THE BLACK SEA 401 



(below the plankton one), it is 6 to 8 in the deep-water grey clay, i.e. almost 

 a typical plankton ratio. 



By calculating the number of thin layers in the grey clay cores, Archangel- 

 sky has determined that (assuming that the layers are annual) the 1 m sedi- 

 mentation of grey clay took 5,000 years to accumulate. From the organic 

 matter content of the grey clay it is possible to calculate that 6 tons of organic 

 carbon accumulated on 1 km 2 in a year during the deposition period. In a 

 similar manner, Archangelsky has calculated that 4-2 tons of organic carbon 

 were accumulated per 1 km 2 of the floor annually during the period of deposi- 

 tion of the Maikop Oligocene clays. The magnitude of these deposits of 

 organic matter, accumulated on the bottom of the Black Sea, can be assessed 

 by the fact that the amount of organic carbon contained in the column of 

 Oligocene and Miocene deposits in the Sulak and Yaryk-Su area (near the 

 Caspian Sea) over about 500 km 2 is approximately equal to the total amount 

 of coal in the Donets basin (67,170x 10 6 tons). 



IV. FLORA AND FAUNA 

 Plankton 



The qualitative composition of phytoplankton. According to the latest data of 

 N. Morozova-Wodjanitzkaja (1954) the phytoplankton of the Black Sea 

 comprises 350 species {Table 160). 



Table 160 



N. Morozova-Wodjanitzkaja and E. Belogorskaya (1957) have recorded 

 1 8 species of coccolithophorides, which had been thought to be absent from 

 the Black Sea.* Some members of this group are abundantly developed in the 

 Black Sea. Morozova-Wodjanitzkaja found up to 850,000 specimens of 

 Pontosphaera huxleyi in the Bay of Sevastopol during her March and April 



* P. Usachev (1947) was the first to record the coccolithophorides in the Black Sea. 

 2G 



