PALEOZOIC ROCKS OF THE CANTON QUADRANGLE 29 



Basal division. The lowest beds of this series have a tendency 

 to form a soHd ledge, 5 or 6 feet high, rising abruptly from the 

 broad surfaces of the Heuvelton with a rounded and glittering 

 white forehead, followed sometimes by one or two other tiers of 

 similar aspect. There may be in all 15 or 20 feet of such beds. 

 They consist of frequent alternations of somewhat calcareous (or 

 dolomitic) sandstones with purer sandstones, and are mostly of fine 

 texture, usually rather weak and granular within but vitrifying 

 and bleaching on the surface into a nearly pure white resistant crust 

 about 3 millimeters thick, just beneath which the oxides of iron 

 form dark stains. Like the Theresa, the limiest bands sometimes 

 show the characteristic " sand crystal " cleavages of the calcare- 

 ous cement noted by Gushing^ as common in these mixed or transi- 

 tion beds between the Potsdam and the Beekmantown ; and nodules 

 of crystalline calcite are not lacking. The color of the fresh rock 

 is a mouse-gray or drab-gray, stained as it leaches with various 

 rusty colors (especially wood-browns) arranged in striking patterns, 

 marbled or clouded. Weathering develops more buffy tones in 

 cracks and seams, but often bleaches the exposed faces as above 

 stated to an ashy white, frequently overgrown with dark 

 Protococcids. 



As compared with the Heuvelton, these layers are darker within 

 and whiten on exposure, while the former is whiter within and gener- 

 ally develops a dark crust on the surface. Moreover that rock tends 

 to maintain angular edges because of its silicious character, whereas 

 these beds become more rounded, with solution along joint planes, 

 and otherwise give testimony of their more calcareous nature.^ 

 The cross-bedding too, while still abundant, is smaller and even 

 more irregular, while the rock when thoroughly weathered is a 

 rottenstone fyll of closely interwoven, branching, fucoidal struc- 

 tures, the Palaeophycus beverleyense of Billings.^ 



The contact of these basal beds with the underlying Heuvelton 

 shows many signs of disconformity, indicating a break in the 



' N. Y. State Mus. Bui. 145, p. 64. 



" They furnish a foothold for such rare lime-loving plants as the slender 

 cliff-brake (at locality 57')- the hulblet bladder-fern, and the walking-leaf 

 (locality 35), besides many commoner forms. 



^Canadian Paleozoic Fossils, 1:97, fig. 86. 



