part 3] 



A COMPOSITE SILL AT NEWTOX ABBOT. 



261 



7. A Composite Sill ^^Newton" Abbot (Devon). By William 

 GrEOEQ-E St.John SHANNON, M.Sc, F.Gr.S. (Eead November 



23rd, 1921.) 



[Plate XL] 



Contents. t, 



Page 



I. Introduction 261 



II. Field Relations 262 



III. Macroscopic Characters 263 



IV. Petrography 264 



V. Summary and Conclusions 269 



I. Introduction. 



The sill which is described in this paper forms the smnmit and 

 part of the northern flank of Knowles Hill, Nev^ton Abbot, 

 6-inch Ordnance-Sm-vey Map 109, S.E. The hill is bomided on 

 all sides except the western by the alluvium of the Teign and its 

 tributary the Lemon ; it forms a prominent hog-back lying in the 

 fork between the two rivers. The base of the hill is formed of 

 Upper Devonian slates, and these are continuous to the west, 



Fig. 1. — Sketch-map of Knowles Hill, Newton Abhot, on the 

 scale of 6 inches to the mile, or 1 : 10,560. 



i^^l Alluvium 

 r^^ Dolerite 

 l^H Picrite 

 M Mugearite 



where, at a distance of about half a mile, another outcrop of 

 dolerite occurs at High week Chm^ch. The occurrence of picrite 

 was discovered by Busz, and a short description of the sill and of 

 the presence of original quartz is given in the Geological Survey 

 Memoir on the ' Greology of Newton Abbot,' No. 339, 1913. 



Q. J. a. S. No. 311. t 



