Galatia Channel:Sullivan Channel

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Sullivan Channel

A large paleochannel that interrupts the Springfield Coal in Sullivan and Knox Counties, Indiana (Plate 1), is here named the Sullivan channel. Several previous authors have mapped portions of the Sullivan channel and described some of its effects. Wier and Powell (1967) mapped two elongate areas where the Springfield Coal is absent in Knox County. Eggert (1982, Figure 2) showed on a small-scale map “known contemporaneous channels” in Knox and Sullivan Counties, and suggested that they join the Galatia channel. Eggert and Adams (1985) discussed these features in more detail. Harper (1988) and Harper and Eggert (1995) presented further maps and information.

  • Figure 2 Correlation chart showing the positions of key units within the Pennsylvanian Subsystem. Global and provincial stage boundaries and ages in millions of years (Ma) are after Gradstein et al. (2012)[1].

Combining information from these sources with newly acquired coal company data, we present a more complete picture of the Sullivan channel (Plate 1). The Sullivan channel is a nearly straight to strongly sinuous belt about 0.6 to 1.6 mi (1 to 2.5 km) wide where clastic rocks occupy the position of the Springfield Coal. Drilling indicates a “precursor” valley, filled largely with sandstone and extending as deep as 213.3 ft (65 m) below the position of the Springfield. This channel truncates the Houchin Creek and Survant Coals, cutting within 16.4 ft (5 m) of the Colchester Coal. Channel filling generally fines upward, grading to siltstone or claystone at the level of the Springfield. These strata are basically identical to the Galatia Member as it occurs in the main Galatia channel.

Belts of interlaminated coal and carbonaceous shale, like those found along the Galatia channel, border the Sullivan channel. For example, at the eastern margin of the channel in the Oaktown Mine in Knox County, the Springfield Coal was thicker than 13.1 ft (4 m) but contained approximately 70% carbonaceous shale laminae (Figure 28). Fossil plant stems (Sigillaria) and foliage (Pecopteris, Neuropteris) were abundant in the shale layers. Shale content gradually diminished eastward, yielding coal with no clastic layers about 5.6 ft (1.7 m) thick at 0.6 mi (1 km) from the channel. The floor also changed from a massive siltstone having few roots and slickensides close to the channel to a well-developed claystone paleosol away from the channel. Shaly coal also occurs along the western margin of the Sullivan channel in the Carlisle Mine, about 9.3 mi (15 km) north of Oaktown in Sullivan County (Figure 29). As in the Oaktown Mine, shale laminae contain abundant fossil plants, including Calamites stems and broken leaves of Neuropteris and Macroneuropteris. In this same area, the floor of the Springfield consists of laminated shale that contains abundant fossil plants and can be lifted out in large sheets. Core drilling demonstrates that shaly coal borders both sides of the channel in Sullivan County.

  • Figure 28 Photograph of interlaminated carbonaceous shale and bright to dull coal close to the margin of the Sullivan channel in the Oaktown Mine in Knox County, Indiana.
  • Figure 29 Photograph of interlaminated carbonaceous shale and bright to dull coal close to the margin of the Sullivan channel in the Oaktown Mine in Knox County, Indiana.

Although details are sparse, previous authors (Kottlowski 1954; Wier 1954; Harper 1988; Harper and Eggert 1995) reported that numerous abandoned underground mines encountered areas of “dirty” or “shaly’ coal, along with lenses of shale or sandstone, near the margins of the Sullivan channel.

Several sizeable tracts of thick, low-sulfur (0.4 to 1%) coal flank the Sullivan channel. Most of the thickest coal, ranging from 6.6 to 10.8 ft (2.0 to 3.3 m) thick, occurs in steep-sided structural depressions. As usual, low-sulfur coal is overlain by thick gray shale, siltstone, and sandstone of the Dykersburg Member. The largest of these areas was the Glendora district in northern Sullivan County (Plate 1), where the coal lay in a structural basin about 29.5 ft (9 m) deep and was topped by up to 29.5 ft (9 m) of Dykersburg shale and sandstone (Kottlowski 1954; Wier 1954; Harper 1988). Nearly surrounded by thin, shaly coal, the Glendora district appears to lie between branches of the Sullivan channel. The active Carlisle and Oaktown Mines both contain steep-sided troughs where the coal thickens markedly and has a gray, siliciclastic roof. However, in most areas of these mines, the Turner Mine Shale lies directly on the coal.

Thus, the Sullivan channel shares all the attributes of the Galatia channel. The Sullivan is either a direct northward continuation of the Galatia or a major tributary.

Primary Source

Nelson, W.J., S.D. Elrick, W.A. DiMichele, and P.R. Ames, 2020, Evolution of a peat-contemporaneous channel: The Galatia channel, Middle Pennsylvanian, of the Illinois Basin: Illinois State Geological Survey, Circular 605, 85 p., 6 pls.


  1. Gradstein, F.M., J.G. Ogg, M.D. Schmitz, and G.M. Ogg, 2012, The geologic time scale 2012, 1st ed.: Amsterdam, Elsevier, 1,144 p.