CANANDAIGUA AND NAPLES QUADRANGLES 



19 



conditions together with the advance of the Hamilton fauna. 

 The estimated thickness of the Canandaigua shale is 

 about 125 feet. It is excellently exposed along Shaffer creek 

 immediately south of the exposure referred to above and about 

 a mile north of the village of Centerfield. At this locality the 

 lower calcareous layers and the shale overlain by the coral 

 beds are admirably exposed and have been a most prolific 

 source of fine fossils. These beds also appear within the village 

 of Canandaigua, there being exposures of the impure calcareous 

 beds on east Gibson street at the now abandoned Maggs 

 quarry and also in the more recently opened quarry on the 

 Robertson property south of the Ohapinville road. Here the 

 beds, when fresh, are a fairly compact limestone but their 

 schistose character soon checks them on exposure, and they 

 have never proved a satisfactory construction stone. They are 

 however enormously prolific in corals and represent the coral 

 reef better exposed on Shaffer creek. It is probable that beneath 

 them lie the shaly beds, but the limestones which lie near the 

 bottom on Shaffer creek and which are of more compact char- 

 acter, though somewhat more argillaceous in composition, may 

 prove to be absent here. Below the Robertson quarry, to the 

 New York Central Railroad tracks, is a small drainage way 

 which gives indications of the underlying beds down to the blue 

 black Skaneateles shale. The exposure however is not sufficiently 

 clear to demonstrate the presence of the limestone beds referred to. 

 If they are here they would serve as a more substantial building 

 stone for rough purposes such as foundations and cellar walls, 

 than the stone above, that is now or has been worked for this 

 purpose. These lower limestones, which are specially character- 

 ized by their fossil contents and have produced some species which 

 have not been found elsewhere, have been designated in a sub- 

 sidiary sense as the Centerfield limestone. 



The upper beds of the Canandaigua shale outcrop on the east 

 shore of Canandaigua lake at Cottage City and in the ravine of 

 Gage's creek and Deep run. On the west side of the lake the shale 

 beds are well shown in the cliffs between Tichenor and Men- 



