756 T. C. BROWN OOLITES AXD OOLITIC TEXTURE 



the oolites are now forming, carries most of its calcinm in the form of 

 sulphate. The great abundance of sodium salts in the lake, some of them 

 even to the point of supersatnration during the winter months (mirab- 

 ilitft. or Glauber's salt, is precipitated in great quantit}^ when the tem- 

 perature goes below 20 degrees F.), and the fact that the calcium indi- 

 cated in all the analyses of the Salt Lake salts is probably present as a 

 sulphate make it very probable that the reaction here is similar to that 

 observed by Linck in the laboratory experiments. The chemistry of the 

 reaction is, however, greatly complicated by the extremely dilute condi- 

 tion of the calcium salts present and the great degree of concentration of 

 the sodium salts, particularly sodium chloride and sodium sulphate. - 



A very much stronger argument for the formation of oolites, accord- 

 ins^ to Linck's reaction, is to be found in PATamid Lake. In this lake 

 the salinity is only .35 per cent, and the composition of the salts differs 

 widely from those of sea-water and those of Great Salt Lake, as can 

 readily be seen by a glance at the table of analyses. Some of the sodium 

 here present is evidently in the form of sodium carbonate. The only 

 locality where oolite is forming in P}Tamid Lake is near hot calcareous 

 springs.^* The lime carbonate of these hot springs is evidently at once 

 precipitated by the sodium carbonate of the lake water and partly in the 

 form of oolites. 



As already stated, the place on the shore of Great Salt Lake where the 

 oolites are forming is also near a source of supply, namely, the mouth of 

 the Jordan Eiver, whose annual tribute of lime can not be small, but this 

 river carries the lime largely as the sulphate. An analysis made in 1900 

 showed that this river near its entrance into Great Salt Lake had a sa- 

 linity of over 1 per cent, and of the contained salts calcium formed over 

 10^ per cent, while only a trace of COg was present.-^ Lentil irrigation 

 became extensive along the banks of this river, a few decades ago, calcium 

 sulphate was present in these waters in excess of all other salts. The 

 effect of irrigation has been to greatly increase the sodium chloride of 

 the river and consequently to lower the relative position of the calcium 

 sulphate; but the important point is still to be noted that the Jordan 

 Eiver, which is generally admitted to be the source of supply of the lime 

 for the oolites, carries that lime as the sulphate and not as the carbonate. 



If the oolites of Great Salt Lake are forming as chemical precipitates, 

 the seasonal variations in salinity would readily explain the zones of dif- 

 ferent texture in the oolites. On the other hand, if the oolites are formed 

 by algae, how is it possible to explain the fact that these are forming in 



2*G. K. Gilbert: Mon. I, U. S. Geological Surrey, p. 169. 

 2SBull. 491, U. S. Geological Survey, p. 145. 



