DETAILED RECORDS. 203 
380. Well at Doltons, Cook County. 
[Well begun in 1905; completed October ii, 1905. Authority, II. W. ITambrecht, superintendent L. Wil- 
son Well Company, contractor. Samples preserved. Geologic correlations checked by G. II. 
Ashley.] 
As the record of this well was apparently kept with much care and the samples and the 
driller's log check nicely, the record probably has greater value than any from Cook County 
jyet published. The formations below the drift are, in downward order, Niagara limestone 
(Silurian); Cincinnati shale, Galena and Trenton limestone, St. Peter sandstone, and 
y ' Lower Magnesi an" limestone (Ordovician). 
A description of the geology of the Chicago quadrangle is given in folio 81 , Geologic Atlas 
of the United States. 
Record of well at Doltons. 
Recent and Pleistocene: Feet. 
Black soil 0- 1 
Light-yellow quicksand . 1- 7 
Gray limy brick clay . 7- 40 
Hard gray clay, hardpan, with limestone pebbles 40- 57 
Niagara : 
Loose gray limestone; water-bearing; water bad quality 57- 60 
Medium hard to hard light-gray to gray limestone, heavy bedded GO 340 
Medium hard light-gray and light-brown limestone 340 440 
Soft brownish-gray limesl one 440- 446 
Cincinnati : 
Soft bluish-gray clayey limestone or calcareous shale 446- 460 
Soft gray limy shale with limestone lentils 460- .500 
Soft dark-gray limy shale 500- 602 
Soft gray add brown limy shale. „ 602- 620 
Galena 'and Trenton: 
Soft brownish and gray limestone with streaks of shale 620- 640 
i Hard brownish and gray limestone with streaks of shale 640- 645 
Soft light-brown and white limestone 645 700 
Soft and hard light-brown limestone with streaks of gray shale 700- 795 
j Hard white to brownish limestone . 795- 805 
Hard brown limestone with streaks of brownish shale 805- 840 
Hard light-gray and light-brown limestone with streaks of gray shale... 840- 850 
Hard to medium gray and brownish limestone 850- 895 
Hard white, dark-brown, and light-brown limestone 895- 910 
St. Peter: 
Hard light-brown sandy limestone and gray shale. 910- 920 
Medium to hard white, gray, and brownish sandstone; no water in upper 
portion of sandstone ; some water in lower layers 920-1 , 036 
Lower Magnesian: " 
Soft greenish shale with brownish limestone. 1 , 036-1 , 041 
Greenish and brown shale and gray limestone 1 , 041-1 , 1 10 
Hard white and brownish, magnesian limestone 1,1 10-1 , 140 
Soft light-buff magnesian limestone 1 , 140-1 , 170 
Hard brownish sandy magnesian limestone 1 , 170-1 , 240 
Soft grayish and brownish magnesian limestone and gray shale 1, 240-1, 260 
Hard white and brownish magnesian limestone 1 , 300-1 , 31 2 
Limestone below 1 ,040 feet full of small crevices. Between 1,200 and 1,300 feet crevices 
f 2 to 18 inches. 
Rig used, cable, Well diameter, 12 inches, to 05 feet; 10 inches, 65 to 203 feex; 8 
nches,203 to 1,073 feet; 6 T \ inches to bottom. Yield by pumping 186 gallons per minute. 
