GEOLOGY OF OGDENSBURG 4! 



The actual base of the formation is not here reached, but the 

 sand grains in the lowest -layer distinctly suggest nearness to the 

 base, certainly not more than 10 feef above it. All the beds contain 

 fossils, the massive blue beds much more abundantly than the thin- 

 bedded gray ones. But the quarry sections are much less favorable 

 places for their observation and collection than are the ledges- along 

 the roadway and in the fields. The thin-bedded, gray dolomites at 

 the summit of the quarry contain occasional Ophiletas, and are 

 followed above by beds of granular, blue dolomite, some of which 

 are crammed with Maclureas and other gastropods, usually in a bad 

 state of preservation (plate 4). They are vastly more fossiliferous 

 than the gray, thin-bedded material beneath. These upper beds 

 are well shown along the road both east and west of the quarry. 



It is hardly worth while to describe all the outcrops along the 

 road, and we shall pass over the intermediate ground to a group 

 of quarries, situated about one mile west of Ogdensburg, at varying 

 levels above the river, which when taken together give a nearly 

 complete section of the formation at that point. The two lower 

 quarries are north of the Pythian Home, between the roadway and 

 the river. Beds in the road and near by at the south are added for 

 completion of that part of the section. The other two quarries lie 

 to the east of these and nearer Ogdensburg, and their sections 

 overlap the others. 



Section at the Pythian Home 



Exceedingly massive bed of finely granular, gray 

 , /> dolomite, banded and laminated ; forms a massive bench 

 back in the field well to the south of the road; no 

 fossils seen. 



Gap, with beds unexposed, except that midway of 

 the interval is a bed of finely granular, gray dolomite 

 with calcite cement, weathering light brown, and full 

 22. 8' o" of small gastropods, Hormotoma and allied forms, the 

 only horizon of these seen in the formation ; the bed was 

 not seen in place but the material was excavated from a 

 post hole, around which it lay. 



Coarsely granular, dark-blue dolomite with calcite 

 cement of extraordinary coarseness of crystallization, 

 forming " sand crystals " often 2 inches in diameter ; the 

 21. 9" layer is full of rounded masses of Cryptozoon, which 

 weather more rapidly than the surrounding rock, leaving 

 circular holes which imitate pot holes; the bed is very 



