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Introduction
The economic importance of the older Paleozoic rocks throughout the Midcontinent region of North America, particularly as a source of petroleum, has led to an increasing desire for a more complete understanding of that part of the geologic section. Accordingly, the Kansas Geological Survey in July 1937 initiated a study of the older Paleozoic rocks in the subsurface of Kansas.
The study was begun by Raymond P. Keroher as part of his duties. In July 1941, Jewell Kirby was also assigned to the work. It was nearly completed when in 1942 the authors left the Kansas Survey for private employment. Research was continued as time permitted and later, after both had joined the staff of the U. S. Geological Survey, H. D. Miser of the Fuels Section extended an invitation to the authors to complete the report. The allocation by the Federal Survey of a part of the time of both writers to the project during the winter of 1943-44 led to the completion of the report earlier than otherwise would have been possible.
Acknowledgments
The authors extend thanks to various oil companies, drillers, and operators in Kansas for their cordial cooperation in the saving of well cuttings; to H. S. McQueen and the Missouri Geological Survey for permission to examine at Rolla, Missouri, cuttings and insoluble residues of Missouri wells and outcrop samples, and for sample determinations of Missouri wells with which lithologic criteria Kansas wells were compared; and to E. C. Reed of the Nebraska Geological Survey for permission to examine samples from wells drilled in Nebraska, on file at the Nebraska Geological Survey. Wallace Lee, Henry Ley, John Garlough, and others have contributed directly and indirectly to the investigation. The mineralogical determinations made by Jewell J. Glass are sincerely appreciated. The samples were prepared and the residues were made by the staff of the subsurface laboratory of the Kansas Geological Survey.
Changes of various maps showing thickness and distribution of formations, based on information obtained subsequent to work by the authors, have been made by Wallace Lee.
Purpose and Scope of the Report
The specific purpose of this study has been to determine the character, thickness, stratigraphic sequence, and distribution of as many zones of the Upper Cambrian and Lower Ordovician rocks as possible. Such information will be useful in petroleum exploration in the state because (1) these beds are important sources of petroleum, (2) some beds within the older formations may be less prolific than others, if not wholly barren of oil, and (3) local variations in the thickness of members of the older formations probably reflect structural conditions that may have been influential in the accumulation of petroleum.
The study is limited to subsurface beds of Late Cambrian and Early Ordovician age that unconformably overlie the granites, schists, and quartzites of Pre-Cambrian age and are unconformably overlain by beds ranging in age from Chazyan to Early Pennsylvanian. In addition to subsurface studies in Kansas, the work included examination of outcrops of these beds in the Ozark region of Missouri, the Black Hills of South Dakota, and the Front Range of the Rocky Mountains. It also included examination of samples and insoluble residues from wells drilled in Missouri which were made available at Rolla, Missouri, by the Missouri Geological Survey.
At the beginning of the project it was intended only to examine samples from wells in Kansas situated east of the Nemaha granite ridge, an area that includes approximately the eastern one-fourth of the state. This area is nearest the outcrop of the formations in the Ozark plateau and is adjacent to western Missouri where the Cambrian and Ordovician rocks in the subsurface have been studied by the Missouri Geological Survey. As the work progressed it became evident that the larger divisions recognizable in the eastern Kansas wells were remarkably persistent westward. Accordingly, it seemed desirable to trace those zones into western Kansas. The time necessary to prepare samples recovered from rotary drilling operations required limitation of the study to those wells in western Kansas that penetrate all or nearly all of the older Paleozoic rocks. In consequence, the work in western Kansas is not nearly so exhaustive as that in the eastern part of the state.
The approach to the regional study has been the correlation across the state of stratigraphic units that are lithologically similar. Correlation with the subdivisions in Missouri is based upon lithologic similarities between the stratigraphic units in the subsurface of Kansas and the formations that crop out in the Ozark region and have been traced in the subsurface into western Missouri and eastern Kansas. No attempt, however, has been made to differentiate all the subdivisions that have been recognized in Missouri. On the whole, only the larger subdivisions, in which the included units are believed to be conformable, have been differentiated.
