48 



Report of the State Geologist. 



firmest layers of sandstone often pass into shale so as to be unfit for any economical purpose. This 

 appears to be unlike the thinning out of the layer, but the proportion of argillaceous matter becomes so 

 great that the mass crumbles on exposure. 



"At the last-named (marry I observed the singular fact of non-conformable strata, as yet the only 

 instance noticed, and which various circumstances seem to render incredible. The strata are parts of 

 the same mass, once continuous, the lower dipping south at an angle of four or five degrees, and the 

 upper dipping north at about the same angle ; and a short distance farther south the whole mass dips 

 north. The only explanation that now offers is that at the time the rocks were subjected to the force 

 which produced the undulations the upper part slipped over the lower, and at this point partook of the 

 elevation south, while the lower was affected only by the uplifting to the north. The point of the 

 greatest depression is a short distance south of this locality. In this quarry was found the only speci- 

 men yet seen of a fern of the genus Sphenopteris, and through the liberality of Mr. Sexton, to whom I 

 am farther indebted, I am enabled to place this specimen in the collection of the State. With the 

 exception of the curved fragments of Fucoides, the upper part of this group is nearly destitute of 

 fossils." 



This description of vertical extent of the Ithaca group, though not giving 

 a definite conception of its lower limit, specifically carries its upper limit so 

 far south as to include the heavier sandstone beds at Millport and further 

 south. Our evidence now points to the fact that these sandstones are contin- 

 uous with the typical Portage sandstones of the Genesee valley. The expo- 

 sures near Millport are of these sandstones; Jefferson is the former name of 

 the village of Watkins, and the rock section there is essentially reproduced 

 in the Havana glen section given in detail in the following pages. All this 

 region of country, then a part, of Chemung county, now constitutes a part of 

 the county of Schuyler. 



The historical Ithaca group is thus the sedimental equal of the major 

 part of the entire Portage formation. Professor Hall's description, while 

 showing the lithologic similarity of the Ithaca group to those beds along 

 the Genesee river to which he subsequently applied the names Cashaqua 

 shales, Gardeau flags and Portage sandstones, also suggests a critical difference 

 in fossil contents though without citing such data as can serve the require- 

 ments of the present day. 



In subsequent reports of geologists Hall and Vanuxem, the Ithaca, group 

 was not similarly construed. Vanuxem, in his Fourth Annual Report (1840), 

 j». 381, places the Ithaca group between the "Sherburne Flagstone 1 ' and the 

 " Chemung group," saying: " Consisting of sandstone and shales, forming a 

 thick mass, highly fossiliferous. Names not [yet] given to the fossils. The 

 top part of this mass terminates in a series of these sandstone flags with 

 fucoides resembling those below the group, and which separates the succeed- 

 ing group from the Ithaca." This view accords with the original definition 

 of the term. 



In his report for the same year Professor Hall made no further reference 

 to the Ithaca group except to include it in tabulations of the New York for- 



