File:Biennial report for 1913 and 1914; administrative report and economic and geological papers (1917) (14779847791).jpg

Identifier: biennialreportfo30illi (find matches)
Title: Biennial report for 1913 and 1914; administrative report and economic and geological papers
Year: 1917 (1910s)
Authors: Illinois State Geological Survey
Subjects: Geology
Publisher: Urbana
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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land County La Salle County Grundy County ILLUSTRATIONS FIGURE 4. Map showing approximate outcrop of the Cheltenham clay in Illinois 5. Graphic sections showing the relations of Cheltenham clay in Missouri and Illinois PAGE 6166666767676868696969707070717171727273 62 64 STRATIGRAPHY Although a clay similar in appearance to tire clay and often loosely re-ferred to as such lies below practically every coal bed in the Pennsylvanianformation, the only refractory clays occur at the base of the formation. Inthe western part of the State these clays outcrop at many points from Altonto Rock Island at the boundary between the Pennsylvanian and Mississip-pian formations and in the north-central part in La Salle County adjacentto the boundary between the Pennsylvanian and Ordovician formations.These boundaries are shown on the geologic map of the State1 and approxi- 1The latest edition was published by the Illinois State Geological Survey in 1914. (61) 2 BIENNIAL REPORT FOR 1913 AND 1914
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Fig. 4.—Map showing approximate outcrop of the Cheltenham clay in Illinois. PENNSYLVANIAN FIRE CLAYS OF ILLINOIS 63 mately also on the map (fig. 4) accompanying this paper. South of Madi-son County the basal portion of the Coal Measures is greatly thickened bybeds of coal, shale, and sandstone that are not present to the north, and theclays are not refractory. In a previous publication of the Survey2 David White has presentedpaleobotanical evidence to show that although the coal itself is not presentin most of the area in which the clays are being exploited, the stratigraphicposition of the fire clays is immediately below the horizon of coal No. 1 ofRock Island County. In the summer of 1909 the writer in connection withthe collection of representative samples of this fire clay studied the strati-graphic environment of these clays with the object of establishing the corre-lation on a lithologic basis. The studies were begun in the southern portionof the field and carried northward. F

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