Nelson, W.J., 2020, Pennsylvanian Subsystem in Illinois: Illinois State Geological Survey Bulletin (in press).
Edited and figures drafted by Jennifer M. Obrad.
Hopkins (1968) mapped a paleochannel that disrupts the Springfield Coal in southeastern Illinois and inferred that the channel partly coexisted with peat formation. Hopkins et al. (1979, p. 148) named this feature the Galatia channel. In an unpublished thesis, Ledvina (1988, p. 641) used the name “Galatia Sandstone Member” for “coarse channel fill and the coarse facies overlying shales and siltstones over the Springfield (No. 5) Coal.”
The name Galatia Member was proposed by Nelson et al. (2020) for the strata that fill the Galatia channel and associated paleochannels that either underlie or intergrade laterally with the Springfield Coal, or both. The name does not include a lithic term because the Galatia Member includes diverse rock types. Although Ledvina (1988) treated the Galatia Sandstone as a coarse facies of the Dykersburg Shale, the Dykersburg is here regarded as a separate entity, distinctly younger than the Springfield Coal and the Galatia Member.
The name is derived from a town that overlies the channel in northwestern Saline County, Illinois. As Callary (2009, p. 130–131) writes, the community was in Gallatin County when it was founded in 1836: “The name was apparently to have been Gallatin, named for Gallatin County, but the final n was either smeared or mistaken for an a by a postal agent or county official. The word Gallatia was then changed to Galatia by someone familiar with the biblical references to Galatia, the [ancient] country in Asia Minor [now part of central Turkey].”
Eggert (1982, p. 7–9) proposed the name Folsomville Member for “the sequence of interrelated lithologies of rash [impure coal], gray shale, siltstone, and sandstone that extensively split the Springfield Coal Member.” Eggert restricted the Folsomville Member to deposits of the Leslie Cemetery paleochannel in Pike and Warrick Counties, Indiana, and did not name deposits of the larger Galatia channel to which the Leslie Cemetery is a tributary. In this report, the Folsomville Member remains restricted as Eggert defined it.
Core from Kerr-McGee Corp. borehole #7629-16 constitutes the type section of the Galatia Member. The hole was drilled about 4 mi (6.5 km) northeast of Galatia in Section 29, T7S, R6E, Saline County (ISGS county no. 26537). W.J. Nelson described the core, and a gamma-ray–neutron log is on file. In the core, the Galatia Member lies in the depth interval of 745.4 to 786.0 ft and is 40.6 ft (12.4 m) thick (Figure 4-54).
Nelson et al. (2020).
Logs of Kerr-McGee #7629-16, including the core description and the gamma-ray–neutron log, are on file at ISGS Geological Records Unit and are available via the ISGS website. Core is archived at the ISGS Geological Samples Library in Champaign (storage number C-14933).
The Galatia Member fills channels that cut downward from near the top of the Delafield Member, truncating the Delafield and older units. The Galatia Member is distinct from the fine-grained sandstone that occurs in the upper part of the Delafield and caps an upward-coarsening sequence. The upper part of the Galatia intertongues with and laterally replaces the Springfield Coal through a zone several hundred yards (meters) wide. Overlying the Galatia is the Dykersburg Member, which resembles the Galatia in lithology. However, cores and exposures in underground mines reveal a sharp, commonly erosive contact between the Dykersburg and Galatia Members. In small areas, the Turner Mine Shale directly overlies the Galatia.
Channels filled with the Galatia Member are of distinctly different ages. Some were abandoned and filled before the Springfield peat began to develop. The main Galatia channel is younger and persisted during Springfield peat formation. The Leslie Cemetery channel in Indiana coexisted with peat formation, but it follows the course of an older, abandoned channel. The Terre Haute channel of Friedman (1956) appears to be similar to the Galatia channel but is not known to connect.
Extent and thickness
“Maps by Potter (1962, 1963), published before the Galatia channel was recognized, portray the thickness of sandstone between the Springfield and Houchin Creek Coals. The sandstone that Potter mapped is largely the Galatia Member of this report. Potter’s 1962 map covers southeastern Illinois at a scale of about 1:250,000, whereas his 1963 map includes parts of Indiana and Kentucky at a smaller scale. An independently prepared map by Wanless et al. (1970, figure 6) shows a closely similar pattern of sandstone distribution. In addition, Hopkins (1968, plate 2) published two cross sections of the Galatia channel” (Nelson et al. 2020). The cross section presented here (Figure 4-55) shows the same relationships.
“Maps portray elongate bodies of sandstone having looping, arcuate boundaries and forming a dendritic pattern. Cross sections illustrate broad sand-filled channels or valleys that were eroded from near the top of the Delafield Member. These valleys have steep sides and broad, nearly flat bottoms” (Nelson et al. 2020) that rest upon or just above the Excello Shale and Houchin Creek Coal. Evidently, black shale and coal (peat) were more resistant to erosion than the Delafield Member. Locally, the Galatia channel truncates the Houchin Creek, and it may cut out the Survant Coal. The overall pattern evokes a series of actively meandering, laterally migrating fluvial channels that operated during the time of underclay (paleosol) development.
