xxxii Trans. Acad, Sci. of St. Louis. 



"oil showing" it makes when penetrated by the drill. If structural 

 and other important geological conditions are favorable, however, the 

 Trenton limestone is likely to be as important an oil producer in this 

 territory. 



As the thin Coal Measures, the thick Sub-carboniferous, the thin 

 Devonian and the thick Silurian formations that underlie St. Louis 

 rise rapidly" and outcrop to the west, the place to expect paying pools 

 of oil and gas is to the east of St. Louis, in Illinois, where the strata 

 flatten to a dip of ten feet per mile, where there are several anti- 

 clinels, and where there are at least three different formations that 

 are favorable for the occurrence of oil and gas in profitable quanti- 

 ties. For Illinois has from 600 to 1400 feet of Coal Measures which 

 contain several thick sandstones with heavy shale caps that are favor- 

 able for oil reservoirs, and in which occur the oil pools of the eastern 

 side of the state. At 600 to 800 feet below the Coal Measures occurs a 

 black Devonian shale, beneath which an excellent grade of oil, 42° B. 

 gravity, has recently been discovered at Peters, ten miles northeast of 

 St. Louis. This horizon has seldom been tested in Illinois, as thus 

 far the drilling has been mainly confined to the shallow Coal Measures. 



The Trenton and Galena formations underlie almost the entire 

 state of Illinois and where they outcrop in the northwest corner of the 

 state they consist of heavy, shale-capped limestones that are more or 

 less magnesian, and, therefore, in a favorable condition for acting as a 

 reservoir for oil. As they lie at a depth of 1500 to more than 2500 feet 

 over most of the state, they are not likely to be tested until the upper 

 sands have been exhausted. 



The structural conditions of Illinois are very favorable for oil 

 and gas, as the state essentially consists of a large, simple basin, whose 

 axis runs through the central portion of the state with a north-north- 

 westerly trend. In fact, it is surprising that oil men have ignored 

 the state until lately, as the conditions are most encouraging for the 

 occurrence of oil and gas on both the eastern and western flanks 

 of the basin. There is an abundance of material for forming, storing 

 and protecting oil and gas and ideal conditions for its concentration 

 into paying pools. A little oil and gas was found forty years ago at 

 a depth of 400 feet at Casey, on the eastern flank of the basin, but 

 the oil pools, that now exceed 80 in number and have been developed in 

 six eastern counties, have all been discovered within the past three 

 years. Since the eastern flank of the basin is being literally drilled, the 

 oil men are beginning to give their attention to the western flank of 

 the basin, where the conditions are fully as favorable. 



Prospecting on a limited scale has been started in several places 

 and the edges of four oil pools have been located at Litchfield and 

 Butler, in Montgomery County (fifty to sixty miles northeast of St. 

 Louis), at Peters, in Madison County (ten miles northeast of St. 



• The saccharoidal or St. Peters sandstone, which is 1452 to 1585 

 feet deep in the Insane Asylum well, outcrops in the Meramec Valley, 

 twenty-four miles southwest of this well, showing an average dip of 

 about 60 feet per mile to the northeast. 



