;i6 



PROCEEDINGS OF COLUMBUS MEETING. 



Structure and Age. 



Sections. — The five sections herewith (figure 5) show the structural relations. In 

 section .1, which crosses the lowest part of the saddle, the Cambrian quartzite forms 

 on the eastern side an anticlinal and a synclinal, the latter infolding some 65 feet 

 of the lower part of the Stockbridge limestone. West of this, owing to a fault, a 

 block of this limestone about 650 feet wide has slidden down between two masses 

 of quartzite. Beyond the quartzite dips normally under the limestone, and this 

 includes a bed 25 feet thick and about a quarter of a mile long filled with fossils, 

 determined by Mr, ('. I>. Walcott as Hyolitlies americamis, Billings,* with the fol- 

 lowing species doubtful : //. imper, IT. communis and //. similis (very doubtful) ; the 

 whole indicating, as he writes, t '"The upper horizon of the lower Cambrian or 

 Olenellns zone." As there are about 470 feet of limestone between this bed and 

 the underlying quartzite, that much of the limestone must be regarded as Cam- 



c 



FAULT 

 CLEAVA&E ; 



s;i. s.c.KCi.c. 



CftmK Quartitte 



FAULT 



t^. cuavaie ; 



A 



D 



fj" Lonqil". 



CTTf* CR. 



Qv&yCh t e 



L'*n»sronp 



Figure 5. — Sections through Ruttand-Dariby Ridge. 



brian. These pteropods appear more frequently in transverse sections, but also in 

 every sort of section. Each individual or fragment generally forms the center of a 

 concretion-like body from ] to 1 inch in diameter (figure 6). These bodies, how- 

 ever, require further study. The rock is bluish-gray. The oolitic structure appears 

 best on weathered surfaces. 



In section />', about a quarter of a mile north of .1, the eastern fault-plane alone 

 appears, the western having died out or merged into it. Mere the quartzite shows 

 a synclinal and an anticlinal, and is broughl by the fault to the level of the schists 

 overlying the limestone. 



* E. Billings— " On some New Species of Paleozoic Fossils: Canadian Naturalist, Dec, 1871, re- 

 printed in Am.Journ. Sei., 3d ser., vol. iii, 1872, p. 352; C. D. Walcott— " Studies on the Cambrian 

 Fauna of North America": Bull. 30 IT. S. Geol. Surv., 1880, p. 132, pi. xiii; also -The Fauna ofthe 

 Lower Cambrian or ( Henellus Zone" : 10th Ann. Rep. IT. S. Geol. Surv., 1890, p. 1520, pi. Ixxv. 



f November 13, L891 . 



