PLEISTOCENE. GEOLOGY OF MOOEBS QUADRANGLE 



27 



lines, iu the form of low ridges-, often crowded closely together, 

 are particularly numerous northwest of the English river along 

 the international boundary between 360 feet and 500 feet. I 

 counted 26 such ridges between the 305 foot and the 450 foot con- 

 tour lines. From Butlifl brook south of Mooers to the southern 

 limits of the sheet, the surface is ribbed with beaches almost 

 everywhere apparent, from 500 feet down to 320. Higher wave 

 marks also occur in this part of the sheet. Lower wave marks 

 are seen on the Rouse Point quadrangle to the east. 



The location of the numerous beaches shown on the map and 

 their position with reference to the contour lines were deter- 

 mined by eye estimates in traversing the areas where they occur. 

 Any single beach ridge can seldom be traced satisfactorily for any 

 distance; it may fade away, merge into other lines, or become lost 

 in second growth timber, where its slight relief, added to the other 

 difficulties named, would make the detailed mapping of the many 

 similar beaches on this area hardly worth the expenditure of time 

 and money. I have reason to believe that many of the short beach 

 lines shown on the map are really more extended. Careful leveling 

 would also, I believe, show a greater divergence between the beach 

 lines and the contour lines. It is to be presumed that the con- 

 tour lines are correctly drawn. It is noticeable however that 

 they are drawn to follow the prominent beach lines; but the evi- 

 dent decline of the principal wave zone from north to south ap- 

 pears to indicate very clearly that the beach lines are not level 

 lines, yet no beach as before noted proved sufficiently distinct 

 and continuous to make the testt of walking one out across the 

 area available for determining the degree of tilting. 



The principal object of the study and mapping of the beaches 

 has been to determine if possible the upper mariue limit in this 

 field, and the question at once arose whether all the beaches were 

 marine or whether some of the higher ones were formed in a 

 fresh-water lake in front of the retreating ice sheet. It has been 

 seen how " the Gulf " would place the marine limit below 045 feet 

 of elevation. 



The lower beaches up to at least 310 feet above the present sea 

 level are shown to have been made by the sea by the existence of 

 marine shells in the contemporaneous deposits. There appear to 



