MARYLAND GEOLOGICAL SURVEY 109 



becomes filled with silica which, with continual deposition, enlarges the 

 original small column into a mass several inches in diameter. Usually 

 in such cases the resulting mass is hollow and lined internally with 

 crystals, thus forming a geode. Sometimes, however, it is solid, in which 

 event a structure not unlike the cauliflower chert results. 



The general problem of silicification is most complicated and little is 

 known yet of either its chemical or physical aspects. Why a certain 

 limestone should, under past or present-day weathering, develop chert 

 products which are so alike over large areas that they can be used in the 

 determination of the bed, is not only an interesting question scientifically, 

 but it is also of such geological importance as to merit the most detailed 

 study. 



Another interesting feature in connection with the cauliflower chert is 

 its occurrence, noted at several places, in a black shale, sometimes regu- 

 larly bedded but again irregularly deposited, much resembling an ancient 

 soil. Such a shale bed at the top of the Beekmantown may be seen in the 

 cut along the National Highway just west of Wilson, Md. Cauliflower 

 cherts are very abundant in this shale bed and its surface outcrop strews 

 the ground with the irregular masses. However, they are not limited 

 to this shale, for here, as well as at other places, the typical chert occurs 

 in regularly bedded dolomite. 



Although discussed here in connection with the Beekmantown, the zone 

 of cauliflower chert, if the above explanation is correct, should be regarded 

 as basal Stones River. It might in reality be regarded as a basal con- 

 glomerate formed, however, in a totally different manner from other 

 conglomerates. 



AREAL DISTRIBUTION. The Beekmantown limestone with its basal 

 Stonehenge member is the most widely distributed early Paleozoic forma- 

 tion in Maryland, as its outcrop covers large areas in both the Appalachian 

 and Frederick valleys where its strata weather rapidly into good soil and 

 produce a gently rolling country with excellent farm land. 



In the eastern belt of outcrop in the Appalachian Valley the formation 

 is closely folded, occupying an area equal to half that of the Valley and 



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