THE STASSFURT SALTS 371 



deposits may legitimately be considered as indices of dry climates 

 during the period of their formation. Since most modern salt de- 

 posits are of continental origin, a similar origin may have obtained 

 for the deposit of past geologic periods. 



ANCIENT SALT DEPOSITS. 



Salt deposits are found in most geological formations from the 

 Cambric ( ?* ) to the Present, and in all cases they are associated 

 with other evidence of continental expansion. Until recently the 

 salt range of India was supposed to hold the oldest salt deposits, 

 these underlying marine strata of Lower Cambric age. It is now 

 held, however, that these salt deposits are of much later age, perhaps 

 even as late as Tertiary time, and that the Cambric strata owe their 

 present position above the salt beds to an ovcrthrust. The thickness 

 of many of the ancient salt deposits is very great, individual beds 100 

 feet tliick having been found in the Siluric deposits of Michigan. 

 Deposits of much greater thickness are known, but these are either 

 complicated by intercalated anhydrite or polyhalite layers, or they 

 are in the form of salt domes, a formation of limited extent, and of 

 secondary origin. 



The Stassfurt Salts. The extensive salt beds of Upper 

 Permic (Zechstein) age in North Germany in the Stassfurt, or more 

 properly the Alagdeburg-Halberstadt region, may be taken as an ex- 

 ample of a complex deposit in which the strata have, on the whole, 

 suiTered little alteration or rearrangement. The order of succession 

 is as follows, in descending order (Walther-65) : 



1. Lower Buntsandstein (capping rock) 



2. Red clay with concretions of anhydrite and salt 



cavities abt. 20 m. 



3. Anhydrite layer (Anhydrite IV) abt. 4 m. 



4. Rock Salt abt. 40 m. 



5. Anhydrite III (Pegmatitanhydrit) abt. 5 m. 



6. Red clay abt. 10 m. 



7. Younger Rock Salt, with about 400 annual rings 



of Polyhalite abt. 80 m. 



8. Main anhydrite (Hauptanhydrit) Anhydrite II 



varying from 30 to 80 m. 



9. Salt clay, averaging from 5 to 10 m. 



10. CarnaUite zone from 15 to 40 m. 



This is sometimes overlain by a layer of rock salt, at others by a kainite layer 

 followed by one of "sylvinite" or "hartsalz" and that by one of schoenite before 

 reaching the salt clay. 



*The Indian salt deposits are the only ones of significance which have been 

 referred to the Cambric. 



