REVIEW OF OLD AND NEW STANDARDS OF PLEISTOCENE DIVISION 427 



coordinate the entirety of the preceding observations on the two banks 

 of the English Channel and the Pas de Calais in relation to the important 

 question of the union of England with France in the Quaternary epoch 

 and to the opening epoch of the Pas de Calais (that is, channel opposite 

 Calais). 



A simple solution, founded on the distribution of the Quaternary 

 marine deposits, follows : One may admit a quite large junction of France 

 and England during the Sicilian and Milazzian epochs (= Periods o!~ 

 Glaciation I and II), represented only by a coastal plain at the altitudes 

 of 100 meters and 60 meters. The English Channel was certainly more 

 contracted than today, without having to determine its limits. The 

 Elephas antiquus warm fauna and hippopotami were thus able to emi- 

 grate freely into England. 



At the Tyrrhenian epoch (= Period of Glaciation III), the 30-33- 

 meter shoreline is well characterized on the French coast (Saint Valery), 

 and above all on the English coast (Sussex), with a marine and terrestrial 

 fauna with southern affinities. One may deduce from this that the 

 English Channel formed then a great Atlantic gulf extending at least 

 as far north as the estuary of the Somme, but separated from the 

 North Sea by a quite large isthmus. This conception explains the absence 

 of arctic shells in the Tyrrhenian fauna of the English Channel and 

 a continuation of the exchanges of the terrestrial fauna between England 

 and the continent. 



But at the Monastirian epoch (= Period of Glaciation IV) the con- 

 tinuity of the marine deposits of the 20 -meter shoreline (and lower 

 lines) reveals to us a geography almost identical with that of the present 

 day, as so perfectly recognized by Briquet. The opening of the Pas de 

 Calais admitted the migration into the English Channel of a colder 

 marine fauna from the North Sea. 



Migration of cold land fauna. — But this simple interpretation is 

 marred by the difficulty of explaining the passage into England of the 

 cold land fauna of terrestrial animals of upper Quaternary times. It 

 becomes necessary, therefore, to introduce into the problem a new ele- 

 ment, which I have abstractly shown here, that of the phases of marine 

 regression (with the lowering of the shorelines to the level and even 

 below the shore), from which begin each of the four Quaternary stages. 

 These phenomena of regression, so sharply marked in the Mediterranean, 

 are geologic events too important not to be found in other seas. In fact, 

 the position of the levels of the present shore of estuarine beds of the 

 Tyrrhenian of Sussex, as well as the Sicilian forest bed of Cromer, not 

 to speak of the submerged forest and submarine valleys of more recent 

 age, show us typical examples of it. 



XXIX — Bull. Geol. Soc. Am., Vol. 33, 1921 



