Dale — Geology of the North End of the Taconic Range. 187 



are shown in the accompanying map and section, Plate XL* 

 The map shows a central tongue of Cambrian slate, quartzite, 

 etc., bordered both on the east and west by narrow strips of 

 Ordovician schist or slate, and, in its southern and eastern side, 

 adjacent to a larger mass of Ordovician schist, two miles wide, 

 which constitutes the north end of the Taconic range proper. 

 This tongue of Cambrian is bordered on the north and at sev- 

 eral points on the sides by the Stockbridge Limestone. The 

 mass of Ordovician schists, shown at the upper edge of the map, 

 which continues, with a possible interruption east of West Corn- 

 wall, 12 miles north to Middlebury and even beyond, is cut off, 

 as was first shown by Wing, from the slate and schist on the 

 south by the Stockbridge Limestone, and is not even indirectly 

 connected, as one of his maps showed, with the Ordovician 

 schists of the Taconic range. The Ordovician part of the 

 Stockbridge Limestone, as shown by fossil localities, touches the 

 Cambrian slates on three sides. The Cambrian partf of that 

 formation, not indicated on the map, crops out near Brandon 

 village, and extends north and east of it, forming a longitudinal 

 belt between the Lower Cambrian quartzite (Vermont Forma- 

 tion) of the Green Mountain range on the east, and the Ordovi- 

 cian part of the Stockbridge Limestone on the west. 



The determination of the age of the slates and schists of the 

 north end of the Taconic range is based upon the following 

 evidence : The Lower Cambrian age of the central slate mass 

 in Sudbury is shown by the occurrence at intervals, as far north 

 as the northern slope of Government Hill, a mile east of Sud- 

 bury Church, of a slightly ferruginous, calcareous, quartz sand- 

 stone, typical of that formation in Washington County, .N". Y. \% 

 by the fact that typical Lower Cambrian roofing slates are being 

 quarried a half mile north of Stiles Mountain in Sudbury ;§ by 

 the presence of six localities of Lower Cambrian fossils in the 

 same belt within two and one-half miles south of the southern edge 

 of the area shown on the map ; by the general petrographic char- 

 ter (massive quartzite, quartzose slates, greenish and purplish 

 roofing slates, calcareous sandstone) of a large part of the area des- 

 ignated as Cambrian. In places, however, petrographic distinc- 

 tions fail, as the slates become schistose and resemble the Ordovi- 

 cian schist. The Ordovician age of the schist and slate masses bor- 

 dering the Cambrian (Sh on map) is shown by the presence of 

 red roofing slates, typical of the Hudson, | a mile S.S.E. of Hyde 



* As to this map : those parts of the geological boundaries which are more 

 or less uncertain are shown in dotted lines to distinguish them from those 

 which are well established and indicated in full lines. The round black dot 

 a half mile E.S.E. of Hyde Manor represents what seems to be an outlier of 

 Ordovician limestone, about 70 x 40 ft. across, resting upon the Cambrian slates. 



f Whether this Cambrian includes some Beekmantown is not yet determined. 



X Horizon E of the slate belt. Op. cit. table facing p. 178. 



§ Locality shown on map by crossed hammers. 



|| Horizon Irs of Slate belt. Op. cit. table facing p. 178. 



