186 Dale — Geology of the North End of the Taconic Range. 



The north end of the Taconic range is an important locality, 

 for • the principal formations of the Taconic region, the Cam- 

 brian slate etc., the Stockbridge Limestone of the valleys, and 

 the Ordovician schists of the Taconic range, all meet there within 

 an area of a few square miles. The topographic map of the 

 Brandon quadrangle, recently finished by the U. S. Geological 

 Survey, has at last made careful exploration of this key locality 

 possible ; and the results amply justify the opinion that careful 

 geological mapping with a reliable topographic base is the only 

 method of settling intricate geological problems, and that this 

 mapping should cover large areas, not only to prevent the over- 

 looking of such crucial localities but also to show the wideness 

 of their significance. 



The writer and his assistants, Messrs. Louis M. Prindle and 

 Fred H. Moffit, were engaged from 1894 to 1896 in going over 

 and extending Mr. Charles D. Walcott's reconnaissance work in 

 the Slate belt of Washington County, N. Y., and Rutland County, 

 Yt. The results were published in 1899 accompanied by a 

 geological map extending from lat. 43° to 43° 45', and covering 

 a strip from 10 to 12 miles wide along the west side of the 

 Taconic range, covering in all about 720 square miles. * The 

 fact wa» there brought out by Mr. Walcott's paleontological 

 data and corroborated by our strati graphical observations^ that 

 in that region along many miles of intricate geological bound- 

 aries, where faulting is out of the question, the Lower Cambrian 

 slates, with their Olenellus fauna, occur in apparently conform- 

 able contact with the Ordovician slates, shales, etc., containing 

 Hudson Graptolites. Similarly, the Ordovician schists of the 

 Taconic range were found to be in contact on the west with 

 Lower Cambrian slates along a stretch of 50 miles south of the 

 township of Sudbury, and at only two points (Hubbardton) was 

 there any marked divergence in the strike of the two forma- 

 tions. This involved the anomalous absence of the Stockbridge 

 Limestone along the west foot of that range, whereas on the east 

 side of it the upper part of this formation (of Chazy and Trenton 

 age). dips everywhere conformably under the overlying schists 

 of the Hudson. 



During the summer of 1903, the north end of the Taconic range 

 and the adjacent country were somewhat carefully, although 

 not exhaustively, explored by the writer assisted by his son. 

 The exposures were found to be sufficiently numerous to show 

 the mutual relations of the several formations, and the results 



*The Slate belt of Eastern New York and Western Vermont, by T. Nelson 

 Dale, 19th Ann. Kept. U. S. Geol. Survey, 1889, Part III, pp. 153-307. Map, 

 pi. xiii. Reviewed in this Journal, vol. clix, p. 382. 



f See ibid. , pi. xiii and pp. 290-295, on the relation of Cambrian and Ordovi- 

 cian. 



