GEOLOGY OF THE PHILIPSBURG REGION OF QUEBEC 329 



stratification are discernible. In the lower beds, and in those just above the 

 middle the dolomite predominates; the middle and upper beds are nearly pure 

 limestone; other beds show on their weathered surface raised reticulating 

 lines of grey dolomite. 



Thickness 295 ft. 



DIVISION A 



Dark iron grey magnesian limestone, usually in beds one or two feet in 

 thickness, more or less siliceous, in some beds even approaching a sandstone. 

 Nodules of white quartz are frequently seen in the upper layers and near the 

 top, large irregular masses of black chert, which, when the calcareous matter 

 is dissolved out by a long exposure, often appears fibrous or scoriaceous. 



Thickness 310 ft. 



Total thickness of section 1,800 ft. 



This section is perhaps the best known and most complete 

 exposure of Beekmantown rock in the western part of the Champlain 

 Valley. Certain faunal and lithological zones, well-marked in this 

 section, are clearly present in the Philipsburg section, sufl&cient, 

 it is believed, for exact correlations. These correlations appear 

 to obtain throughout the Champlain Valley whenever good sections 

 of Beekmantown strata occur. In view of this fact, it would seem 

 that the term Beekmantown should no longer be used in a vague, 

 indefinite sense, pertaining in general to any strata above the Pots- 

 dam and below the unconformity at the base of the Chazy. It is 

 the opinion of the writer that the terms Lower, Middle and Upper 

 Beekmantown, can be used in a definite, formational sense, and he 

 therefore proposes those names for the Beekmantown in the Cham- 

 plain Valley, to be applied in the following manner. 



LOWER BEEKMANTOWN 



Unfortunately the lower part of the Philipsburg section is cut 

 off by a fault, while that of the East Shoreham section rests in 

 uncertain relationship on the underlying so-called Potsdam sand- 

 stone. Nevertheless it is apparent that Brainerd and Seely's 

 Divisions A, B, and C at East Shoreham are lithologically similar 

 to Logan's Divisions Ai, A2, A3 at Philipsburg. Dark iron grey 

 magnesian limestone, usually in beds one or two feet in thickness, 

 more or less siliceous, in some beds even approaching a sandstone, 

 characterize the lowest members of both sections. Nodules of 



