552 NEW YORK STATE MUSEUM 



Uticafannaof Mechanics ville with Con . trentonensis 



and Climacogr. caudatus 

 Utica fauna of Yan Schaick island with Cryptogr. 



tri cornis 

 Utica < Typical Utica graptolite fauna of Rural cemetery, etc. 



with Diplogr. quadrimucronatus and 



Diplogr. putillus 

 Upper Utica beds of old Dudley observatory and Green 



Island 

 Typical Lorraine beds of Waterford and Block island 



Which of these minor faunas constitute constant sub-horizons 

 of the larger divisions has not been established thus far; but it is 

 expected that a continuation of this investigation in the areas^ 

 adjoining north and south will furnish the desired information. 



EXPLANATION OF THE OVERTURN OF THE STRATA 



All these beds now dip east and the Lorraine beds are, hence,, 

 the lowest in the series {see fig. 5, p. 556). It is, therefore, neces- 

 sary to assume either a series of parallel overthrusts which 

 brought up deeper beds successively or a complete overturn of 

 the whole series of strata. The former assumption would seem 

 to find some support in the abundance of slickensides and small 

 faults in /some localities, as specially in the Brothers's quarry at 

 south Troy and along Dry creek, west of Watervliet. But it 

 could hardly be supposed that a system of larger faults could 

 produce such a regular succession of zones following the general 

 strike of the beds as that found in the investigated area, without 

 repetition of zones or other irregularities. The slickensides, 

 which are often not a foot apart, might be assumed to indicate 

 an upward movement of the entire mass along an infinite number 

 of small faults, such that the more easterly beds were regularly 

 pushed a little farther up, in a manner illustrated by Van Hise 

 (58) to show the possible great surficial elongation of the crust 

 by small displacements along shearing joints. Under such as- 

 sumption the whole orogenic movement would evidently have 

 been uniform and would have, regularly and gradually, brought 



