MARYLAND GEOLOGICAL SURVEY 81 



Maryland. East of the Massanutten syncline these sandy strata are 

 known only in the western part of the broad expanse of Conococheague 

 limestone south of Hagerstown. 



TOPOGRAPHY. The topographic features of the Conococheague lime- 

 stone are not as distinctive as those of the adjacent formations, still its 

 presence is indicated by relatively minor topographic pecularities that 

 after all are decidedly characteristic. The siliceous beds at the base of 

 the formation are most resistant to weathering and as a result give rise 

 to a line of low hills trending in the direction of the outcrops. The 

 considerable amount of scoriaceous chert arising from the weathering of 

 these lower beds also tends to form highlands. The hills formed by the 

 siliceous basal beds are most conspicuous in the northeastern part of the 

 valley in Maryland from the state line southeast through Bowman's Mill 

 to Chewsville. The siliceous character of the upper portion of this forma- 

 tion likewise resists weathering, but not in as great a degree as the lower 

 division. In general the areas of Conococheague limestone are somewhat 

 elevated and exhibit rugged topography in comparison with the adjoining 

 formations. Outcrops of the limestone are numerous, in fact foiling 

 country with low hills and numerous rocky exposures is its characteristic 

 feature in northern Maryland, but in the broad area in the southern part 

 of the state the rocks themselves are seldom seen. Here the land is well 

 cultivated and all evidence of the outcrop has usually been removed. The 

 stone fences, however, are indicative of the underlying formation, as the 

 rock employed in them has usually been taken from neighboring fields. 

 Stone fences built of the characteristically banded Conococheague lime- 

 stone are a sure indication of the presence of the formation. 



AREAL DISTRIBUTION. The Conococheague limestone forms the sur- 

 face rock of a comparatively broad area in the eastern half of the Great 

 Valley in Maryland, little interrupted by infolds of other formations. 

 This is bordered on the east by the older Elbrook formation, the line of 

 contact being quite regular except in the northern part of the state where 

 faulting brings two narrow tongues of the Elbrook to the surface. The 

 western boundary of this area is less regular due to several infolds of the 



