Galatia Channel:Baker Coal and Winslow-Henderson Channel: Difference between revisions

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Revision as of 15:03, 14 July 2020

Baker Coal and Winslow-Henderson Channel

The Baker Coal constitutes an important economic seam in the southeastern part of the Illinois Basin. The following is a summary of information we have assembled from mine and borehole data. A longer report on the Baker Coal is in preparation.

Glenn (1912) named the Baker Coal for the Baker Mine in Webster County, Kentucky. Kosanke et al. (1960) gave the name Allenby Coal Member to a thin seam in southeastern Illinois. In southern Indiana, geologists used the informal name Lower Millersburg coal. Our subsurface cross sections (unpublished) demonstrate that the Baker, Allenby, and Lower Millersburg coals are the same bed. Because Baker was the first name to be used formally, we are using Baker Coal in this report.

Thick Baker Coal is largely restricted to narrow belts along a paleochannel that was partly contemporaneous with peat formation (Figure 44). Friedman (1960) mapped this paleochannel in Pike County, Indiana, and named it the Winslow channel. Eggert (1985, 1994) extended the Winslow channel farther south in the subsurface. Beard and Williamson (1979) mapped a paleochannel in Henderson and Webster Counties, Kentucky, and called it the Henderson channel. Because the Winslow and Henderson channels align directly at the state border, we recognize them as the same feature and use the compound name Winslow–Henderson channel.

  • Figure 44 Map showing the Winslow–Henderson channel.
  • Figure 45 Interpretive cross section of the Winslow-Henderson channel. BR, Brereton Limestone; HR, Herrin Coal; BH/BT, Briar Hill/Bucktown Coal; SD/AC, St. David/Alum Cave Limestone; TM, Turner Mine Shale.

Like the Galatia channel, the Winslow–Henderson comprises a broad, deeply incised valley that was filled largely with sand prior to peat development and a younger, narrower segment that was filled with finer grained sediments during the time of Baker peat formation (Figure 45). Borehole data and exposures in surface mines show that the channel cut downward from above the Bankston Fork (upper Providence) Limestone, a short distance beneath the Baker Coal. The channel carved a valley 1.9 to 8.1 mi (3 to 13 km) wide and as deep as 196.9 ft (60 m), removing units as old as the Springfield Coal. Sandstone of the lower valley-fill displays large-scale lateral accretion on mine highwalls, signifying a meandering system. Sandstone grades upward to finer grained, heterolithic strata that bear tidal rhythmites. Approaching the Winslow–Henderson channel, the Baker Coal thickens to 9.8 ft (3 m) or more, and it has multiple laminae and thin interbeds of carbonaceous claystone. The Baker is absent or reduced to stringers within a meandering belt that varies from about 0.9 to 3.1 mi (1.5 to 5 km) wide.

The principal difference between the Springfield and the Baker is that the latter lacks marine roof strata and has no gray shale wedge analogous to the Dykersburg. Covering the Baker is a succession of fluvial and floodplain deposits, including mudstone, thin lenticular sandstone, thin coal, and paleosols. Lenses of gray shale a few feet (meters) thick bear fossil plants, including upright tree stumps. Brackish to marine strata did not appear until after the next younger major peat deposit, the Danville Coal. These observations suggest that (1) preserved Baker Coal developed farther up the coastal plain than did preserved Springfield Coal, or (2) the sea level did not rise much following Baker peat accumulation.

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.