GEOLOGY OF LAKE PLEASANT QUADRANGLE 45 



rock area. Or again, the Canajoharie black shale at Wells is both 

 faunally and lithologically distinctly marine and precisely like that 

 of the Mohawk valley. Estuarine deposits would show certain dis- 

 tinct local variations and hence the very uniformity of sediments 

 in the outliers precludes the possibihty of deposition in estuaries. 

 Thus we are forced to conclude that when the early Paleozoic sea 

 encroached upon the southern Adirondacks, the shore line was fairly 

 regular, with possibly some very small local embayments along the 

 eastern side, and that a general mantle of sediments was deposited 

 over the whole southeastern Adirondack region. 



FAULTS 

 General statements 



The whole area of the quadrangle is cut to pieces by many nor- 

 mal faults, about forty of which are shown on the accompanying 

 geologic map. In certain cases where the presence of the faults 

 is not regarded as wholly conclusive, they are represeated by broken 

 lines. It is certain that other, chiefly minor, faults exist but because 

 of insufficient data they can not be shown on the map. Most of 

 the prominent faults form a distinct group with an average strike 

 north-northeast, thus harmonizing with the general faulted region 

 of the eastern and southern Adirondacks. Another, though less 

 important group, shows an average west-northwest strike or at right 

 angles to those of the major group. The few remaining faults strike 

 about north-south or east-west. As a result of this arrangement 

 of earth fractures, many fault ridges, troughs and blocks have been 

 developed. 



Wherever the fault surfaces are exposed they are seen to stand in 

 practically vertical position so that there can be little doubt that all 

 are vertical faults, which is quite the rule for the eastern Adiron- 

 dack and Mohawk valley regions. In the igneous and metamorphic 

 rocks of the quadrangle it is impossible to work out the elements 

 of the faults in anything like such detail as could be done in typical 

 stratified deposits. Exact amounts of displacements can never be 

 determined though approximate minimum figures can often be given. 



For a detailed discussion of the age of Adirondack faulting, the 

 reader is referred to the work of Gushing.^ Suffice it to say here 

 that some of the faulting is known to have occurred in Precambric 

 time, though no positive examples were noted within the quadrangle ; 



IN. Y. State Miis. Bui. 95. p. 403-12; 422-24; 428-29. 



