GEOCHRONOLOGY DE GEER 689 



of the clay layers was so seldom exposed, that the particular stages 

 of ice recession could be determined on|y at six points on the whole 

 line. Though it is thus impossible to compute the exact rate of ice 

 recession in this region, his numerous measurements of long varve 

 series have afforded valuable material for detailed comparison with 

 the time scale in Sweden, and for satisfactory verification of the 

 thickness variation of the varves in some otherwise unverified parts 

 of the Swedish scale. 



Since the initiative, organization, and method of this investigation 

 are of Swedish origin, and it is apparently only in Sweden that the 

 lime scale can be continued right up to the present day, it seems fair 

 to name this standard }me of chronology " the Swedish time scale," 

 even where it is verified and completed by parallel measurements in 

 other countries. The main purpose of an exact international 

 chronology must be the reference of different kinds of events every- 

 where, to one and the same standard of time. The necessary condi- 

 tion for the introduction of such a time scale was, of course, the 

 possibility of identifying synchronous varve variations even at great 

 distances. This condition seems now to be realized. Thus almost 

 all the varve series measured in 1920 by the Swedish expedition to 

 North America have, with certainty, been identified with correspond- 

 ing series in the time scaje in Sweden. This was illustrated by ex- 

 amples representing a few thousand years published (in English) in 

 the Geografiska Annajer, Stockholm, 1926. I have also quite recently 

 succeeded in identifying a series of nearly 600 varves, carefully 

 measured in Argentina by one of my former pupils, Dr. Carl 

 Caldenius. In the same journaj was published a description of E. 

 Norin's varve measurements in the northwestern Himalayas, carried 

 out and identified by him in 1925 and 1926, and also late glacial 

 clay varves in Iceland measured in 1919 by H. Wadell and recently 

 correlated with the Swedish time scale by Ebba IIu)t De Geer. A 

 continuous series of eight hundred varves measured by Dr. Caldenius 

 in southern Chile has also been dated by myself and will soon be 

 published by the Geological Survey of Argentina. Among other 

 correlations performed, here it may only be mentioned that the 

 Swedish time scaje has now become extended to the very limit of the 

 Gotiglacial ice oscillation or to the beginning of the corresponding 

 ^subepoch, giving not quite 8,000 years before the end of the Ice Age 

 and thus considerably less than the 9,500 which were earlier tenta- 

 tively suggested. 



Considering that the distances from Sweden and to these other 

 regions range from 6,000 to 14,000 kilometers, the similarity of more 

 than 80 per cent of the whole identified varve series is very striking. 

 It is especially noteworthy that this similarity continues for century 



