Galatia Channel:Other Channels Related to the Galatia Channel: Difference between revisions
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[[Galatia Channel:Effingham Channel|Effingham Channel]]
==Leslie Cemetery Channel==
==Leslie Cemetery Channel==
Revision as of 14:02, 14 July 2020
Several paleochannels have been mapped that are similar to the Galatia channel in age and mode of formation. Previous authors have named some of these channels; others are named herein.
Leslie Cemetery Channel
Eggert (1978, 1982, 1984, 1994), Eggert and Adams (1985), and Willard et al. (1995) described a belt of “split” Springfield Coal in southwestern Indiana and called this feature the Leslie Cemetery channel (Figure 34). Further information comes from observations in active surface mines by ourselves and other ISGS geologists. A revised map of the channel (Figure 35) is based on newly available data from active mines and boreholes. In addition, a cross section (Plate 6 and Plate 6 Overview map) has been constructed using borehole data.
The Leslie Cemetery channel is slightly sinuous in map view and varies from about 0.9 to 3.7 mi (1.5 to 6 km) wide. It trends northwest from the outcrop in Warrick County into eastern Gibson County, where it intersects the Galatia channel. In sectional view (Plate 6 and Plate 6 Overview map), the Leslie is lens-shaped, reaching 65.6 ft (20 m) thick along its central axis. Unlike the Galatia channel, the Leslie Cemetery splits the Springfield Coal, with the upper “bench” of coal overriding the clastic rocks that fill the channel (Figure 36, Plate 6 and Plate 6 Overview map). The Turner Mine Shale and St. David Limestone directly overlie the upper coal bench.
The lower bench of the Springfield Coal is generally 2 to 3.9 ft (0.6 to 1.2 m) thick and lacks clastic layers. Ash and sulfur content are moderate to low. In terms of petrography and palynology, the lower bench is similar to Springfield Coal near the Galatia channel elsewhere (Willard et al. 1995). The lower bench dips into a trough below the channel (Figure 36) and is nearly continuous, except in a few places where the channel truncates the coal.
Filling the Leslie channel is a succession of gray mudstone, siltstone, and fine-grained sandstone that Eggert (1982) named the Folsomville Member. Near the margins of the channel, the Folsomville consists largely of nonfissile, slickensided claystone and thinly laminated, organic-rich carbonaceous shale. As the Folsomville thickens, it changes to layered gray mudstone and siltstone containing laminae and lenses of sandstone along with siderite nodules and concretions. Toward the axis of the Leslie Cemetery channel, sandstone becomes more prevalent and commonly shows cut-and-fill features. Cross-bedding is unidirectional and indicates paleocurrent toward the northwest; no indications of tidal sedimentation have been recognized (Willard et al. 1995). Fossil plants are locally abundant in the finer grained rocks, especially prone stems and logs of lycopsids and pteridosperm foliage, along with roots of lycopsids, pteridosperms, and calamites. A rooted “seat earth” commonly occurs below the upper coal bench (Willard et al. 1995). Eggert (1982) reported fossil tree stumps in growth position, and we observed several at the Cypress Creek Mine near the margin of the channel. These stumps were rooted in, or a short distance above, the lower coal bench. Spirorbid worm tubes, as reported by Willard et al. (1995), are the only invertebrates.
The upper bench of coal ranges from a few inches (centimeters) to 2.3 ft (0.7 m) thick and carries much higher ash and sulfur content than the lower bench. In places, the upper bench grades to carbonaceous shale or to thinly interlaminated coal and shale (Figure 36). In some places, the upper coal is continuous above the channel, but in other sites, it pinches out. The flora is dominated by lycopsids accompanied by calamites, pteridosperms, and tree ferns; but ground-cover plants are uncommon (Willard et al. 1995). Calcareous coal balls occurred in the upper bench at both the Lemmon Brothers and Lynnville Mines, on opposite margins of the channel (Willard et al. 1995; Phillips and DiMichele 1998). Conodonts were recovered from coal balls near the top of the upper bench in the Lynnville Mine.
Like the Galatia channel, the Leslie Cemetery channel overlies an older “precursor,” which Eggert (1984) named the Francisco channel. The well-log cross section (Plate 6 and Plate 6 Overview map) illustrates this relationship. Underlying the Springfield Coal, the Francisco channel truncates the Delafield Member and is filled with an upward-fining succession of sandstone, siltstone, and shale. Borehole data (Eggert 1982) indicate that underclay is at least locally absent below the lower coal bench, which rests directly on sandstone. The Francisco channel is less deeply incised than the Galatia channel; the Francisco does not cut out the Houchin Creek Coal. Evidently, the Francisco was a tributary to the Galatia channel.
The observations outlined above suggest the Leslie Cemetery channel developed by the following sequence of events (Figure 37). The Francisco channel was a northwest-flowing tributary of the Galatia precursor channel. Prior to the onset of peat formation, the Francisco channel was filled with clastic sediments and abandoned (Figure 37a). The channel course, however, remained as a trough through the peat swamp; the lower coal bench formed in this trough (Figure 37b). Partway through peat formation, flowing water reoccupied the trough, depositing clastic sediment in the Leslie Cemetery channel. The active channel migrated laterally, and plants grew in standing water along its margins. Peat and sediments compacted, making space for more sediment. During later stages of Springfield peat development, the channel again was largely abandoned, and peat accumulated above channel sediments (Figure 37c). Marine transgression finally terminated peat formation. Coal balls developed, and the Turner Mine and St. David Members were deposited above the Leslie Cemetery channel (Figure 37d).
Potter (1962, 1963) mapped other channel-form sandstone bodies below the Springfield Coal that do not correspond to interruptions in the coal. These include a series of branching, strongly meandering channels in southern Illinois, largely Franklin, Hamilton, Saline, and Gallatin Counties (Figure 8). Widths are in the range of 0.6 to 1.9 mi (1 to 3 km). Portions appear dendritic with tributaries, but the overall drainage direction is unclear. These likely represent more than one channel; one segment appears to cross the Galatia channel at nearly a right angle. More channels mapped by Potter are in Bond, Clinton, Washington, and Perry Counties of southwestern Illinois. These sinuous features branch and rejoin but do not exhibit (as mapped) an integrated drainage. We have not investigated these channels and will offer no further comments.
Friedman (1956, 1960) mapped an area near Terre Haute, Indiana, where the Springfield Coal is split and partly replaced by sandstone and shale. He called this feature the Terre Haute channel. Friedman’s map (Figure 38) shows a southwest-trending channel about 1,312.3 ft (400 m) wide, with several short branches joining from the southeast. In one area, the coal divides into a continuous lower bench and an upper bench that thins and pinches out toward the channel axis. In another area, shale layers occur in the coal along a linear trend, although the coal is not cut out. Sandstone is largely confined to the main channel. Maximum clastic thickness is about 39.4 ft (12 m). Harper (1985, p. 19–20) discussed the Terre Haute channel in relation to the Dresser underground coal mine but did not shed further light on the nature of the disturbance. Friedman inferred a dendritic fluvial system that was active during later stages of peat formation. The Terre Haute channel may be similar to the Leslie Cemetery channel, but not enough data are at hand to offer a theory of its origin.
W. John Nelson, Scott D. Elrick, William A. DiMichele, and Philip R. Ames xxxx, Evolution of a Peat-Contemporaneous Channel: The Galatia Channel, Middle Pennsylvanian, of the Illinois Basin FINISH CITATION