PAPERS ON GEOLOGY AND GEOGRAPHY 219 



THE EFFECTS OF FAULTS AND DYKES IN THE 

 SALINE COUNTY COAL FIELD 



Clarence Bonnell 

 Harrisburg Township High School, Harrisburg, III. 



(Synopsis Only.) 



At Carbondale this paper was accompanied by a large 

 map of Saline County showing the coal fields, existing work- 

 ings, and the faults and dykes known when Co-Operative 

 Mining Bulletin No. 19, Coal Resources of District V., was 

 issued from Urbana. Additional faults and dykes, dis- 

 covered or indicated in the workings and drillings since 

 that time, were added. The effects of these dykes and 

 faults in working the field in the past and the difficulties 

 to be overcome in future operations were discussed. The 

 value of published geological facts concerning such features 

 of a mining field was pointed out. It was shown that the 

 data collected and chiefly published by the Department of 

 Geology of the University of Illinois, working with the 

 United States Bureau of Mines, is of great value in de- 

 termining the location of new mines and especially of shafts. 



Since the main lines of faulting are now pretty well 

 known in this field, future operations will be carried on 

 without the losses formerly sustained in encountering un- 

 suspected dykes and faults. Since dykes are more local, 

 their size and character and, in fact, their location cannot 

 be foretold except by actual boring. The largest dyke so 

 far found in Saline county was discovered in sinking a shaft 

 a short distance from a drill hole which showed no evi- 

 dence of such a geological feature. The work was made 

 much more expensive due to the hardness and extent of the 

 igneous rock encountered. 



Since the general trend of the large faults is now fairly 

 well known, as they are found in actual workings or shown 

 by drill hole records, it is not probable that the mistake of 

 sinking a shaft near a 150 foot fault will be repeated. 



