13S //. P. Gushing — Lower Paleozoic Rocks of New York. 



pinch out before the upper end of Lake Champlain is reached; 

 and are wholly absent at Ticonderoga and all points south of 

 that within the State. 



In the Champlain valley the group is separable into three 

 well-marked formations, as Brainard and Seely were the first 

 to show.* These were named by Gushing the Day Point, 

 Crown Point and Valcour limestones, f More recently a for- 

 mation of supposed Chazy age has been recognized and de- 

 scribed in the Watertown region and named by Cushing the 

 Pamelia limestone.:}: It has a length of outcrop of some 70 

 miles in the State of JSfew York, and probably an even greater 

 extent across the border in Canada. In this district it rests 

 either on Tribes Hill, Theresa or Potsdam, or else on the Pre- 

 cambrian, and is overlain unconformably by the Lowville. It 

 cannot be successfully correlated with any of the Champlain 

 Chazy, either lithologically or faun ally, and seems to repre- 

 sent a deposit in a wholly separate basin ; and therefore evi- 

 dence as to its precise position must be obtained from without 

 the State. 



In 1896 Winch ell and TJlrich revived Safford 's name Stones 

 River group for the deposits of the interior basin, or basins, 

 representing the Chazy interval ; or more strictly speaking, the 

 lower and middle Chazy interval (Day Point and Crown Point) 

 of the Champlain section.§ The Chazy and the Stones River 

 basins of deposit were for the most part separate, with but 

 slight and interrupted opportunity for commingling of faunas. 

 The Pamelia limestone is the New York representative of the 

 Stones River group, but represents only its extreme upper 

 portion. 



The southern Pennsylvania section which has recently been 

 described by Stose seems to furnish the evidence desired for 

 closer correlation of the Pamelia. | TJlrich studied the faunas 

 and furnished the correlation statements for that folio, and the 

 correlation with the New York formations, as here given, is 

 due to him. The Beekmantown of the Chambersburg region 

 is overlaid by the Stones River formation, with a maximum 

 thickness of 1050 ' ; and this by the Chambersburg limestone, 

 of 750 ' maximum thickness. Ulrich regards the Pamelia as 

 the equivalent of the upper part of the upper division of the 

 Stones River of the Chambersburg section. The middle divi- 

 sion, which carries Maclurea magna and other fossils is re- 

 garded as the equivalent of the New York middle Chazy 

 (Crown Point limestone). 



* Am. Geol., vol. ii, pp. 323-330. 



fBull. 95, N. Y. S. M.,p. 368. 



% .Bull. G. S. A., vol. xix, p. 161 ; Bull. 145, N. Y. S. M., pp. 68-79. 



§ Geol. Surv..Minn., vol. iii, p. xc. 



|| Mercersburg-Chambersburg Quadrangles, Folio 170, U. S. G. S. 



