MARK IN CALCAREOUS SEDIMENTS 145 



Bucher^ has brought together measurements of a number of 

 limestone ripples with large wave-lengths which are "nearly 

 symmetrical," and has raised the question whether the formation 

 of such large ripple marks by wave action is possible.^ He writes, 

 "Since a neutral name is desired for the large, nearly or completely 

 symmetrical ripples showing no assortment of grain, I suggest the 

 term 'pararipples. ' "•^ 



The writer considers the pararipples to represent metaripples 

 sufficiently modified either by wave action or reversed tidal currents 

 to have lost their original asymmetry. 



The association of mud cracks with limestone ripple marks 

 having a wave-length of 2 feet in the Ordovician of southeastern 

 Indiana, reported by Shannon,'* would be significant in this con- 

 nection if it should be found that they are symmetrical. Ripple 

 marks 2 feet from crest to crest certainly could not have been formed 

 by wave action in water shallow enough to permit the formation 

 of mud cracks at low tide. 



Limestone ripple marks of large amplitude have sometimes been 

 inferred to represent water of considerable depth.^ The writer's 

 observations on the large ripples, now being formed in the shallow 

 waters of the Bahamas, on calcareous sediments have convinced 

 him that no trustworthy conclusion regarding the depth can be 

 drawn unless the ripples can be shown to be of the oscillation type. 

 The widely spaced ripple marks frequently met with in limestones 

 have probably been in nearly all cases formed by currents. Since 

 the wave-length and amplitude of current ripples depends chiefly 

 upon the velocity of the current, and not at all upon depth, no reli- 

 able deductions regarding the latter can be drawn from them. 



' Op. cit., p. 260. 



2 Ihid.y p. 262, 3 Ibid., p. 263. 



4 "Wave-Marks on Cincinnati Limestone," Proc. Ind. Acad. Sci. (1894-95), pp. 

 53-54. 



5 J. Locke, "Professor Locke's Geological Report," Ohio Geol. Surv., Second Ann. 

 Rept. (1838), p. 247, Plate 6. 



