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NEW YORK STATE MUSEUM 



river beds are much disturbed. Between faults 18 and 17 ex- 

 posures of both rocks allow the tracing of the contact line with 

 fair accuracy, but beyond that the contact can be only approxi- 

 mately determined, since the exposures of th-i Hudson river beds 

 are found only at intervals and then at some distance from the 

 Manlius exposures. 



That there actually is an unconformity between the two sets 

 of strata hardly admits longer of a doubt. Besides the clear 

 indication of the disturbance of the Hudson river strata and 

 the erosion of their upper surfaces, the great time hiatus, extend- 

 ing from the middle Lower Siluric to near the top of the Upper 

 Siluric, is sufficient indication of an unconformity and would 



Fig. 3 Contact of Manlius limestone (6), with Hudson river shales (a) and Coeymans 

 limestone (c), northern margin of Becraft mountain 



be, even if this were not brought out in the structure. Such an 

 absence of formations, when not due to faulting, as is clearly 

 not the case here, can be accounted for only by nondeposition 

 or by subsequent erosion. And the former in this region at least 

 is, like the latter, indicative of land conditions. 



