426 



Report of the State Geologist. 



The shales and conglomerate terminate at both ends of Pine hill by 

 faulting or thinning out. 



The Longwood shales are overlaid by a thin covering of Helderberg 

 limestone, with small amounts of limonite along the contact. The outcrops 

 of the Helderberg are a short distance northeast of Highland mills. They are 

 siliceous in character, and the following fossils have been recorded by 

 Dart on : Orthis oblata, L&ptama rhomboidaJ /*, Spi riftf macroph-u m.s. The 

 Helderberg limestone dips unconformable under the Monroe shales, due 

 to a probable overthrust ; but no actual contacts are observable on account 

 of the drift. Another exposure of possible Helderberg limestone occurs 

 one mile south of the Highland mills station ( 271). 



The Area West of Cornwall. 



West of Cornwall station is a small ridge holding several members of the 

 Medina and Helderberg formations. The relations of this area were briefly 

 referred to by Professor \V. B. D wight* some years ago, and subsequently in 

 greater detail by Darton.f Figure 10, giving map and sections of this area, 

 is adapted from Darton's paper. 



The eastern side of the hill, a few rods from the Erie railroad, is formed 

 of coarse-grained red siliceous conglomerate (Oneida), with red sandstones 

 and shales of Medina age. The conglomerate is massive and the bedding 

 irregular. 



At the northern end of the hill, in a cut of the New York, Ontario and 

 Western railroad, there is exposed a section of the Helderberg limestone, 

 which lies west of and over the Medina beds, forming the eastern face of 

 the hill. 



The members exposed in the cut are : 



Mediua sandstones, shales and conglomerate, . . . .25 feet. 



Tentaculite limestone, 10 " 



Pentamerus and shaly limestone, 40 " 



The beds strike northeast with a dip of nearly 90°, and there is no sharp 

 distinction between them. Veins of quartz and limonite are common along 

 the bedding planes. 



There ait- several exposures south of the road crossing the ridge and at 

 points where limonite has been mined, but as they were covered with debris 

 at the time of the w riter's visit, Darton's account of them is quoted: 



• W. I?. Dwigbt. Trait* Vauar UrOs. Inst. 

 + N. H Darton. A J S 3, XXXI., p 209. 



