk limestones, but inasmuch as they contain no limestone and show considerable weathering they are not in place.
In southeastern Sedgwick county (Shell and Tatlock No. 1 Gouldner well, sec. 6, T. 29 S., R. 2 E.) an uninterrupted section of noncherty limestone, 278 feet thick, overlies the Chattanooga. At the base is 66 feet of fine-textured limestone and limy dark-green shale overlain by 50 feet of red and gray shale and fine-textured limestone. No chert occurs in this part of the section nor in the overlying 162 feet of gray crinoidal limestone. The nearest well in which adequate samples are available is 6 miles to the north. In this well (T. C. Johnson No. 1 Janssen well, sec. 11, T. 28 S., R. 2 E.) a similar but sparsely cherty limestone section was drilled. The basal shaly section is present to 44 feet above the Chattanooga. Pink limestone was noted to 98 feet above the Chattanooga. Granular gray limestone with some semitranslucent bluish chert typical of the upper Fern Glen is present to 153 feet above the Chattanooga. The remainder of the Osage section, 75 feet thick, extending to 233 feet above the Chattanooga, is chiefly crinoidal limestone, but the insoluble residues contain small amounts of opaque white chert and drusy quartz characteristic of the Burlington.
Another area of similar variations occurs in T. 28 S., Rs. 6 and 7 E. In Sheldon and Wixon No. 1 Houston well (SE NW sec. 15, T. 28 S., R. 7 E.), gray crinoidal noncherty limestone, broken only by slight variations in texture, extends to 252 feet above the Chattanooga. The lower shaly member of the St. Joe is 47 feet thick. No division of the rest of the limestone can be made from the samples. The lower part to 100 feet above the Chattanooga, however, yielded microscopic crusts of mammillary chalcedony of probable Fern Glen age. The remaining 175 feet of the noncherty limestone to 252 feet above the Chattanooga is characterized by insoluble residues consisting chiefly of drusy quartz, and probably represents both Burlington and Keokuk. A well (National Refining Co. 4 Sutter well, NE SE NW sec. 1, T. 28 S., R. 6 E.), 4 miles distant, contains enough chert to distinguish the formation without the aid of insoluble residues, although the residues also were examined. The St. Joe and the equivalent of the upper part of the Fern Glen extend to 105 feet above the Chattanooga; the remainder of the Osage section, 55 feet thick, is cherty limestone and dolomite of undivided Burlington and Keokuk age.
In view of the propensity of the St. Joe limestone and its correlatives to develop bioherms over a very broad region, as pointed out by Laudon (1939) and as most of the thick masses of crinoidal limestone correspond to the descriptions of the bioherm phase of the St. Joe, it seems possible that these abnormally thick bodies of noncherty limestone are bioherms. Whatever the cause, there was a striking absence of chert in certain areas in limestones deposited during a period that included Fern Glen and at least a part of Burlington time.
The St. Joe limestone averages about 15 feet in thickness in southeastern Kansas, but it is no more than 5 feet thick in some areas. In Montgomery county its thickness is irregular, but locally reaches 45 feet.
In Cowley county the cuttings, including the red shales, show thicknesses as great as 65 feet and in Sedgwick county thicknesses of 80 to 90 feet. In Barber county the thickness including the shale is at least 120 feet (McPherson No. 1 Rule well, sec. 10, T. 33 S., R. 13 W.). Rocks that are lithologically similar to the St. Joe but are probably in part correlatives of the upper part of the Fern Glen and the BUrlington, as already noted, reach a thickness of 278 feet in Sedgwick county.
