SALT LAKBi OOLITES 757 



Pyramid Lake at only one point, and that near a hot calcareous spring, 

 while throughout the lake calcium carbonate, or some calcium salt, is 

 present in amounts considerably above the percentage generally present 

 in Great Salt Lake ? It seems to the writer that the chemical precipita- 

 tion theory is the only one which will explain the origin of oolites in a 

 body of water like Great Salt Lake, where the salinity may be almost 28 

 per cent and the calcium content less than one-sixth of 1 per cent, and 

 also in Pyramid Lake, where the salinity is about one-third of 1 per 

 cent, and yet the necessary reagents for the precipitation of aragonite 

 oolites are at hand. The association of algse with the oolites in Great 

 Salt Lake is perhaps not merely a fortuitous condition, but really a causal 

 relation; but it is because they die and their organic tissue decays, thus 

 forming sodium carbonate, that they aid in building the oolites rather 

 than by any organic process of secreting lime while yet alive. 



Calcareous Oolites from Cambrian and Ordovician Beds of 



Pennsylvania 



The occurrence of oolitic limestone in the Upper Cambrian and Lower 

 Ordovician limestones of both eastern and central Pennsylvania was re- 

 corded by Rogers in his final report of the first geological survey of the 

 State.^^ He also recorded its occurrence at the same horizon in Virginia 

 and eastern Tennessee, and remarked that: "So wide a geographical 

 range manifests a remarkable extension of that peculiar condition in the 

 waters which gave rise to the oolitic structure.^^ 



The calcareous and dolomitic oolites on which the following descrip- 

 tions are based came from Center County, Pennsylvania. The calcareous 

 oolites came from a fossiliferous layer of Upper Cambrian limestone out- 

 cropping in a hill about one-half mile south of the Waddle station of the 

 Bellefonte Central Eailroad. The dolomitic oolites came from the upper 

 part of the Beekmantown limestones, where they outcrop near Spring 

 Creek, in Bellefonte, a few hundred yards south of the Central Railroad 

 of Pennsylvania station. This bed contains numerous nodules of the 

 oolite replaced by silica and will be mentioned again under siliceous oolite. 



The oolitic layer in the Upper Cambrian is dark gray, almost black in 

 color, and frequently stained with iron rust. On a weathered surface it 

 is medium gray in color and the oolites show distinctly. The following 

 analysis, made for the writer by W. A. Royce, of State College, gives its 

 chemical composition. An analysis of the oolitic sand from Great Salt 

 Lake is placed beside it for comparison : 



a« Geology of Pennsylvania, vol. 1, 1858, p. 238. 



