H. B. Willman and John C. Frye
The Richland Loess is named for Richland Creek, Woodford County (Frye and Willman, 1960).
This loess formerly was identified by age and called Tazewell Loess (Leighton, 1933).
The type section is a roadcut north of the creek, NW SE SW Sec. 11, T. 28 N., R. 3 W., which exposes 6 feet of Richland Loess.
The lower 4 feet is calcareous and fossiliferous and overlies 2 feet of sand and gravel (Henry Formation) and 3 feet of calcareous, pink sandy till (Tiskilwa Till Member of Wedron Formation). It rests on till of the Wedron Formation, and beyond the limit of Woodfordian glaciation (the Wedron Formation) it is equivalent to the upper part of the Peoria Loess.
Spatial relations are shown diagrammatically in figures 8 and 14.
Extent and thickness
It has a maximum thickness of 20 feet locally in the Illinois Valley bluffs in Woodford County northeast of Peoria. The thickness of the Richland Loess is shown on plate 3, where all the loess shown within the Woodfordian boundary is Richland. Where it is more than 6 to 8 feet thick in the southern part of the area and where it is more than 4 to 6 feet thick in the northern part, it is calcareous below the soil. The calcareous loess locally contains fossil snail shells (Leonard and Frye, 1960).
The unit consists of yellow-tan massive loess and contains the Modern Soil in the top. The Richland Loess has been described by Willman and Payne (1942); Leonard and Frye (1960); Wascher et al. (1960); Frye, Glass, and Willman (1962, 1968); and Glass, Frye, and Willman (1968). In this report, the Richland Loess is described in the Farm Creek, Maiden South, and Wedron Sections (table 6). Representative previously published sections include the Buda East, Partridge Creek, Sturdyvin School, Ten-Mile School, Varna South, and Walnut Southeast Sections (table 7). Mineral composition has been reported by Frye, Glass, and Willman (1962, 1968) and in table 5.
|Table 6 -- Stratigraphic Sections (partial)|
The following 21 stratigraphic sections describe exposures in Illinois and illustrate many of the aspects of Pleistocene stratigraphy. These sections contain the type localities for 21 rock-stratigraphic units, 4 soil-stratigraphic units, and 3 time-stratigraphic units and include paratypes for several other units. The sample numbers preceded by "P" are the numbers used in the Illinois State Geological Survey collections. Analytical data on many of these samples are on file at the Survey. The sections are arrange alphabetically by name.
Age and correlation
The Richland ranges from middle to latest Woodfordian, and it may locally contain some deposits of Valderan age. The basal contact of the loess is strongly time transgressing. When traced from the central Illinois River Valley toward the northeast, it rests on progressively younger tills of the Wedron Formation. Wherever the base of the loess is calcareous, the top of the underlying till is also calcareous, indicating that the loess began to accumulate as soon as the ice melted.
FRYE, J. C, H. D. GLASS, and H. B. WILLMAN, 1962, Stratigraphy and mineralogy of the Wisconsinan loesses of Illinois: Illinois State Geological Survey Circular 334, 55 p.
FRYE, J. C, H. D. GLASS, and H. B. WILLMAN, 1968, Mineral zonation of Woodfordian loesses of Illinois: Illinois State Geological Survey Circular 427, 44 p.
FRYE, J. C., and H. B. WILLMAN, 1960, Classification of the Wisconsinan Stage in the Lake Michigan Glacial Lobe: Illinois State Geological Survey Circular 285, 16 p.
GLASS, H. D., J. C. FRYE, and H. B. WILLMAN, 1968, Clay mineral composition, a source indicator of Midwest loess, in The Quaternary of Illinois: University of Illinois College of Agrculture [Urbana] Special Publication 14, p. 35-40.
LEIGHTON, M. M., 1933, The naming of the subdivisions of the Wisconsin glacial age: Science, v. 77, no. 1989, p. 168.
LEONARD, A. B., and J. C. FRYE, 1960, Wisconsinan molluscan faunas of the Illinois Valley region: Illinois State Geological Survey Circular 304, 32 p.
WASCHER, H. L. (et al.), J. D. ALEXANDER, B. W. RAY, A. H. BEAVERS, and R. T. ODELL, 1960, Characteristics of soils associated with glacial tills in northeastern Illinois: University of Illinois [Urbana] Agricultural Experiment Station, 155 p.
WILLMAN, H. B., and J. N. PAYNE, 1942, Geology and mineral resources of the Marseilles, Ottawa, and Streator Quadrangles: Illinois State Geological Survey Bulletin 66, 388 p.
|Stratigraphic Code||Geo Unit Designation|