egies Proceedings of Indiana Academy of Science 
FIG. 2. 
Fig. 2. Three concretions, each about two feet in diameter, in place in the ravine 
wall. 
part of the zone contain considerable calcium, iron and aluminum. An 
examination of a specimen from the extreme top of the zone under the 
petrographic microscope resulted in the following estimate of contents: 
quartz, 8/9; calcite, 1/9; traces of limonite, pyrite and kaolinite. A 
chemical analysis of a specimen from the lower part of the zone gave 
the following results: 
Side vii 2s, 4648 % 
Caron 2 17.92 
era Delon an 19.87 
Mg 0 395% 
oh Nee oe 14.69 
S02. h ee 
Total ...... 99.435 % 
The concretions of this zone resemble those of the Olentangy shale 
of Ohio in size, mode of occurrence and general appearance but those of 
the Olentangy shale are of very wide distribution. Beds of limestone 
occur in the Knobstone south and east of this zone at about the same 
horizon. Small concretions are found at many horizons in the Knobstone. 
So far as known there is no relation between this bed of concretions 
and the concretions of other parts of the Knobstone nor do they seem 
to be related to the limestone beds. So far as known there is no similar 
zone of concretions in the Knobstone or elsewhere in Indiana. 
Acknowledgement is made to Prof. W. N. Logan who made the 
petrographic estimate, Mr. Luther S. Ferguson, who made the chemical 
analysis, and Mr. Arch R. Addington, who developed and mounted the 
pictures. Indiana University. 
