Stratigraphy, Depositional Environments and Coalbed Methane Resources of Cherokee Group Coals (Middle Pennsylvanian)--Southeastern Kansas
Kansas Geological Survey
Open-file Report 2003-82

Chapter 2: Coal Deposits of the Cherokee Basin

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Previous work by Harris (1984) and Stanton (1987) divided the Cherokee Group into ten stratigraphic intervals using laterally persistent dark-gray to black “core” shales as stratigraphic markers (Figure 2.01). These highly radioactive black shales (150-300+ API units) are readily identifiable on gamma-ray well logs and are correlatable throughout eastern Kansas and into adjacent states. These “hot” gamma-ray shales serve as marker beds for the major coals within the study area. A composite section illustrates the stratigraphic relationship between marker beds and other units used in the study (Harris, 1984; Figure 2.02). In this study, an additional interval (Little Osage interval) was added above the Cherokee Group. The Little Osage interval contains the Summit coal of the Fort Scott Limestone a significant coal and important exploration target in southeast Kansas (Figure 2.01).

Depositional environments in the Cherokee Group range from relatively deep, low energy marine environments to shallow, marginal marine and nonmarine environments. Due to significant hiatus before and after peat development, depositional environments of coals may not be directly related to the environments of the overlying or underlying sediments (McCabe, 1984). Depositional environments of coals may be better reflected by their geometry, average thickness, areal extent, orientation, ash content, and sulfur content (Flores, 1993, McCabe and Shanley, 1992).

Figure 2.01 - Type log of the Cherokee Group and lower Fort Scott Limestone in the Cherokee Basin with designated intervals defined by marker beds, which are primarily dark gray to black shales (after Staton, 1987).


Composite Section of the Cherokee Group
Southeastern Kansas

Figure 2.02 - Composite section of the Cherokee Group in southeastern Kansas showing relationship of marker beds, which are primarily dark gray to black radioactive shales and major named coals (modified from Harris, 1984)

2.1 Lithofacies and Depositional Environments of the Cherokee Group

Ten lithofacies were recognized in the Cherokee Group of southeast Kansas (Table 2.1). The depositional environment of each lithofacies was interpreted based on mineralogy, sedimentary structures, ichnology, log response and stratigraphic position of described cores (Table 2.1; Appendix 1). Individual lithofacies are listed below, along with an interpretation of the depositional process and sedimentary environment.

Table 2.1 - Facies scheme for the Cherokee Group in the Cherokee basin.
Depositional Process
Sedimentary Environment
Coal to carbonaceous shale Peat growth Mire
Blocky mudstone Pedogenesis Paleosol
Pyritic shale Sediment fallout Coastal marsh-swamp
Interlaminated sandstone and siltstone Tidal currents and slack-water sediment fallout Marginal marine
Sideritic gray shale Sediment fallout and low-energy tidal currents Marginal marine
Laminated muddy sandstone Tidal currents and slack-water sediment fallout Muddy tidal flat
Bioclastic packstone to grainstone Reworking by waves or tides and bioturbation Marine, above fair-weather wave base
Bioclastic mudstone to wackestone Bioturbation Open marine, below fair-weather wave base
Dark gray shale Storm action and sediment fallout Offshore transition
Phosphatic black shale Sediment fallout Low oxygen shelf

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Last updated January 2004