1888.] NATURAL SCIENCES OF PHILADELPHIA. 181 



ON THE FOEMATION OF ROCK-SALT BEDS AND MOTHER. 



LIQUOR SALTS. 



BY DR. CARL OCHSENIUS. 



As is well known that ocean-water, from which all primitive rock- 

 salt masses have been formed, contains on the average 82 % fixed L 

 e. saline constituents, of which 2^ % is sodium chloride, the remain- 

 der consisting of magnesium compounds, calcium sulphate, potassium 

 chloride, sodium bromide and small quantities of boron, iodine and 

 lithium salts, as well as traces of every other element, of which indeed 

 there exists one or the other compound, soluble in water and much 

 more so in salt-water. 



The open sea precipitates no salt, but in bays partially cut off 

 from it, a deposition can take place under certain circumstances, in 

 such a way that gypsum forms the base, and anhydrite the upper- 

 most layer of the salt deposit; this is plainly seen in every large 

 rock-salt bed. In considering the mode of formation of such deposits 

 we are' met on all sides by three questions, which hitherto have re- 

 mained somewhat inexplicable: — 1st the absence of fossils in the 

 salt, whilst the neighbouring rocks often contain them well preserved 

 and in abundance, 2nd the small quantities of easily soluble mag- 

 nesium and potassium salts, though they were contained in the sea- 

 water, and .3rd the replacement of these latter by one of the most 

 insoluble constituents, viz. sulphate of lime in the form of a cap of 

 anhydrite, the so-called Anhydrithut. These facts can, however, be 

 explained, if we take a hydrographical element, viz. the bar, into 

 account in the process of formation. When a nearly horizontally 

 running bar cuts off a bay from the sea, so that only as much sea- 

 water runs in over it as is compensated by evaporation from the 

 surface of the lagoon, and the so partially separated portion receives 

 no large additions of fresh — , i. e. rain or running water a deposition 

 of salt takes place in the Avay to be described. 



In such a bay the following phenomena may be observed : — The 

 sea-water running in evaporates, and by the amount of salt it adds, 

 the solid constituents of the bay are continually increased. The 

 upper sheets of water, warmed by the sun, sink as they get specific- 

 ally heavier from the larger amount of salt, and in the course of time, 

 a vertical circulation setting in, the whole aqueous contents become 



