GEOLOGY OF THE VICINITY OP LITTLE FALLS 15 



The time since the departure of the ice has been so compara- 

 tively short, that the surface is substantially as the retreating 

 glacier left it. During the retreat of the ice a slow movement 

 of uplift was in progress in the region, and continued thereafter ; 

 in fact there are strong reasons for the belief that it even yet 

 continues. Because of this change the Little Falls region stands 

 today at an elevation exceeding by from 250 to 300 feet what it 

 had when the last ice lay on it. 



The streams of the region have either reexcavated their old 

 valleys or are engaged in cutting new ones, but the time is not 

 sufficiently long to have enabled, them to make great progress in 

 the latter task. Besides, the recent rising movement of the region 

 has constantly lowered the level to which the streams can cut. 

 Even the Mohawk is not down to base level at Little Falls and 

 elsewhere. Away from the streams the glacial topography has 

 been but little changed. 



THE ROCKS 



Pre-Cambrian rocks^ 



These ancient rocks are found at the surface over a large area 

 occupying the northeast portion of the map, extending thence 

 northward without a break through the entire Adirondack region. 

 In addition, they appear at three disconnected localities, at Little 

 Falls, Middleville, and at a spot locally known as the " Gulf/' 2| 

 miles northeast of Little Falls. 



The Little Falls and Middleville outliers. The pre-Cambrian 

 rocks exposed at these two localities are identical, are quite 

 homogeneous throughout, and are somewhat different in character 

 from those exposed elsewhere. They are quite certainly old 

 igneous rocks andf belong to the syenite family of these rocks. 

 They consist mainly of feldspar, always show some quartz, 

 usually from 5^ to 15^ of the rock in quantity, and usually have 

 only a small content of dark colored minerals, magnetite, horn- 

 blende, pyroxene and black mica. These minerals form a granu- 



^A more detailed and technical description of these rocks will be given 

 in the closing pages of this report'. 



