PORTAGE AND NUNDA QUADRANGLES 47 



The introduction of the name " Nunda " as an alternative term 

 was unfortunate and is not now easily explainable, as the town 

 of Portage was set off from the town of Nunda, March 8, 1827, 

 and the new town included all of the territory along the banks of 

 the Genesee river previously lying in the town of Nunda; but in 

 April 1846, that part of Portage township on the west side of the 

 river with a strip taken -from the town of Pike, was erected into a 

 new town and named Genesee Falls. 



Of the units composing the Portage group, the Cashaqua shale 

 is not exposed at all within the present limits of the township of 

 Nunda, and the Gardeau shale and flags as delimited by Hall appear 

 in but a few small isolated exposures, the heavy sandstones (Port- 

 age sandstones) at the top being the only part of the group that 

 can be said to be fairly well exposed in the town and only to these 

 can the name Nunda with any propriety be applied. 



The term " Portage group " has been in use for more than 60 

 years by students of geology and has acquired recognition by the 

 general public as the designation of the strata between the Genesee 

 black slate and the Chemung sandstones. Historically, logically and 

 legitimately it is substantially fixed. 



Exhaustive studies of the stratigraphy and paleontology of the 

 rock section in the Genesee gorge have shown that Table rock at 

 the top of the Lower falls, differs from other sandstones above and 

 below it only by being slightly harder and more calcareous, and by 

 a more abrupt transition to soft shale in the upper surface, the sedi- 

 mentation above it up to nearly the top of the Upper falls being of 

 the same character as the beds below it down to the mouth of Wolf 

 creek ; the same fossils occur above and below it. Therefore recent 

 publications by this department have fixed the upper limit of the 

 Gardeau flags at the base of the heavy sandstones near the top of 

 the Upper falls. 



To avoid the confusion by duplication of the original group term 

 " Portage " with the later unit term " Portage sandstones," we shall 

 here substitute for the latter the term " Nunda sandstone " as the 

 designation for the upper terminal member of the Portage group as 

 Hall defined it. 



Description of formations 



All the geologic formations represented on the area hew con 

 sidered belong to the upper division of the Devonic system. 



