Pleasantview Sandstone Member
Nelson, W.J., 2020, Pennsylvanian Subsystem in Illinois: Illinois State Geological Survey Bulletin (in press).
Edited and figures drafted by Jennifer M. Obrad.
Searight (1925–1927) first described the Pleasantview Sandstone in its type area, but his manuscript was never published. Citing Searight, Wanless (1929) applied (in passing) the name Pleasantview to sandstone cropping out in Mercer County, Illinois. Credit for the first full description belongs to Ekblaw (1931).
Now called Pleasant View, the community is in northeastern Schuyler County, Illinois, about midway between Beardstown and Rushville.
The section consists of outcrops along Mill Creek just east of Pleasant View in sec. 31, T 2 N, R 1 E and sec. 36, T 2 N, R 1 W, Schuyler County, on the Beardstown 7.5' quadrangle.
Ekblaw (1931, p. 395) located the type section and illustrated the style of bedding; Wanless (1957, geologic section 5, p. 190–191) published a complete description.
These outcrops have been partly removed and covered by strip mining for coal.
No reference section is proposed at this time.
The name Pleasantview has been applied to sheet- and channel-phase sandstone overlying the Purington Shale and underlying the Houchin Creek Coal in western Illinois. The relationship of the Pleasantview to the Survant Coal Member (Wheeler and Bevier Coal Beds) has not been addressed because these coals are generally not developed in the area where the Pleasantview crops out.
In this report, the Wheeler and Bevier Coals are recognized to rise in the section on the Western Shelf and pinch out into the underclay of the Houchin Creek Coal, above the Pleasantview. In addition, the Cardiff, Kerton Creek, and Roodhouse Coals are Survant equivalents that developed in abandoned channels at the top of the Pleasantview Sandstone. On this basis, the Pleasantview is older than at least part of the Survant Coal. The critical question is whether the Pleasantview is older than the Wheeler Coal (lower Survant) or younger than the Wheeler but older than the Bevier (upper Survant). Although evidence is not conclusive, it favors the latter option. Extensive well-log analysis and construction of (unpublished) regional cross sections in the deeper part of the Illinois Basin reveal no channels or incised valley deposits older than the Wheeler Coal and younger than the Colchester Coal. The weakly developed underclay beneath the Wheeler Coal suggests a regression too brief to form a thick paleosol and incised valley system. However, incised valleys cutting down from near the base of the Bevier Coal occur in southeastern Illinois and in Gibson County, Indiana (Eggert 1994).
In summary, the Pleasantview Sandstone probably fills channels that were eroded contemporaneous with development of the paleosol (underclay) that underlies the Bevier Coal. The “Pleasantview Sandstone” of south-central Iowa, as discussed by Laury (1968), overlies the Bevier Coal and therefore is younger than the Pleasantview of Illinois.
Extent and thickness
In sheet facies, the Pleasantview ranges up to about 20 ft (6 m) but commonly is less than 10 ft (3 m). The channel facies attains a thickness of 80 ft (24 m) and may reach 100 ft (30 m) (Rusnak 1957; Wanless 1957; Laury 1968). Previously known occurrences of the Pleasantview are in western Illinois, mainly west of the Illinois River (Wanless 1929, 1957; Ekblaw 1931).
Weiner (1961) mapped lithofacies of what he considered Pleasantview Sandstone throughout the Illinois Basin. However, Weiner interpreted the Pleasantview to be younger than the Survant Coal, so his map actually depicts sandstone within the Lagonda Member. My own regional cross sections show a channel phase of the Pleasantview in Edwards and Wabash Counties, southeastern Illinois. The channel cuts down from just below the Bevier Coal, truncating the Wheeler and nearly reaching the Colchester. A channel that Eggert (1994, figures 6 and 10, plate 1) mapped in Gibson County, Indiana, is likely related to the one in Illinois. The channel in Indiana is 1 to 6 mi (~2 to 10 km) wide and forms a large south-bending loop.
In channel facies, the Pleasantview Sandstone is largely fine grained and very micaceous. Conglomeratic sandstone near the base contains pebbles to small cobbles of siderite, shale, limestone, and other sedimentary rocks along with fossil logs. Large-scale cross-bedding in the lower part gives way upward to smaller-scale structures, and the content of shale and siltstone increases. The upper part is largely siltstone and silty shale, which may be capped by coal. Wanless (1957) and Rusnak (1957) noted a wide divergence of cross-bed orientations.
