GEOLOGY OF THE PARADOX LAKE QUADRANGLE 469 



until the Pleistocene the region w^s a land area and of the events 

 of this immense period of time there is very little record. What- 

 ever the details may have been, erosion was going on, and the 

 covering of early Palaeozoic rocks was being removed. A peneplain 

 was finally produced.' 



An uplift followed which was greatest in the northwest, and which 

 was accompanied by block faulting. A new cycle of erosion began, 

 continuing to remove the Palaeozoics from the Prepotsdam valleys, 

 and also developing new lines of drainage adjusted to the faults. 

 Another uplift followed, which was also' greatest in the northwest. 

 The next erosion cycle was interrupted by the glacial period. I 

 believe that these conclusions are in a general way in accord with 

 Dr Cushing's observations in the north.^ 



Age of lower base-level 



The age of this lower level in the Adirondacks can be fixed within 

 probable limits. The valley floor on which the drift was deposited 

 belongs to it and the streams had just begun to incise their channels. 

 Since therefore they had just begun to lower their channels before 

 the glacial period, the date of rejuvenation must have been late 

 Pliocene. If the rejuvenation of them closed the Pliocene, the 

 cutting of the lower level must have taken place in the earlier 

 Pliocene and Miocene. 



Glacial deposits and drainag^e modifications 



When the ice entered the region it encountered a drainage long 

 established and well-adjusted, but physiographically young in that 

 the region had recently been rejuvenated. After its withdrawal it 

 left the valleys completely drift-filled and the courses of the rapidly 

 cutting streams determined by the slope of the drift. 



The glacial deposits in this area are divisible into two groups; 

 those of unassorted material, consisting of heterogeneous mixtures 

 of all sizes of constituents from large boulders to fine sand, with 

 occasional admixture of clay ; and those composed of fine gravel, 



^Analogy with other regions would suggest Cretaceous age for this first 

 base level and Tertiary for the second, but no evidence of the age was found 

 within the region itself. 



^Geology of Franklin County. N. Y. State Geologist i8th An. Rept 1899. 



