﻿VoL 64.] 



TWO EARTH-MOVEMEISrTS OF COLONSAY. 



303 



IV. The Eelation of the Eaeth-Movements 

 TO the Lamprophyees. 



A large number of the lamprophyre dykes so abundant in Colonsay 



-r^. , „ . -, -, , .are obviously intru- 



-cig. 4. — Section on the shore south-east of 



Eilean Duhh^ and north of Port na Cuilce 



(Colonsay), showing a lamprophyre sill 



(A) in the phyllite intruded along the 



primary cleavage and folded and cleaved 



by the secondary movement. 



[A small dyke (B) of later age than the secouclarj 

 movement is seen at the bottom of the section. 

 Scale : 2 feet = approximately 1 inch.] 



ded along the first 

 cleavage, and as 

 obviously folded and 

 cleaved by the se- 

 condary movement. 

 These run in a 

 general way parallel 

 to the strike of the 

 first cleavage, dip 

 with it, and occasion- 

 ally cut across it in 

 such a manner as to 

 leave no doubt that 

 they are subsequent 

 to it. Moreover, mar- 

 relations such 

 as that shown in 

 fig. 5 (below) are not 

 uncommon, and are 

 quite inconsistent 

 with the idea that 

 the primary cleavage 

 could be subsequent 

 to the dykes. The 

 relations of the 

 secondary 

 are quite as 

 Again and again 



cleavage 

 clear. 



this cleavage can be 

 traced from the adjoining schists right into the body of the lampro- 

 phyre, and repeatedly we find the lamprophyre afi'ected by the folds 



Fig. 5. — Margin of lamprophyre in phyllite^ on the coast north of 

 Kiloran Bay, showing its relation to the first cleavage, which 

 stops short at the edge of the sill, and does not penetrate it. 



which contort the planes of primary cleavage along which it 

 lies. Moreover, the distribution of cleiived lamprophyre dykes 

 Q. J. G. S. Xo. 254. X 



