QUATERNARY DEPOSITS OF BRITISH ISLES BROOKS. 



353 



CORRELATION. 



Direct correlation with the north German plain is difficult and can 

 only be made on general grounds. In his chronological studies in 

 Sweden, De Geer found that the retreating ice reached the south 

 of Scania about 12,000 years ago, and he allowed another 5,000 years 

 for the recession across the Baltic, making the maximum of the 

 Baltic readvance 17,000 years ago ; this agrees very well with Penck 

 and Bruckner's datum of 16,000 years for the age of the Biihlstadium. 

 Working backward from this, we have — 



NORTH GERMANY. 



Baltic readvance. 



Baltic interstadial. 



Third glaciation. 



Interglacial with P. Duboisiana. 



Second glaciation. 



Interglacial with P. diluviana. 



First glaciation. 



ALPS. 



Buhl. stadium. 

 First interstadial. 

 Wurni glaciation. 

 Riss-Wurm interglacial. 

 Riss glaciation. 

 Mindel-Riss interglacial. 

 Mindel glaciation. 

 Gunz-Mindell interglacial. 

 Gunz glaciation. 



The interglacial with P. diluviana in Germany and the Mindel- 

 Eiss interglacial in Switzerland were both long periods with con- 

 siderable tectonic disturbance. 



Correlation with Holland and the lower Rhine can be made by 

 means of the Rhine terraces. In the upper Rhine, at say Basel, we 

 have the upper Dekkenschotter, lower Dekkenschotter, high terrace, 

 and low terrace, corresponding to the first, second, third, and fourth 

 glaciations. As has been described in the section on Holland, when 

 these are traced downstream they converge, the lower Dekkenschotter 

 become the chief terrace and overlie the continuation of the upper 

 Dekkenschotter, separated from them by finer deposits and by the 

 equivalents of the Tegelen clays. The high terrace becomes the 

 series grouped together as high and middle terraces, and the low 

 terrace remains unchanged. I have already correlated the chief 

 terrace with the maximum glaciation of Holland and this with the 

 first glaciation of north Germany, and the high and middle terraces 

 with the second glaciation of Holland and Germany, so that the three 

 districts form a triangle in which all the correlations agree. These 

 fit in better with the archeological views of Gagel and Penck than 

 with those of Schmidt and Obermaier, but this point must be left 

 till later. 



10. FRANCE. 



The Alps extend into France, but nothing need be added to the 

 section dealing with the glaciation of that mountain group as worked 

 out by Messrs. Penck and Bruckner. In addition to this there were 



