240 E. B. BRANSON THICK GYPSUM AND SALT DEPOSITS 



salt beds had this extent the basins may have been on a larger scale, but 

 as the beds are not all contemporaneous the l)asins postulated are prob- 

 ably larger than are required. 



The same author states "that for every great salt deposit formed in 

 the neighborhood of the sea by concentration of sea-water, there should 

 be a corresponding fossiliferous series of normal marine type of sedi- 

 ments.'^ ^ For salt and gypsum deposits formed as postulated in this 

 paper this would be true only in part. There would be no fossils in the 

 contemporaneous deposit, as the waters in the supplying basins were too 

 highly concentrated to support abundant life, and as the salts were de- 

 posited Avith great rapidity the clastic deposits would be thin and it 

 would be difficult, if not impossible, to correlate the salt beds with them. 



The accompanying map makes no attempt to postulate the areas of the 

 overflow basins, but is presented to illustrate the hypothesis. The outline 

 of the sea and the areas of salt deposits are copied from Schuchert's map 

 of the Salina Sea. 



The Gypsum Deposits of the upper Red Beds of Wyoming 



In as far as the writer has been able to learn from the literature and 

 from his own observations, the gypsum of the upper Red Beds of Wyo- 

 ming covers an area of some 10,000 square miles. Over about four-fifths 

 of the area the deposits are thin, probably not averaging over 1 foot in 

 thickness; over some 2,000 square miles they average 9 or 10 feet, and 

 over some 200 square miles the beds are 30 to 50 feet thick in widely 

 scattered patches. The gypsum is remarkably pure and has no salt asso- 

 ciated with it. The following is a brief statement of the application of 

 the modified bar hypothesis to these deposits : 



1. Original area of isolated sea, 1:0,000 square miles. 



2. The average depth of the water necessary was 1,080 feet, but l)asins 

 500 to 800 feet deeper occurred. 



• 3. By the time 80 per cent of the water had been evaporated the area 

 had decreased to 10,000 square miles. 



4. The time necessary for this reduction, with GO inches evaporatiou, 

 10 inches of rainfall, and 10 inches of inflow, was 260 years. 



5. At the time of 3 it is assumed that the water was in isolated lakes, 

 about four-fifths of it being near the lands to the west and one-fifth to 

 the east, separated by low barriers from the western lakes. The eastern 

 lakes had a depth of at least 1,400 feet. 



= Principles of stratigraphy, p. 366. 



