Report of the State Geologist. 



13 



lying strata and fauna. The latter is a peculiarly perplexing problem. East 

 of the Chenango river the Tully limestone and Genesee slate are wanting, 

 and the sandy shales of the Hamilton group pass upward into those of the 

 Ithaca group with slight lithologic changes and with alterations of the fauna 

 so gradual as to be perceptible only upon very careful observation. The Sher- 

 burne sandstones, of Vanuxeni, are shown to be a mass of virtually barren 

 deposits separating the faunas of the Hamilton and Ithaca groups, corre- 

 sponding with the lower barren sandstones shown in some sections of the 

 Portage of western New York, especially at Ithaca, where these beds have 

 been designated as the "Lower Portage." There is good reason for recogniz- 

 ing this old and well-defined term in application to this mass of barren 

 sands coming in between the Genesee slate and the overlying fossil-bearing 

 beds. The term " Sherburne sandstones 11 would, then, designate an horizon 

 pretty clearly defined from Cayuga lake eastward into Otsego county or beyond 

 the disappearance of the Genesee and Tully formations. The rocks in the 

 Chenango valley sections lying above this horizon, which have heretofore been 

 referred to the Ithaca group, are shown to contain a fauna which bears a much 

 greater resemblance to that of the Hamilton group beneath than to the fauna 

 contained in the typical exposures of the Ithaca rocks at Ithaca, It is true 

 that the section at Ithaca is through rocks whose organic content is a com- 

 mingling of the species more fully and typically represented in Cortland and 

 Chenango counties, with those which are properly members of the normal 

 Portage fauna. 



The Stratigraphic Position of the Portage Sandstones in the Naples Valley 



and the Adjoining Region. 



By D. D. Luther. 



The purpose of this work was to ascertain approximately the line of 

 division between the Portage and the overlying Chemung group in western 

 New York. The problem is a difficult one, so far as based upon lithologic 

 grounds, for the rock series consists of sandstones, flags and sandy shales, 

 varying among themselves. The original upper limitation of the Portage 

 group, however, was fixed by a mass of heavy bedded sandstones, which 

 were termed the " Portage sandstones." 



The author introduces his work by giving a detailed account of a care- 

 fully studied section of the entire Portage formation in the Naples valley, in 



