/. Clifton Ward — On Rock Staining. 389 



III. — On Kock-Staining. 



By J. Cmfton Ward, F.G.S., Associate of the Eoyal School of Mines ; 

 Of the Geological Survey of England and "Wales. 



IN a paper on " The Permian Beds of Yorkshire," Mr. Lucas ^ 

 maintains : 1st, that the present western edge of the Magnesian 

 Limestone, at all events to the north of Eipon, marks the old shore- 

 line ; 2nd, that the iron and other salts found in Permian deposits 

 were derived from the neighbouring grit and limestone land ; 3rd, 

 that the colouring-matter, as it was brought down, stained the rocks 

 forming the bed of the inland sea, and hence the purple and red 

 colour of the grit and other beds between Knaresborough and Leeds. 

 A few words may be said upon each of these points in turn. 



1. The Magnesian Limestone boundary, for some miles to the 

 north and south of Leeds, certainly has not the appearance of having 

 been the actual western shore-line of the limestone sea, since it 

 forms, in most parts, a long low escarpment facing west, and there 

 are outliers at various distances, up to two miles, from the main 

 mass. North of Eipon, however, Mr. Lucas shows the facts to be 

 otherwise; and here it is interesting to think that it may be possible 

 to mark out approximately the old coast-line. 



2. If the Millstone-grit and Coal-measure rocks formed the 

 neighbouring land, undoubtedly much iron would be carried into the 

 sea by the streams and rivers, supposing the strata then to have been 

 in much the same state of consolidation and mineralization as now. 

 They must certainly have been exposed to much pressure and 

 alteration, as well as denudation, in the formation of the Pendle 

 anticlinals.^ 



3. Mr. Lucas "■ cannot avoid the conclusion that the date at which 

 the Plompton grit received its purple colour was during the deposi- 

 tion of the earliest red sediments below the limestone, and that the 

 carbonate of iron sank into the Plompton grit from Permian waters, 

 and not from subsequent infiltration from colourless limestone." 

 Now, strangely enough, in this particular neighbourhood, where the 

 red grit and shale beds are mostly found, there were no red beds 

 deposited below the limestone, but it in all cases rests directly upon 

 Millstone -grit or Coal-measure strata;^ whereas north of Eipon, 

 where Mr. Lucas says the red colour is nat generally found, the 

 Marl Slate does come on beneath the limestone. 



The question therefore arises, is the colour belonging to the rocks 

 themselves, or has it been produced through changes due to percola- 

 tion from the overlying limestone ? 



First, as regards the shales of the Lower Coal-measures. These, 



1 See Geol. Mag. (August, 1872), Vol. IX., p. 338. 



- Mr. Lucas speaks, by inadvertence, of the east and west anticlinals as the 

 Pennine, whereas the Pennine anticlinal, ranging north and south, was post-Permian 

 in its formation, and helped to give the easterly tilt to the Magnesian Limestone. — 

 See Prof. Hull's paper, Quart. Journ. Geol. Soc, vol. xsiv., p. 323. 



^ See my paper '* On Beds of supposed Eothliegende Age, near Knaresborough," 

 etc. Quart. Journ, Geol. Soc, vol. xxv., p. 291. 



