SALT LAKE OOLITES 755 



A. Mean of 77 analyses of ocean water from many localities, collected by 

 the Challenger expedition, rated in Bnll. 491, U. S. Geological Survey, page 

 113. 



F. Great Salt Lake. Collected in 1904. Bull. 491, U. S. Geological Survey, 

 page 144. 



G. Great Salt Lake. Collected in October, 1907. Bull. 491, U. S. Geological 

 Survey, page 144. 



H. Great Salt Lake. Collected in February, 1910. Bull. 491, U. S. Geo- 

 logical Survey, page 144. 



A comparison of F, G, and H with A for normal sea-water shows that 

 in composition the total salts of Great Salt Lake vary in only minor de- 

 tails from those of the oceans. The most notable variations are in the 

 higher percentages of sodinm and potassium, lower percentages of cal- 

 cium and magnesium, and the total lack of the CO3 radicle. The degree 

 of salinity, on the other hand, is not only very much greater but at the 

 same time is very variable. There is a seasonal rise and fall in the salinity 

 of the water, which changes with the change in the level ot the lake, due 

 to the seasonal variation in the relation between the supply from precipi- 

 tation and inflow and the loss by the evaporation of the water. The sea- 

 sonal variation in the height of the lake is from 15 to 18 inches, being 

 highest in June and lowest in November. There is also a periodic varia- 

 tion extending through a cycle of years and amounting in all to about 13 

 feet of change. The water of the lake was at a low stage in 1850 ; from 

 that date it continued to rise till 1873, when it reached a maximum in 

 elevation and a minimum in salinity (13.79 per cent in 1877). From 

 1873 to 1906 the volume of the lake decreased and the salinity increased 

 (27.72 per cent in 1904). Among all the analyses of this water collected 

 by Clarke, only one records the presence of the CO3 radicle, and that 

 sample was taken in 1877, when the salinity was near the minimum. 



These facts concerning the composition of the salts and the salinity of 

 the water have a direct bearing on the problem of the formation of the 

 oolites. Gilbert remarked that : "Despite the fact tnat calcium carbonate 

 is precipitated on the shore in the form of an oolitic sand, none of the 

 analysts have succeeded in finding it in the brine ; and it is probable that 

 the weighable calcium found in two of the samples exists in the form of 

 sulphate." ^^ It is a well known fact that calcium carbonate is one of the 

 important salts in the river waters tributary to Great Salt Lake f^ but it 

 is evidently all destroyed by double decomposition immediately on enter- 

 ing the lake, and the greater part is eventually precipitated in the form 

 of oolitic sand. Moreover, Jordan Eiver, entering the lake near where 



22Mon. I, U. S. Geological Survey, p. 252. 



23 See Bull. 491, U. S. Geological Survey, p. 145. 



