430 NEW YORK STATE MUSEUM 



vestigation. In connection with a brief description of the Alta- 

 mont well (already mentioned) he says, " If the geologist follows 

 along the contact of the Hudson series with the Lower Helderberg 

 to the Schoharie kill and then proceeds down stream to the valley 

 of the Mohawk he will pass over a large portion of the section 

 penetrated by the well, and in the valley of the Mohawk find that 

 the series rests conformably upon the Trenton limestone, and that 

 the base is formed of dark Utica shales."^ 



Topography 



Topographically the area under consideration may be divided 

 into three regions accurately corresponding to as many types of 

 geologic formations. These regions are i) the limestone region 

 comprising all the area of the outcrop of the Calciferous-Trenton 

 formations; 2) the region of the outcrop of the Utica shale and 

 3) the region of the outcrop of the Hudson river shales and sand- 

 stones. Besides these there are slight modifications of the typical 

 topography of these formations due to glacial drift. 



The first region, that of limestone, is characterized by a low rolling 

 relief and shallow stream valleys, except where the streams have 

 been forced to cut new courses through morainic material or 

 because of the obstruction offered by such material have been 

 turned aside to make new rock cuts. The latter is probably the 

 case with the lower courses at least of the North Chuctanunda and 

 Evakill, for while they are at present making rock cuts their 

 banks show deep cuts through boulder clay and their beds are in 

 no respect those of mature streams, both from the abundance of 

 waterfalls and the irregularity of their slope. The northwestern 

 portion of this region is heavily covered with drift and the topog- 

 raphy is more angular on this account. 



Along the eastern border of the limestone belt the topographic 

 features are determined by the presence of the Hoffman ferry 

 fault, and along most of this line there is a distinct escarpment as 

 described in another part of the present paper. At its northern 

 end this escarpment is dissected, leaving only a number of isolated 

 hills with their longer axes in a northeast-southwest direction. The 

 southern end however stands out in a bold cliff just back of HofT- 



*Geol. soc. Amer. bul. Ap. 1890, 1:346. 



