GEOLOGY OF THE AUBURN-GENOA QUADRANGLES Q 



Also Leperditia scalaris Jones and a few Orbiculoideas 

 and Lingulas and traces of the seaweed Bythotrephis les- 

 q u e r e u X i Grote and Pitt. 



Bertie waterlime was exposed at the top of the wall in nearly all of 

 the old gypsum quarries and small outcrops and loose blocks are still 

 to be found at such localities. It is to be seen at the south end of the 

 quarry at the plaster works ; along the railroad at Cayuga Junction and 

 at Crossroads; in several of the old pits near the four comers i^^ 

 miles north of Crossroads and at the top of the wall of the old 

 quarry at Cayuga. 



Cobleskill limestone 



Succeeding the Bertie waterlime there are three or four layers ag- 

 gregating 8 to 10 feet of harder, darker limestone that has received the 

 above designation from the favorable exposures of this rock in its 

 most typical condition along Cobleskill creek, Schoharie county, 

 where it has a thickness of 6 feet. 



It thins out toward the west, from the Cayuga lake region to 

 Phelps, Ontario co., but reappears farther west and attains its 

 greatest thickness at Falkirk, Erie co., where it is known as the 

 " bullhead " and is 14 feet thick. 



On these quadrangles this limestone is seen to the best advantage on 

 Frontenac island at Union Springs where the sharp elevation of the 

 strata toward the north brings the three layers of the formation succes- 

 sively into view. The upper layer has a thickness of 3 feet 2 inches 

 and breaks readily under the hammer into small angular fragments. 

 This is the most fossiliferous layer except in Stromatopora. 

 The middle layer is 2 feet 10 inches thick and contains Stroma- 

 topora concentrica Hall in great abundance, and except that 

 it is a little darker colored, it has precisely the same appearance as the 

 Stromatopora layer of the Manlius limestone which is 50 to 60 feet 

 higher in the section. 



The lower layer, 2 feet 6 inches thick, weathers to a lighter color 

 than the two upper ones and is less fossiliferous, approaching the 

 character of the upper layers of the Bertie waterlime below it. The 

 thickness of these divisions is probably not maintained for any great 

 distance but the character of the rock is quite uniform. 



On the mainland the most southern exposure of this limestone is on 

 the southeast side of Rowland point where the upper layers are well 

 displayed. 