The approximate northern limit of the St. Joe limestone is shown in plate 8. The southern limit is irregular on account of the unconformity below the Cowley to be discussed later, whereby in local areas the St. Joe as well as the overlying younger Osage rocks are absent. Evidence of slight, early movement along the trend of the Nemaha ridge fold in pre-Chouteau time was noted. The distribution of the St. Joe, as shown in plate 8, suggests that slight movements along the trend of the Nemaha ridge were revived prior to the deposition of the St. Joe and were responsible for the bifurcation of the St. Joe basin. The wells showing red and green shale in the St. Joe are located in the reentrant between the Nemaha ridge and the central Kansas uplift, suggesting that the near-by unsubmerged areas were a factor in localizing these deposits. The green shale continues westward in increasing amount around the southern side of the central Kansas uplift. In Harvey county and adjoining areas in southeastern McPherson county rocks of late Fern Glen age are underlain by brown limestone, which is in part slightly silty and argillaceous. In some localities these brown limestones are dolomitic or are underlain by a thin bed of dolomite. These dark and brown slightly earthy limestones have been included in the St. Joe. They probably represent a phase of the St. Joe deposited at the head of the reentrant west of the Nemaha ridge fold. No green or red shales, however, are present in these deposits.
In the area south of the central Kansas uplift on the northern margin of the Dodge City basin in Barber county much red and dark shale and red crinoidal limestones are interstratified with cherty limestones. The nearness of the shore line to the rising central Kansas uplift seems to have caused irregular deposition in this area and the introduction of much shale and silt throughout Osage time. In consequence, the lithologic criteria for distinguishing the St. Joe, the rocks of late Fern Glen age, and the Burlington in this area are inadequate to distinguish these units with confidence.
The absence of Chouteau and of rocks of possible younger Kinderhook age in much of the area of the St. Joe limestone in Kansas indicates its unconformable relation to the Chattanooga shale. It is similarly unconformable upon the Northview and in one well in Wilson county (Union Gas Company No. 5 Mary Watts well, sec. 34, T. 28 S., R. 17 E.) it rests unconformably upon 5 feet of gray sucrose dolomite above the Northview, which, the writer believes, represents an outlier of the Sedalia. The relation of the St. Joe limestone to the overlying Reeds Spring or to equivalent rocks representing the upper part of the Fern Glen is more obscure because the presence or absence of chert does not provide a very sharp or dependable boundary. Bioherms also, if present, tend to make an irregular contact. The St. Joe limestone is everywhere overlain by rocks of later Fern Glen age of which the Reeds Spring of the outcrops in southwestern Missouri seems to be a local variant. As no local variations in the thickness of the St. Joe abrupt enough to offset the indefiniteness of its contact with the overlying rocks have been noted, there seems to be no reason to conclude that the St. Joe is not conformable below rocks of late Fern Glen age.
Reeds Spring Limestone
Surface character and distribution
In the outcrops of southwestern Missouri and northeastern Oklahoma the St. Joe limestone is overlain by the Reeds Spring limestone, first described by Moore (1928, p. 169) as a member of the Boone formation. Cline (1934, p. 1143) describes the Reeds Spring as consisting of "thin alternating, regularly bedded, fine-grained, dense, and sparsely fossiliferous limestone and dark, blue-gray, or black chert." The proportion of limestone and dolomite, the color and amount of chert, and the distribution of the chert in the limestone vary greatly in different localities. Moore reports a maximum thickness on the outcrops of 225 feet near Wentworth in Newton county in southwestern Missouri and an average of 150 feet for the Joplin district. In northeastern Oklahoma, Laudon (1939, p. 328) reports its thickness as 186 feet on Grand river in northern Delaware county. Moore (1933, p. 203) correlated the Reeds Spring and the St. Joe limestones with the Fern Glen formation of southeastern Missouri, which consists largely of greenish-gray or blue-gray semigranular crinoidal limestone with reddish limestone and red and green shale beds. The upper part is similar lithologically to the dense cherty limestones of the Reeds Spring of southwestern Missouri.
