154 Mathews — Structure of the Piedmont Plateau. 



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area. Apparently plunging to the northeast, but this is not 

 clear. These two axes lie within the limits of what are 

 regarded as possibly Archean gneiss areas. 



Caves-Forest Hill Syncline. — A well-defined synclinorium 

 extending southward from Scarboro to the area between Green 

 Spring and Worthington valleys in the Baltimore quadrangle. 

 Plunging to the sonthwest. At the Caves the center of this 

 synclinorium is occupied by a small anticline wmich brings the 

 limestone to the surface. Southward from the Caves the 

 axis apparently extends to the Clarksville-Highlandtown region 

 and probably corresponds to the sag between the two lines of 

 uplift in Keith's anticlinorium. The synclinal basin east of 

 Buck's Ridge, Pennsylvania, may represent a continuation of 

 this general line. 



Cahin John-Jarrettsville- Bucks Pidge Anticline. — An 

 overturned anticline beginning west of Jarrettsville on the Tay- 

 lor Valley road and extending southwestward through Manor 

 and Western Run on the Parkton quadrangle ; is probably part 

 of the general anticlinal axis which is represented to the south- 

 west by the imperfectly studied axial line determined in great 

 measure by the strong synclines on either side. It is approxi- 

 mately in the same position as the strong uplift recognized by 

 Keith near Cabin John on the West Washington quadrangle. 

 Eastward from Jarrettsville the anticlinal axis is less marked 

 and is apparently occupied by the long band of serpentine 

 which crosses the Susquehanna river at Bald Friar and extends 

 eastward into Pennsylvania, where it is represented by the Bucks 

 Ridge anticline. 



Glencoe Syncline. — A small synclinal axis extending from 

 Glencoe on the Northern Central Railroad southwest through 

 Priceville to Mantua on the Parkton quadrangle and appar- 

 ently separating the lines of the anticlinal axes on either side, 

 bringing to the surface along Western Run some of the over- 

 lying limestone. The structure in this region has not been 

 thoroughly worked out and there may be a small thrust fault. 



Cardiff Syncline. — A strongly-marked synclinal basin with 

 its greatest depth in the neighborhood of Cardiff, Maryland. 

 This conforms to the center of the phyllite belt as far as that 

 has been traced. It apparently connects with the synclinal axis 

 recognized by Keith as passing just east of Great Falls. This 

 syncline carries the youngest rocks of this portion of the Pied- 

 mont Plateau and has been recognized as a structural feature 

 for many years by the Pennsylvania and Maryland geologists. 

 The bedding in this basin is no more distinct than in the basins 

 and folds previously described, but the presence of the small 

 quartz conglomerate at the base of the slates as well as the 

 slates themselves have made the recognition of its presence 



