1s The American Geologist. January, 1892 
Seven years ago Prof. White asserted that the first oil-sand is 
the same with his Lachawacen, and suggested that the A/legrip- 
pus might prove to be the same with the third Venango. There 
is no room for doubt respecting the accuracy of these surmises. 
The interval between the sands is not far from what we should 
expect, for in western Bedford it is not more than 600 feet, and 
the decrease in the upper part of the column continues westward 
to the last exposure under Chestnut ridge. Some red rock occurs 
in this interval at Pittsburg and at Petrolia in eastern Butler as 
well as at Edenburg, 20 miles further east in Clarion county. 
Red shales, from 60 to more than 100 feet thick overlie the 
Lackawaxen at many places in Butler county, though oceasion- 
ally they are separated by a few feet of variegated shale. <A sec- 
tion on Bullion creek,* in Venango county, about thirty miles 
north from Thorn creek, shows 100 feet of red rock immediately 
over the Lackawawxen or first oil-sand and 55 feet of red rock in 
the 215 feet interval between that and the <A//egrippus or third 
oil-sand. The distance here from the Pocono to the Lackawazxen 
is 385 feet, almost the same as in Brady township and on Thorn 
creek of Butler county. 
It is unnecessary to go into further detail respecting the features 
of the Venango group, as the variations, aside from those of 
thickness, are inconsiderable,and they are all shown in full in Mr. 
Carll’s several reports. 
The whole series comes to the surface again in Crawford and 
Krie, the northwest counties of Pennsylvania, where the sub- 
divisions have been worked out in great detail by Prof. White. I 
give his generalized sectiont somewhat condensed and differently 
divided: 
PoOcoNo. 
1. Shendneo sandstone 25' 
°2. Meadville shale and limestone 66! 
3. Sharpville flags and limestone 64! 
4. Orangeville shale ron 
5. Corry sandstone 20' 
250° 
CHEMUNG, 
1. Cussewago shale and limestone — 37 
2. Cussewago sandstone 25' 
5. Riceville shales 80’ 
4, | Lackawaxen] first oil-sand 20' 
*Carll in loc. cit. p. 647. See Pl. 3, Fig. 14. 
tGeology of Crawford and Erie Counties. I. C. White. Harrisburg, 
1881. pp. 66-119. 