Subsurface character in Kansas
There are no outcrops of the Reeds Spring in Kansas. In Cherokee county, Kansas, the well cuttings from the Reeds Spring resemble the exposures in adjacent parts of Missouri and Oklahoma. The limestone is gray or buff and mostly dolomitic and finely sucrose in texture. Some semigranular and fine-textured and slightly dolomitic, grainy limestone is, however, present. In Cherokee county the chert is predominantly bright, translucent and semitranslucent, although some semiopaque chert and opaque chert are also present. The semitranslucent chert breaks with a smooth conchoidal fracture, and is mostly dark gray, dark blue. or bluish, although some is gray and some dark brown. The black chert of the outcrop shows in the thin fragments of the well cuttings as brown chert. In most samples, the chert is of two or more shades, which some of the larger fragments show to be due to banding or mottling. Most of the chert is smooth and eventextured, but cross sections of spicules and spines occur on the surface of some fragments. The semiopaque and opaque chert breaks in blocky chips and is mostly dull, dark gray or buff gray. Like the more flaky semitranslucent chert, the semiopaque chert is particolored. In some zones where the limestone is grainy with minute dolomite crystals, the chert also shows a grainy texture with dark-gray or buff semitranslucent stippling. In some beds the dots are blurred and cloudy and run together. The insoluble residues of the lower part of the formation show bands and patches of fossiliferous spongy silica in the dense chert.
The Grand Falls chert of the Joplin district was recognized in the subsurface in Cherokee county (see p. 46) by Miss Hundhausen of the Missouri Geological Survey. It contains no limestone and consists of lighter-colored, slightly yellowish and gray semiopaque. even-textured chert and some similar gray opaque chert. It is not mottled or banded and is more even in texture and color than the underlying chert. Moore, Laudon, and Cline are reported by Cline (1934, p. 1142) to be in agreement that the Grand Falls chert is a local variant of the Reeds Spring, but Moore in 1928 and at present (Moore, Fowler, and Lyden, 1939, p. 7) regards it as Keokuk in age. Somewhat similar chert, associated with dolomite and limestone. was noted in the upper part of the Reeds Spring in parts of Butler, Chase, and Lyons counties, but definite correlation with the Grand Falls chert does not seem to be warranted. Typical Grand Falls chert has not been recognized with confidence outside the lead and zinc areas and its development may be due in part to the mineralization of that area. It is shown in this area on the cross sections as indeterminate between the Reeds Spring and the Keokuk.
Toward the west there is a lithologic change in the character of the Reeds Spring. The cuttings become less cherty and less dolomitic, and though slightly sucrose and dolomitic in places, consist increasingly of semi granular and fine-textured limestone. In Labette county there is a considerable increase in the amount of dull blocky particolored dark-gray chert and there is an increase of chert with grainy texture. The semitranslucent flaky chert, which is paler blue and more closely resembles chalcedony, is less abundant in most zones but continues prominent in the lower part. The spongy silica in the insoluble residues of the lower part of the formation persists. Farther west and northwest there is a progressive increase in the amount of granular gray limestone and a decrease in the amount of chert. In many areas as far west as Sedgwick county and as far north as Chase county the dark bluish and brownish or buff semitranslucent chert occurs only in certain zones in the Reeds Spring. The greater part of the chert is pale bluish or gray and semitranslucent or translucent; and much of it resembles chalcedony. In the insoluble residues microscopic crusts of chalcedony seemingly representing the lining of minute pockets occur. In this respect the residues contrast with those of the overlying Burlington limestone in which drusy quartz crusts are commonly present.
The presence of areas of noncherty crinoidal limestones at the horizon of rocks of late Fern Glen age in Sedgwick and Butler counties has already been discussed. If these rocks represent bioherms they seem to have continued their growth during the later part of Fern Glen time, for the insoluble residues show the microscopic mammillary crusts of gray chalcedony characteristic of this part of the Fern Glen. In areas where the St. Joe is thick and shaly the insoluble residues of the cherty limestones, referred to as limestone of Fern Glen age, contain some paper-thin flakes of shale suggesting continuity of deposition with the St. Joe.
North and northwest of the sparsely cherty crinoidal limestone area in Sedgwick and Butler counties, abundant translucent chert again appears in amounts adequate to identify these rocks as a lithologic unit without resorting to insoluble residues. The limestones are semigranular and gray in color. The usage in this report is to refer to the limestone containing dark chert as the Reeds Spring and to the semigranular limestone containing the light-colored semitranslucent bluish chert as limestone of late Fern Glen age. One seems to be a local variant of the other.
