PALEOZOIC ROCKS OF THE CANTON QUADRANGLE 45 



burying the intervening irregular promontory of granite-gneiss that 

 now became mostly a group of islands. Thus the upper " white " 

 Potsdam strata were deposited. At the close of this stage the quad- 

 rangle had changed into a sandy tidal flat many miles across, 

 inhabited by wormlike creatures of which our knowledge is limited, 

 and the burrowing Lingulas. 



As the shore pushed farther south and west, giving more open, 

 deeper waters hereabouts, various lime-secreting organisms of the 

 ocean found living conditions on the clean, sandy bottom no longer 

 churned by the waves. These may have been mostly calcareous 

 algae, precipitating magnesium, as well as calcium, carbonates. 

 Thus the white sands began to have thin interbedded layers of 

 dolomitic muds washed inshore from the reefs. The amount of 

 such calcareous inwash soon about equaled the landwash of sand, 

 and fluctuating currents built up the alternating beds of the Theresa 

 formation. 



Submergence, perhaps always intermittent and oscillating, event- 

 ually gave place to renewed elevation, and once more a beach deposit 

 of white, cross-bedded, ripple-marked sand was spread out across 

 several quadrangles with a rather remarkably uniform thickness of 

 about 20 feet, the Heuvelton sandstone. In these sands the waves 

 sowed large sea-snails' shells, drifted gas-buoyed from deeper 

 haunts, and burrowing " worms " still found sustenance. 



The immediate sequel is not decipherable on our quadrangle, but 

 before very long afterward the area again became land for a short 

 time. Whatever deposits lay above the Heuvelton were swept off, 

 and the summit of the latter more or less pared away in places. 

 This paring may have been mostly the work of waves during the 

 return of the sea in the next period. 



Submergence was resumed at no remote time, and somewhat the 

 same succession of events was repeated; the advancing sea spread 

 beach-sands, the basal Bucks Bridge, this time more calcareous 

 from the presence of the Theresa dolomites in the area undergoing 

 erosion and of gastropods along the strand, followed by fairly 

 heavy sandy dolomites carrying plenty of molluscan shells, suc- 

 ceeded in turn by the sandier sediments of the withdrawing waters 

 as uplift again ensued. Finally we have barachois ("lagoon") 

 conditions and the precipitation of fine lime-muds streaked with 

 storm sands — the Hewittville beds. 



The sequel again is not recognizable until areas to the east are 

 better known. Land was finallv established and a distinct erosion 



