120 THE CAMBRIAX AXD ORDOVICIAN DEPOSITS OF MARYLAND 



distinctly older than the Murfreesboro limestone of the type area or it 

 represents the basal part of that' formation which does not reach the 

 surface in central Tennessee. A weak, though typical representative of 

 the Lenoir limestone fauna, is found in Maryland in the middle third 

 of the Stones River and it is probable that the upper and lower thirds of 

 the formations here developed represent all the remaining sedimentation 

 of Stones River time. 



Although there is no continuous section in Maryland where the com- 

 plete sequence may be observed, a generalized section in areas where the 

 three divisions are well developed is as follows : 



Generalized Section of Stones River Limestone in Maryland 



Feet 



Nodular, argillaceous strata of the Chambersbur g limestone 



3. Massive and thin bedded fine grained, pure, dove-colored limestone. . 300 

 2. Massive pure limestone, blue to dark gray in color, compact, granular 

 and oolitic, on weathering leaving black, blocky chert; contains 



the Maclurites magnus fauna 200 



1. Massive and thin bedded, pure, dove limestone in the lower part 



interbedded with magnesian layers 600 



Light gray, finely laminated magnesian limestone of Beekmantown 



age, with cauliflower chert at top 



This generalized section holds, also, for southern Pennsylvania, but 

 from here northward the Stones River limestone diminishes in thickness 

 due to progressive loss of the lowest beds by overlap. Between Green- 

 castle and Chambersburg, Pennsylvania, the three divisions of the forma- 

 tion have a combined thickness of about 1000 feet. At Carlisle the lowest 

 division and a part of the middle are missing, leaving the formation only 

 about 450 feet thick. Farther north at Harrisburg the middle member 

 has been diminished by another hundred feet. Throughout the Lehigh 

 Valley in Pennsylvania and its continuation in New Jersey, the Stones 

 River is absent altogether. In eastern New York this formation is still 

 absent until the upper Champlain region is reached where the Stones 

 River interval is occupied by Chazyan limestones. The Middle Chazyan 

 Crown Point limestone contains the Maclurites magnus fauna and thus 

 offers a means of correlation with the more southern Stones River 

 limestone. 



