﻿THE 



QUARTERLY JOURNAL 



OF 



THE GEOLOGICAL SOCIETY OF LONDON. 



Vol. LXVI. 



1. On the Dyee at Crookdene (Northumberland) and its Relations 

 to the Collywell, Tynemouth:, and Morpeth Dykes. By 

 Miss M. K. Heslop, M.Sc, and Dr. J. A. Smythe, F.C.S. (Com- 

 municated by Prof. G. A. Lebour, M.A., D.Sc, F.G.S. Bead 

 November 17th, 1909.) 



[Plates I & II — Microscope-Sections.] 



Contents. 



Page 



I. The Oookdene Dyke 2 



II. The Collywell Dyke 9 



III. The Tynemouth Dyke 12 



IV. The Morpeth Dyke 14 



V. Comparison of the Dykes 10 



VI. Conclusions 16 



Of the four dykes dealt with in this paper, only one, the Crookdene 

 Dyke, appears not to have been investigated before, although its 

 position is marked on the Geological Survey Map, Sheet 106 N.E. 

 As it has many points of interest, we shall describe its mode of 

 occurrence and properties in some detail. The other three dykes 

 have already been investigated by Dr. Teall 1 ; what observations we 

 have to make upon them are thus only supplementary to his work, 

 and serve chiefly to bring out the relationships which exist among 

 these dykes in a clearer light. It should be mentioned that Teall 

 had already come to the conclusion that the Collywell, Tynemouth, 

 and Morpeth Dykes fall into a distinct group, and this inference 

 we are in a position to substantiate ; the Crookdene Dyke belongs 

 also to the same group, having the strongest analogies to the 

 Collywell Dyke. The field-relationships of the Collywell, Tynemouth, 



1 ' Petrological Notes on some North-of-England Dykes ' Quart. Journ. Geol. 

 Soc. vol. xl (1884) pp. 209-46. 



Q. J. G. S, No. 261. b 



