GENERAL STRUCTURE AND CORRELATION. 



11 



unconformable. At about the same time Mr. Wolff had found the two dikes 

 of eruptive basic rock in Stamford in the granitoid gneiss and at its contact 

 with the quartzite. (Figs. 1 and 2.) 



Fig. 1. — The Stamford dike, showing the Cambrian conglomerate deposited in dike fissure; C, 

 conglomerate j c, lower layers of conglomerate rentier'*. I Bchistose l>\ admixture of materiHl from 

 the altered dike d, diabase of the dike rendered schistose bj metaroorpbisnl e, altered clike ma- 

 terial; ;/, pre Cambrian granitoid gfteiss 



We could hardly have wished for better evidence than that offered by 

 one of these. At the contact the quartzite strikes N. 40° E., dips 50° SE. 

 The dike strikes X. 60° W., between vertical walls; but the rock of the dike 

 has undergone changes that have given it a lamination, and the planes of 

 this strike N. 35° W. and dip 45 easterly. The structure of the granitoid 

 gneiss is here quite irregular and obscure. No trace could be found of the 

 dike cutting into the quartzite, and as 



this is continuously exposed on both ;' > /\vV;,/ 



sides, the possibility of its absence by w ^-.. -,'?'',■ 



faulting was eliminated. But there is A jj-dj 



more direct positive evidence in the fact wMil 



that the quartzite beds thicken and sag y vy /: 



down over the dike — indeed, into the ' '^Cy/#-4$; 



V ' \.'fj 



dike fissure, as Mr. Whittle and I found » '' 



by digging. The evidence is conclu- 

 sive, as I satisfied myself during several 

 visits, that the Cambrian transgression 



Fio. 2.— The Stamford dike plan, c, conglomerate; 



found here a flSSUre, either open Or filled ■'. dike rock, uietamorphic, with foliati altered 



dike material ; <7. Stamford gneiss. 



with a rotten dike, which was washed 



out to a depth of several feet and refilled with beach sand and pebbles, 

 the dark material contributed by the dike increasing toward the bottom. 

 The sudden thickening and sagging of the quartzite over the fissure, taken 



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