26 NEW YORK STATE MUSEUM 



of the line of the profiles (C-D of plates 4 and 9) makes an angle 

 of over 30 degrees with tlie direction of steepest tiptilting, 20 

 degrees east of north. In consequence of this variance in direc- 

 tion the stations north of the line of the profile have an excess 

 of altitude, while those south show a deficiency. Examples of 

 the higher value are seen in all the stations on the marine shore 

 profile between Chateaugay and Dexter; and on the Iroquois pro- 

 file west of Ontario. The effect of southing is clearly seen at 

 Rome, Woodard and Sodus. 



The shore features which stand much above the profile, all the 

 way from Lacona to Chateaugay, indicate some uplift of that 

 region in excess of the uplift at the outlet, since the height of the 

 outlet controlled the water level. In other words, the territor}- 

 north of the isobase of Rome was lifted out of the Iroquois Avaters, 

 The question is, AVhen did this occur? The matter will be dis- 

 cussed in the next chapter. 



DEFORMATION AND ALTITUDES IN THE ONTARIO 



BASIN 



TABULATION OF DATA, PLATE 12 

 The uniform vertical interval of 290 feet between the Iroquois- 

 and marine planes in the St Lawrence-Ontario basin provides us 

 with a master key to the amount of land uplift during two time 

 divisions, the Iroquois or glacial time, and the Post-Iroquois or 

 postglacial time. Wherever we can determine the height of either 

 the closing Iroquois or the marine plane we can calculate the 

 other one. The marine or sea-level altitude in the Ontario basin 

 measures the amount of Post-Iroquois uplift. By subtracting this 

 from the total uplift, as shown by the isobases (plate 9), we 

 determine, for that point in space, the amount of uplift previous 

 to the extinction of Iroquois, which for New York is glacial time. 

 And the total uplift, the isobasal value, when subtracted from the 

 present altitude of the point, gives us the height of that point 

 before uplifting began. 



The tabulation gives examples of the analysis ; and comparison 

 of the data in the table with the map of isobases reveals some 

 interesting facts. It is found that Hamilton, Ontario, at the 

 extreme west end of Lake Iroquois, received during glacial time 

 more than half, about three-fifths, of its total uplift. Rome, at 

 the southeastern extremity of the lake, and the outlet, suffered 

 more than half its rise during glacial time. And these two- 