The thickness of the Reeds Spring or the equivalent rocks of late Fern Glen age in the subsurface is fairly regular where they are overlain by the Burlington but more variable where overlain by the Keokuk. The Reeds Spring, combined with the Grand Falls chert in the Ballard mine well (see p. 46) in Cherokee county, has a thickness of 142 feet, exclusive of 13 feet of sparsely cherty St. Joe limestone at the base. Exclusive of the Grand Falls chert, which is 45 feet thick, the Reeds Spring in this well is 97 feet thick. In Labette county (Union Gas Corporation No. 3 Hudson well, sec. 26, T. 32 S., R. 15 E.), the Reeds Spring is 130 feet thick. Farther west it is 80 to 110 feet thick along the lines of the cross sections F-F' (pl. 7) and A-A' (pl. 5). Where it is overlain by unconformable beds its thickness is reduced. The combined thickness of the St. Joe and rocks of late Fern Glen age shows less variation than that of the separate members. Toward the west where the shaly section of the St. Joe thickens, the rocks of Fern Glen age as a whole also become thicker.
Limestone of late Fern Glen age extends beyond the area of the St. Joe and overlap" upon the Kinderhook surface. Plato 8 sham- the northern limit of limestone of Fern Glen age; and its relation to the underlying rocks is shown in the several cross sections. The relation of the distribution of rocks of Fern Glen age to the known structural features of the region is so striking that there seems little reason to doubt that structure was the controlling factor in determining the configuration of the basin of deposition. The removal of the Mississippian rocks from the northern part of the Nemaha ridge before the deposition of the Pennsylvanian prevents the examination of the section in that area. Rocks of late Fern Glen age, however, wedge out beneath the Burlington on the west flank of the ridge and wore therefore not deposited on the subsequently eroded crest of the ridge. Rocks of the same age similarly wedge out beneath the Burlington on the east side of the central Kansas uplift, the Burlington encroaching farther upon the area of the uplift than do the underlying rocks. The distribution suggests very strongly that the central Kansas uplift and the Nemaha ridge were both gently deformed before or during the deposition of lower Osage rocks. The thinning and overlap toward the north, as shown in the cross sections, indicate a southerly tilting of the whole region. which is also shown by the similar overlap of younger Mississippian rocks.
The probable conformity of rocks of late Fern Glen age on the St. Joe has already been discussed, The fluctuations in the contact as shown in the cross sections seemingly are due mainly to the irregular presence of chert and possibly in part to the presence of bioherms, The Reeds Spring or upper part of the rocks of Fern Glen age is unconformable on all the older Mississippian rocks except the St. Joe. The relations to the Burlington and Keokuk will be discussed more fully in a later chapter. but the Reeds Spring seems to be conformable below one lithologic unit regarded as the Burlington and unconformable beneath another tentatively identified as the Keokuk. Moore, Cline, and Laudon have pointed out in different publications that in northeastern Oklahoma and in parts of southwestern Missouri the Burlington is absent and the Keokuk is disconformable upon the underlying Reeds Spring. This relation seems to exist in some places in the subsurface in Kansas.
Burlington and Keokuk Limestones
Surface character and distribution
The rocks of the upper part of the Osage have been identified from the Appalachians to regions beyond the Rocky Mountains. The type localities of the Burlington and Keokuk limestones are in southeastern Iowa where these rocks are composed of cherty limestone, though some of the limestone is dolomitic. The Keokuk in northern Iowa and Indiana becomes shaly (Laudon, 1937, p. 1158). At the type locality these formations are distinguishable lithologically as well as faunally, but the lithologie characteristics are not persistent enough to be a safe guide at distant points.
The Burlington limestone of the outcrops nearest to Kansas is described by Moore (1928, p. 167) as a coarse-grained crystalline crinoidal limestone. Parts of the formation contain considerable amounts of dolomite, which is interbedded with limestone or is present as irregular masses within the limestone beds. The formation contains considerable white opaque chert in thin uneven beds, irregular nodules, and scattered lenticular masses. In some outcrops chert comprises half the section. In others very little chert is present. The lower part of the Burlington is reported to be less cherty than the upper part, but the lower beds and probably the higher beds also show varying amounts of chert. along the outcrop. The Burlington is reported to have an average thickness in Missouri of about 150 feet.
