AGE OF GYPSUM OF CENTRAL lOlVA 745 



tributed in the marl of the old Bonneville bed, as well as along 

 the shore/ Still, the fact that calcium carbonate deposits were 

 favored at the shores by the aeration associated with wave action 

 is particularly significant. Even more significant is the fact that 

 near the streams which contribute to the lake the greatest amount 

 of lime carbonate, the calcareous oolite already mentioned, accu- 

 mulates as a shore deposit in considerable quantities. If in this 

 or some similar way the lime carbonate was localized, the Medi- 

 terranean hypothesis would appear satisfactory. 



The experiments of Thoulet, quoted by Bailey Willis,^ seemed 

 to show that carbonate of lime in the form of marble, shells, 

 coral, and globigerina ooze are much less soluble in ocean water 

 than in fresh water. If this is true, when river water enters a 

 salt sea, conditions for unstable equilibrium of the bi-carbonate 

 of lime might arise which would result in the formation, and 

 probably the deposition, of the neutral carbonate, and the greater 

 the salinity of the sea, the more prompt and complete would be 

 the precipitation. In this way streams on entering a salt sea 

 inight precipitate all of their calcium carbonate near their mouths, 

 while gypsum would be deposited on subsequent evaporation in 

 more remote parts of the basin. Willis calls attention to the lime- 

 stone deposited beyond the delta of the Rhone. He says :3 



This is referred to by Thoulet and described by Lyell who says : " In the 

 Museum at Montpelier is a cannon taken up from the mouth of the river 

 imbedded in crystalline calcareous rock. Large masses also are continually 

 taken up of an arenaceous rock cemented by calcareous matter, including 

 multitudes of broken shells of recent species." Lyell attributes the precipi- 

 tation of lime to the evaporation of the Rhone water, which, when it is spread 

 upon the salt water, he compares to a lake. But this one cause is no doubt 

 combined with the chemical and mechanical conditions which have been sug- 

 gested in the preceding discussion. These conditions are favored at the mouth 

 of the Rhone by the salinity of the Mediterranean and the absence of strong 

 currents. 



The experiments of Cameron and SeidelH gave results which 

 differ radically from those of Thoulet. These chemists found 

 'U. S. Geology Survey, Monograph 2, " Lake Bonneville," p. 190. 

 ^Journal of Geology, Vol. I, p. 510. ^ /did., p. sid- 



* Cameron and Seidell, in Journal of Physical Chemistry, Vol. VI, No. i, p. 52. 



