OKOLOGIC SECTION AND ITS INTKItFKETATlOX 179 



rock cuts, which afford very interesting exposurefcS.'^" In the first cut a 

 fairly coarse augite-syenite is shown which has not been severely gran- 

 ulated, is practically non-foliated, and has a very evident cataclastic 

 structure (plate 19).t The second cut shows quite similar material, 

 though more crushed and with a better foliation. The third cut is 

 quite extensive, and a generalized section of the exposures is given in 

 the accompanying figure. 



The augite-syenite constitutes the center and south end of the section. 

 It is more thoroughly granulated and more gneissoid than in the pre- 

 ceding exposures. Separating the two syenite areas is a thickness of 

 12 feet of well banded gneisses. Above is a hiyer 2 feet thick of a white, 

 granular rock composed of quartz and white pyroxene in the proportion 

 of 1 to 2. This is followed 1)}^ layers of granular, black i)yroxene gran- 

 ulite and light colored quartzose rocks, the latter consisting essentially 



C_ A D B A 



Kn.rur. 1. — ^^'fcfioii in Hailroad (Jut iiuw Loon Lahi\ Xttr York, 



A, uugite-syenitt'. B, well handed quartzose gneis.ses. C\ qtuu'tzo.se ft-neis.ses, D, biotitic 

 sheared strip— strike* north 10 dejj;ree.s west. Dip of Ix'eMiiiij and tbliatioii (m degree^^ to the west. 



of quartz and potash feldspars, the (luartz forming from 60 to 70 per 

 cent of the rock. The structure and composition indicate a sedimentary 

 origin for these included bands, and they ai'e precisely like rocks which 

 invariably accompany the crystalline limestones of the region, the white 

 pyroxene being especially characteristic. At the lower contact Avith the 

 S3^enite is a probable shear- plane, along which biotite is abundantly de- 

 veloped. This syenite is succeeded to the north by finely granular, red, 

 granitic gneisses of doubtful origin, but also very similar to rocks which 

 are of common occurrence associated with the limestones. The foliation 

 planes of the syenite have the same dip and strike as the included 

 gneisses. 



There can be no question of the sedimentary origin of the gneisses in- 

 cluded under ^' B '^ in the section (see plate 20). With that as a start- 

 ing point, the uniform dip and strike in the exposure, together with the 

 finely granular character of the syenite, give the impression that the 

 whole forms a regularly bedded series ; but when the syenite is coni- 

 ])ared with the rock in the other cuts it is seen to be unquestionably the 



*'rhese exposures were visited in eoinpuiiy with I^rofos^or A. ('. Ixill iu July, 1<S97, and with 

 Professor J. F. Kemp in August, 18U8, neither of whom objected to the interpretation here given. 



t A photograph of this exposure is reprodu<*e<l iw jilate U) to indicate the color change due to 

 weatliering. 



