GEOLOGY OF MASON COUNTY
Page 52
By H. M. Bannister

[The Geology of Mason county being reported by the above author in connection with Tazewell, McLean and Logan, we are compelled to give data from those counties; also from Menard and Cass, from the fact that the geological formations of these six counties are so uniformly the same that a description of one is nearly a description of all. It is also true that the geological surveys of these six counties have been very superficial and neglected. Our State Geologist, Prof. A. H. Worthen, being only remarkable for giving little attention to the important work which the State employs him to do. We shall extract from the work of Mr. Bannister, done for the Geological office of this State, and add such personal investigations as we have been able to make.] "The surface of the country over a great portion of the district composed of the counties of McLean, Logan, the greater part of Tazewell, and the eastern part of Mason, is a high, undulating prairie, with here and there groves and belts of timber. The soil is generally a rich brown mould, varying somewhat in different localities in the proportions of clay, etc., which it contains, some portions being more argillaceous than others. In the timber, however, which occupies scarcely more than one-fifth or one-sixth of the entire surface, and the broken country along some of the principal streams, the soil is somewhat of a different character, the lighter colored and more argillaceous subsoil appearing at or near the surface. In the greater part of Mason county, and over considerable tracts in the southwestern part of Tazewell county, the surface configuration varies from that which we have described. The prairies are low and comparatively flat, and in many places were originally overflowed, or marshy, at some seasons of the year. The soil of these prairies is a rich alluvium, generally more or less arenaceous, which forms, when sufficiently elevated or drained, one of the best producing soils in the State. Along the Illinois and Sangamon rivers, in this region, we find rather extensive sandy tracts of river formation, and on the Sangamon river in Mason county, and on the Illinois in Mason and Tazewell, the bold bluffs of the Loess are, in some localities, conspicuous features of the general landscape. The principal streams occurring in this district, besides the Illinois and Sangamon rivers, which form a portion of its borders, are the Mackinaw, in Tazewell, Mason and McLean counties; Salt Creek, in Mason and Logan counties; Kickapoo and Sugar creeks, in Logan and McLean counties. These, with many minor streams and nameless tributaries, drain nearly the whole surface of this whole district. With the exception of the Illinois and Sangamon rivers, none of the streams have extensive tracts of bottoms adjoining them, and even along these rivers the bottoms are either of inconsiderable extent or wanting altogether. The geological formations appearing in this district are almost entirely of the drift or later formations, the older rocks outcropping only at a comparatively few localities in Tazewell and Logan counties. The underlying rock, as far as can be ascertained from these outcroppings, as well as from artificial exposures, by shafts, etc., in various parts of the district, consists entirely of the different beds of the coal measure series.

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