Correlation of smaller stratigraphic units is possible in those areas where cores and uncontaminated samples are available and where wells that penetrate considerable depths of the beds are closely spaced. With the exception of local areas, such control generally is lacking in Kansas. Therefore it has seemed in keeping with the purpose of this report to make the degree of detail consistent with the amount of control available. It is realized that more detailed study of these wells and the drilling of new ones doubtless will call for revisions. The subdivision of these beds into the larger units, however, supplies a framework into which more detailed information may be fitted later.
The project involved several steps: (1) development of a method of study making possible differentiation and recognition of lithologic zones by microscopic examination of original samples and insoluble residues; (2) summation of the lithologic characteristics of the subdivisions on the basis of microscopic examinations; (3) correlation across the State of the recognizable units and construction of geologic cross sections representing the stratigraphic sequence of units as they occur in representative wells; (4) summary interpretation of the geo- logical history of the older beds, based on the correlation, thickness, distribution, and sequence of formations.
Nomenclature
The Upper Cambrian and Lower Ordovician rocks crop out to the east of Kansas in the Ozark region of Missouri, to the south in the Arbuckle and Wichita Mountains of Oklahoma, to the west along the Front Range of the Rocky Mountains, to the northwest in the Black Hills of South Dakota, and to the northeast in Minnesota, Wisconsin, and Michigan. They occur in the subsurface of all the intervening region except locally in structurally high areas from which they have been removed by erosion. The correlation table (Fig. 1) indicates the nomenclature and subdivisions of the lower Paleozoic beds in most of these areas.
Figure 1--Subdivision, nomenclature, and correlation of Upper Cambrian and Lower Ordovician rocks at the outcrop and in the subsurface of Kansas and adjacent states. An Acrobat PDF version of this figure is available.
Exploration for petroleum in northern Oklahoma and in Kansas has shown that the oldest Paleozoic rocks are composed of a series of beds consisting for the most part of dolomite but with minor amounts of interbedded sandstone and shale. These beds have been divided in the Arbuckle Mountains of southern Oklahoma into the Arbuckle group, the Honey Creek limestone, and the Reagan sandstone, as indicated in the correlation chart (Fig. 1).
The Upper Cambrian and Lower Ordovician dolomitic sequence, which is easily recognized, has become known among Oklahoma drillers as "Arbuckle lime," "Arbuckle formations," and "Siliceous lime." These names have also become common in Kansas.
On account of the difficulty of recognizing zones within the dolomite, no subdivisions of the Cambrian and Ordovician have become well known to drillers in Kansas, except the basal sand or conglomerate that is present in some places. Because of its position below the dolomites, this basal sand was correlated with the Reagan sandstone of the Arbuckle Mountains, which occupies the same stratigraphic position. Thus the term "Reagan sand" which is correlated with the Lamotte sandstone of Missouri was introduced into the Kansas driller's terminology.
The Upper Cambrian and Lower Ordovician formations are well exposed in the Ozark region of Missouri, where their study by the Missouri Geological Survey has led to their detailed classification. From the study of insoluble residues developed by the Missouri Geological Survey, the various stratigraphic units of the Ozark outcrops have been traced westward in the subsurface to western Missouri and eastern Kansas, where their correlation with the outcrops has been established. (Since this report was written an investigation by H. A. Ireland [1944] has traced stratigraphic units of the Ozark outcrop in the subsurface into northeastern Oklahoma.) For these reasons it seemed desirable to correlate recognizable units in the subsurface of Kansas with equivalent units in the Ozark region.
On the other hand, the name "Arbuckle" is so well established among geologists and others in the petroleum industry that its abandonment and the substitution of other names would confuse and complicate the records of oil companies and drilling organizations. On recommendation of oil geologists in Kansas therefore the name "Arbuckle" has been retained as a group name for all Paleozoic beds older than those included in the Chazy group (St. Peter sandstone or Simpson formation of Kansas) and subdivisions of the Missouri classification have been adopted. It is realized that older beds are comprised under this definition of Arbuckle than were included in the original Arbuckle formation (Abernathy, 1940, pp. 10-13; Jewett, 1940, pp. 12-14). Lee (1943, fig. 3, p. 19) has indicated the desirability of using the group name "Arbuckle" as restricted by Ulrich (1911) in the Arbuckle Mountains. Revision of the nomenclature of these beds on the basis of information now available seems premature.
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Kansas Geological Survey, Geology
Placed on web Jan. 22, 2010; originally published June 1948.
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