958 



NEW YORK STATE MUSEUM 



Chazy time. Toward the east the Levis channel was bounded 

 by the Green mountains fold, which is supposed to have already 

 emerged in middle Cambric time. This, as far as our knowledge 

 goes, bounds also the upper Cambric graptolite shale. 



Ulrich and Schuchert hold that the region of the later Levis 

 channel had emerged during the Potsdam period [see the un- 

 classified time scale, opposite page 658, I. c.]. This is in accord- 

 ance with Professor Dale's conclusions, 1 who not only found 

 the middle and upper Cambric beds to be missing, but also 

 observed an unconformity between the Lower Siluric and Lower 

 Cambric, indicating the emergence of the lower Cambric beds 

 during the succeeding Cambric time. Our observations agree 

 thus far fully with these results of Mr Dale's elaborate investi- 

 gation with the exception of the closing upper Cambric time, 

 represented by the Dictyonema shale. 



Toward the west and north of this strip of upper Cambric 

 land, forming the " Vorland " of the Green mountain fold, ex- 

 tended the more or less broad " St Lawrence channel," which 

 effected the communication between the Atlantic and Missis- 

 sippian seas, indicated by the distribution of the Dicellocephalus 

 fauna. 



The question whether this late Cambric " Levis " channel per- 

 sisted throughout the Beekmantown period in this southern part 

 of the present slate belt or the broader St Lawrence channel 

 extended freely from the Adirondacks to the Green mountains 

 is a problem, the solution of which is dependent partly on the 

 exact correlation of the limestones occurring in the slate belt 

 and partly on that of the three Deep kill zones of graptolites, 

 corresponding to the Phyllograptus horizons of Europe. It will 

 necessitate much detailed investigation to obtain conclusive 

 facts and to decide between the differing views held in regard 

 to these beds. 



1 New York- Vermont State Belt, U. S. Geol. Sur. 19th An. Rep't, 1S97-S. 



