36 NEW YORK STATE MUSEUM 



Theresa and Canton sheets while the Brier Hill sheet was barely 

 reached by its waters; or else it was deposited on the Brier Hill 

 sheet, and eroded away before deposition of the Ogdensburg divi- 

 sion of the Beekmantown commenced. The evidence for deciding 

 between these two views is not at hand. But certain facts do 

 suggest the first view rather than the second. The first of these 

 is that the lithologic character of these beds differs quite materially 

 on Theresa and on Canton ; the second is the considerable dift'erence 

 in thickness, coupled with the fact that the beds at Theresa more 

 strongly resemble the middle division of the formation at Canton 

 than they do the basal ; whereas if they represented parts of a con- 

 tinuous formation whose summit had been eroded away to varying 

 degree, the remnant left at Theresa should be the basal portion. 

 Our preference therefore is for the view that the Tribes Hill 

 formation is absent from the Brier Hill sheet because it was not 

 deposited there. It should also be noted that Chadwick describes 

 the Tribes Hill base on the Canton quadrangle as coming down 

 almost, locally quite, to the Heuvelton sandstone, while on Brier 

 Hill, 15 to 20 feet of calcareous Heuvelton beds overlie the sand- 

 stone. In other words, the Tribes Hill base rests on quite different 

 beds as it is followed across the district, so that the evidence of a 

 considerable break at its base is quite clear. At Theresa it rests 

 on the normal Theresa; at Morristown a considerable thickness 

 of the Heuvelton beds rests on the normal Theresa, and the Tribes 

 Hill, if present at all, rests on the Heuvelton ; on the Canton 

 quadrangle it rests on the Heuvelton sandstone, the upper Heuvel- 

 ton beds being absent, presumably because of erosion antedating the 

 Tribes Hill deposition. 



Since the Tribes Hill formation on the Ogdensburg sheet is almost 

 completely drift-covered, a description of the formation can not 

 be written from the exposures here present, and hence we present 

 a short account of the formation as shown on the Canton sheet, 

 which we owe to the courtesy of Professor Chadwick. 



Three divisions of the formation are recognized. The lower 

 division consists of mostly thin-bedded, more or less calcareous 

 sandstones, gray when fresh, but weathering to rusty rotten stone. 

 They are ripple-rharked, have fucoidal markings on their surfaces, 

 are fine-grained, and vary considerably in the amount of lime, some 

 beds having very little, and some having the characteristic '' sand 

 crystal" cleavages which characterize all the rocks from the 

 Theresa up, when the calcareous cement is abundant. Their thick- 

 ness runs from 15 to 25 feet. 



