in the Pleistocene and Post-Pleistocene. • 19 



Evidence somewhat similar to that which has been so strik- 

 ingly presented by Fernald is found on the shores of north- 

 western Europe, of land emergence above the present level 

 involving regions beyond the limits of glaciation and occurring 

 in a warm stage following; the retreat of the ice. This is 

 presented in comprehensive form by W. B. Wright of the 

 Geological Survey of Ireland in his recent book on " The 

 Quaternary Ice Age." Before the glacially depressed region 

 had recovered in Scandinavia all of its present elevation, there 

 was a rapid uplift to the south which cut off the connection of 

 the Yoldia (enlarged Baltic) Sea with the Atlantic and pro- 

 duced the Ancylus lake. The climate was notably warmer 

 than at present, as recorded by the advance of the hazel 

 (Corylus avellana) and other plants to regions well beyond their 

 present northern limits. The same climatic optimum has been 

 proved in Finland, for at a certain floral horizon (the upper 

 portions of the Birch-Fir zone) certain warmth-requiring plants 

 made their appearance in localities far north qf their present 

 northerly limits.* In southern England forest beds which are 

 correlated with this stage are found submerged now to a depth 

 of 55 to 60 feet, indicating a post-glacial uplift of land to a 

 height well above the present sea level. 



Wright considers the breadth of this movement as indicative 

 of a general lowering of sea level and seeks its cause in a 

 recrudescence of some one of the ice sheets, possibly that of the 

 Antarctic continent. f But the general warmth of climate ex- 

 isting at that time does not favor such a view. So far as the 

 evidence goes two other hypotheses are preferable. 



One of these hypotheses is that the post-glacial emergence 

 and following submergence represent a diastrophic emergent 

 cycle entirely unrelated to glaciation, one of the movements in 

 the complex rhythms which have been traced in southern New 

 England through Tertiary and Quaternary times. If so, it 

 should be in part a sea-level movement, and traceable widely 

 over the earth. 



The other hypothesis involves less widespread effects. It is 

 that which was discussed in the pages leading up to the botan- 

 ical evidence. This hypothesis is, that the weight of the ice 

 sheets caused crustal depression directly below the load, but 

 moderate elevation in a wide zone beyond the load. ITpon 

 the removal of the ice it appears the first isostatic upwarping 

 carried up higher this marginal upwarped zone with it. Being 

 already an upswollen tract the broader regional movement 

 carried it up to a level where it became unstable and a slow 

 settling back occurred as an after effect, coincident with the 



*W. B. Wright, loc. cit., p. 437, 1914. 

 fLoc. cit., p. 417, 1914. 



