MARYLAND GEOLOGICAL SURVEY 69 



of these showed the interesting occurrence of two sets of intersecting mud 

 cracks, one set about a foot apart and the other about four inches. 



TOPOGRAPHIC FORM. Faulting is so frequent along the eastern edge 

 of the Waynesboro outcrops in Maryland that the normal sequence of 

 strata is seldom apparent. Siliceous strata always form a part of the 

 Waynesboro wherever developed, so that its topographic form is always an 

 elevated area. If the strata have been strongly folded this highland area 

 assumes the form of elongated hills paralleling South Mountain. Should 

 the normal sequence of the three divisions of the Waynesboro occur, the 

 basal siliceous strata will give rise to a range of low hills nearest the 

 mountain and the upper sandy shales will occasion another range to the 

 west, the narrow depression between them being underlain by the less 

 resistant limestones of the middle portion. 



TOMSTOWN-WAYNESBORO BOUNDARY. The base of the Waynesboro 

 formation is formed of a very siliceous gray limestone which weathers to 

 slabby, porous sandstone. Except in very fresh exposures the limestone 

 nature of this part of the formation is not apparent and it seems to be 

 made up of sandstone entirely. Sandstone slabs are very abundant on the 

 weathered slopes and associated with them are large masses of contorted, 

 minutely laminated, iron stained, sandy rocks, with numerous cavities 

 filled with beautiful drusy quartz. These masses are sometimes several 

 feet in diameter and their presence in the fields and especially in the 

 fences identifies this basal portion of the Waynesboro. Wherever in 

 Maryland the Waynesboro sequence is normal such iron stained, drusy 

 quartz masses are found in abundance. Associated with this sandy rock 

 and also in the higher strata of the lower portion of the Waynesboro are 

 numerous fragments of secondary white vein quartz which in connection 

 with the other siliceous rock helps in identifying the basal beds. Plate 

 VII represents a small fragment of the contorted sandy masses in 

 which all the crevices are filled with minute quartz crystals. An enlarged 

 view of a drusy quartz portion of one of these masses is shown on the 

 same plate. The crystals, though perfectly formed, are so small as to be 

 indistinguishable without a magnifying lens. To the unaided eye the 



