PORTAGE And nunda quadrangles 6i 



H. major Clarke B. lupina Clarke 



H. desmata Clarke Paracardium doris Hall 



Posidonia attica {Williams) Pterochaenia fragilis (Hall) 



Ontaria suborbicularis (Hall) Cladochonus 



O. clarkei (Beushausen) Lignites 



Euthydesma subtextile Hall Fucoides graphica Hall 



Buchiola retrostriata (v. Buck) F. verticalis Hall 



Nunda sandstone 



A stratum of sandstone 7 feet thick, the bottom of which is 28 

 feet below the top of the Upper fall is the basal layer of this sub- 

 division. It is succeeded by 7 feet of shales and thin flags, overlain 

 by the somewhat shaly sandstone 13 feet, 6 inches thick seen at the 

 crest of that fall. 



A bed of hard blue shale 4 feet, 4 inches thick overlies this sand- 

 stone, another 12 feet higher is 2 feet thick and a third 70 feet 

 above the top of the falls is 6 feet thick with an 8 inch layer of 

 sandstone in the upper part. 



Except these three beds of shales and a few thin shaly partings 

 between the heavy layers the formation as exposed in the Genesee 

 river gorge section is composed entirely of light blue gray sand- 

 stone in layers from 3 to 10 feet thick, some of which are calcar- 

 eous to a greater or less degree, and hard, while others are schistose 

 or coarsely shaly in many laminations. Large and usually obscurely 

 defined concretions or burls occur in some of the layers. 



The cliffs at Portageville by long exposure have weathered to a 

 yellowish or olive-gray color, and that is commonly the color of 

 these beds in old outcrops everywhere, but when newly quarried 

 the rock has a handsome blue gray tint and is popularly known as 

 " bluestone." The more compact layers are extensively quarried on 

 the west side of the river iy 2 miles south of Portageville by the 

 Portageville Bluestone Co., and at Bluestone by the Genesee Valley 

 Bluestone Co., and near Rock Glen by the American Bluestone Co., 

 and the Warsaw Bluestone Co., sawed into flagging and house 

 trimmings, the handsome color of the rock combined with its 

 durable character making it extremely popular for such use and of 

 considerable importance economically. 



The 6 foot bed of shale seen at the line of the Pennsylvania 

 Railroad at the south end of the high Erie Railroad bridge, con- 

 tains large numbers of small irregularly shaped calcareous con- 

 cretions that give the bed a distinctly nodular expression not seen in 

 shales east of these quadrangles but common in the western part 



