Stratigraphy, Depositional Environments and Coalbed Methane Resources of Cherokee Group Coals (Middle Pennsylvanian)--Southeastern Kansas

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

2.2 Distribution and Vertical Relationships of Facies

The Cherokee Group is composed of numerous repetitive successions of interbedded gray to dark gray shale, rippled sandstone and siltstone, underclay, thin coal, and thin argillaceous limestone. The following table lists a typical succession starting with marine facies progressively transitioning to marginal marine to non-marine facies (Table 2.2).

Table 2.2 – Distribution and vertical relationships of facies
		Vertical Relationships
Lithofacies	Distribution	Underlying facies	Overlying facies
Phosphatic black shale	Entire basin & into adjacent states	Coal or blocky mudstone	Dark gray shale
Dark Gray shale	Across basin & throughout Cherokee Group	Phosphatic black shale	Interlam. Ss & Xs, lam. muddy shale, bio wackestone or pyrite sh
Bioclastic-mudstone to -wackestone	Observed in upper Higginsville, Black Jack Creek & Breezy Hill limestones	Phosphatic black shale	Bioclastic-packstone-to-grainstone
Bioclastic-packstone-to-grainstone	Observed in upper Higginsville, Black Jack Creek & Breezy Hill limestones	Bioclastic-mudstone-to-wackestone	Blocky mudstone or phosphatic black shale
Interlam. Ss and Xs	Observed as fill above incision surfaces and discontinuous	Phosphatic black shale or dark gray shale	Coal, sideritic gray sh or poorly developed blocky mudstone
Sideritic gray shale	Observed as fill above incision surfaces and discontinuous	Interlaminated Ss & Xs	Blocky mudstone or laminated muddy sandstone
Laminated Muddy Ss	Observed in middle and upper Cherokee Group	Dark gray shale	Poorly developed blocky mudstone or coal
Pyritic black shale	Observed in Krebs Fm and in upper Cherokee Group	Dark gray shale or sideritic shale	Blocky mudstone or coal
Blocky mudstone	Throughout basin and Cherokee Group	Pyritic black shale, cross-lam. muddy Ss, interlam. Ss & Xs, or bio-packstone-to-wackestone	Coal of phospatic black shale
Coal	Highly variable across basin & throughout Cherokee Group	Blocky mudstone	Dark gray shale or phospatic black shale

2.3 Coal Bearing Intervals of the Cherokee Group

Division of the Cherokee Group into ten intervals is based on regionally extensive marker beds, which serve to define mappable units. These marker beds are the black phosphatic shale lithofacies. Typically, the base of marker beds will be interpreted as flooding surfaces. The intervals also serve as a basis for identifying and mapping individual coals in the Cherokee Group. Coal thickness and distribution of individual coals can be related to the paleostructure reflected in the underlying units.

2.3.1 Mississippian Basement

In southeastern Kansas, Cherokee Group clastic rocks unconformably overly Mississippian limestones (Meremecian Stage; Merriam, 1963; Figure 2.13). The top of the Mississippian is characterized by a chert residue (Watney et al., 2001). Depth to the karstic Mississippian basement in the Cherokee basin ranges from 0 feet at outcrops in the extreme southeastern corner of Kansas, to more than 2500 feet (762 m) in Elk and Chautauqua counties, as the Mississippian and Cherokee Group rocks gradually dip to the west and southwest (Figure 2.14).

Figure 2.13 - Polished core section showing the unconformable contact between the Mississippian and Middle Pennsylvanian. The Cherokee Group shale overlies the karstic Mississippian Warsaw Limestone (Meremecian) and chert residium ("chat"). Sample from 1,081' in the Hinthorn CW#1 well, 14-T32S-R16E, Montgomery County, Kansas

Figure 2.14 - Structure map on top of the Mississippian limestone showing regional dip to the west (CI:100 ft). The surface is characterized by extensive karst features resulting in a highly irregular topography for deposition of the overlying Cherokee Group coal bearing intervals.

Figure 2.15a - Symbols for depositional sequences in figures 2.15, 2.17, 2.20, 2.22, 2.24, 2.28 and 2.30

e-mail : webadmin@kgs.ku.edu
Last updated December 2003
http://www.kgs.ku.edu/PRS/publication/2003/ofr2003-82/chapter202.html