REVIEW OF OLD AND NEW STANDARDS OF PLEISTOCENE DIVISION 417 



One may observe, moreover, four sheets or deposits of gravel (nappes 

 de caUloutis) standing at four different levels and related to four distinct 

 morainal formations, which are sometimes separated by considerable 

 spaces — that is, by notable differences of altitude. These four deposits 

 of gravel (nappes de caUloutis) correspond to four different glaciations 

 (alluvionnement glaciaire). During the first phase of each interglacial 

 recession period there is produced an erosion (creusement) , more or less 

 intense, but always rapid, by the abundant water-floods born in the 

 fountain of ice and establishing their stream-bed in the glacial pebbles 

 (caUloutis glaciaire). 



Terraces 



On either side of the glacial stream, against the declivity of the valley, 

 there may persist a part of the glacial layer not encroached upon and not 

 transported by the stream. Thus is constituted the terrace, a witness 

 to the topographic surface built up in course of the preceding glaciation 

 and connected with the moraines of the same glaciation. For example, 

 as we ascend the river, the terraces are related : 



{a) to the outer moraines of Glaciation II, the terraces at levels of 50-60 



meters ; 

 (Z>) to the intermediate moraines of Glaciation III, the terraces at levels of 



35 meters ; 

 (c) to the inner moraines of Glaciation IV, the terraces at levels of 18-32 



meters. 



These altitudes in meters (18-60) are calculated above the present 

 stream or river level (thalweg actuel) and in the broad valleys, farther 

 down stream than declivities, often very steep, of cones of glacial 

 transition. From these terrace altitudes and moraines Deperet makes 

 the following generalization: "A chaque glaciation correspond done une 

 valeur different e du creusement de la vallee des cours d'eau.r issus des 

 glaciers de cette periode." To each glaciation corresponds the distinctive 

 level of erosion of the valley produced by the occurrence of water issuing 

 from the glaciers of the corresponding period. There is thus placed in 

 evidence to the glaciologists of the peri-Alpine region a collection of 

 valuable data for the division of the Quaternary Glacial Epoch, which 

 includes the large part of the Pleistocene of Europe. Penck and 

 Bruckner in their classic work (1909.1) have given to the four great 

 phases of extension of the glaciers, the four glaciations, the following- 

 names, which we may refer to in their descending geologic order: 



Postglacial Period 



Behind the Wiirm moraines there occurs a limited number of morainal 

 formations, moraines stadiaires [= of stadial or substage rank and not 



