Correspondence — Dr. A. Irving. 239 



AECH^AN LIMESTONES ON THE ELANK OF THE MALVERN 



EANGE. 



Sir, — The works which have been in progress for some weeks 

 for the new reservoir of the Great Malvern Waterworks on the north- 

 east flank of the Hereford Beacon have already brought to light a 

 fact of no inconsiderable importance in its bearing upon the geology 

 of this most interesting region. Briefly it may be described as 

 follows : — The reservoir is to be formed by a huge dam to be con- 

 structed across the deep valley which runs down from the north- 

 eastern flank of the Beacon, between the two most northerly of the 

 four spurs or buttresses which most geological writers on the 

 district have noticed abutting upon the Triassic plain of the Severn. 

 It is in the deep wide trench which has been excavated for the 

 foundations of this dam that the limestone is best exposed. The 

 rock is a compact crystalline limestone, with a more or less distinct 

 bedding, though much jointed in all directions, as if by incipient 

 crushing, probably somewhat dolomitic, of a light-grey colour on 

 fresh fractures, but in the more decomposed portions stained with 

 oxides of the heavier metals ; secondary crystals of calcite are often 

 formed in quantity on the divisional planes of the rock. 



Of the age of the roch (which so far appears to be absolutely 

 unfossiliferous) there cannot be very much doubt. As the field- 

 relations show that it cannot be younger than the complex of lavas 

 and altered tuffs and volcanic muds of the hills between which the 

 valley lies, a complex of rocks which two of the most capable 

 judges on this question (Drs. Callaway and Hicks) refer to the 

 Pebidian (later Archaean). My first visit to the spot was in company 

 with Dr. Callaway, about a week ago ; and the suggestion that tlie 

 rock is one " archa^an limestone of chemical origin " was made by 

 him. On a second visit yesterday with my friend Mr. H. D. Acland, 

 of Malvern, I was able to follow the exposition which the foreman 

 of the works gave of its position in relation to what he called the 

 " whin-rock." It strikes nearly north-west, and dips at an angle of 

 about 80°. It alternates with the " whin-rock," which seems related 

 to it as an " interbedded trap " (as if the two rocks were contempor- 

 aneous portions of the Pebidian series of this locality), or possibly, 

 from the fact stated to us that the limestone is " softer and easier to 

 work against the "whin" (as if the latter were intrusive), even 

 somewhat older than the volcanic series. Macroscopic examination 

 of some specimens seemed, however, to indicate contemporaneity by 

 the apparent presence of pyroclastic materials in some portions of 

 the limestone. 



The presence of limestones (even massive limestones) in the later 

 Archaeans is known ; and until quite recently it was generally 

 assumed in this country that they illustrate those extreme views of 

 " regional metamorphism " so much in vogue, the metamorphism 

 having been so complete in such cases as to have obliterated all 

 traces of organic remains. In 1888 I challenged that view, on the 



