MOUNT GREYLOCK. 191 



AREAL AND STRUCTURAL. 



The geologic map of the Greylock, East and Potter mountain masses, 

 presents a great body of the schists of the Berkshire schist formation, sur- 

 rounded by the underlying Stockbridge limestone. It is probable, although 

 not demonstrable, that this limestone passes around the north end of the 

 Greylock mass, between the schist on the south and the quartzite (Vermont 

 formation) of Clarksburg mountain on the north. It is also probable that 

 that quartzite underlies the entire Greylock synclinorium, for it occurs on 

 the north on Clarksburg mountain, on the cast on Hoosac mountain, and 

 on the west on Stone hill, and is also brought up again by a fault on the 

 east side of Deer hill. 



The Berkshire schist sends out tongues corresponding structurally to 

 synclines into the lower limestone area, as west of Zvlonite on the east side 

 of the range, and at Deer hill on the west side ; also at Constitution hill, 

 west of Lanesboro. There are also reentering angles of limestone in the 

 schist area, corresponding to anticlines, as north of Lanesboro, and about 

 New Ashford. 



There are isolated schist areas, generally lenticular in form, corre- 

 sponding to more or less open synclines, as a little southwest of South 

 Adams, anil south of Constitution hill, in Lanesboro ami about New Ash- 

 ford. The most interesting of these is Sugarloaf mountain, which is a 

 canoe-shaped open svncline. (See Fig. 74, Appendix B, and Sections 

 M, R.") 



There are also isolated limestone areas, corresponding to compressed 

 anticlines, projecting through the overlying schists, exposed by their erosion. 

 Two of these occur between New Ashford and Lanesboro, and a smaller 

 one is described in Appendix B, at Quarry hill, New Ashford. (Figs. 



remarks before tho International Geological Congress, London, September, 1888), in Nature, vol. 38, No 23, October i, 

 1888, p. 551 . also In- paper, " Stratigrapkic Position of the Oleuellus Fauna in North America and Knrope," American 

 • I.Mirii. S I - r '."I 37 Mav 1889 p 374 



I ,.■ ,, .1. i.u- ol El is's cla«ifii ition see Pala-nntnlogic ami Siratigraphic Principle of tin- adversaries of the 



Taconii by Jules M tr m Am n.au Geologist, July, 1888; and for Mr. Mareoii s own elassifnation of the Taconic 

 . his raemoii 'The raconic - stem and it- p-.-itiun in stratiuiaphie -rnlo L '\ I'i...... .fu._:s of t ho American 



Academy ol \.t- I Sciences, vol 12 Cambridgi I8e5, p. 174. 



For a aununaxy of the different phases ol oninionin regard to the age ol the Taeoin. r..ek- see A briei history of 

 Loom, ideas by J. D. Dana. Am Jour. Sci., 3dser., vol, 36 December, 1888 p.40. 



For the literature ami a systematic presentation ol the T.u onic question -r I'.nlleini -il Si leol. Survey. Correla- 

 tion Papers— Cambrian, l.v ('has. li Walcott. For evidence of the Lower I brum age ol the lower part of the Stockbridge 



limestone, see article by J. E. Wolff, "On the Lower Cambrian age of the Mo.- 1,1. ml-. ■ limes tone,' Hull ileol. Soc. Am., vol. 

 2, 1890, p. 3U1. Also paper l>\ T. Nelson Dale, "iiu the struoture and asje of the Stockbridge limestone in the Vermont 

 valley,'' Bull. Gool. Soc. Am., vol. 'J, 1891, p. 514. 



