QUATERNARY DEPOSITS OF BRITISH ISLES BROOKS. 



9. THE ALPS. 



351 



Having now dealt with the whole area covered by the north Euro- 

 pean system of ice sheets, I can return to central Europe, and refer 

 to the glaciation of the Alps. Here one great work — Penck and 

 Bruckner's "Die Alpen in Eiszeitalter " (117a) — entirely dominates 

 the literature. The authors adopt a fourfold glaciation, with re- 

 treat stadia since the last glaciation, the complete scheme being as 

 follows : 



Pliocene. 



Duration about- 



Gap. — Elevation of 500 to 600 meters on the southern margin of the Alps. 



Gunzian glaciation. — Our knowledge of this is slight, but the snow line probably 

 lay 1,200 meters lower than now. Upper Dekkenschotter of Rhine Valley. 



Gunz- Mindel interglacial. — Nothing is known with certainty. From the rela- 

 tions of the gravels of the Gunz with those of the Mindel glaciation, its duration 

 was probably similar to that of the Riss-Wurm interglacial. 



Mindel glaciation. — The maximum glaciation over the northeast, east and south- 

 east of the Alps. Snowline about 1,300 meters below the present Lower Dekken- 

 schotter of Rhine Valley. 



Mindel-Riss interglacial. — Very long in duration; a great amount of erosion and 

 weathering was effected. At Leffe peat with Elephas antiguus and Elephas 

 meridionalis is referred to this. Chellean. Elevation occurred during this 

 interglacial. 



Riss glaciation. — Maximum glaciation in the Rhine Valley, France, Switzerland 

 and the Po Valley. Snowline about 1,300 meters below present. Early Mous- 

 terian. High terrace of Rhine Valley. 



Riss- Wurm interglacial. — Relatively short amount of erosion and weathering 

 Indicate a duration only one-fourth as great as that of the Mindel-Riss inter- 

 glacial. Warmer than the present. Flora of Hotting breccia indicates a 

 temperature 2° higher. Fauna includes Elephas antiguus and Rhinoceros 

 Mercki. Late Mousterian. Most of the loess dates from the conclusion of this 

 interglacial. 



Wurm glaciation. — Less in extent than the Riss glaciation. The snow line lay 

 about 1,200 meters lower than at present. Fauna and flora arctic. In the 

 middle of the Wurm glaciation was an interstadial period, the Achen intcr- 

 stadial. — Solutrean, and at its close, early Magdalenian. Low terrace of Rhine 

 Valley. Next occurred a retreat of ice, followed by a slight re-advance, the 

 Buhlstadium, snow line 900 meters lower than now. Magdalenian. 



Followed by — 



Gschnitz Stadium. — Snow line COO meters lower. Daun Stadium— Snow line 

 300 meters lower. Middle neolithic. 



? C0,000 years. 



210,000 years. 



C0,000 years. 



Post- Wurm period, 



20,000 years. 

 Post-Buhl period, 



16,000 years. 

 Post-Daun period, 



7,000 years. 



The authors have no data for the duration of the glacial periods, 

 but assume arbitrarily that the duration of the Wurm glaciation 

 was equal to that of the Riss- Wurm interglacial, or 60,000 years. 

 This appears to me far too long, for on their own showing the 

 retreat stadia can not have lasted more than about 4,000 years each, 

 yet these sufficed to accumulate well-marked end moraines, and in 

 Sweden, De Geer has shown that a few centuries sufficed to form 

 the great end moraines of that country. 



