Vol. 56.] THE ROCKS OF SOUTH-EASTERN JERSEY. 307 



18. The Rocks of the South-eastern Coast of Jersey. By John 

 Parkinson, Esq., F.G.S. ("Read March 7th, 1900.) 



Contents, 



Pago 



I. Introduction 307 



II. The Eastern District 308 



(1) Characters of the Earlier Acid Intrusion. 



(2) Nature of the Earlier Intrusive Magma. 



(3) Phenomena attending the Earlier Acid Intrusion. 



(4) The Granite or Later Acid Intrusion. 



(5) Comparison with Bocks in Guernsey. 



III. The Western District 315 



(1) General Characters of the Acid Intrusion. 



(2) Relation of the Intrusive Acid Rock of the Western to 



that of the Eastern District. 

 IV. Conclusions 318 



I. Introduction. 



In a recent communication to this Society 1 1 described the intrusion 

 of a granite into a diabase at Sorel Point, on the northern coast of 

 Jersey, and in concluding remarked on another parallel case to be 

 found on the southern side of the island. It is to this that the 

 present paper relates. The rocks from north and south, both 

 intrusive and intruded into, show a resemblance one to another 

 sufficient to indicate that they are closely related. The interior 

 of the island is occupied by the rather varied assortment of igneous 

 and sedimentary rocks depicted on M. Noury's map. 2 



From the town of Sfc. Helier's to La Eocque Point, the south- 

 eastern termination of the island, the receding tide exposes to the 

 view of an observer standing on the low shore an assemblage of 

 jagged rocks which stretch far out towards the horizon. Near the 

 centre of St. Clement's Bay an intrusive granite is found about high- 

 water mark, and forms at the western end the more outlying crags 

 of Le Nez Point. At Greve d'Azette, the next bay to the west- 

 ward, it again approaches the shore. Diabase and other closely- 

 related rocks make up Le Nez itself. At the junction of the two 

 the granite sends innumerable offshoots and dykes into the older 

 rock, which are well seen to the west of Le Nez. Generally these 

 dykes are clearly cut and well denned ; but occasionally peculiar 

 rocks make their appearance, so similar to those non-homogeneous 

 and mixed rocks which I described from Sorel Point (op. cit.) that 

 we cannot doubt, after a comparison between them, that a local 

 incorporation of fragments of the diabase has taken place. So far 

 the matter appears clear enough, and it is only when the diabase 

 itself is studied that complications, arising from its non-homogeneous 



1 Quart. Journ. Geol. Soc. vol. lv (1899) p. 430. 



2 • Geologie de Jersey,' 1880. 



