walcott.J SUMMARY ADIRONDACK SUB-PROVINCE. 343 



SECTION. 



(From the base upward.) 



Feet. 



(1) Coarse sandstone with occasional layers of conglomerate near the base 75 



Color reddish brown near the base, buff, gray, and buff and gray, spotted 

 with grains of reddish brown sand. Texture compact and hard, with 

 bands of a soft friable nature. 



(2) Massive bedded, grayish and buff, rather coarse sandstone, many of the lay- 



ers cross-bedded 150 



(3) Compact, fine-grained white sandstone, some of the layers of which are dis- 



colored and broken by small reddish brown cavities. Lingulepis acuminata 

 occurs in the upper portion, and 10 feet higher up Ophileta compacta, 

 Dikelocephalus sp. ?, Ptychaspis sp. ? 25 



The stratigraphic exposures are not continuous, the section being 

 broken in places by concealment under the drift. Nos. 1 and 2 are 

 fairly well connected by lithologic features and No. 3 rests on typical 

 strata of No. 2, only a short distance intervening between the outcrops. 

 No. 3 is well shown on Marble Eiver one mile southeast of the Cha- 

 teaugay Chasm, and the Calciferous sandrock is shown a little farther 

 down the stream. The species found in the upper part of No. 3 are 

 identical with those found in the limestones of the Upper Cambrian in 

 Saratoga County, New York and fully prove that the fauna of the 

 Potsdam sandstone is the same as that of the St. Croix sandstones of 

 Wisconsin. 



Section in Hemmingford. — To the northeast of Chateaugay, across 

 the boundary, in Hemmingford, Canada, a section of the sandstone 

 according to Sir W. E. Logan, is 540 feet in thickness. On the south 

 side of Hemmingford Mountain about 180 feet of a coarse gray 

 sandstone are visible, in some parts constituting a conglomerate, with 

 rounded pebbles of white quartz, varying in diameter from an eighth 

 to three-quarters of an inch, while in some parts of the rock there are 

 thinly disseminated flat pieces of black or green shale 1 or 2 inches 

 in diameter by an eighth of an inch thick. The general color of the 

 rock is gray, but greenish and reddish beds occur, and the three col- 

 ors sometimes follow one another in thin stripes with various alterna- 

 tions. Above the strata of the ravine the hill contains about 120 feet 

 of gray sandstone, the lower half of which is rather coarse grained, and 

 below the same strata 240 feet. Neither the base nor the summit of 

 the sandstone was observed. 1 Farther to the north along the shore of 

 the St. Lawrence occur the celebrated fossil track localities described 

 by Logan. 



Section at Keeseville and in An Sable Chasm. — About one-quarter of a 

 mile above the village of Keeseville, on the Au Sable Eiver, a rounded 

 boss of granite shows on the south bank. Nearly 400 feet lower down 

 the stream, on the opposite side, an evenly bedded and cross-bedded 



1 Geological Survey of Canada : Report of Progress from its commencement to 1863. Montreal, 1863, 

 p. 88. 



