QUATERNARY DEPOSITS OF BRITISH ISLES BROOKS. 285 



trees in the south Baltic regions would certainly allow the forma- 

 tion of peat southeast of Brunswick. 



The latter view is supported by the mode of occurrence of the loess 

 referred to later. It is sufficient to remark here that in the south 

 Baltic region loess cccurs on the outer moraines of the last glacia- 

 tion, preceding the Baltic interstadial, but not on the inner moraines, 

 succeeding that interstadial. Correspondingly, in the upper Weser 

 Valley, loess, w^eathered to a depth of 2 to 4 meters, occurs on the 

 higher and middle terraces, but not on the lower terrace. For this 

 reason Gruj^e places it in the last interglacial, and Siegert in the late 

 glacial period, while its true position, as in the Baltic, would seem 

 to be interstadial. We may therefore summarize the conditions in 

 the Weser Valley as follows : 

 Postglacial: Alluvium. 



Third glacial pei'iod : Post-interstadial, lower terrace. Interstadial, 

 loess ; peat at base of terrace at Hameln, Pre-interstadial, middle 

 terrace, upper part. 

 Second interglacial : Lower part of middle terrace. Peat, etc., of Nach- 



tigall with Gorylus avellana. Mammal fauna of base of gravels. 

 Second glacial: Banded clays, marl sands, ground moraine and end mo- 

 raines from Hameln downstream. Upi>er part of Weser high terrace. 

 First interglacial : Lower part of Weser high terrace with northern 



material. 

 First glacial : Remains of glacial formations older than high terrace., 

 Preglacial and Pliocene: Weser higher terraces, formed of local ma- 

 terials. 



THE BALTIC INTERSTADIAL. 



The end moraines known as the Baltic Hohenriicken have been, as 

 by the late J. Geikie, referred to a fourth glaciation, but hitherto 

 all attempts to find deposits referable to the corresponding inter- 

 glacial have failed. Fossiliferous deposits intercalated in the upper 

 bowlder clay are known, and are fairly common in East Prussia, but 

 the fauna and flora are in every case of an arctic or subarctic type, 

 such as could well have lived in close proximity to the ice margin. 

 These fossiliferous deposits were investigated by E. Harbort in 

 1910 (12), the Mollusca and plants being described by H. Menzel and 

 J. Stoller. The fauna indicates " arctic " but not " polar " conditions, 

 all the species extending south into the tree zone ; the plants indicate 

 a July temperature of at least 10° C. and a vegetation period of 

 three to four months with a temperature of 3 to 6° C. Harbort con- 

 siders the oscillations to have been slow and irregular, ice free periods 

 lasting sometimes for decades and possibly centuries before the peat 

 deposits and small trees were buried by a readvance. 



Similarly no interglacial can be proved older than that with 

 Paludina diliwiana and Ta/pes aureus eerrdensis^ nor do the older 

 river terraces which should correspond with this interglacial bear 



