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Stratigraphy--Permian System, continued
Leonardian Series
The Kansas Geological Survey has adopted the term Leonardian as the name of the second series from the base in the Kansas Permian section, in accordance with the classification of the North American Permian rocks published in 1939 by Adams and others (1939, pp. 1673-1681). The base of the Leonardian Series in Kansas is somewhat arbitrarily placed at the top of the Nolans formation, which is the top of the Herington limestone. As already explained, the Odell shale and Nolans limestone are lithologically similar to the beds lower in the Chase group and hence there is no reason for placing a group or series boundary in this part of the section lower than the top of the Herington limestone.
Sumner Group
The term Sumner, from Summer County, Kansas, was introduced as a stratigraphic name by Cragin (1896, p. 9). He defined the "division" as including strata between the "Marion concretionary limestone" and the "redbeds." This placed the lower boundary at the top of the Winfield formation. Bass (1929, p. 93) defined the group to include the Luta limestone, the Enterprise shale, the Herington limestone, and the Wellington formation. The first three of these names had been introduced by Beede (1908, p. 253), and at the same time Beede had introduced the name Pearl share for strata lying between the Herington limestone and the Wellington formation as it had been defined by Cragin in 1896. Bass did not recognize the Pearl shale as a natural unit and redefined the Wellington formation, fixing its base at the upper surface of the Herington limestone. Condra and Upp (1931, p. 63) believed that the Pearl shale is a well-defined unit and that it is overlain by a persistent limestone, which they named Hollenberg and which later was called the basal in member of the "Donegal formation" by Moore, Newell, and Elias (1934). The "Hollenberg" limestone is several scores of feet below the top of the Pearl shale as defined by Beede. Recent studies by Moore, however, reveal that it is not certain that the "Donegal formation" is well defined, and hence the Wellington formation is now understood to lie directly above the Herington limestone and is not definitely divided into smaller units. As already explained, the base of the Leonardian series is placed at the top of the Herington limestone. The Sumner Group, as the term is now being used, lies between the Herington limestone and the Harper sandstone. It comprises the Wellington shale, Ninnescah shale, and Stone Corral dolomite. The lower 45 or 50 feet of the Wellington shale is present in the extreme northwestern part of Riley County. Permian beds above the lower part of the Wellington shale were eroded from western Riley County before Cretaceous sediments were deposited.
Wellington Formation
The term Wellington was introduced as a stratigraphic name by Cragin (1896, p. 16-18). The original definition placed the base of the formation at the top of the "Geuda salt" (within the Wellington formation as now defined) and the top was placed at the base of the Harper sandstone. The base of the Harper sandstone is now regarded as the top of the Sumner Group. As explained under the heading, Summer Group, Beede applied to the strata between the Herington limestone and Cragin's Wellington formation the name "Pearl shale." Bass (1929, p. 99) redefined the Wellington formation as extending downward to the top of the Herington limestone. Later, Condra and Upp redefined the "Pearl shale" as lying between the top of the Herington limestone and the base of the "Hollenberg limestone" and the Kansas Geological Survey later erected the "Donegal formation," of which the "Hollenberg limestone" was the lowest member. According to such a classification the present Sumner Group includes in ascending order: Pearl shale, Donegal limestone, and Wellington shale, each as a formation. Recent investigation by Moore (oral communication), however, throws doubt on the validity of such a classification, and now the Wellington formation is regarded as conforming to the definition of Bass and it is not deemed expedient to subdivide the formation until more detailed studies can be made.
In the northwestern part of Riley County about 45 feet of variegated shale is exposed above the Herington limestone. Next above this shale is a few feet of limestone and shale that probably correlates with limestone that has been called "Hollenberg." Hence this shale comprises the lower part of the Wellington formation as it is now defined.
Lithologic Character and Thickness--The lower part of the Wellington shale formation in western Riley County is predominantly red, but there are noticeable amounts of gray and green shale. The shale is well bedded and is blocky. It consists of very fine silt and clay particles. The thickness of the variegated shale lying between the top of the Herington limestone and the next limestone above is approximately 45 feet. The limestone just mentioned is yellow and earthy where exposed. It contains casts of small pelecypods. The observed thickness is 6 inches. Sandstone of the Dakota group lies upon this limestone.
Distribution--The beds assigned to the lower part of the Wellington formation crop out only in secs. 1 and 2, T. 6 S., R. 4 E., in the northwest corner of Riley County. It is probable that a few feet of Wellington shale is present under soil cover in a fairly large area in northern and western Riley County in the uplands above the Herington limestone.
Detailed sections--For a detailed section including a part of the Wellington shale see number 1 at the end of this report.
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Kansas Geological Survey, Geology of Riley and Geary Counties
Web version Nov. 2000. Original publication date Dec. 1941.
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