GEOLOGY OF MOUNT MARCY 8l 



line features of the glacial lakes. It has been shown by Fairchild 

 in a number of papers^ that the character of the postlacustrine uplift 

 was a lifting in the form of a warped plane with the amount of 

 warping greater to the north. The lines of equal uplift since the 

 time of the marine level incline in this portion of the State west- 

 northwest to east-southeast (20 degrees from the latitude parallels). 

 The zero isobase passes far south of New York City. The 600 foot 

 isobase touches the northeast corner of the quadrangle, while the 

 553 foot isobase enters the sheet in the southeast corner. These 

 figures give the total uplift for the region since the marine waters 

 occupied the Hudson-Champlain embayment. The figure for the 

 amount of tilting for this marine plane in this region is 2.71 feet a 

 mile taken along a north and south line, or 2.83 feet perpendicular 

 to the isobase. 



Although Fair child's papers form a very valuable contribution to 

 this subject, there exists some uncertainty as to the character of the 

 uplift, (i) Was the upward movement gradual and uniform or (2) 

 was it in the nature of a wave or a series of sudden uplifts? The 

 writer believes that the problem will be clarified by the measurement 

 of beaches, deltas etc. situated at higher levels than the marine plain 

 to supplement those mapped at the lower altitudes. The shore 

 phenomena of the lakes above described afford an opportunity to 

 determine the amount of tilt of the land surface, for they furnish a 

 series of datum planes higher than those in the Champlain valley, 

 which was occupied by the ice during the entire period that these 

 lakes existed. Fairchild believes that his figures give the total uplift 

 since glacial times. The writer feels, however, that this conclusion 

 is based upon the state of affairs that prevailed during and after the 

 marine stage and overlooks the shore phenomena of higher lake 

 levels. Although accurate measurement of the amount of tile of the 

 lake levels of the Mount Marcy and adjacent sheets is exceedingly 

 difficult, for the chances of error are great, the table given below 

 would indicate that the uplift was taking place ivhile the ice was 

 melting from the area. 



^ Fairchild, H. L., " Pleistocene Uplift of New York and Adjacent Terri- 

 tory," Bui. Geol. Soc. Am. 27 :235-62 ; " Post-Glacial Marine Waters in 

 Vermont," Rep't of Vt. State Geol. for 1915-16. 



