GEOLOGY AND PALEONTOLOGY OF THE SCHOHARIE VALLEY 171 



that the Silurie was present and was removed by erosion before 

 the deposition of the Devonic. Thus it would appear that as 

 Helderberg deposition went on, and a gradual westward migra- 

 tion of the shore took place, beyond the limits of the old Cumber- 

 land trough higher and higher members of the Helderberg series 

 came to rest, not merely on the upper Manlius as would have 

 been the case had there been no erosion, but on lower and lower 

 beds of the Manlius progressively or on even lower formations. 



How far westward in New York the Helderberg invasion ex- 

 tended is not known. The present extent of the formation is of 

 course no index to its former maximum extent, for subsequent 

 erosion may have removed a large portion of this series of forma- 

 tions. No actual shore deposits have been located in any of the 

 present typical outcrops of the Helderberg in New York, either 

 east or west, and from this we may argue that the former shores 

 of the Cumberland basin were at a considerable distance east and 

 west from the present extent of the formation. If the higher 

 members of the formation, i. e. the beds of Becraft and Port Ewen 

 age, ever extended over central New York they were entirely 

 removed by erosion before Onondaga time, for the Onondaga 

 formation rests on the Manlius at Cayuga lake with only a rep- 

 resentative of the Oriskany intervening. On the whole it seems 

 that the Helderberg transgression could not have been a very 

 markedly westerly one, inasmuch as the evidences for westward 

 overlap are meager. 



Examples of overlap of the Helderberg beds on lower forma- 

 tions are known from only a few localities within the State of 

 New York. One of them is a short distance north of Warwick on 

 the Lehigh and Hudson River railroad in southern Orange county. 

 Here Kemp and Hollick 1 record a purplish shale resting on cherty 

 Cambro-Champlainic limestone, and containing fossils possibly of 

 New Scotland age. South of Cornwall station on the' Erie rail- 

 road in Orange co. highly fossiliferous New Scotland shales rest 

 on the Longwood (Salina) shales. The possibility of a fault in 



X. Y. Acad. Sci. Ann. 7:650. 



