54 GEOLOGY OF ERIE COUNTY 



Toad Hollow. The upper of these two beds crosses about half a 

 mile farther upstream and the contact with the Dunkirk shows 

 at a small cascade on the east side of the road before turning to 

 Clarksburg. There is a pronounced fault at this point- An 

 excellent exposure occurs in a small gully running east from the 

 state road two miles south of North Boston, and another is in 

 Grace's gully three miles south of Orchard Park. In the Grace 

 gully the contact with the Dunkirk is shown as well as the two 

 black bands- This gully follows a long fault. The Hanover 

 forms the cliffs along Pipe creek which joins Cazenovia creek 

 above West Falls, and forms the bed of the creek from West 

 Falls to the bridge above Pipe creek- The lower black band 

 forms a cascade just below the bridge and the gray nodular shale 

 forms another immediately below it. The cascade at West Falls 

 is formed by a ledge of sandstone 16 inches thick, capping a 

 series of gray shales the lower layers of which are hard and 

 nodular. This seems to be part of the Hanover shale. 



Fossils are rare in the Hanover shale. Plant remains are to be 

 found in the black bands in abundance. I found one orthoceras 

 in the nodular shale at West Falls. 



Dunkirk Shale. 



Bedded in the gray shales above theRhinestreet black shales 

 are four other black bands three of which have been included 

 in the Hanover and the description of which is to be found in 

 the preceding pages. The fourth band is of sufficient thickness 

 to warrant giving it a name. It crops out at Dunkirk, Chau- 

 tauqua county, hence has been designated the Dunkirk shale. 



The Dunkirk shale is a deposit of black shale fifty-five feet 

 thick, overlying the Hanover shales beneath. Hartnagel includes 

 it in the Gardeau shale as its basal member. It extends 

 beyond the eastern boundary of the county and seems to be 

 represented in the Genesee valley outcrops by a band of rusty, 

 black shale and thin flags exposed in the cliff at Wolf creek. 

 These are the Grimes sandstones. It has all the characteristics 

 of the Rhinestreet shale. It shows alternation of dense, black 

 shale and fissile, black shale with iron stained laminae. A row 

 of large concretions occurs near the middle of the formation. 

 The upper part is crossed by numerous thin, sandstone layers 

 the thickest of which is twelve inches thick and several of which 

 are between six and twelve inches thick. 



