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Introduction
The State Geological Survey of Kansas has issued summaries from time to time indicating current classification and nomenclature of rock units in the State. These summaries have proved of value in unifying and clarifying stratigraphic usage in the State and have served as an easily accessible reference for those unfamiliar with Kansas stratigraphy. A tabular description of the rocks of Kansas was prepared in chart form by the State Geologist and distributed to those attending the annual meeting of the American Association of Petroleum Geologists in Wichita in March 1935. In October 1944, a more detailed description of the outcropping rocks of the State was issued as "Tabular Description of Outcropping Rocks in Kansas" [available online]. The usefulness of these two earlier publications is demonstrated by the rapid exhaustion of available copies of each and the continuing requests for them that come to the Survey office.
Figure 1--Generalized column of Kansas rocks showing eras and systems.
The present contribution is similar to "Tabular Description of Outcropping Rocks in Kansas" in that it presents a generalized composite rock column for the State in graphic form supplemented by brief text. It differs from this earlier report, however, by treating subsurface as well as outcropping rocks, by giving specific measured sections or well logs which are judged to be typical of parts of the rock column, and by inclusion of pertinent summaries of areal distribution, structural relations, and cyclic sequences.
A conference of State Geological Surveys representing Iowa, Kansas, Missouri, Nebraska, and Oklahoma was held at Lawrence in May 1947. As a result of this conference classification of the Pennsylvanian rocks in the northern midcontinent area is now essentially uniform on opposite sides of all state boundaries, except for divergence in classification in Oklahoma required by southward changes of facies (Moore, 1948, 1949). Although a comparable degree of uniformity has not as yet been possible in other systems, considerable progress toward uniform classification for the northern midcontinent has been made in recent years, particularly in the Cenozoic rocks.
Rocks of Kansas are of Cenozoic, Mesozoic, Paleozoic, and Cryptozoic (Pre-Cambrian) age. Exclusive of the Pre-Cambrian, which constitutes a more or less deeply buried basement complex, these rocks are assigned to 11 (possibly 12) geologic systems which embrace a time span of approximately 500 million years. They record the successive invasions of shallow seas that covered much or all of the State during many thousands of years. Some rock layers and unconsolidated deposits are of nonmarine origin, having been deposited by streams, the still water of lakes, air currents, or ice sheets. Such formations lack fossilized marine organisms, like those which are so abundant in many sea-laid strata of Kansas; they may contain remains of land plants, or traces of fresh-water life, or air-breathing animals. Also, there are numerous records of more or less widespread and prolonged erosion, when varying quantities of previously formed rocks were removed. These times of denudation indicate an emergent condition of the earth's surface in Kansas. They are defined by the local or regional absence of strata recognized elsewhere, and commonly also by irregularities along the contact of the sedimentary units which are separated by a hiatus in deposition. The hiatus is termed a disconformity if adjoining strata lie parallel, and it may be called a nonconformity if locally or regionally the rocks on opposite sides of the break show some divergence in structure. The term unconformity embraces both disconformity and nonconformity.
Except for revisions relating to Cenozoic deposits, the distribution of outcrops belonging to all main divisions and many subdivisions of the rock column of Kansas is adequately shown on the 1:500,000 scale geologic map of the State, on which 1 inch equals approximately 8 miles (Moore and Landes, 1937).
Figure 2--Generalized column of Kansas rocks showing systems and series.
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Kansas Geological Survey, Geology
Placed on web Oct. 28, 2008; originally published Jan. 1951.
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