78 THE CAMBRIAN AND ORDOVICIAN DEPOSITS OF MARYLAND 



General Section of the Conococheague Limestone in the Hagerstown 

 Valley, Maryland 



Feet 



Massive, rather pure, light colored limestone with cephalopoda and gastro- 

 pods of the Stonehenge limestone. 



Pink marbles, oolite, granular limestone with edgewise conglomerate and 

 massive fine grained light colored limestone separated by beds of 

 banded dark blue siliceous limestone. Vein quartz with crystals and 

 yellow chert are left in soil upon weathering 400 



Dark impure banded limestone weathering to slaty fragments and banded 



chert. Occasional beds of edgewise conglomerate 600 



Wavy, blue to black siliceous banded impure limestone with layers of 



edgewise conglomerate 400 



Siliceous banded dark blue limestone with intercalcated sandy beds, oolite 

 and edgewise conglomerate. On weathering some of the strata give 



rise to large chunks of scoriaceous chert 200 



'Massive dark blue to light colored rather pure limestone with reefs of 



Cryptozoon proliferum Hall and C. undulatum new species 50 



Light colored calcareous shale and laminated impure limestone of the 

 Elbrook formation, weathering shaly. 



Total 1650 



Because of the discontinuous exposure of the formation and the folding 

 to which it has been subjected the thickness is a difficult matter to deter- 

 mine. The above total of 1650 feet is apparently a fair average for 

 Maryland. 



Although five divisions are shown above in the general section of the 

 Conococheague limestone, the rocks may be conveniently grouped for 

 purposes of study into three divisions. First, a basal division of 250 feet 

 of oolite, edgewise conglomerate and Cryptozoon reefs; second, the main 

 mass of the formation about 1000 feet or more in thickness made up of the 

 usual banded limestone; and third, an upper part of 400 feet which con- 

 tains pink marbles in addition to the usual rocks of the formation. All 

 three divisions are indicative of shallow water conditions during their 

 deposition, but the basal beds are particularly so. The edgewise con- 

 glomerate and the oolites are shallow water deposits and the rounded 

 grains of quartz occurring with them indicate nearby land. In these 

 beds are also inclusions of red clay which closely resemble clays resulting 

 from the surface weathering of limestone. The most interesting residual 



