Nelson, W.J., 2020, Pennsylvanian Subsystem in Illinois: Illinois State Geological Survey Bulletin (in press).
Edited and figures drafted by Jennifer M. Obrad.
Lamar (1925, p. 84–85) introduced the name “Wayside sandstone and shale member” for the lowest part of the Pottsville Formation.
In 1886, the Oakville Post Office was established in a general store in northeastern Union County, Illinois. The community boasted a church, mill, doctor’s office, blacksmith shop, and two stores. For reasons unknown, the name was changed to Wayside in 1906. The post office closed in 1917; today, Wayside is reduced to a small cluster of houses (Sneed 1977).
Lusk Shale Member (now abandoned).
Wanless (1939) called the unit Wayside Formation. Weller (1940) omitted the Wayside in favor of Lusk Formation. Wanless (1956) inconsistently used Wayside sandstone or Wayside marine zone in the Lusk formation or cyclothem, Caseyville Group. Kosanke et al. (1960) recognized the Wayside Sandstone and Lusk Shale Members as lateral equivalents. Recognizing that this portion of the Caseyville contains diverse rock types, Nelson et al. (1991, p. 18) shortened the name to Wayside Member and abandoned the Lusk Member.
Lamar (1925) did not designate a stratotype. Wanless (1956) listed, but did not describe, exposures in Secs. 30 and 31, T11S, R2E in Union County, Illinois.
A highway cut on Interstate 57 (SE¼ SW¼, Sec. 24 and NW¼ NW¼, Sec. 25, T11S, R1E, Union County, Illinois) is the principal reference section. This is the lower part of Caseyville Formation reference section 3 (Figure 2-2, column 4).
Nelson and Weibel (1996, p. 19) presented this section graphically. Additional descriptions are in Ethridge et al. (1973) and Palmer and Dutcher (1979).
The highway cut is still in good condition, although the base of the Wayside never was exposed.
By definition, the Wayside Member comprises all Pennsylvanian strata underlying the Battery Rock Sandstone Member. Where the Battery Rock is absent or not identified, the Wayside cannot be distinguished.
Extent and thickness
The Wayside Member is largely confined to paleovalleys on the sub-Pennsylvanian surface along the southern belt of Caseyville outcrops, although the member overlaps interfluves in the deepest part of the basin. Thickness varies from zero to more than 150 ft (45 m) within short distances. In deep valleys where the Wayside is thick, several cycles of deposition are evident. The Wayside has not been traced more than a few miles (kilometers) north of the outcrop in the subsurface.
The Wayside contains highly variable proportions of shale, siltstone, and sandstone along with minor conglomerate, nonfissile mudstone, and coal. As seen in the reference section, thinly interlayered sandstone and shale make up much of the member. Ripple marks, tool marks, load casts, and small-scale soft-sediment deformation are prevalent. The Wayside locally contains thick-bedded to massive, cliff-forming sandstone bodies as thick as 80 ft (24 m). Although such sandstone is commonly fine grained, quartz pebbles can be abundant, inviting confusion with the Battery Rock Sandstone (Weibel et al. 1993; Nelson and Weibel 1996). Coal is thin and lenticular.
The lower contact is the sub-Pennsylvanian unconformity. The upper contact is the base of the Battery Rock Sandstone, which is commonly erosive, with both active and passive fill.
Well log characteristics
Reflecting diverse lithology, the well log response is highly variable.
Conodonts and other marine fossils occur locally in the Wayside (Rexroad and Merrill 1985; Jennings and Fraunfelter 1986; Weibel and Norby 1992). Logs and other transported plant remains are common in sandstones. Trace fossils are present but have not been described systematically.
Age and correlation
Without great precision, the Wayside Member may be assigned to the early and middle Morrowan Stage and to Namurian C and early Westphalian A (Langsettian) Stages of western Europe (Peppers 1996). The Wayside is equivalent to part of the Breathitt Group older than the Bee Rock Sandstone in eastern Kentucky and to correlative portions of the New River Formation in West Virginia. Morrowan strata are significantly thicker and contain more distinct sandstone units in the Appalachian Basin. They may also contain Pennsylvanian strata older than any preserved in the Illinois Basin (Greb et al. 2002).
