The Cinciinuitian Series and its Bnuhiopods. 35 ■ 



The foldin<; of strata just below the Kden-Fairview 

 contact is usually of a very irregular nature, thus dilTerinj^ 

 from the folding at the lower horizon, which is much more 

 regular. At this higher horizon the axes are parallel to the 

 stream valleys. Only two or three feet vertically are affected 

 the distortion seldom extending u])ward to the Dalmanella 

 layer. 



Two possible explanations of these folds and faults in 

 the Eden shales present themselves: (1) lateral compression 

 due to dynamic action during the formation of the Cincinnati 

 anticline; (2) buckling due to removal of load in stream 

 valleys in recent times. The observed folds seem to be 

 separable into two groups- — or possibly three groups if 

 those reported from the Maysville be considered— differing 

 in regularity of folding and extent of distortion. The first 

 group includes those folds of the Eden shale (McAIicken) 

 found at horizons 30 to 50 feet below the Eden-Fairview 

 contact. The axes of these folds are apparently somewhat 

 parallel to the stream valleys (or to the general trend of 

 the valleys), and are without accordance of direction. 

 These folds are usually quite regular and sometimes almost 

 symmetrical. The second group includes those folds found 

 at the top of the Eden, with their axes parallel to the stream 

 valleys. These are always very irregular, and the strata 

 seem to be crushed and broken rather than distinctly and 

 regularly folded. 



Considering first the folds and faults of the lower series 

 (McMicken), uniformity of horizon would favor the first 

 explanation, as it would seem probable that these folds at 

 a common horizon, should have a common origin. Lack of 

 accordance of direction of axes is opposed to it, as lateral 

 compression, working over the area through which these 

 folds are distributed, would produce a general parallelism 

 of axes. Their existence in stream valleys would suggest 

 the second explanation, affecting possibly an inherently 



*For a known example of buckling due to a similar cause, see Bull. Geol. Soc. Amer. vol., 

 20, p. 625. 



