284: M. I. Goldman — Catahoula Sandstone of Texas. 



carried away as described. Now the character of the clay 

 galls in the Catahoula sandstone supports the belief that the 

 material is derived from the washing out of seolian sand, for 

 its lack of coherence proves it to be more a rock flour than 

 true clay material. 



Distribution. — There remains to be considered the special 

 abundance of these " galls " in the flat leaf accumulations. It 

 may be that this is due to the fact that the bodies of water in 

 which these leaves are supposed to have accumulated were inter- 

 mittent (field relations could throw much light on that ques- 

 tion) and that the clay forming the " galls " remained from a 

 previous filling of the same basin. But it seems more probable 

 that if this had been the case the clay material would again 

 have been spread over the bottom rather than have survived in 

 the form of fragments to be distributed among the leaves 

 during their accumulation. I think it is more likely that the 

 general process deduced above for the burial of the leaves 

 explains the " clay galls " also. That is, they were blown in 

 with the sand, and the water being quiet and accumulation 

 rapid they were buried without being disintegrated. In the 

 subaerially accumulated sand they may be less abundant 

 because here they did not come to rest but were blown about 

 with the sand and so became more disseminated, or perhaps, 

 not being very coherent, were disintegrated by the continued 

 wear. 



III. Summary and Conclusions. 



In the first part of this paper I have described the petrographic 

 characters of the Catahoula sandstone ; in the second I have 

 pointed out their possible interpretation as evidence of the 

 conditions under which the sandstone originated. It remains 

 now to bring together, compare, and weigh these various lines 

 of evidence in order to draw the conclusion that seems to 

 harmonize best with all the facts ascertained. 



It may be well to begin by listing the factors considered. 

 They are : 



Proportion of different sizes of grains present. 

 Rounding. 



General character. 



Lower limit of rounding. 



Proportion of rounded grains present. 

 Ratio of feldspar to quartz. 

 Weathering of the feldspars. 



General character. 



Ratio of fresh and weathered feldspars to each other 



Ratio of different species of feldspar to each other 

 Ratio of heavy to light minerals. 

 Species of heavy minerals present. 



