GEOLOGY OF THE GENEVA-OVID QUADRANGLES 



23 



and its eastern branches and the upper part in Simpson creek in 

 the State Hospital grounds at Willard below the Tully limestone at 

 the quarry, and in the cliffs at Perry point and the adjacent ravine. 

 They appear in the banks of the Keuka outlet and the floor and 

 sides of Bruce's gully afford an ideal display of the upper shales 

 conveniently situated for the collection of fossils, and the entire 

 section may be seen in the Kashong creek ravine between the top of 

 the middle fall and the Tully limestone at the crest of the upper 

 fall. 



Tully limestone 



The Tully limestone, so named by Vanuxem in the Third Annual 

 Report of the Third Geological District for 1838, from large ex- 

 posures and superior development in the town of Tully, Onondaga 

 co., is specially interesting not only on account of its own 

 composition and structure, but also from the fact that it is inter- 

 stratified 250 feet below the top of a series of soft shales that 

 succeed the Onondaga limestone for a thickness of a thousand 

 feet and in which the Tichenor is the only other continuous lime- 

 stone. The rock is fine grained blue black rather impure limestone 

 that weathers light bluish gray. It is very compact and hard when 

 fresh, but brittle, breaking easily under the hammer and, after long 

 exposure, inclined to crumble into small angular fragments. This 

 tendency impairs the value of this limestone for building purposes, 

 and its impurity for the production of quicklime for which pur- 

 poses it was formerly quarried to a considerable extent. Its chief 

 economic value at present lies in its adaptability as road metal and 

 in the manufacture of Portland cement. 



It is 9 to 15 feet thick on these quadrangles and usually separated 

 into 4 or 5 distinct layers, the lower one 5 to 7 feet thick, the others 

 varying from 1 to 3 feet. Frequent joints divide the strata into 

 massive blocks and these are strewn along the ravines and the lake 

 shore at the foot of the cliffs in which the limestone occurs. The 

 change from the soft dark Moscow shale to the Tully limestone is 

 abrupt, but at the top the overlying Genesee shale is quite calcareous 

 for 3 to 5 feet. 



The Tully limestone is an important, easily recognized and reliable 

 stratigraphic datum plane from Chenango county on the cast where 

 it is 30 feet thick to Gorharh, Ontario co., on the west, where 

 it disappears by thinning out. It is 9 feet thick at the head of the 

 Kashong creek ravine; 12 feet, 6 inches to 13 feet, 6 inches along 

 the Keuka outlet; 14 feet, 6 inches at Miller point; 14 feet at Lodi 



