PALEOZOIC ROCKS OF THE CANTON QUADRANGLE 37 



range from a few millimeters up to several inches in size, or some- 

 times become veinlike and parallel to the bedding. They vary 

 from white to salmon or flesh colors, buff, or even gray like the 

 matrix. Less commonly, but specially near the base of the forma- 

 tion, small geode cavities are found, lined with dogtooth calcite, 

 dolomite rhombohedrons, or clear, sparkling quartz crystals. 



Although a firm rock when fresh, even running quite tough and 

 hard to work, it usually weathers rather weak or even very soft, 

 with rounded edges. In the typical sections near Ogdensburg occur 

 two or three lentils of hard, creamy white sandstone abruptly inter- 

 calated in the limestones, each in turn overlaid by a bed composed 

 of the peculiar spongelike fossil, Cryptozoon. These may be mostly 

 of higher horizons than the basal stuff that appears on our map 

 area ; but Cryptozoon masses are so abundant in the drift of the 

 northwest corner (locality 3) as to suggest a local derivation, and 

 a Cryptozoon stratum in place occurs in the Rutland Railway cut 

 at the Madrid-Potsdam turnpike crossing (locality 10). The under- 

 lying sandstone lentils have not, however, been observed here. 



" Black " shaly partings in the lower beds, such as are shown 

 well in the Cedar Croft quarry on the state road west of Ogdens- 

 burg, have been noted in the old quarry north of the Rutland Rail- 

 way a mile west of Norwood (locality 16) and also in the state 

 road quarry on the east bank of the Raquette river 2 miles south 

 of Norwood (on the Potsdam quadrangle) where one of the shale 

 seams divides this formation from that next below (Hewittville 

 beds). Dark ("black") chert nodules have been found along the 

 Raquette river in loose blocks apparently from these lower beds, 

 associated with or replacing Cryptozoa and Orthocerata. 



The dolomitization of the rock, or perhaps rather its recrystalliza- 

 tion during dolomitization, has fairly obliterated what must once 

 have been an abundant fauna, ^ judging from the faint traces of 

 fossils common in many of the layers. Occasionally something of 

 interest has withstood the process. A loose block in the river at 



^Doctor Ulrich comments (in litt.) : "According to my observations 

 there is no warrant for the common belief that dolomitization has oblit- 

 erated any considerable part of the fossil contents of dolomitic forma- 

 tions." Blackwelder, however, in his study of the Bighorn dolomite 

 (Geol. Soc. Amer. Bui. 24, p. 624 et ante) has reached a different con- 

 clusion; and the writer knows of no other explanation for the facts seen 

 repeatedly in dolomites, such, for example, as the Lockport of western 

 New York. Compare also Van Tujd in Science No. 1141, Nov. 10, 1916, 

 especially p. 688. 



