94 



ILLINOIS ACADEMY OF SCIENCE. 



The structure of the cross-section is indicated by the "lay" of 

 the coal. The coal outcrops several miles east of St. Louis, along 

 the bluffs of the Mississippi. It dips gently from that point but 

 irregularly at several places along the section. In the vicinity 

 of Sandoval the coal is seen to lie rather flat and then dip sud- 

 denly into the deeper part of the basin. The new oil field at 

 this town lies along this deformation, which extends southward 

 to Duquoin and possibly northward between Brownstown and 

 Vandalia, Pana and Tower Hill to Niantic. The rocks rise from 

 the axis of the basin to the LaSalle anticline at a fast rate and 

 then decline gently and rise again into Indiana. The main oil 

 fields of Southeastern Illinois lie at the top of the anticline. The 

 formations below the No. 6 coal rise in a similar fashion and 

 corroborate the structure. The Kirkwood sand correlation line 

 indicates the sharp rise over the LaSalle anticline. 



It may be mentioned at this point that the survey has collected 

 complete samples from about 20 wells over the main fields, from 

 depths of 800 to 2000 feet. Studies of these will almost certainly 

 identify the No. 6 coal over the anticline and permit closer classi- 

 fication of all the oil producing formations. 



The promising structural features along the A-A section are, 

 the flat "terrace" at O'Fallon, the mild arch at Aviston, the slight 

 arch at Carlyle, the irregular Sandoval and Odin "terrace" and 

 the luka fold. 



The C-C section (plate III) is plotted along a line from New 

 Athens to Duquoin, Benton, Rileyville and Eldorado. It follows 

 the Illinois Central railway closely between these points and is 

 especially valuable since it is based on a large number of coal 

 bores and mine records. There are several attractive structural 

 features exhibited, especially one at Duquoin. After passing the 



