318 CD. Walcott — The Taconic System of Emmons. 



line and contains: Orthis tesfaidinaria, StrophodoJita alter- 

 nately Maclurea and other gasteropods, Calymene senaria and 

 fragments of Asaphus jplatycephalus. Details of all the ex- 

 posures observed where the " Upper Taconic " shales" and the 

 rocks of the Lower Silurian come in contact will be given in a 

 report on the geology of Washington and Rensselaer counties. 

 Another section,* taken by Dr. Emmons just east of the 

 village of Whitehall, is reproduced in fig. 13. The object of 

 this is to show the presence of a mass of calcareous sandrock, 

 d', resting unconformably upon the Taconic slate, which Dr. 

 Emmons identified as the Calciferous formation of the Lower 

 Silurian. I studied the section in 1886, also in 1887, and found 

 Cambrian fossils, represented by the heads of the Olenellus 

 and fragments of Ptychoparia, imbedded in the sandrock, d', 

 and also found the strike and dip of the sandrock and shales to 



Figure 13, a, a. — Easterly prolongation of the mountain, which is surmounted 

 by the Calciferous sandrock : b b, Tertiary clay ; c, c. Taconic and black slate ; 

 d, d, Calciferous sandstone, unconformable to the Taconic slates, and dipping- 

 southeast at an angle of 40-45°. (After Emmons.) 



be conformable. Another section on the same pagef is en- 

 tirely within the Champlain series on my map and west of the 

 great fault line. It is 30 miles north of Bald Mountain and in 

 the township of Whitehall. I found the Potsdam sandstone at 

 its base, in the village of Whitehall, and then, superjacent to it, 

 the Calciferous Terrane, with a band of dark argillaceous shale, 

 lithologically similar to that of the Hudson Terrane, between 

 it and the superjacent Chazy limestone. Resting on the Chazy 

 limestone there is a second band of dark shales, 175 feet thick, 

 that is subjacent to the Trenton limestone, and the latter is 

 subjacent to the argillaceous and sandy shales of the Hudson 

 Terrane. The strata of the entire section are conformable ; 

 and the limestones were identified by contained fossils. East 

 of the shales of the Hudson Terrane, the existence of the great 

 fault line is shown by the presence of strata, resting against, 

 and on, the Hudson Terrane, that carry Middle Cambrian fos- 

 sils. These interbedded shales, between the limestones, and, 

 also, the Hudson shales, were considered, by Dr. Emmons, to 

 be of Taconic age, and the limestone to lie unconformably 

 above them.;}: 



* Agric. N. Y., vol i, p. 56. fig. 2, 1847. f Loc. cit., p. 56, fig. 3. 



X One fact, not recognized by Dr. Emmons at Bald Mountain or along the 

 great fault fine, is that in many localities belts of dark argillaceous shale occur 

 between the Calciferous, Chazy and Trenton limestones ; that, in others, one or 

 more of these formations is entirely a shale formation, and that the Potsdam Ter- 



