92 NEW YORK STATE MUSEUM 



along the north shore, thus producing a most complete and ac- 

 cessible section. The eastern portion is separated by a fault, first 

 recognized by Brainerd, and traceable into Vermont. Its down- 

 throw is to the east and the throw about lOO feet. The greatly 

 different levels of the formation and the opposite dips of the blocks 

 furnish also fairly conclusive evidence that an important, probably 

 meridional, fault passes under Bulwagga bay. The configuration 

 of Bulwagga mountain points to the same inference. 



Chapter p 



GLACIAL AND POSTGLACIAL GEOLOGY 



From the close of the epoch of the Utica slate, until the oncoming 

 of the great ice sheet of the glacial epoch, we have no records other 

 than physiographic. This fact would lead to the inference that 

 land conditions prevailed during at least a great part of the time. 

 If any sedimentation took place, the beds were again removed by 

 erosion which must have been of very extended character. The 

 faults which have broken the Utica as well as all the older forma- 

 tions can only be described as coming at the close of Ordovicic 

 time or in the subsequent interval. It is natural to connect them 

 with the upheaval of the Green mountains which occurred at the 

 close of this period, but they may have been long after. The evi- 

 dence of a Cretaceous peneplain has been earlier mentioned and 

 its possible faulting during the Tertiary, but the evidence must be 

 admitted to be extremely vague. There is little doubt that at the 

 time the great ice sheet invaded the country from the northeast as 

 the scratches show, the relief was much as it is now. The ice 

 plucked away the loose rock and freshened up the escarpments ; 

 it sculptured amphitheaters and cirques and gave to the rocky ex- 

 posures much of the rugged character which they exhibit today. In 

 the closing stages the deposits of drift and the later postglacial clayc 

 served to smooth over this roughness in the depressions and made 

 the rocky, glaciated district tillable and habitable. 



In the preglacial times, the land must have stood at a higher level 

 with regard to the sea. Lake Champlain obviously lies in an old 

 river valley, whose bottom is now at least 300 feet below tide or 

 400 feet below the present surface of the lake. This elevation of 

 300 feet and more is probably but a small fraction of what really 

 took place, as we have long since learned from the various sub- 

 marine channels, opposite our large rivers, and from the drowned 

 fjords such as that of the Saguenay. At all events we are locally 

 assured of more than 300 feet. 



