354 PRINCIPLES OF STRATIGRAPHY 



The Karabiigas Gulf. The Karabugas Gulf on the eastern bor- 

 der of the Caspian Sea is frequently cited as a typical example of 

 the salt lagoon, cut off from the main body of the Caspian Sea by 

 a long, partly submerged bar. Ochsenius himself used it as an 

 illustration. As we have seen, the salinity of this body of water, 

 while sufificient for the deposition of gypsum, is not great enough for 

 the deposition of salt. As will be seen by a reference to the analysis 

 of the water of the Karabugas (p. 158), which is an example of 

 a sulphate chloride bittern, magnesium entirely replaces the cal- 

 cium. This is also shown in the deposits at the bottom of this 

 basin, where over an area of 1,300 square miles a deposit of Epsom 

 salts (sulphate of magnesia) is formed, 7 feet thick and amounting 

 to an estimated total of 1,000,000,000 tons. (Fig. 68.) 



This gulf further illustrates the enormous destruction of organ- 

 isms due to the intense salinity, a destruction which would render all 

 salt deposits of such a gulf highly fossiliferous. Andrussow calls 

 attention to the large number of fish which are carried across the 

 bar into the Karabugas, where they perish. "Their carcasses float 

 about as long as the water flowing into the gulf moves them, after 

 which they either sink to the bottom, or are driven onto the shore. 

 The carcasses of Clupca, Athcrina, Cyprinus, Lucioperca, Acipenser 

 and Sygnathus piled upon the shores are partly eaten by the native 

 birds, and the quantities of dead fish which lie upon these shores in 

 March can be measured by the fact that the gulls at this season of 

 the year feed only on the eyes of the fish, and do not even take the 

 trouble to turn over the fish to get at the other eye."' (Andrussow- 

 3 -.2^ ; and Walther-62 -.Q^. ) 



Among other organisms killed in the saline waters of this gulf, 

 Cardiitin cdule should be mentioned. This euryhaline organism 

 abounded in the gulf before it reached the stage at which sulphates 

 were deposited. The shells of this species occur in enormous num- 

 ber on the shores of the Karabugas. (Andrussow-3 :?5.) 



It is a significant fact that all deposits of salt along the borders 

 of the present seas, as well as inland, are found in regions of rela- 

 tive aridity ; that, in other words, salt deposition demands a suffi- 

 ciently dry climate to allow an excess of evaporation over precipi- 

 tation or influx. Thus salt deposits of all ages and occurrence are 

 indicative of dryness of climate. 



Natural Salt Pans. 



Of the natural salt pans in the vicinity of the seashore, the 

 Rann of Cutch on the northwestern coast of India is perhaps the 