The Keokuk limestone of the outcrops is described by Moore (1928, 1939) as mainly bluish and gray or buff medium- to coarse-grained more or less crystalline limestone. The color in general is more bluish than that of the Burlington. Shale seams separate the limestones in southeastern Iowa, but little or no shaly material is present in central and southwestern Missouri. Chert is abundant especially in the southwestern part of Missouri. The amount and distribution of the chert and the texture and purity of the limestones vary greatly in different localities not far apart.
Moore (1928, pp. 143,207; Moore, Fowler, and Lyden, 1939, p. 9) observed a hiatus between the Burlington and the Keokuk in southwestern Missouri; and in the Joplin district the Keokuk rests disconformably on the Reeds Spring. Laudon (1939, p. 329) reports that the Keokuk is disconformable on the Reeds Spring throughout northeastern Oklahoma.
The thickness of the Keokuk in Iowa averages about 70 feet, but in southwestern Missouri, where the Keokuk rests on the Reeds Spring, the thickness, as noted by Moore, is 100 to 150 feet. Laudon (1939, pp. 330-332) noted a maximum of 80 feet in outcrops in northeastern Oklahoma, where the Keokuk is in contact with the Reeds Spring.
Occurrence in Kansas
In the examination of the well cuttings from Kansas the Missouri Geological Survey found it impracticable to separate the Burlington from the Keokuk limestone. Two readily distinguishable types of chert, however, were noted in the examination of the Kansas well cuttings, but whether these actually represent the Burlington and the Keokuk has not been determined by direct comparison of insoluble residues of surface and subsurface rocks, One type is well represented in the Ballard mine well (sec. 10, T. 35 S., R. 24 E.) reported by Mary Hundhausen [earlier in this report]. This well is near the margin of the small area of outcrop of Mississippian rocks in southeastern Kansas and is only 15 miles from it locality in Oklahoma (sec. 31, T. 27 N., R. 24 E.), where the Keokuk is reported by Laudon to overlie the Reeds Spring. As Moore reports the Burlington to be absent in the Joplin area, in the Kansas part of which the Ballard mine well was drilled, it seems probable that the undivided Burlington and Keokuk reported by Miss Hundhausen in the Ballard well is of Keokuk age.
Laudon (1937, p. 1160) reports an upper Burlington index fossil (Pentremites elongatus Shumard) in a core from a well (Sinclair Prairie-Gentry, sec. 1, T. 33 S., R. 15 W.) in Barber county, Kansas. This fossil, which came from a bed a short distance below the contact with the Pennsylvanian rocks, is not directly associated with chert, but it occurs in an area in which the first type of chert is absent and the second type of chert is present directly above rocks of Fern Glen age. These limestones having contrasting types of chert are therefore tentatively regarded as representative of the Burlington and the Keokuk in the subsurface.
Burlington Limestone in Subsurface in Kansas
The limestone, tentatively referred to the Burlington. consists chiefly of white and gray semigranular crinoidal limestone interstratified with relatively thin beds of gray dolomite and limestone grained with minute dolomite crystals. Large quantities of chert are present in most places. but the amount of chert is variable. In southern Sedgwick and Butler counties, beds believed to represent the Burlington are entirely devoid of chert in some places and in other pads of the same area contain very small amounts. Normally the Burlington contains 20 to 75 percent chert and in places where the Burlington was folded and eroded in pre-Pennsylvanian time, as along the Voshell anticline, leaching to considerable depths below the surface has removed most of the limestone in its upper part, so that the cuttings are principally chert.
