362 E. B. MATHEWS AND W. J. MILLER — COCKEYSVILLE MARBLE 



separated on their sides by synclinoria, the axes of which run parallel 

 to the general structure of the larger folds, which are found farther to 

 the north and west, where they partake of the structural characteristics 

 of the eastern portion of the continent. 



FOLDING 



The folding of the rocks within the region, as opposed to the minor 

 textual features, such as crinkling, cleavage, and schistosity, may be 

 broadly characterized as consisting of a series of open folds of simple 

 character, the individual portions of which are marked by numerous 

 sharply compressed smaller folds, with axes parallel to those of the gen- 

 eral structure. 



The character of the folding is most readily seen by an examination 

 of a few exceptional localities and the areal distribution of the various 

 formations involved. It is not easy, usually, to recognize the structural 

 characteristics from given exposures, though these may generally be de- 

 tected within the individual formations when the general structural lines 

 have been determined. This fact has rendered most attempts to work 

 from the more detailed to the more general barren of structural results. 



The simple open character of the major folding is well indicated in 

 the structural sections across the face of the accompan} 7 ing map, but 

 the detailed complexity of this exceedingly intricate region is only 

 shown diagrammatically. 



A feature of the folding which should not be overlooked is a tendency 

 toward unsymmetrical folds and often to overturned folds. The unsym- 

 metrical folding seems to be a property characteristic for the entire re- 

 gions, though never very sharply brought out, while the overturned fold 

 is a feature of local development, as along the south border of the south- 

 west anticlinal dome, where there is an intertonguing of the quartzite 

 and marble, with dips indicating overturned folds. This overturning is 

 also shown in many minor folds of the northern anticlinal dome, but 

 the similarity of the beds and the poor exposures in this area render it 

 difficult to do more than decipher the local structure here and there. 

 The intervening well cultivated fields or soil-clad forested areas make it 

 impossible to carry minor structures across the folds. 



FAULTING 



The faulting in the area, so far as it is seen, introduces one of the 

 most interesting structural features noticed and brings out the influence 

 of the continental structures on this region. Although many small faults 

 of slight throw may be detected during the course of field study, only 

 three faults of considerable magnitude have been noted, and these are 



