640 



NEW YORK STATE MUSEUM 



Lower Dicel- 

 lograptus 

 fauna 



Normans kill 

 shale 



tive faunas and the lithologic character of the deposits in the 

 twin channels are so different that we can not doubt the thor- 

 ough effectiveness of the Quebec barrier during the whole of 

 Chazy tin.e. 



At th< close of the Chazy the northwest channel, and per- 

 haps the Levis channel as well, was drained. This emerg- 

 ence continued in the Chazv basin till Black river time, 

 but, if the drainage occurred simultaneously in both chan- 

 nels, appears to have been of briefer duration in the Levis 

 channel. On the other hancL, it seems very likely that 

 the Chazy bay was emptied sometime in advance of the Levis 

 channel, allowing deposition in the latter of beds holding the 

 lower Dicellograptus and Agnostus, Ampyx, Aeglina and Pate- 

 rula fauna, which is common to Europe and the Levis channel. 

 The earlier emergence of the Chazy channel is rendered very 

 plausible if we assume a period of compression at the close of the 

 Chazy, causing the strata in the western channel to be pushed up 

 on the sloping Adirondack and Laurentian masses beneath them, 

 and high enough to empty the western channel but not the Levis 

 channel. The same assumption would explain the development 

 of the supposed barrier, referred to a page or two farther on, 

 across the mouth of the Ottawa arm of the Chazy bay, which, 

 if it ever existed, must have arisen about this time. 



The deposits and fauna of the supposed lower Dicellograptus 

 zone in the Levis channel are now known chiefly, if not solely, 

 from limestone pebbles and boulders preserved in the conglom- 

 eratic horizon at the base of the Normans kill shale, the bed 

 itself possibly being now entirely covered by overthrust Cambric 

 rocks. The fauna contained in these pebbles, a.s worked out by 

 Ruedemann, 1 contains species indicating some communication 

 with the Mississippian sea in the vicinity of Albany N. Y.; or it 

 may be that the sea of the Normans kill shale, which trans- 

 gressed farther westward, also washed surfaces laid down by 

 Black river and early Trenton seas. 



The Normans kill shale, which, as we have just said, trans- 

 gressed a little farther west, also extended farther southward 



X N. Y. state mus. Bui. 42. 1901; Bui. 49, 1902. p. 89-94. 