Burlington chert is characteristically even-textured, opaque, and gray, gray white, or bluish white. The surface of the bluish-white chert in some places shows lines and tracings of individual spines and tubes and cells of microorganisms. Chert in dolomitic limestones usually shows a grainy or stippled texture. In the insoluble residues of dolomitic rocks, where silicification has been incomplete, the acid removes the unreplaced very minute dolomitic crystals, leaving their angular molds. Most of the chert breaks with a smooth fracture in blocky fragments, but some rough-surfaced chert is present in most samples. Some of the smooth chert is semiopaque; but semitranslucent chert, though present in minor amount in Rome localities, is confined to thin horizontal zones and is unusual. Drusy quartz and minute pockets lined with fine quartz crystals are common constituents of the insoluble residues, and coarse fragments of quartz, like broken glass, are not uncommon even in the samples. In the upper part of the formation in the Kasper-James well (sec. 8, T. 13 S., R. 25 E.) in Johnson county and neighboring wells broken fragments of minute fossils have been preserved in a glassy matrix. This zone is unique and occurs 197 feet above the Chattanooga shale in the Kasper-James well. It was also noted at about the same stratigraphic position in some other wells in northeastern Kansas. This chert and some of the more opaque spicular chert are not unlike some of the chert in the Warsaw.
As the Burlington is everywhere unconformable below the overlying rocks its thickness varies widely. Its thickness is 147 feet in the Kasper-James well. In Sedgwick county (Fitzwilliams No. 1 Struthers well, sec. 34, T. 28 S., R. 2 W.), its thickness is 143 feet and in Butler county (Prairie No. 1 Linier well, sec. 34, T. 29 S., R. 5 E.) it" thickness is 165 feet. Thicknesses of 50 to 100 feet are usual, but in some place", as in Cherokee and pads of Labette counties, where it is replaced by Keokuk limestone, the Burlington is entirely absent. In western Kansas it has an apparent thickness of 180 feet in Logan county (Alma and McNeeley No. 1 Watchorn well, sec. 13, T. 15 S., R. 33 W., well No. 2, cross section F-F', pl. 7) and 101 feet in Scott county (Watchorn and McNeeley No. 1 Spangler well, sec. 23, T. 20 S., R. 33 W., well No. 3, cross section F-F', pl. 7).
The Burlington is the most widespread of the Mississippian limestones of Kansas. It is present throughout the state except in southeastern counties, in the central Kansas uplift, on deeply peneplaned anticlines along the Nemaha ridge, and locally on the peneplaned crest of the Voshell anticline. It was removed from parts of southeastern Kansas before the deposition of the Keokuk and in parts of the most southern tier of counties from Montgomery county to Clark county by the erosion that preceded the deposition of the Cowley formation. It overlaps beyond the margin of rocks of Fern Glen age on the Central Kansas uplift (see cross section E-F', pl. 6). As thicknesses exceeding 150 feet are known in some areas it may well have buried that area, though no Burlington rocks are now present on the uplift and the marginal thickness, where covered by the Keokuk, is now less than 100 feet in most places.
There is no evidence in the subsurface of unconformity between rocks of Fern Glen age and the Burlington. Where the full thickness of the Fern Glen equivalents is present, rocks of Fern Glen age maintain a fairly even thickness of 90 to 120 feet below the Burlington, the thickness increasing toward the west. In some places there seems to be a transition from the rocks of Fern Glen age to the Burlington, for the semi translucent chert that characterizes the upper part of the Fern Glen extends upward in some places into beds containing gray even-textured opaque chert characteristic of the Burlington. Cline (1934, p. 1154) observed that "in northern Arkansas the lower Burlington rests with apparent conformity upon the Reeds Spring formation and it is followed by upper Burlington limestone and chert…"
Rocks tentatively correlated with the Keokuk overlie the Burlington unconformably and in some places, as in the subsurface of extreme southeastern Kansas, rest on rocks older than the Burlington.
The Cowley formation and the Warsaw limestone, which conformably succeeds the Cowley, both overlie the Burlington unconformably in parts of eastern Kansas where the Keokuk is absent.
