82 NEW YORK STATE MUSEUM 



has argued that the major rehef features immediately prior to 

 the advent of the Potsdam sea were valleys carved out along 

 the belts of weaker Grenville strata, especially the limestones. 



Positive evidence regarding the physiographic condition of the 

 interior Adirondack region during Cambric time is of course 

 lacking, but there is no reason whatever for thinking that it was 

 essentially different from the immediately surrounding regions 

 except probably that the general altitude was somewhat greater. 



Encroachment of the late Cambric sea. Gushing^ has proved 

 that the Potsdam sea encroachd upon the Adirondack region 

 from the northeast toward the southwest because the sandstone 

 formation of that age progressively thins from a thickness of 

 over one thousand feet to disappearance in the southwest. Dur- 

 ing the encroachment of this late Cambric sea, did the waters 

 enter distinct embayments or estuaries as Kemp^ has suggested 

 or did they form a more regular shore line? Along the eastern 

 side, where the topography was moderately rugged, such embay- 

 ments were quite likely physiographic features of some impor- 

 tance due to a drowning of the valleys which had been cut out 

 along the belts of weaker Grenville strata. In the southern 

 Adirondacks, however, the evidence is decidedly against the en- 

 croachment of the late Cambric sea by setting up anything like 

 well-defined embayments or estuaries extending into the area of 

 Precambric rock. 



The outliers of Palezoic rock in the southeastern Adirondacks 

 are of first importance in this connection. All the definitely 

 known outliers well within the Precambric rock area of this 

 region are given in the following list : 



I A small exposure of Potsdam sandstone near the south- 

 western corner of the Elizabethtown quadrangle and near the 

 village of North Hudson. 



2, 3, 4 Three outliers of Potsdam sandstone along the eastern 

 side of the Paradox Lake quadrangle. 



5 The Little Falls dolomite outHer (probably with underlying 

 Potsdam) at Schroon Lake village, Schroon Lake quadrangle. 



6 A small outlier of Potsdam sandstone one and one-half 

 miles west of the village of North River in the northeastern 

 corner of the Thirteenth Lake quadrangle. 



3 Pages 279-80. 

 6 Pages 408-12. 



