138 



GREEN MOUNTAINS IN MASSACHUSETTS. 



TYPES OF STRUCTURE. 



In order to present this matter more clearly, a few typical localities 

 will here be described in some detail. 



CASK I. 



On Quarry hill, close to the village of New Ashford, 1 there are several 

 minor folds in the limestone and the over- 

 lying- schist, where the two rocks may be 

 seen in contact. Fig'. 31 represents the 

 structure at one of these points of contact, 

 locality 602 on sketch map, Fig'. 78. 



The banding- in the limestone, the plane 

 of contact, the small quartz lamina?, and the 

 general, slightly undulating foliation in the 

 overlying coarse, feldspathic schist, all dip 

 in the same direction at an angle of about 



Fig Sl.-Diajrrainmatie sketch showing al- 3 Q° * There is little lYtOlU for (loul)t that 



htlii schist in cmiformamr <<nil;itt with unririiv- 



tag crystalline limestone, the foliations of both fa e foliation ill the Schist here, whatever its 



reeks dipping 30° SE. Localitj 802, Quarry hill. 



New Ashtoni. cause, is parallel with the stratification, and 



that both rocks are conformable. This is the normal structure. 



T. Nelson Dale: The Rensselaer Grit Plateau in New York. Thirteenth Annual Report, U. S. 

 Qcol. Survey, 1893, pp. 291-340. 



i If the older well-known works on this subject the following are the. most important: 



A. Sedgwick: On the structure of large mineral masses. Trans. Geol. Soc. of London, 2ml ^-r. 

 vol. 3, 1835, pp. 68, 461. 



Charles Darwin: Geological observations on South America, being part m of the geology of the 

 voyage of the Beagle. London, 1846. Chap. VI. Plutonic and metamorphic rocks; cleavage and 

 foliation. 



Daniel Sharpe: On slaty cleavage. Quarterly Journal, Oeol. Soc London, vol. 3, 1S47, p. 74. 



Henry Clifton Sorhy: On the origin of slaty cleavage. Edinb, New Philosophical Journal, vol. 

 53, 1853, p. 137. 



John Phillips : Report on cleavage and foliation in rocks, and on the theoretical explanations of 

 these phenomena. Report of British Association for the Advancement of Science. Part I. 1856, p. 369. 



Henry Clifton Sorhy: On slaty cleavage as exhibited in the Devonian limestone of Devonshire. 

 Philosophical Magazine, ser. iv. vol. 12, London, 1856, p. 127. 



John Tyndall: On the cleavage of slate rocks. Philosophical Magazine, ser. IV, vol. 12, London, 

 1856, p. 129. 



Samuel llaughton : On slaty cleavage ami the distortion of fossils. Phil. Mag., ser. IV, vol. 12, 

 London. 1856, p. 409. 



See Appendix B, Figs. 77, 78. 



-All compass readings in this report are corrected for variation. 



