24 



A. P. VINOGRADOV 



As part of the overall change in the composition of the ocean we must also 

 take into accoimt the appearance of a considerable amount of S04~ ~ in the 

 water. In the primary atmosphere sulphur was present, for the greater part, as 

 H2S or S and, although these could have been oxidized photochemically on the 

 surface of the Earth in the presence of water, the process of oxidation probably 

 did not take place to any great extent until a considerable amount of O2 had 

 appeared. 



The most ancient and the primary ocean seems to be the depression in the 

 Pacific ocean, the bed of which is not covered by the granitic envelope. The beds 

 of the Atlantic and Indian oceans are covered by the granitic shell (except, 

 possibly, in their deepest parts) and, in the opinion of most geologists, they were 

 formed in the palaeozoic, or perhaps even the mesozoic, age owing to the subsi- 

 dence of the crust of the Earth and the consequent submergence of the granitic 

 shell beneath the waters. 



INDICATIONS OF THE EARLY BIOSPHERE 



Among these indications may be considered the skeletons of organisms, 

 imprints and other morphological structures preserved in the geological forma- 

 tions, biogenic rocks themselves and, finally, the character of the weathering of 

 rocks and their composition. As we can see from Fig. i, none of these indications 

 very rapidly disappear in time. 



Fig. I. Diagram showing conservation of the different biogenic formations 

 through the ages. 



