ALLEGHENY FORMATION OF WESTERN PENNSYLVANIA BASINS 101 



mistaken at times for that bed, as the interval to the Vanport varies from 

 45 to 90 feet, diminishing westwardly. This bed is 10 to 60 feet below 

 the Upper Kittanning, which is 110 to 130 feet above the Vanport, and in 

 some of the townships is largely a cannel. The interval between Upper 

 Kittanning and Lower Freeport is as variable as in Elk, Clarion, and 

 Armstrong, the extremes in a single township being 55 and 91 feet. 

 Where the Freeport sandstone, occupying this interval, is divided by shale, 

 a coal bed, the Currie, occasionally appears. The Lower Freeport is 

 roofed by laminated shale and coal a few inches to 10 feet thick, and the 

 Upper Freeport, 50 to 60 feet higher, is uncertain, apparently wanting at 

 many localities. 



The Scrubgrass, Clarion, and Brookville coal beds below the Vanport 

 limestone may have been deposited in the greater part of northern Butler, 

 but they are now wanting in the western portion, where for the most part 

 the Clarion sandstone is continuous with the Pottsville. The Freeport 

 limestones appear in only a few sections and the Johnstown cement 1; 

 absent.* 



The surface rocks in southern Butler for the most part are Conemaugh, 

 but the Allegheny beds are reached on the east side in deep valleys tribu- 

 tary to Buffalo creek and on the north and west in the valley of Conno- 

 quenessing creek. Two measurements on the east or Armstrong side are 

 important for correlation: 



Feet. Inches. Feet. Feet. Inches 



Upper Freeport . . 3 2 



Interval 65 



Lower Freeport Blossom 1 to 2 



Interval 80 ^ 



Darlington [Upper Kittan- 14 „ 



ning] 3 



Interval 70 



Kittanning [Lower] 10 9 3 



Interval 55 55 O 



Ferriferous limestone [Van- 

 port] 15 16 6 



Interval 20 12 



Clarion 2 3 



Interval 10 30 



Ki » Si - : 4 



to sandstone. The interval from Lower Freeport to the Upper Kittan- 

 ning (Darlington) is very like that in much of northern Butler and 

 northwest Armstrong, but nearly double that in southwest Armstrong, 

 while the interval from Lower Freeport to Lower Kittanning is actually 



* H. M. Chance: Northern Butler (V), pp. 17, 28, 95, 97, 103, 105, 121, 123, 125, 

 129, 130, 132, 134, 137. 



