TITLES AND ABSTEACTS OF PAPERS 103 



SILICEOUS OOLITES IN SHALE 

 BY W. A, TARR^ 



{Abstract) 



The unusual occurrence of oolites in shale from the red beds is noted. The 

 oolites are in a sandy shale of varying colors, red, yellow, and green predomi- 

 nating. The oolites are of two sizes, the larger averaging about .65 mm. and 

 the smaller from .1 to .13 mm. They make up approximately 50 per cent of 

 the rock. The large oolites are concentrically banded in their- outer parts only. 

 The oolites are believed to be original and to have been formed through the 

 precipitation of colloidal silica along with the materials of the shale. 



Eead in full from manuscript. 



INORGANIC PRODUCTION OF OOLITIC STRUCTURES 

 BY W. H. BUCHER^ 



{AJ)stract) 



A preliminary account was given of the results of successful experiments 

 made to prove that oolitic structure can be produced without the direct or 

 indirect help of organisms in substances other than calcium carbonate. The 

 bearing of these results on the origin of various oolitic sediments was dis- 

 cussed. 



Artificial and natural specimens were exhibited. 



Presented in full from notes. 



Discussion 



Mr. E. G. Woodruff: There are publications describing oolites from oil 

 wells at Sour Lake, Texas. These oolites are from an oil-producing well which 

 is being pumped. The well is lined with strainer and openings too small to 

 admit oolites, but will admit nuclei-forming materials. Saline solutions enter 

 the well. The fluids are agitated and the salts are precipitated about any 

 solid fragment in the well. Salts are deposited in concentric layers, forming 

 oolites as large as one-fourth of an inch in diameter. These oolites are 

 artificial. 



Dr. G. H. Cox : The tendency of colloidal materials to assume a circular 

 form has now been appealed to by various authors to explain oolites and 

 rounded forms. Are we therefore to assume that this is the natural structure 

 of colloidal silica, and that therefore non-oolite cherts are of secondary origin? 



Dr. A. R. Crook : The statement that certain oolites lack nuclei should raise 

 a question, since physicists and meteorologists know that raindrops always 

 form around a nucleus of dust, it is reasonable to assume that oolites always 

 have a nucleus, even though it may be so small as to escape detection. 



Dr. E. V. Emerson: In the Middle Eocene of Louisiana are beds of ostrea 

 marl underlain by stiff plastic bluish clay. In some places there is a narrow 

 zone in the clay, varying in width up to 10 inches, in which the clay has an 

 apparent oolitic texture. The oolites have diameters up to 10 mm. and are 



1 Introduced by E. B. Branson. 



~ Introduced by Nevin M. Fenneman. 



IX — Bull. (Jkol. Soc. Am.. Vol: 21, 1!)17 



