GEOLOGY OF THE PORT LEYDEN QUADRANGLE 43 



thickness just west of Port Leyden is only 500 feet. Between these 

 places, which are 39 miles apart, the thickness has diminished 400 

 feet or at the rate of over 10 feet per mile toward the east. 



At Central Square it is 8o5 feet from tdie top of the Trenton to 

 the Precambric, while at Port Leyden it is 500 feet. Thus in a 

 distance of 45 miles the thickness has diminished 306 feet or at the 

 rate of nearly 7 feet per mile toward the northeast. 



In the Stillwater well the top of the Trenton lies "^^2 feet abovv^ 

 the Precambric, while at Martinsburg it is about 600 feet. This 

 shows a decreased thickness in 2J miles of 172 feet or at the rate of 

 over 6 feet per mile toward the northeast. 



Thus we see that there is an increasing thickness of these forma- 

 tions toward the southwest and west at from 6 to 10 feet per mile, 

 and these figures may, in a general way at least, be taken to indicate 

 the slope of the surface upon which the Paleozoic deposits were be- 

 ing laid dowm. 



These results are significant when compared with the results 

 similarly obtained by Gushing for the Little Falls district and by the 

 writer for the Remsen quadrangle. In the Little Falls region the 

 slope receiving Beekmantown deposition was about 30 feet per mile 

 southward ; while in the Remsen district the slope receiving Trenton 

 deposition was from 6 to 20 feet per mile southwestward, the great- 

 est slope being in the southeastern portion of the district. Thus it 

 is pretty well established that the slope of the surface receiving 

 Paleozoic deposition was very considerably greater in the vicinity of 

 Little Falls than in the vicinity of Port Leyden and that there was a 

 gradual change from the steeper to the more nearly level surface. 



The results obtained for the Port Leyden quadrangle are also 

 •significant in another way. The thickness of the formations here, 

 from the top of the Lorraine to the Precambric, is approximately 

 1400 feet. This thickness is great enough so that even after allow- 

 ing for decreased thickness due to overlap and a possibly increased 

 slope (receiving sediments) as the heart of the Adirondacks wa- 

 approached, we seem to have here a strong argument in favor of the 

 submergence of the region for many miles to the east and north- 

 east of Port Leyden, so that by the close of the Lower Siluric the 

 submergence extended to, or close to, the heart of the Adirondacks. 

 This conclusion is quite different from that reached by Gushing by 

 similar reasoning for the southern Adirondacks. He says •} '' This 

 line of evidence would therefore, so far as it may be worth anything, 



1 N. Y. State Mns. Biil. -j-j. 1905. p. 61-62. 



