350 E. B. MATHEWS AND W. J. MILLER — COCKEYSVILLE MARBLE 



deciphering the structure of the Maryland area, consist of calcitic and 

 dolomitic varieties. The main mass of the rock is magnesian and would 

 be classed as a crystalline dolomite. This is not a mapable unit as op- 

 posed to the marbles, which are of pure calcium carbonate, and the 

 investigations of the junior author, so far as they have progressed, do not 

 warrant any statement indicating a stratigraphic difference in position 

 between the lime and magnesian rich rocks. The intimacy of association 

 may be judged from the following detailed section made by the junior 

 author : 



Section showing alternations of calcitic and dolomitic marble 



Feet Inches 



Medium grained, calcitic 5 



Kather coarse grained, clear, white, calcitic 1 2 



Coarse grained, bluish, pyrite, calcitic 4.5 



Very fine grained, friable, dolomitic 1.5 



Very pure, coarse grained, calcitic 6 



Fine grained, gray, micaceous, dolomitic 10 



Fine grained, grayish brown, impure, calcitic 4 



Fine grained, pure, dolomitic 6 



Medium grained, blue, calcitic 1 8 



Medium to coarse grained, white, calcitic 10 



Fine grained, pure, dolomitic • . . 7 



Medium grained, blue, calcitic 1 5 



Fine grained, white, dolomitic 5 



Medium to coarse grained, brown, calcitic 1 



Medium grained, impure, bluish, calcitic 1 6 



Fine grained, micaceous, gray, dolomitic 2 



Medium grained, pale blue, impure, calcitic 1 8 



Coarse grained, white, calcitic 2 



Fine grained, brown, dolomitic 1 5 



Medium to coarse grained, calcitic 1 11 



Very coarse grained, white, calcitic 9 



Fine grained, brown, dolomitic 2.5 



Medium grained, blue brown, calcitic 4 6 



Fine grained, micaceous, white, dolomitic 2 



Coarse grained, pure, calcitic 5 



Fine grained, micaceous, dolomitic 2 



Coarse grained, white, calcitic 4 



Fine grained, micaceous, dolomitic 1 



Coarse grained, pure, white, calcitic 1 



Fine grained, pure, dolomitic 1 2 



Fine grained, micaceous, dolomitic 6 



Fine grained, brown, dolomitic 7 



Coarse grained, pure, friable, calcitic 2 



Fine grained, brown, dolomitic. 1 



Coarse grained, pure, calcitic 1.5 



Fine grained, brown, micaceous, dolomitic. 3 



