The Ciuciunatiati Series and its Brachiopods. 31 



Wave-marks. — Many limestone layers of the Eden and 

 Fairview formations have undulating upper surfaces and 

 plane lower surfaces. Such undulations are wave-marks or 

 the so-called "giant-ripples." The crests and troughs of 

 the wave-marks are in general a])proximately parallel. The 

 distance from crest to crest varies from two to four feet. 

 The thicknesses of the wave-marked strata vary from one 

 to three inches in the trough, to three to six inches at the 

 crest. The material of which these wave-marked limestones 

 are composed is, as far as has been observed, always frag- 

 mental. The wave-marked strata are usually overlain by 

 shale, which is sometimes laminated, but more often homo- 

 geneous. Where laminated, the laminae usuallv conform 

 to the wave surface of the limestone stratum, the waves 

 gradually dying out before the next bedding plane is reached. 



The direction of the wave-marks is not uniform. In 

 some cases waves have been observed to trend at almost 

 right angles to those of other strata but a few inches above 

 or below. Of fifteen wave-marked strata observed, ten 

 have the crests and troughs extending in directions included 

 in the northeast-southwest quarter of the compass, and five 

 have the crests and troughs extending in a general north- 

 west-southeast direction. That is, in general there seems 

 to be a division into two groups, (1) those with NE-SW 

 trend, and (2) those with NW-SE trend. One slope of the 

 wave-marks is steeper than the other. Five examples of 

 the first group (NE-SW) were observed for position of 

 steeper slope, and one of the second group (NW-SE). In 

 the first group the steeper side was toward the southeast; 

 in the second, to the northeast. This indicates that the 

 waves moved in a southeasterly direction when forming 

 those wave-marks having a NE-SW trend, and in a north- 

 easterly direction when forming those with NW-SE trend. 

 The southeasterly movement appears to have been the more 

 general. 



* The following table records observed data for sixteen 

 wave-marked strata. 



