GEOLOGY OF THE NORTHERN ADIRONDACK REGION 361 



For such sections recourse must be had to the district nearer 

 the upper end of the kike. Here the dips are steeper, and there 

 are two localities in Shoreham Vt, where the full section is 

 shown, and the section about Fort Ticonderoga is quite complete 

 also. These sections have been studied in detail by Brainard 

 and Seeley, and the results obtained there applied to other parts 

 of the Ghaniiplain regiou.i No other work approaching this for 

 detail and accuracy has been done on the formation in the Cham- 

 plain region. In their type section at Shoreham they have recog- 

 nized five subdivisions of the formation, as follows :- 



Feet 



A Dark iron-gray magnesian limestone, usually in beds 

 1 or 2 feet in thickness, more or less silicious, 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 impure black chert, which, when the cal- 

 careous matter, is dissolved out by long exposure, often 

 appears fibrous or scoriaceous. Thickness 310 



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 



C, r Gray, thin bedded, fine grained, calciferous sand- 

 stone, 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 S c o 1 i t h u s m i n u t u s by Mr. Wing. . . 60 



2 Magnesian limestone in thick beds, weathering drab 100 



3 Sandstone, sometimes pure and firm, but usually cal- 

 ciferous or dolomitic 70 



4 Magnesian limestone like no. 2, frequently containing 

 patches of black chert 120 



Thickness of C 350 



^Am. Mus. Nat. Hist. Bui. 3:1-23. 

 "Op. cit. p.2-3. 



