60 NEW YORK STATE MUSEUM 



been tilted since its formation, rises in elevation toward the north, 

 and Fairchild estimates its altitude at some 900 feet at the south 

 edge of the Brier Hill sheet. East of Cape Rutland, owing to the 

 broken and uneven character of the coimtry along the north side 

 of the Adirondacks, this shore line is much broken and difficult to 

 trace. But even the altitude at Cape Rutland is far above any 

 elevation on the Brier Hill and Ogdensburg quadrangles, which 

 were therefore covered for a time with the fresh waters of this 

 lake, w^aters over 500 feet deep on these quadrangles. The morames 

 left by the retreating ice were deposited underneath these waters. 



As the ice retreated down the valley and neared the Champlain 

 region, the lake waters began to find outlets to that valley between 

 the ice front on the north and the valley walls on the south, and 

 the level of the lake began to fall. Successive stages were passed 

 through until finally the ice entirely unblocked the valley, and the 

 waters fell to an altitude estimated at some 450 feet, using Fair- 

 child's figures.^ Even this altitude would carry the water to the 

 very top of Mount Lona, the highest point on the Ogdensburg quad- 

 rangle. And at this level, and the lowxr ones which succeeded it, 

 the whole surface of the district would have been subjected to the 

 leveling effect of wave action, laying bare surfaces of hard rocks, 

 and filling hollows with water-laid clays. 



At this stage the fresh waters of Lake Iroquois were succeeded 

 by the brackish waters of a marine estuary, the lower altitude of 

 the region permitting the marine waters of the Gulf of St Lawrence 

 to extend up the valley to Lake Ontario, involving the lake itself in 

 this marine extension. The marine fossil shells buried in the 

 deposits of these waters have been found as far west as Ogdens- 

 burg, and farther east are abundant. Those found near Ogdens- 

 burg have all been on low grounds, only 30 to 40 feet above the 

 river, but at Norwood, Woodw^orth reports them at elevations of 

 from 335 to 360 feet.- The clays and sands containing these shales 

 were obviously laid down below the marine level. The lack of 

 these fossils west of Ogdensburg is likely due to the water not 

 being sufficiently salty there. 



In the few thousand years that have elapsed since the marine 

 waters were in the region at their highest stage, a slow uplift has 

 been in progress, an uplift most prominent at some point well to the 

 northeast of Ogdensburg. This uplift not only slowly brought this 



IX. Y. State Mus. Bui. 145, p. 139. 

 2 N. Y. State Mus. Bui. 84. p. 208-9. 



