300 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



the present and even the great river valleys did not yet exist. They 

 were compared by Pavlov with the old bowlder beds of Germany 

 and Switzerland, and, especially with the bowlder beds with a 

 Pliocene fauna in southwest France, with the lower weathered 

 moraine of the serra chain of Piedmont, and with the immigra- 

 tion of the polar fauna in the Mediterranean during the fourth upper 

 Pliocene transgression, which corresponds to the first great European 

 glaciation. 



Professor Pavlov explains the lack of northern crystalline erratics 

 partly by their slight durability in comparison with chert and partly 

 by the mechanics of glacier work and nourishment; on the enormous 

 stretch of the Russian plain there was heaped up, before movement 

 began in a definite direction, a mass of snow, fern, and ice; in this 

 erratics were frozen; nourishment and movement continued for a 

 certain period, during which the bowlders from central Russia were 

 carried into the Zaritzyn district, but the Finnish erratics only 

 reached central Russia. 



Although the existence of these bowlder beds with erratics is 

 fairly established, there are difficulties in the way of giving them 

 such a liberal interpretation. The existence of an isolated occurrence 

 of ground moraine so far south, and entirely unconnected with any 

 center of glaciation by similar deposits, does not seem probable. In 

 Germany, as we have seen, the evidence for a Pliocene glaciation is 

 of the scantiest, in spite of the immense detail of the researches in 

 that country, and it seems certain that such a glaciation did not 

 overstep the limits of the first of the well-known glaciations. 



A more probable agent for the formation of beds in question seems 

 to be river ice, which would easily deposit erratic bowlders of central 

 Russian type in fluviatile sands. If we accept the late Pliocene age 

 of the beds which is suggested by their position with regard to the 

 drainage system, they may then represent, as suggested by M. Pavlov, 

 a cold period corresponding to the first Alpine glaciation, though we 

 have no proof that it was accompanied by the formation of an inland 

 ice sheet in central Russia. 



SUMMARY. 



Late Pliocene. — Considerable elevation in all parts of European 

 Russia. 



Close of Pliocene. — Cold period. River ice on the Volga. 



First glaciation. — Finnish ice attained its maximum extent, reach- 

 ing far into the central Russian plain. 



First interglacial. — (i) Lake -wood phase, (ii) Steppe phase, 

 (iii) Wood phase. 



Second glaciation. — Ice did not reach far into the central Russian 

 plain, stopping short of Wolhynia. 



