158 mk. w. s. boulton on the [May 1904, 



13. On the Igneous Rocks at Spring Cove, near Weston-super- 

 Mare. By William S. Boulton, Esq., B.Sc, A.R.C.S., F.G.S., 

 Lecturer in Geology at University College, Cardiff. (Plead 

 January 20th, 1904.) 



I. Introduction. 



In the Summary of Progress of the Geological Survey for 1898 

 (pp. 104-11), Sir Archibald Geikie & Mr. Strahan, in a description 

 of a * Volcanic Group in the Carboniferous Limestone of North 

 Somerset,' published for the first time the evidence for the contem- 

 poraneity of these igneous rocks. 1 The authors refer briefly to the 

 basalt and associated tuffs at Spring Cove, immediately to the west 

 of the town of Weston, and describe in more detail the basalt-lava 

 and beds of tuff interbedded with the fossiliferous limestone along 

 the ridge of Middle Hope, 2 miles north of Weston. 



At the time of the publication of this account, I had already 

 made a detailed examination of these rocks in the field, and of 

 microscopic and cliemical preparations ; but as my results seemed 

 in general accord with those of the authors named, especially in 

 regard to the rocks of Middle Hope, I felt that little or nothing- 

 was to be gained by the publication of my work as a whole. 



In the rocks at Spring Cove, Weston, however, there appear to 

 me to be points of considerable iuterest which arc only briefly 

 touched upon, or not mentioned at all, in the account to which I 

 have referred, and I therefore venture to submit some additional 

 observations in regard to them. 



II. General Description of the Hocks. 



The basalt at Spring Cove, immediately north of Weston Pier, 

 runs obliquely to the high road, and is exposed from low-water 

 mark along the foreshore into the face of the cliff, the exposed 

 length being about 150 yards. The massive beds of Carboniferous 

 Limestone, between which the basalt is intercalated, strike north- 

 eastward, and dip south-eastward (towards Weston) at about 40°. 

 The basalt-sheet is parallel to the bedding of the limestone, and has 

 a thickness of about 45 feet. 



A traverse from end to end of the exposure shows clearly that 

 the rock varies considerably in structure and appearance, and that 

 it is by no means a simple basalt-lava flow. Starting from low- 

 water mark, the rock is a hard, compact, red, slightly-amygdaloidal 



1 In this account reference is made to the observations of previous in- 

 vestigators. 



