NOTES ON RIPPLE MARKS 



J. A. UDDEN 

 University of Texas, Austin, Texas 



In a paper on ripple marks, recently published in the Journal 

 of Geology, by Dr. E. M. Kindle, the opinion is expressed that the 

 size of ripple marks may bear some relation to the depth of the 

 water in which they were formed. Entertaining the same idea, 

 I have on various occasions taken notes on the size of ripple marks. 

 That most ripple marks vary in size with depth of the water seems 

 to me hardly to admit of a doubt. Ripple marks from 3 to 4 

 inches in width appear to be most common. They are often to be 

 seen in thoroughly sorted beach sands of all ages, from the Cam- 

 brian up to the Pleistocene. 



In the Lower Comanchean, in Pecos County, in Texas, I have 

 found some ripple marks of very small size, the smallest I have 

 seen, with one exception. These were noted at several points in 

 some thin-bedded layers of sandstone of fine texture. These sandy 

 layers are interbedded with clays and limestones. A piece of this 

 ripple-bedded rock is shown in Fig. 1, in natural size. Twelve 

 ripples measure together 3 inches across, making an average of 

 one-fourth inch for each ripple, from crest to crest. The depth 

 of the troughs measures about one twenty-fifth of an inch. These 

 ripple marks are symmetrical. A rough mechanical analysis of 

 the sand in this rock is as follows : 



Diameter of Grains Percentages 



in Millimeters by Weight 



l/8 -l/l6 80 



1/16-1/32 20 



Two years ago I found ripple marks of the same size, or possibly 

 slightly smaller, forming in some fine sandy silt in the Rio Grande, 

 in Webb County. The silt had been washed up on some large 

 blocks of sandstone, which were strewn in the channel of the river. 

 It lay in shallow depressions on these rocks, and the water covered 



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