Ekblaw (1931) mapped portions of two channels that trend in a southward direction across western Illinois. One channel averages approximately 1.5 mi (2.5 km) wide, whereas another may be more than 10 mi (16 km) across (Wanless 1957). Lateral margins are sharply eroded and, in places, dip steeper than 30 degrees. Although not mapped with great accuracy, channel margins appear to be gently arcuate in map view. Tributary “barbs” point north, whereas the depth and width of incision increase to the south, suggesting the paleocurrent flowed toward the south.
In nonchannel facies, the sandstone is mostly very fine grained and exhibits planar, ripple, and cross lamination. It is commonly calcareous and contains large, flattened concretions. The sandstone grades upward and laterally to siltstone and sandy shale, and locally contains fossil plants (Wanless 1957).
The “sheet” facies generally has a gradational lower contact to shale and a sharp but conformable contact to overlying coal. The channel facies has a sharply erosive lower contact, dipping steeper than 45 degrees in places along the channel margins. The upper contact may be gradational to overlying shale or mudstone or sharp to overlying coal.
Well log characteristics
In southeastern Illinois and Gibson County, Indiana, the channel phase of the Pleasantview has a “Christmas tree” profile on electric logs, indicating an upward decrease in grain size.
Fossil plant material is plentiful but largely fragmentary. Wanless (1957, p. 95) reported, “The lower 2 or 3 ft [60 or 90 cm] has a concentration of stem impressions of Cordaites, Lepidodendron, Sigillaria, Calamites, and other plants.” The same author (p. 98) noted “well-preserved plant leaves” in the upper part of the member at one locality. As in most Pennsylvanian sandstone units, animal remains are rare. Laury (1968, p. 576) remarked that teeth and dermal tubercles of sharks occur in the channel phase but may be reworked from older units.
Age and correlation
Environments of deposition
Ekblaw (1931) and Wanless (1957) did not address the origin of the sandstone and its channels. Ekblaw mentioned “drainage patterns” and inferred that paleocurrents flowed toward the south because channels are incised more deeply in that direction. These authors probably envisioned fluvial channels. Rusnak (1957) suggested tidal channels on a shallow marine shelf similar to the modern Dutch Wadden Sea. Rusnak interpreted paleocurrents toward the north (flood tide?) based on cross-bedding and microscopic grain orientation.
In counterpoint, Pleasantview channels may be incised valleys that developed during marine lowstand and were filled predominantly by meandering fluvial processes. Widely divergent cross-bedding orientations are consistent with point-bar deposition, and the valleys are wide enough to allow lateral channel migration. During late stages of valley filling, peat accumulated in some of the abandoned meanders.
- Eggert, D.L., 1994, Coal resources of Gibson County, Indiana: Indiana Geological Survey, Special Report 50, 36 p. and 1 pl.
- Ekblaw, S.E., 1931, Channel deposits of the Pleasantview Sandstone in western Illinois: Illinois State Academy of Science Transactions, v. 23, p. 391–399.
- Laury, R.L., 1968, Sedimentology of the Pleasantview Sandstone, southern Iowa and western Illinois: Journal of Sedimentary Petrology, v. 38, no. 2, p. 568–599.
- Rusnak, G.A., 1957, A fabric and petrologic study of the Pleasantview Sandstone: Journal of Sedimentary Petrology, v. 27, no. 1, p. 41–55; see also Discussion by J.E. Sanders, v. 27, no. 2, p. 198–201, and G.A. Rusnak, v. 27, no. 3, p. 346–350.
- Searight, W.V., 1925–1927, Geology and mineral resources of Beardstown Quadrangle: Illinois State Geological Survey, unpublished manuscript, 282 p. plus illustrations.
- Wanless, H.R., 1929, Geology and mineral resources of the Alexis Quadrangle: Illinois State Geological Survey, Bulletin 57, 230 p., 4 pls.
- Wanless, H.R., 1957, Geology and mineral resources of the Beardstown, Glasford, Havana, and Vermont Quadrangles: Illinois State Geological Survey, Bulletin 82, 233 p.
- Weiner, J.L., 1961, Environmental study of stages within the Summum cyclothem of Illinois: Urbana, University of Illinois, M.S. thesis, 31 p.
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