114 KANSAS ACADEMY OF SCIENCE, 



So it is thought the water in the old seas and gulfs of Kansas and 

 Iowa received additions of salt and gypsum by inflowing waters, thus 

 increasing the thickness of the deposits. The same theory is used to 

 explain the great thickness of salt at Stassfurt (1000 feet) and at 

 Sperenberg (8000 feet), in Germany. 



QUANTITY OF GYPSUM IN THE ANCIENT MICHIGAN SEA COMPARED WITH 

 THE PRESENT SUPPLY. 



The area of rocks in Michigan after the Marshall or Kinderhook 

 series is approximately circular in outline, with a radius of eighty- five 

 miles, giving an area of 22,686 square miles. As will be shown later, 

 the sea covering this area in Osage times was approximately 700 feet 

 in depth, and assuming an average depth of 326 feet, based on well 

 records, there would have been about 1,280,000 billion gallons of water. 



The analysis of Atlantic ocean water given above shows 93.3 grains 

 of gypsum to the gallon. If this Michigan sea had this same pro^jor- 

 tion, it would have yielded 8,500,000,000 tons of gypsum. 



The thickness of gypsum at Grand Rapids is eighteen feet and at 

 Alabaster twenty feet. The gypsum in the Grand Rapids quarries 

 is shown in plates XIII and XIV. The approximate area at Grand 

 Rapids is twenty-four square miles and at Alabaster ten square miles ; 

 and while the gypsum does not by any means keep the thickness given 

 over the entire area, and is even absent in places, it has probably been 

 removed by solution since its deposition. 



These figures would give a total quantity of 1,237,764,000 tons of 

 gypsum. Where gypsum is found in the deep wells it is usually in 

 thin beds, and in many of them it is entirely absent. It is thus evi- 

 dent that the quantity of gypsum held in this old Michigan salt sea is 

 sufficient to explain the quantity of gypsum actually in existence to- 

 day in its basin. 



If the assumption is made, and there is no basis for it, that the 

 gypsum covered all the interior sea area with a thickness of twenty 

 feet, then it would require 917 billion tons of lime sulfate in the sea, 

 more than a hundred times the quantity probably in the basin. 



CASPIAN SEA AS AN ILLUSTRATION OF THE MICHIGAN SEA. 



The gypsum deposits in Michigan do not occur uniformly dis- 

 tributed through all parts of this old sea basin, but they appear con- 

 centrated in certain areas of comparatively small size. For the cause 

 of this localization of the deposits we may look for a modern illustra- 

 tion of the conditions in the Caspian sea. 



Into the northern part of the Caspian sea empty the Volga, Ural 

 and Terek rivers, bringing in a large quantity of fresh water, so that 

 in this portion of the sea the water is nearly pure, with a specific 

 gravity of 1.009. This small percentage of salt is, according to Van 



