11*2 



Report of the State Geologist. 



the region of Ithaca, X. Y. The picture of Taughannoek falls gives an excellent 

 idea of the Lower Portage of the Cayuga lake region. Estimating from other 

 sections in the Chenango and Unadilla valleys, we may safely refer to the 

 Portage, the 130 feet of overlying covered rocks of this station, which would 

 give a thickness of at least 270 feet for the lower Portage near Smyrna. 

 Vanuxem, in 18-10, proposed the name " Sherburne flagstone" for this forma- 

 tion, the typical locality being near Sherburne, Chenango count)', and 

 described it as composed of " stones * * * of various grades of thickness, 

 alternating with greenish or olive-colored shales; Fucoids resembling the 

 stems of plants are frequent in this rock, and also fragments of plants like the 

 grasses. The flagstone mass extends from Cayuga lake through the district " 

 [Third Geological district, which extended from Cayuga lake eastward to 

 Delaware and Schoharie counties] 1 . In the final report on the Third District 

 Vanuxem referred the Sherburne flagstones and shales to the Portage orroup. 2 

 After considering the differences in lithology and fauna between the 

 rocks constituting the Portage formation of western New York and the 

 synchronous formations of eastern Xew York, it seems advisable to revive 

 Vanuxem's name of Sherburne sandstones as the name of a formation. 

 If we study the sections of the Portage formation in different parts of 

 the State, we will find that in western Xew York, along the Genesee, 

 river, Professor Hall made the following subdivisions of the formation in 

 ascending order: Cashaqua shale, Gardeau shale and Portage sandstones. 3 In 

 Ontario county, along Canandaigua lake, Professor J. M. Clarke divided this 

 formation into the Naples shales and Portage sandstones, regarding the Naples 

 shales as representing the Cashaqua and Gardeau shales of the Genesee valley. 4 

 For the outcrops along the meridian of Cayuga lake Professor H. S. Williams 

 has used the names Low er Portage, Ithaca group and Upper Portage. 5 In the 

 Chenango valley at the base are Vanuxem's Sherburne flagstones, which are 

 equivalent to the Lower Portage of the Cayuga lake region, and therefore 

 represent only a -part of the Portage formation ; next above is the Ithaca 

 group, capped by the Oneonta sandstone. The evidence seems to show that 

 at least all of the rocks referred to the three formations just mentioned for the 

 Chenango valley are represented in western New York by the Portage forma- 

 tion. Since in the Chenango valley and eastward, the rocks which are 



1 Fourth Annual Report, Third Geological District ( Assembly Document No. 50, 1840i. p. 881. . 

 » Geology of New York, 1'art III., 1849, p. 172. 

 ' Geology of New York, Part IV.. pp. 226-228. 



Bulletin United State? Geological Survey, No. 16, p. 88 and p. 67. 

 ■'■ Bulletin United States Geological Survey, No. 3, p. 20. and Transactions American Institute of Mining Engineers. Vol. XVI., 

 p. MS. 



