54 



NEW YORK STATE MUSEUM 



midst of that part of the Adirondacks here considered. The small 

 outlying mass of Paleozoic strata at Wells, so far separated from 

 the main body of similar strata, lies within a valley of the Lake 

 Pleasant quadrangle. This valley and its immediate surroundings 

 exhibit perhaps a greater variety of important geologic phenomena 

 than any other small area within the whole Adirondack region (see 

 map figure 9). A fault whose total length in over 30 miles passes 

 along the western side of the valley where the mountain wall of 

 pre-Paleozoic rock (see figure 9) rises 1000 to 1500 feet, while the 



Canajohan'e 

 shale 



ZJ Black River-Trenton 



1J lir 



imesfones 



Ljttie Falls 

 ^•^ dolomi'Te 



Zl Pofsdatn- Theresa 

 ij sandstone 4-do!cmite 



X X X 



jSvenile 





Granl+i'c 

 syenite 



■■'' i^ lA Pt-ecambric 



HOR\ZON-TAL SCALE 



VERTICAL SCALE 



J rocK 



MILE 



^% 



Fig. 10 Detailed structure section across the valley at Wells, Hamiltoft 

 county. This represents a vertical slice through the earth's crust at this 

 locality. The dolomite, sandstone, limestone and shale are Paleozoic strata. 

 Heavy vertical lines show positions of faults. (By W. J. M.) 



eastern or valley side of the fault represents a portion of the 

 earth's crust which has moved downward at least 2000 feet (figure 

 10). The Paleozoic strata in the valley were formerly at a level 

 corresponding nearly to the present mountain top3 just to the west 

 of the fault. Having dropped down so near sea level, these strata, 

 now about 500 feet thick, have been protected against complete 

 removal by erosion to the present time. Another, though smaller, 

 fault bounds the valley on the east, so that the valley really repre- 

 sents a block of earth which has dropped down between two faults. 



