GEOLOGICAL P-\PERS - 9I 



of the State relative to the region of our investigation is the 

 La Salle anticline. Its position is indicated on the map. (Plate I.) 

 Its character has been discussed so frequently that it has become 

 familiar. The fold is more in the nature of a monocline than 

 an anticline, the west side being thrown down along the axis of 

 disturbance and the east side thrown up. The details of the struc- 

 ture at La Salle will be shown by the cross-section. 



The two new logs to be presented are from wells located in the 

 lowest part of the trough west of the anticline. 



Log of well Xo. 16, at the Western Clock \\'orks in Peru, is 

 as follows, continuing from the base of coal Xo. 2, or the third- 

 vein coal, as it is locally known. This log is diagrammatically 

 shown on the chart. 



Fireclay 5 feet 



Sandstone 30 '" 



Gray shale, dark, indications of coal 70. base 500 feet deep 



White calcareous sandstone. , 15 feet 



Hard red shale 3 " 



Gray and green shale 30 " 



Hard red shale 3 '' 



Green and gray shale 85-90 ft., bottom 650 ft. 



White dolomite 36 feet 



Brown 8 " 



Light gray dolomite 96 " 



Butt dolomite 15 " 



Light gray dolomite 23 '" 



Buff dolomite 12 " 



Light gray dolomite 13 feet, bottom 853 feet 



Bluish gray dolomite 70 feet 



Broun shale 10 " 



Gray shale 100 feet, Ixrttom 1035 



Brown dolomite 85 feet, bottom 1120 



Log of well X'o. 27, at X'^o. 5 mine of La Salle Count}- Carbon 

 Coal Co. Coal Xo. 2. or third-vein coal, at elevation of 135 A. T. 

 depth 565 feet : 



Gray shale 125 feet 



Fine sandstone 40 " 



Gray shale 35 "' 



Sandstone 10 " 



Light gray shale 25 " 



Gray and green shale 25 feet, bottom 825 ft 



White dolomite 75 feet 



Brownish dolomite 25 " 



Light gray dolomite 25 " 



White dolomite 50 " 



White, slightly calcareous dolomite 25 " 



White. chalk>- calcareous dolomite 25 " 



Buft dolomite 23 " 



Gray dolomite 20 " 



Shaie 5 " 



Blue and brown shale 145 " 



Brown dolomite 255 feet, bottom 1498 ft. 



the last i^ ft. somewhat calcareous. 



