502 Kryshtofovich — Cretaceous Age of the 



Art. XVIII. — On the Cretaceous Age of the ''Miocene 

 Flora" of Sakhalin; by A. N. Keyshtofovich. 1 



The following pages form a summary of the results of 

 the elaboration of a part of plant fossils collected on 

 Sakhalin Island during 1917, the balance of the collec- 

 tions having been shipped to Petrograd. 



The fossil flora of the island of Sakhalin comes chiefly 

 from two localities, Dui and Mgach. It was described 

 originally by Heer 2 in 1878 who referred it to the Mio- 

 cene. Since it is rather extensive it has usually been taken 

 as a type for purposes of comparison with other Tertiary 

 floras despite the presence of Nilssonia, a genus quite 

 unusual in Tertiary deposits. No doubts as to the Ter- 

 tiary age of this flora have been expressed except that 

 on purely geological grounds Messrs. Tikhonovich and 

 Polevoi 3 have suggested recently that the Dui series (and 

 consequently its flora) was of considerable older Tertiary 

 age than the Mgach series, which is also characterized by 

 a rich flora, and which they regarded as belonging to the 

 Miocene. The matter of special interest is that Nilssonia 

 was believed to be a member of this Mgach flora. 



Having been despatched by the Comite Geologique in 

 1917 to Sakhalin, I have been able to prove that the fossil 

 flora of Sakhalin does not belong merely to the Miocene 

 or Tertiary, but comprises several different horizons 

 from the Miocene down to the Cenomanian and in 

 part probably still more ancient. Heer unfortunately 

 described mixed collections from Mgach, where, as I 

 noticed, the exposures of plant-bearing Cenomanian and 

 Miocene beds outcrop close together, although the two 

 are unconformable, a fact which Schmidt and other 

 explorers failed to observe. The predominance of speci- 

 mens collected in the upper Tertiary exposures in the 

 Heer collection convinced him that the whole flora was 

 Tertiary. However, the presence in my collections made 

 at this locality of Dammara borealis, Protophyllocladus 

 subintegrifolius, many ferns, cycads and typical Angio- 



1 Communicated and edited by Prof. Edward W. Berry. 



2 Heer, 1878, Die Miocene Flora der Insel Sachalin, Fl. foss. Arct., vol. 

 5, pt. 3. 



3 Tikhonovich and Polevoi, 1915, Geomorphological Sketch of Russian 

 Sakhalin, Memoires de la Comite Geologique, Russia, vol. 120 (new series). 



