TITLES AND ABSTRACTS OF PAPERS 77 



OOLITIC AND PISOLITIC BARITE FROM THE SARATOGA OIL FIELD, TEXAS 



BY E. S. MOORE ^^ 



(Read before the Society December 31, 1913) 



Contents „ 



Page 



Introduction 77 



The physical characters of the concretions 77 



Chemical composition and origin of the concretions 79 



Introduction 



While drilling in the Saratoga oil field of Texas the geologists of the Rio 

 Bravo Oil Company recently found some peculiar concretions. Through the 

 kindness of Messrs, E. T. Dumble, the vice-president and chief geologist of 

 the company, and C. L. Baker, who respectively granted permission to publish 

 an account of them and sent material for investigation, the writer has been 

 able to present the following report on these structures, and has concluded that 

 it: is the first time this particular type of concretion has been described. 



The concretions came from two localities — Batson and Saratoga — the former 

 about eight miles west of the latter and at practically the same surface eleva- 

 tion. The wells from which they were obtained are of nearly the same depth, 

 varying from 1,120 to 1,350 feet, and in one case at least they were found in 

 wells in both areas at 1,350 feet. The formations pierced by the wells are 

 reported to be heavy sands, then limy shales, which are followed by gumbo, 

 and this in turn by loose, fine, dark-colored sands, containing oil at a tempera- 

 ture of 125° Fahrenheit. The heavy sands locally carry large concretions of 

 sandstone from 2 to 12 feet in diameter, and the lower side of the sand bed, 

 as well as that of the concretions, is frequently mammillated, the mammlllse 

 often being translucent. Associated with the oil are waters carrying some 

 sulphuric acid, and the concretions occur with the oil in the fine sand. The 

 strata of the area are of Miocene or Pliocene age. 



The physical Characters of the Concretions 



The concretions take several different forms. Some of those from a well 

 1,350 feet deep, at Saratoga, are pisolitic, as they consist of concentric spheres 

 and are from 3 to 5 millimeters in diameter. They are of a dirty-white color. 

 Other samples show irregular structures and the material is porous, somewhat 

 like very fine textured pumice in appearance, and this type was found in wells 

 in both areas. In some cases the structures take the form of rings and re- 

 semble travertine, which has been deposited around stems or roots of trees. 



The most interesting type, however, came from a well at Saratoga at a 

 depth of 1,130 feet. These are large oolites ranging in size from 1.25 to 3 

 millimeters in diameter and varying in shape from nearly perfect concentric 

 spheres to ovoids. In thin-section they usually show a great number of ex- 

 tremely fine lines marking the outlines of the spheres. The mineral is crypto- 

 crystalline to amorphous and somewhat opalescent in appearance. 



In the center of the oolite there is generally an area of irregular shape 

 occupied by material which is more porous than that surrounding it and it is 



2» Manuscript received by the Secretary December 31, 1913. 