Keokuk Limestone in Subsurface in Kansas
Rocks tentatively correlated with the Keokuk limestone in the subsurface include much more dolomite and dolomitic limestone than the Burlington, although where the Keokuk is thick much limestone is present in the lower part. The thickest section of Keokuk rocks is in the Ballard mine well (sec. 10, T. 35 S., R. 24 E., [earlier in this report]) in the Tri-State mining district. The lower rocks, exclusive of the much-discussed Grand Falls chert, consist of calcareous gray dolomite alternating with buff-gray semigranular crinoidal limestone. The limestone is less siliceous than the dolomite. In general the Keokuk dolomites are extremely siliceous and contain large quantities of opaque white cotton rock and calcareous white pitted and porous opaque chert. Most zones contain no eventextured chert, though this type of chert is present sparingly in some samples. Occasional grains of disseminated glauconite occur in the pitted limy cherts in the northwestern part of the area of deposition, but they were not noted elsewhere. The distinguishing feature of the rocks, tentatively referred to the Keokuk, is the pitted and porous calcareous chert and abundance of siliceous cotton rock in some zones. These characteristics are in strong contrast to the even-textured opaque chert of the Burlington.
The insoluble residues of some zones in the upper part of the Keokuk consist almost entirely of soft friable cotton rock. Much cotton rock occurs also in the lower part ; but in this part, as exemplified in the Ballard mine well, the cotton rock residues are denser and firmer. The residues of the calcareous pitted chert consist of hard white, porous, and spongy aggregates, which in some zones are unaccompanied by cotton rock. In the more siliceous beds the porous and pitted insoluble residue constitutes 50 to 90 percent of the samples by volume. The insoluble residues from the interbedded limestones of the lower part of the formation are usually Jess than 10 percent of the sample.
A bed of oolite 5 to 10 feet thick. tentatively correlated with the Short Creek oolite of the outcrops in southwestern Missouri, occurs in occasional wells from Cherokee county to Rice county. This oolite is gray, and the ovules are moderately well sorted as to size. The bed is erratic in occurrence, being absent in many of the wells examined. Its position is from 160 to 240 feet above the Chattanooga shale; the thinner interval occurs west of the axis of the Nemaha ridge. As shown in cross section E-F' of plate 6, the interval increases southeast of the ridge and remains fairly constant.
A dark glauconitic silty limestone, known in the Joplin area as the "J bed", occurs at the irregular lower boundary of the Warsaw in some areas. The interval from the glauconitic zone down to the top of the oolite in the Keokuk varies widely; in the Ballard mine well the interval is 30 feet. In several wells in southeastern Kansas the glauconitic zone is in contact with or only a few feet above the oolite. As shown in cross section E-F' of plate 6, a considerable thickness of Keokuk rocks occurs above the oolitic limestone in places east of the central Kansas uplift. In well No. 5 of cross section E-F' 80 feet of typical Keokuk rocks occurs above the oolitic limestone. They are overlain by 47 feet of cherty Warsaw limestone, which has at the base a well-developed glauconitic zone. In well No. 6 of cross section E-F', the Keokuk limestones above the oolitic limestone are 92 feet thick and there is 37 feet of residual chert above, none of which is of the Warsaw type. It seems probable, therefore, that the Keokuk limestones were originally much thicker over the whole region but were greatly reduced in thickness by pre-Warsaw erosion.
The chert in some zones above the oolitic limestone includes eventextured white or gray opaque chert, some of which is vaguely grainy in texture and not strikingly different from that in the Burlington. In such zones, however, this chert is accompanied by cotton rock or by pitted siliceous limestone characteristic of the Keokuk but in less than the usual volume. The chert from this interval is distinctly unlike the chert in the Cowley or in the Warsaw. Near the top of some of the thicker post-oolite limestones, some bluish semi translucent chert has been noted.
Moore (1928, p. 232) originally regarded the Short Creek oolite, with which this oolitic limestone is tentatively correlated, as the basal member of the Warsaw, but now includes it in the Keokuk. Laudon (1939, p. 331) refers to the Short Creek oolite rather vaguely as lying "on top of the Keokuk." In view of the varying interval of this bed beneath the unconformity and the similarity of the chert in the interval above to that below the oolite, it seem plausible from purely lithologic evidence to regard this oolite and the rocks up to the unconformity as Keokuk in age. This interpretation has been advanced by Fowler and Lyden (1934, addendum, p. 62) and is accepted by Moore, Fowler, and Lyden (1939, p. 9).