The thickness of the Galatia Member is commonly 65 to 100 ft (20 to 30 m), thinning rapidly to zero along channel margins.
“The Galatia Member is an upward-fining succession, commonly 65 to 100 ft (20 to 30 m) thick. The lower part is dominantly sandstone. As seen in cores, the sandstone is very fine to fine grained, locally medium grained, overall fining upward. Cross-bedding in the lower part gives way upward to rippled, wavy, and contorted or slumped laminations. Layers of shale–pebble conglomerate occur in the lower part. Also present are siderite pebbles and fragments and stringers of coal. Upper channel filling consists of laminated to massive siltstone and silty shale or mudstone containing carbonaceous flakes and scattered plant fragments. Several cores showed rhythmic lamination, with probable neap–spring tidal cycles, near the top of the member. The uppermost part of the Galatia Member, lateral to the Springfield Coal, is largely dark, carbonaceous shale and claystone containing numerous ragged layers and stringers of coal.” (Nelson et al. 2020).
“The lower contact is erosive, cutting into the Delafield Member and locally into older units, including the Houchin Creek Coal. This erosive basal contact is readily apparent in cores and in most geophysical logs. The upper contact with the Dykersburg Shale is at least locally erosive, as shown by drill cores and underground exposures in the now-abandoned Galatia Mine. Because upper Galatia and Dykersburg Members contain similar rock types, this contact can be difficult to pick in well logs. Lacking lithologic evidence, the contact may be mapped at the elevation of the top of the coal adjacent to the channel.” (Nelson et al. 2020).
Well log characteristics
Generally typical for sandstone, showing an upward-fining profile.
Fragmentary fossil plants are common.
Age and correlation
The age is slightly older than and partly contemporaneous with the Springfield Coal.
Environments of deposition
“Maps and sections portray a series of actively meandering, laterally migrating fluvial channels. Superimposed onto Potter’s  map of sandstone thickness, the Galatia channel of Hopkins (1968) coincides with a large, southwest-trending sandstone meander belt. Therefore, this meander belt appears to have been a direct precursor to the Galatia channel that flowed through the Springfield peat swamp. The Galatia precursor channel is the work of a river that flowed across the emerging coastal plain prior to peat accumulation. Eroding soft sediments on a low gradient, this river freely meandered and carried a large sediment load, derived partly from upland sources and partly from recycling its own banks and bed. A broad, sandy meander belt was rapidly established. Through time, the valley aggraded and stream energy declined, reducing the sediment load. Tidal influence became evident in the late stage of channel filling.” (Nelson et al. 2020).
The Galatia channel is economically significant in an indirect fashion because it controlled the distribution, thickness, and quality of the Springfield Coal.
- Callary, E., 2009, Place names of Illinois: Urbana, University of Illinois Press, 425 p.
- Eggert, D.L., 1982, A fluvial channel contemporaneous with deposition of the Springfield Coal Member (V), Petersburg Formation, northern Warrick County, Indiana: Indiana Geological Survey, Special Report 28, 20 p.
- Friedman, S.A., 1956, Split and channel sandstone cutout in Coal V in the Dresser area, Vigo County, Indiana: Proceedings of the Indiana Academy of Science for 1955, v. 65, p. 165–168.
- Hopkins, M.E., 1968, Harrisburg (No. 5) Coal reserves of southeastern Illinois: Illinois State Geological Survey, Circular 431, 25 p., 2 pls.
- Hopkins, M.E., R.B. Nance, and C.G. Treworgy, 1979, Mining geology of Illinois coal deposits, in J.E. Palmer and R.R. Dutcher, eds., Depositional and structural history of the Pennsylvanian System in the Illinois Basin, Part 2, Invited papers: Ninth International Congress of Carboniferous Stratigraphy and Geology, Field Trip 9: Illinois State Geological Survey, Guidebook 15A, p. 142–151.
- Ledvina, C.T., 1988, The mining geology of the Herrin (No. 6) and Springfield (No. 5) Coals in Illinois—Discrete features: Chicago, Northeastern Illinois University, M.S. thesis, 670 p.
- 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.
- Potter, P.E., 1962, Shape and distribution patterns of Pennsylvanian sand bodies in Illinois: Illinois State Geological Survey, Circular 339, 36 p., 3 pls.
- Potter, P.E., 1963, Late Paleozoic sandstones of the Illinois Basin: Illinois State Geological Survey, Report of Investigations 217, 92 p., 1 pl.
- Wanless, H.R., J.R. Baroffio, J.C. Gamble, J.C. Horne, D.R. Orlopp, A. Rocha-Campos, J.E. Souter, P.C. Trescott, R.S. Vail, and C.R. Wright, 1970, Late Paleozoic deltas in the central and eastern United States, in J.P. Morgan and R.H. Shaver, eds., Deltaic sedimentation, modern and ancient: Society of Economic Paleontologists and Mineralogists, Special Publication 15, p. 215–245, https://doi.org/10.2110/pec.70.11.
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