Current Research--Brownfield et al.--page 4 of 9

Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 241, part 2
Distribution of the Bandera Shale of the Marmaton Group, Middle Pennsylvanian of Southeastern Kansas--page 4 of 9

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Sandstone Distribution

An isopach map was prepared of the interval between the Lake Neosho and the Anna Shale Members, including the Amoret Limestone Member and Pawnee Limestone as well as the Bandera Shale (fig. 6). Initially, this map was constructed manually; then the contours were traced into our computer (using Canvas^TM for Windows). The mapped interval, which is coeval to the Oologah Limestone of Oklahoma (see fig. 2), thickens to the southeast from less than 80 ft (24 m) in Coffey and Cowley counties to over 180 ft (54.9 m) in Montgomery County, Kansas. This distribution of sediments reflects variations in siliciclastic sediment accumulations, suggesting an easterly source for siliciclastic sediments. Configuration of contour lines in the southeastern portion of the isopach map area suggests sandstone bodies that are elongated in a southwest-northeast direction (fig. 6). Gamma-ray log characteristics from wells in this area indicate the presence of sandstones but lack the blocky well-log curve characteristics usually associated with channel-fill lithologies (e.g., eastern end of cross section B-B', fig. 5). The overall geometry of the Lake Neosho-Anna interval suggests that sediments accumulated in a generally podlike form (fig. 7).

Fig. 6. Lake Neosho-Anna Shale Members isopach map of study area. Thickest portion of the interval is in the southeast, and the interval thins northwestward. Dashed line represents western margin of Bandera outcrop belt. Contour interval = 20 ft (6.1 m).

Fig. 7. Sandstone isolith map of the Bandera Shale show concentrations of sandstone units in northeast-southwest orientation, with highest sandstone content in the southeastern portion of study area. Dashed line represents western margin of Bandera outcrop belt. Contour interval = 20 ft (6.1 m).

An isopach map of the Bandera Shale in the northern tier of Oklahoma counties, constructed by A. P. Bennison (personal communication, 1997), shows that the siliciclastic complex in southeastern Kansas thins southward and disappears as the Bandera gives way to the Oologah Limestone. This precludes the possibility of a southern source for siliciclastics. Post-Pennsylvanian erosion northeast of the study area prevents us from evaluating the possibility that siliciclastics were brought into the area from the northeast by southwest-flowing fluvial systems. A sandstone isolith map of the cumulative thicknesses of sandstone in the Bandera Shale (fig. 7), constructed in the same way as the isopach map, indicates that these sandstones were lenticular and elongate in a northeast-southwest direction. Cumulative thicknesses of sandstone range from 0 ft to 81 ft (0-24.7 m) and include at least 79 counted sandstone beds that were thick enough to be detected by gamma-ray logs. The presence of much thicker sandstone bodies in the southeastern portion of the study area also suggests an easterly source for the sand. As mentioned above, the presence of the Oologah carbonate-dominated platform in east-central Oklahoma during the time of Bandera deposition makes a southerly source for these sands unlikely (Krumme 1981, p. 45). It seems more likely that the Bandera sands entered southeastern Kansas from a more easterly source, perhaps even a northeasterly source.

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Kansas Geological Survey
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