The oolite is not present at any place in rocks herein tentatively correlated with the Burlington. Within the belt in which the Keokuk occurs the oolite is a fairly constant bed. It is, however, not present in all Keokuk areas, partly because the oolitic zone was eroded either before the deposition of the Warsaw or by pre-Pennsylvanian peneplanation.
Cross section E-F' of plate 6 runs lengthwise across the area in which the pitted beds. tentatively correlated with the Keokuk, have been recognized. It shows these rocks in contact with the Reeds Spring toward the southeast and with the Burlington toward the northwest. The cross section has been plotted using the top of the oolite as a datum plane. The interval from the oolite to the top of the Chattanooga shale is fairly constant west of the position of the subsequently deformed Nemaha ridge fold, but is 80 to 100 feet thicker east of it. These relations seem to indicate that east of the Nemaha ridge a gentle monoclinal displacement downward toward the east occurred during the interval between the end of Chattanooga time and the deposition of the oolite zone.
This displacement seems to have been a forerunner of the major movement that later, at the close of the Mississippian, produced the Nemaha ridge fold, and supports the evidence shown by the distribution of the Chouteau and of the lower Osage reeks that deformation on the trend of the Nemaha ridge began in early Mississippian time.
In the Ballard mine well, where the Burlington is absent and the Keokuk overlies the Grand Falls chert and Reeds Spring limestone, the Keokuk is 130 feet thick exclusive of the Grand Falls. This unusual thickness is due partly to the fact that in this well 33 feet of the portion of the Keokuk limestone above the oolite has been preserved from erosion and partly to the depth of the basin at this point, the whole of the Burlington having been eroded. Farther northwest the Keokuk is thinner; in some places very little limestone of post-oolite age has survived subsequent erosion and the basin in which the Keokuk was deposited was not eroded so deeply into the Burlington. On the south side of the area of deposition pre-Warsaw erosion has partly or completely removed the Keokuk. In some areas thinning of the section below the oolitic limestone is compensated by the preservation of thicker rocks above. In well No. 6 of cross section E-F', plate 6, the Keokuk rocks below the top of the oolitic limestone are 60 feet thick. This, with 92 feet of Keokuk rocks above the oolite, makes it total thickness of 152 feet. Thicknesses exceeding 100 feet of Keokuk are not unusual. The Keokuk becomes thinner toward the northwest on the line of the cross section and the pre-oolite portion wedges out before reaching the central Kansas uplift.
The distribution of the Keokuk is shown in plate 8. It has not been recognized in western Kansas. It occupies a broad belt, 80 to 150 miles wide, trending northwest from the TriState mining district toward the central Kansas uplift. Cross sections A-A', B-B' of plate 5 and cross section C-C' of plate 6 show its lenticular character in cross section and its relation to the Burlington and Warsaw limestones. The width of the belt of Keokuk rocks in southeastern Kansas was originally considerably greater, but the erosion preceding the deposition of the Cowley formation cut off the southwestern margin of the Keokuk in parts of Montgomery. Chautauqua, and probably Cowley counties.
The subsurface relations of the lithologic units, tentatively identified as Burlington limestone and Keokuk limestone, are in conformity with the relations at the surface described by Moore, Laudon, and Cline, who have most recently studied the unconformity between the Burlington and Keokuk in Missouri and Oklahoma. The writer finds that the Keokuk is unconformable below the Cowley and the Warsaw formations.
The trend of the Keokuk basin, as mapped, does not correspond to any known synclinal movements, but follows roughly the trend of the Chautauqua arch, which, however, does not seem to have been conspicuously active during the Mississippian or at its close. The basin in which the Keokuk was deposited in southeastern Kansas seems to have been an erosional basin. Greater depth of erosion toward the southeast implies drainage in this direction. The maximum relief of the pre-Keokuk surface, indicated by the removal of all the Burlington and part of the Reeds Spring, could hardly have been less than 150 feet in extreme southeastern Kansas.
Kansas Geological Survey, Geology
Placed on web Jan. 27, 2013; originally published Sept. 1, 1940.
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