54 THE OCEAN RIVER 



foundations of today's oil fields began. It is much more prob- 

 able that the bulk of these organic materials in the oil-breeding 

 muds of the ancient sea floor came from very much smaller 

 varieties of life. 



Minute animals and plants, drifting helplessly in the salt 

 waters everywhere^ go to make up what we call plankton. 

 Though small, sometimes even invisible to the naked eye, this 

 drifting life of the plankton many times exceeds in bulk the 

 entire mass of fishes, clams, Crustacea, and other more obvious 

 creatures, even though these may individually be thousands 

 of times larger. The energy of sunlight, trapped by the minute 

 plants of the plankton, is used through the green magic of 

 their chlorophyll to build up within their tissues, from the ever- 

 present carbon dioxide disolved in sea water, the chemical 

 foodstuffs we call carbohydrates. The teeming microscopic 

 plants of the plankton and the infinite numbers of small 

 planktonic animals that feed upon them have lived their short 

 lives, and their dead bodies have rained ceaselessly down upon 

 the sea floors throughout the entire history of the fossil sedi- 

 ments, carrying with them the sun's energy transformed into 

 this chemical energy of the carbohydrates. As they became 

 buried in the accumulating sediments their bodies decayed 

 and their substance was converted into the starting materials 

 from which petroleum is formed. 



This process did not take place in all the ancient sea floors. 

 Parker Trask, Claude Zobell, and others, from their investiga- 

 tions of modern sediments have given us some insight into the 

 nature of these deposits. It seems fairly certain now that oil 

 was mainly formed from plankton remains in the sediments of 

 shallow seas. This was especially true when these seas became 

 partly cut off from the main ocean, just as parts of the great 

 ancestral gulfs of North America and of Tethys, the ancient 

 Mediterranean, were sometimes cut off from the North 

 Atlantic basin. It seems probable too that, just as today the 



