By Wallace Lee
With Report on Fossils of Mississippian Age from Well Cores in Western Kansas
By George H. Girty
Originally published in 1940 as Kansas Geological Survey Bulletin 33. This is, in general, the original text as published. The information has not been updated.
This report embodies the results of a study of the Mississippian rocks that lie below the surface in Kansas. The study has been carried on as a cooperative project of the State Geological Survey of Kansas and the Federal Geological Survey. The object of the investigation has been to acquire and publish information that will be of value in the further development of the oil and gas resources of the state. A report dealing with the thickness of the Mississippian limestones and the relation of their thickness to the structure of the rocks and to oil and gas pools has already been published. The present paper deals chiefly with the stratigraphy of the Mississippian rocks, and will also be of interest to the oil industry.
Criteria for distinguishing the various units of the Mississippian have been determined by a microscopic study of the cuttings and cores of the Mississippian rocks and by the examination of insoluble residues. The significant results as to the character and relations of the formations are here briefly mentioned in the order of age, beginning with the oldest units.
The Chattanooga shale, of Kinderhook (?) age, is black and relatively thin in southern Kansas, but toward the north it is a dark or a gray-green shale, more than 250 feet thick. The Chattanooga sea was confined on the west by land in the region of the central Kansas uplift and in Clark county. The surface on which the Chattanooga was deposited was essentially a plain in eastern Kansas, but had some relief along the east side of the central Kansas uplift.
The Compton limestone and Northview shale, of Kinderhook age, are present only in southeastern Kansas. They are the correlatives of the Chouteau limestone of northeastern Kansas and northern Missouri. The Compton limestone is a noncherty grayish-green limestone and the Northview a silty calcareous shale. Both the Compton and the Northview are thin in southeastern Kansas, but they thicken toward the north and grade laterally into the Chouteau, an impure cherty limestone. The Chouteau and its correlatives are confined to the area east of the subsequently formed Nemaha ridge fold; and the basin in which they were deposited seems to have been limited on the west by minor pre-Chouteau movements along the trend of this fold.
A relatively thin bed of slightly cherty dolomite, which may represent the Sedalia limestone of the outcrops in Missouri, overlies the Chouteau limestone. West of the Nemaha ridge, this dolomite overlaps beyond the Chouteau and rests upon the weathered surface of the Chattanooga shale. In north-central Iowa, brown dolomites and limestones of Hampton age, in places as much as 200 feet thick, were deposited above the Chouteau. A part of these rocks may be the equivalent of the Sedalia as tentatively identified in the subsurface of northeastern Kansas.
Rocks tentatively correlated with the Gilmore City limestone, which crops out in Iowa, overlie the Sedalia in northeastern Kansas and pre-Chattanooga rocks in western Kansas. The limestone beds of the Gilmore City are white and semigranular, and in some zones are oOlitic. They are probably unconformable upon the underlying rocks in Kansas, for a disconformity was noted at their base in Iowa. Rocks of Gilmore City age in Kansas lie in the southwestern prolongation of the Gilmore City basin of Iowa and seem to have been deposited in an erosional basin that lay athwart the central Kansas uplift. Rocks correlated with the Gilmore City limestone are the oldest Mississippian rocks southwest of the Nemaha ridge.
The lower part of the rocks of Osage age is represented by the St. Joe limestone and Reeds Spring limestone, which are the correlatives of the. Fern Glen limestone of southeastern Missouri. The St. Joe limestone is noncherty, in part argillaceous and in part semigranular white limestone. It has a somewhat restricted distribution in southeastern Kansas. The Reeds Springs is dolomitic and contains much dark chert, but toward the northwest grades into semigranular limestone with some semitranslucent bluish chert. It seems to be conformable above the St. Joe and overlaps upon Kinderhook rocks beyond the margin of the St. Joe. The distribution of these formations suggests that the configuration of the basin in which they were deposited was controlled by early movements along the trend of the Nemaha ridge anticline and slight elevation of the central Kansas uplift.
Gray limestones and dolomites, with opaque white even-textured chert, correlated tentatively with the Burlington limestone, conformably overlie limestone of Fern Glen age and spread far beyond its area of deposition. These rocks are unconformably overlain in some areas by a lithologic unit composed of limestone and dolomite with pitted chert and "cotton rock." This unit corresponds in lithologic character to the Keokuk in the Tri-State mining district and is therefore here regarded as of Keokuk age. The rocks tentatively assigned to the Keokuk are confined to a belt trending northwest toward the central Kansas uplift. In the mining district they overlie the Reeds Spring limestone, but toward the northwest they rest upon varying thicknesses of rocks believed to be of Burlington age.
