126 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



The strata of the Calciferous seen at various exposures in this monocline are as follows, in 

 ascending order: 



Division A. 



Feet. 



Dark iron-gray magnesian limestone, usually in beds 1 or 2 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 massee of impure black chert, which, when 

 the calcareous matter is dissolved out by long exposure, often appears fibrous or scoriaceous. 



Thickness 310 



Division B. 



Dove-colored limestone, intermingled with light-gray dolomite, in massive beds; sometimes for 

 a thickness of 12 or 15 feet no planes of 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 surfaces raised reticulating lines 

 of gray dolomite. Thickness 295 



Division C. 



1. Gray, thin-bedded, fine-grained calciferous sandstone, on the edges often weathering in fine 



lines, 40 or 50 to the inch, and resembling close-grained wood. Weathered fragments are 



■frequently riddled with small holes, called ScoUthus minutus by Mr. Wing 60 



2. Magnesian limestone in thick beds, weathering drab 100 



3. Sandstones, sometimes pure and firm, but usually calciferous or dolomitic 70 



4. Magnesian limestone like No. 2, frequently containing patches of black chert 120 



Thickness of C 350 



Division. C is followed in ascending order by division D, which Whitfield 

 assigned to the Chazy. (See p. 187, Chapter IV.) Ulrich, however, regards divi- 

 sion D as the most typical part of the Beekmantown. As observed by Brainard 

 and Seely, whose section Gushing ^"^^ reprints with approval, division D is made 

 up as follows : 



Feet. 



Blue limestone in beds 1 or 2 feet thick, breaking with a flinty fracture, often with considerable 

 dolomitic matter intermixed, giving the weathered surface a rough curdled appearance; becom- 

 ing more and more interstratified with calciferous sandstone in thin layers, which frequently 

 weathers to a friable, ocherous rotten stone 80 



Drab and brown magnesian limestone, containing also toward the middle several beds of tough 

 sandstone 75 



Sandy limestone in thin beds, weathering on the edges in horizontal ridges 1 or 2 inches apart, 

 giving to the escarpments a peculiar banded appearance. A few thin beds of pure limestone 

 are interstratified with the siliceous limestone 120 



Blue limestone in thin beds, separated from each other by very thin rough slaty layers, which 

 protrude on the weathered edges in undulating lines. The limestone often appears to be a 

 conglomerate, the small inclosed pebbles being somewhat angular and arenaceous 100 



Thickness of D 375 



E. Fine-grained magnesian limestone in beds 1 to 2 feet in thickness, weathering drab, yel- 

 lowish, or brown. Occasionally pure limestone layers occur, which are fossUiferous, and 

 rarely thin layers of slate. Thickness 470 



Gushing continues: 



Cassin formation. — In the upper part of division D and in division E are numerous f ossil- 

 iferous horizons carrying a rather abundant fauna. These beds are confined to the Cham- 

 plain Valley, so far as the immediate region is concerned, and have therefore the same restricted 

 distribution as the following Chazy. In discussing Brainard and Seely's paper, Prof. Whitfield 

 recognizes and emphasizes this point and the considerable differences between these upper beds 

 and the ordinary sparingly fossihferous character of the normal Beekmantown. He urges the 

 similarity of the fauna to that of the Quebec, group of Canada, argues that these beds have 

 more natural affinity with the Chazy than with the Beekmantown, and that they should either 

 be placed with that formation or else considered as distinct from either and given a separate 



