DISCRIMINATIVE CRITERIA 199 



ABSENCE OF MARINE FOSSILS 



The entire absence of marine fossils in the higher sand-plains and 

 tliroughout some valleys has been sufficiently explained in former writ- 

 ings. Only fresh water existed in the Hudson, Champlain, and Saint 

 Lawrence valleys until the ice-front receded from northern New Bruns- 

 wick and Gaspe Peninsula. Then salt water passed up the Saint Law- 

 rence Valley ; but by that time the wave uplift had raised the lower Hud- 

 son district to something like its present height, and the primitive and 

 highest sealevel shoreline was lifted much above the marine waters. W. A. 

 Johnston says that marine fossils do not occur above 510 feet in the 

 Ottawa district (48, page 27). This is 190 feet beneath the uplifted 

 marine plane. 



Because of the free connection with the sea, marine fossils might be ex- 

 pected in the early deposits of the New England valleys. But the physical 

 factors argue for unfavorable biologic conditions when the early deposits 

 were laid. The waters in the broader, lower stretches of the estuaries 

 must have been affected by the copious glacial flood added to the land 

 drainage. The coarse detritus was piled near the mouths of the streams 

 and only the deeply submerged clays could preserve the salt-water or- 

 ganisms. As the ice-front receded and uncovered the upper stretches of 

 the estuaries, the constriction of the valleys increased the percentage of 

 the fresh water. No marine fossils are found anywhere in the deposits 

 near the summit water level, and they should not be expected. 



Eegarding fossils in the inferior deposits, Stone v^rites : 



"The fact that fossils are rarest where the clay is deepest proves unfavor- 

 able conditions for marine life near the mouths of both the glacial rivers and 

 the ordinary rivers. In other words, the vast influx of ice-cold and muddy 

 fresh water during the final melting of the great glacier was destructive of 

 marine life. 



"The rarity of fossils contained in the upper clays and silts makes it very 

 difficult to determine where the marine beds end and those of estuarine and 

 fresh-water origin begin" (page 56) . 



Absence of marine organisms can never be taken as proof of non- 

 marine water or lack of confluence with the sea. 



ABSENCE OF SHORE FEATURES 



The lack of positive shore features even on long stretches of the old and 

 uplifted shorelines is not valid negative proof. In production of shore 

 inscriptions the principal factor is duration, and the rise of the land more 

 01- less promptly after the removal of ilie ice-load prevented conccntraicd 

 attack by the waves not only at the initial level, but at all inferior levels. 