Erosion, accompanied by slight southerly tilting of the region, followed the deposition of the Keokuk limestone; a basin in southern Kansas that extended westward along the Oklahoma line as far as Clark county, was eroded in the Osage rocks. The basin had a relief exceeding 350 feet in its deepest parts and in some places in Cowley and Chautauqua counties erosion cut through the Chattanooga shale. This basin was filled with somewhat diversified limestone and dolomite, in part dark and cherty and in part silty, with a concentration of glauconite at its base. These deposits are succeeded conformably by clean gray cherty limestone, which was deposited after the seas had spread over the partly dissected upland area that bordered the basin on the north and east. The dark and silty deposits filling the basin are herein called the Cowley formation. The gray cherty limestones of the upper part are believed by some geologists to be of Warsaw (Meramec) age. The Cowley, which underlies these beds of Warsaw age, is also placed in the Meramec, because it is apparently conformable below the Warsaw and unconformable above Osage rocks. No direct faunal evidence, however, is available for the age assignment of the Cowley rocks. The Warsaw seems not to have reached Logan county, Kansas, and is absent also in a well in Lane county on the flank of the central Kansas uplift.
The Warsaw limestone is overlain conformably by the Watchorn formation, consisting of white oolitic and semi granular essentially noncherty limestone and some dolomite. This formation has a maximum known thickness of 690 feet in Clark county. George H. Girty, who examined fossils collected from cores of wells from this formation in western Kansas, found them to be of probable Warsaw, Spergen, and St. Louis age and thus a part of the Meramec rocks. The Ste. Genevieve limestone may be represented in some areas. H. S. McQueen and Mary Hundhausen, of the Missouri Geological Survey, by the use of insoluble residues, have also identified rocks of Spergen and St. Louis age in the Watchorn. The Watchorn is intended as a term for Meramec rocks younger than the Warsaw where it is not convenient to differentiate the subdivisions of the upper part of the Meramec. Lithologic units believed to represent the Spergen and St. Louis limestones have been identified in several areas east of the Nemaha ridge. It seems probable therefore that the rocks of the Watchorn formation were deposited across the central Kansas uplift, from which they were subsequently eroded during pre- Pennsy lvanian base-leveling.
Rocks of Chester age are recognized in Kansas in Cherokee county in the southeastern corner of the state and in parts of southwestern Kansas. In Cherokee county the rocks are represented by a limestone of Batesville age, which rests unconformably upon Warsaw limestone. In Mayes county, Oklahoma, this limestone rests upon dark shaly deposits containing a († Spring Creek) lower Moorefield fauna. These two limestones together constitute the Mayes formation. The writer believes that the lower Moorefield part of the Mayes is the southeastern extension of the Cowley formation, which in Mayes county was partly eroded before the deposition of rocks of Chester age.
Not fewer than six unconformities have been recognized within the sequence of Mississippian rocks of Kansas. In addition, peneplanation preceded and followed Mississippian sedimentation. Other less conspicuous interruptions of sedimentation may also have occurred within the various formations, for the seas were in the main not deep and oscillations of the sea level were probably frequent. The structural relations of the upper part of the Mississippian are not clear, for the rocks of late Meramec age were much reduced in thickness and extent by folding and peneplanation in post-Mississippian time; also rocks of Chester age are so scantily represented that little is known of the history of Kansas during Chester time.
The following is a list of the recognized unconformities:
- An unconformity in the Salina basin west of the Nemaha ridge between the Chattanooga shale and the dolomite provisionally referred to the Sedalia.
- An unconformity reported by Laudon below the Gilmore City limestone in Iowa. Inasmuch as some formations present in Iowa between the Gilmore City and the Sedalia are absent, there is probably also an unconformity in Kansas, but the evidence in northeastern Kansas is slight.
- An unconformity between the Northview shale and the St. Joe limestone in some areas. The Reeds Spring and the Burlington overlap beyond the St. Joe and rest unconformably upon the Chouteau. 4. An unconformity between the Burlington and Keokuk limestones.
- An unconformity between the Cowley formation and older rocks.
- An unconformity at the base of the Chester rocks.
A southerly tilting of eastern Kansas is indicated by the progressive overlap of the lower Osage rocks toward the north. The thinning of the Warsaw toward the north and the overlap of the St. Louis limestone upon older rocks of Iowa suggests that southerly tilting of Kansas and the region toward the north was resumed immediately preceding or during Meramec time. Pre-Pennsylvanian tilting in the same general direction, although accompanied by local deformation, lowered southwestern Kansas relative to northeastern Kansas. In consequence greater thicknesses of rocks of late Meramec age were preserved from pre-Pennsylvanian erosion in southwestern Kansas than elsewhere.
Kansas Geological Survey, Geology
Placed on web Jan. 27, 2013; originally published Sept. 1, 1940.
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