QUATERNARY DEPOSITS OF BRITISH ISLES BROOKS. 



303 



finding of littoral species of Mollusca at great sea depths off the west 

 coast of Norway, Brogger concludes that at one period during the 

 early Quaternary this region lay 2,600 meters higher than now. 

 Further, on the coastal banks of west Norway littoral arctic Mol- 

 lusca extend to depths of about 200 meters, indicating, in Brogger's 

 opinion, that the land lay at nearly 200 meters above the sea even 

 during the last glaciation. 



The question of the occurrence of deposits of the Baltic inter- 

 stadial in Scandinavia is quite different, and can be only approached 

 by a careful comparative study of the history of the Baltic. The 

 sequence in Denmark has been partly described already : 



Third glacial period. — Fluvioglacial deposits and moraines with 

 erratics from south Norway. Land slightly above present level. 



Older Dryas period and younger Toldia period. — Slight sub- 

 sidence. 



Allerod oscillation. — A decided amelioration of climate. Land 

 above present level. 



Younger Dryas period. — Return of cold climate. 



ZirpJiaea sands. — Cold conditions; slight submergence. 



After the deposition of the Zirphaea sands there is a gap, during 

 which no deposits are known to have been formed, probably because 

 of the considerable elevation of the land. This may correspond to 

 the Ancylus period. It is followed by the older Tapes beds, repre- 

 senting the maximum subsidence in Denmark and also probably the 

 temperature maximum. 



Above the older Tapes beds are the younger Tapes or Dosinia 

 beds, intermediate between the older Tapes time and the present 

 both in level and climate. Lastly come the still forming beds with 

 My a arenaria. 



The latter part of this sequence agrees very well with that in south 

 Sweden, as described by numerous authors (56), but the earlier 

 part is at variance. We may make the following comparison : 



liKNIIARK. 



Mya arenaria layers. 

 Younger Tapes beds. 

 Older Tapes beds. 



(Climatic optimum.) 

 (Gap.) 

 Zirphaea beds. 



Upper shore sand and 

 younger Dryas period. 



Allerod gyttja. 



Younger Yoldia clay. 



Lower shore sand. 



Older Dryas period. 



Last glacial period. 



Mya armaria layers. 



Litorina beds. 



(Climatic optimum.) 

 Ancylus lacustrine beds. 

 Deposits of Yoldia Sea. 



Great Scanian end moraine. 



Baltic ice lake. 



Ice over Schonen. 



Arctic plant beds of Schonen. 



Last glacial period. 



