Vol. 65.] THE CAULDRON-SUBSIDENCE OF ©LEST COE. 611 



32. The Cauldron-Subsidence of Glen Coe, and the Associated 

 Igneous Phenomena. 1 By Charles Thomas Clough, M.A., 

 F.G.S., Herbert Brantwood Maufe, B.A., F.G.S., and Edward 

 Battersby Bailey, B.A., F.G.S. (Bead May 26th, 1909.) 



[Plates XXXII-XXXIV.] 



Contents. 



Page 



I. Introduction 611 



II. The Glen Coe Volcanic Series. 



(a) Type Section 615 



(b) General Distribution and Variation of the Volcanic Series... 617 



(c) The Uneven Floor upon which the Volcanic Series reposes . 620 



(d) Summary of the Volcanic History 623 



III. The Boundary-Fault and the Fault-Intrusions. 



(a) General Description 624 



(1) Distribution of the Volcanic Series in relation to the 



Faulting 625 



(2) Distribution of the Highland Schists in relation to 



the Faulting 626 



(3) The Inclination of the Boundary-Fault 628 



(4) Mechanical Evidence of Faulting 629 



(5) The Fault-Intrusion and its Relation to the other 



Plutonic Rocks of the District 632 



(6) The Early Fault-Intrusions 638 



(7) The Dykes and their Relation to the Cauldron- 



Subsidence 640 



(b) Special Description of Selected Sections 647 



IV. General Conclusions and Discussion 661 



I. Introduction. 



During Lower Old Bed Sandstone times the district of Glen Coe 

 furnished an arena wherein terrestrial disturbance and igneous 

 activity combined to produce effects of imposing magnitude and, as 

 we believe, of some theoretical importance. The paper now pre- 

 sented embodies an account of a cauldron-subsidence which affected 

 an area roughly oval in shape, and measuring not less than 5 miles 

 from side to side. We show that the subsidence took place in at 

 least two stages, and that it was accompanied in a complementary 

 fashion by the uprise of a series of marginal intrusions. 



In the first instance the nature of the volcanic succession in Glen 

 Coe will be dealt with, its variations from point to point will be 

 described, and evidence will be adduced to illustrate the marked 

 inequalities of the floor of Highland Schists upon which these 

 volcanic rocks accumulated. The second portion of the paper is 

 devoted to the evidences of the cauldron-subsidence, and treats in 

 some detail of its tectonic features and the accompanying plutonic 



1 Communicated by permission of the Director of H.M. Geological Survey. 



