BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 26, PP 231-242 JUNE 28, 1915 



OKIGIN OF THTC'K GYPSUM AND SALT DEPOSITS^ 



BV E. B. BRANSON 



(Read before flie Society Becemher 30, U'l.'^) 



CONTENTS 



Page 



Introduction 231 



Phenomena not explained by published hypotheses 231 



Some conditions for salt and gypsum deposits 232 



Modified bar hypothesis 235 



Origin of thick salt deposits 237 



Tlie example of the Caspian Sea 238 



The Salina salt 238 



The gypsum deposits of the upper Red Beds of Wyoming 240 



Summary 241 



Introduction 



The origin of thick deposits of gypsum without associated deposits of 

 salt and of deposits of salt of great thickness are still open questions and 

 no published hypothesis seems adequate to explain them. This was 

 brought forcibly to the writer's attention by a study of the gypsum 

 deposits of the Red Beds of Wyoming, some of which are more than 40 

 feet thick, and the modified bar hypothesis outlined below was gradually 

 evolved. As the various theories have Ijeen fully explained in many 

 pUices,^ it is not necessary to restate them; but a consideration of the 

 more important phenomena that thoy do not explain seems worth while. 



Phenomena not exi'i.aim;i) i'.v itiblished Hypotheses 



The main diflRculties in explaining the origin of thick gypsum deposits 

 are: 1. In accounting for the volume of water required to contain the 

 calcium sulphate in solution, necessitating a depth of basin in excess of 

 any kno^vn continental depression; 2. In explaining the rarity of other 



> Manuscript rpcelvrrl hy ihc Socrptary of the Society February 8, Ifllo. 

 = See particularly A. W. Oraban : rrinclples of stratlprnphy. pp. 347:180. 



(231) 



