66 Natural Brines of Oil Fields [264 



but it is hardly possible that the reactions between the 

 waters and the rock material would produce a brine so simi- 

 lar to ocean water, since the alteration of river water to ocean 

 water is effected largely by the action of organisms in the 

 sea. 



The perpendicularity of the lines uniting the brines and 

 the ocean water indicate the similarity between the chemical 

 nature of the present ocean and that of former seas. The 

 variations from the straight line,, with the exception of the 

 graphs for calcium and sodium, is readily explained by the 

 possible reactions which may have occurred between the rock 

 material and the chemicals in solution. It will be noted, 

 however, that there is a definite increase of calcium and 

 decrease in sodium in passing downward from the Pennsyl- 

 vanian to the Lower Devonian brines. If the waters are 

 assumed to be of meteoric origin, then there is the anomaly 

 of the more soluble sodium being replaced by the less soluble 

 calcium ion as the water penetrates the earth's crust. If, 

 however, the waters are considered to be of connate origin, 

 then this change in depth may be a function of the geological 

 age of the strata and hence indicate changes in the chemical 

 content of the ocean during different geologic periods. 



If the salts of the ocean have been added by the rivers, 

 then, of course, the salinity of the ocean would increa.se with 

 the age of the earth. This increase in salinity will not affect 

 the chemical nature of the water if the relative amount of each 

 salt remains constant. However, since organic matter and 

 changes in physical conditions remove some salts from solu- 

 tion, the waters will change in nature as well as concentration. 

 Thus the relative increase in sodium may be explained by 

 the fact that but little of the enormous amount of this salt 

 added continually by the rivers is lost by the ocean, while 

 most of the other salts are constantly being removed from 

 solution. The variation in amount of calcium in the differ- 

 ent brines is likely due to fluctuation in the amount of C0 2 

 in the air during different geologic periods. This fluctuation 



