24 NEW YORK STATE MUSEUM 



Exposures. The West River shale outcrops in the banks of 

 the ravines west of Alexander, and along Tannery creek at Attica 

 to the little falls below the second highway bridge; at Griswold 



25 rods south of the Erie Railroad in the west bank of Murder 

 creek; along Ellicott creek below the railroad west of Darien 

 Center; at the falls in Durkee creek southeast of Alden; in the 

 west bank of Cayuga creek at the Iron bridge and in the small 

 ravine half a mile north; also along Little Buffalo creek below 

 Marilla; in the banks of the Buffalo Creek gorge one-half mile south 

 of the Bullis bridge, and in the gorge of Cazenovia creek one and 

 one-half miles south of Spring Brook. 



MIDDLESEX BLACK SHALE 



A band of black slaty shales about 20 feet in thickness succeeds 

 the West River beds and is followed by argillaceous shales of a 

 much lighter color. This band was formerly considered as a part 

 of the upper Genesee shales, but differs from the beds below it 

 not only in respect to its lithologic character, but also in its fauna, 

 the characteristic fossils of the West River beds being absent from 

 these. 



In United States Geological Survey Bulletin 16, 1885, Clarke 

 separated this black shale from the Genesee, and considered it 

 under the term " Lower Blank Band of the Portage Group." In 

 New York State Museum Bulletin 63 it received the designation 

 Middlesex black shale on account of its abundant exposure in the 

 Middlesex valley in Yates county, from which locality it is con- 

 tinuous westward without change of character, though diminishing 

 gradually in thickness to about 6 feet at the point where it dips 

 under the water of Lake Erie, in the town of Evans in Erie count}'. 

 It is nearly barren of fossils except lignites. A small lingula. 

 L . 1 i g e a , occurs in this horizon near the mouth of Pike creek. 



Exposures. At the cascade on Tannery brook one-half mile 

 northwest of Attica; on Murder creek 30 rods south of the rail- 

 road bridge at Griswold; near the Erie Railroad bridge over Elli- 

 cott creek ; along Durkee creek ; Little Buffalo creek at Marilla ; 

 Buffalo creek one mile below East Elma and along Cazenovia creek 

 one and one-half miles south .of Spring Brook. 



CASHAQUA SHALE 



This formation is composed of light bluish or olive clayey shales 

 having an aggregate thickness on the east line of these quadrangles 

 of about 80 feet, decreasing to 50 feet on the west line. Calcareous 



