MARYLAND GEOLOGICAL SURVEY 121 



LITHOLOGIC CHARACTER. The Stones Eiver rocks in Maryland are in 

 general heavily bedded dolomitic layers alternating with greater thick- 

 nesses of relatively pure dove-colored limestones. In color and texture 

 the purer rock varies from fine-grained dove to a dense black with the 

 dove-colored rock predominating. Many of the layers run as high in 

 magnesia as the underlying Beekmantown limestone, but the Stones River 

 formation differs in that at least a few pure dove limestone layers are 

 found in almost every exposure. The pure limestone is most abundant at 

 the top of the formation, which portion therefore is most extensively 

 quarried. Many of the layers throughout the formation and especially 

 the purer strata are penetrated by the thin calcite strings belonging to 

 the single-tubed species of the coral Tetradium, which, in connection 

 with the smooth, homogeneous ground mass and color of the main rock, 

 gives it a very characteristic aspect. Another method of distinguishing 

 the Stones River from the Beekmantown lithologically lies in the char- 

 acter of the soil to which each gives rise on weathering. The soil result- 

 ing from the decomposition of the Beekmantown limestone is of a deep 

 red color, and generally contains a considerable quantity of broken chert. 

 Stones River rocks, on the other hand, are practically free of chert except 

 the middle division ; and one soon learns to discriminate this chert from 

 all the varieties formed in the decomposition of the Beekmantown 

 limestone. 



Soil formed by decay of Stones River rocks seems to be particularly 

 suited for the growth of cedar trees. Indeed, the presence of a consider- 

 able number of cedar trees in an area of Ordovician strata is quite a 

 reliable sign that the underlying rocks are of this age. Of course, this 

 preference of cedars for Stones River areas is due primarily to the nature 

 of the rock itself, in this case, the pure dove strata being cedar-bearing. 

 The extensive well-known cedar glades of central Tennessee are located 

 upon the pure, dove-colored Stones River limestone. 



PALEONTOLOGY. Dove limestones which make up the greater part of 

 the formation do not as a rule afford well-preserved fossils, although 

 traces of organic remains in the rock may be very numerous. In fact 

 some of these pure limestone layers are crowded with gastropods, but 