Environments of deposition
A variety of fluvial and marginal marine environments are represented. Where confined to paleovalleys, the Wayside represents both fluvial and estuarine settings.
Coal is present but is too thin to mine. Laminated sandstone has been quarried on a small scale for use as flagstone. Valley-bound sandstone lenses in the basal Wayside serve as reservoirs for oil.
- Ethridge, F.G., G. Fraunfelter, and J. Utgaard, eds., 1973, Depositional environments of selected Lower Pennsylvanian and Upper Mississippian sequences of southern Illinois: 37th Annual Tri-State Field Conference: Carbondale, Southern Illinois University, 158 p.
- Greb, S.F., C.F. Eble, and D.R. Chesnut, Jr., 2002, Comparison of the Eastern and Western Kentucky coal fields, U.S.A—Why are coal distribution patterns and sulfur contents so different in these coal fields? International Journal of Coal Geology, v. 50, p. 89–118.
- Jennings, J.R., and G.H. Fraunfelter, 1986, Preliminary report on micropaleontology of strata above and below the upper boundary of the type Mississippian: Transactions of the Illinois State Academy of Science, v. 79, p. 253–261.
- Kosanke, R.M., J.A. Simon, H.R. Wanless, and H.B. Willman, 1960, Classification of the Pennsylvanian strata of Illinois: Illinois State Geological Survey, Report of Investigations 214, 84 p., 1 pl.
- Lamar, J.E., 1925, Geology and mineral resources of the Carbondale Quadrangle: Illinois State Geological Survey, Bulletin 48, 173 p., 3 pls.
- Nelson, W.J., J.A. Devera, R.J. Jacobson, D.K. Lumm, R.A. Peppers, B. Trask, C.P. Weibel, L.R. Follmer, M.H. Riggs, S.P. Esling, E.D. Henderson, and M.S. Lannon, 1991, Geology of the Eddyville, Stonefort, and Creal Springs Quadrangles, southern Illinois: Illinois State Geological Survey, Bulletin 96, 85 p., 1 pl.
- Nelson, W.J., and C.P. Weibel, 1996, Geology of the Lick Creek Quadrangle, Johnson, Union, and Williamson Counties, southern Illinois: Illinois State Geological Survey, Bulletin 103, 39 p., 1 pl.
- Palmer, J.E., and R.R. Dutcher, eds., 1979, Depositional and structural history of the Pennsylvanian System in the Illinois Basin, Part 1: Road log and descriptions of stops: Illinois State Geological Survey, Field Trip 9/Ninth International Congress of Carboniferous Stratigraphy and Geology, Guidebook 15, 116 p.
- Peppers, R.A., 1996, Palynological correlation of major Pennsylvanian (Middle and Upper Carboniferous) chronostratigraphic boundaries in the Illinois and other coal basins: Geological Society of America, Memoir 188, 111 p., correlation chart.
- Rexroad, C.B., and G.K. Merrill, 1985, Conodont biostratigraphy and paleoecology of Middle Carboniferous rocks in southern Illinois: Frankfurt-am-Main, Germany, Courier Forschunginstitut Senckenberg, v. 74, p. 35–64.
- Sneed, G.J., 1977, Ghost towns of southern Illinois: Royalton, Illinois, G.J. Sneed, 309 p.
- Wanless, H.R., 1939, Pennsylvanian correlations in the Eastern Interior and Appalachian coal fields: Geological Society of America, Special Paper 17, 130 p., 9 pls.
- Wanless, H.R., 1956, Classification of the Pennsylvanian rocks of Illinois as of 1956: Illinois State Geological Survey, Circular 217, 14 p.
- Weibel, C.P., W.J. Nelson, L.B. Oliver, and S.P. Esling, 1993, Geology of the Waltersburg Quadrangle, Pope County, Illinois: Illinois State Geological Survey, Bulletin 98, 41 p.
- Weibel, C.P., and R.D. Norby, 1992, Paleopedology and conodont biostratigraphy of the Mississippian-Pennsylvanian boundary interval, type Grove Church Shale area, southern Illinois: Oklahoma Geological Survey, Circular 94, p. 39–53.
- Weller, J.M., 1940, Geology and oil possibilities of extreme southern Illinois: Illinois State Geological Survey, Report of Investigations 71, 71 p.
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