at Calclon Loiv, Staffs. 63 



The only record of a rolled-shell conglomerate on the eastern side 

 of the limestone massif appears to be that of Cracknowl quarry, near 

 Hassop Station. 1 



It is interesting to note that Dr. Sibly ~ and Mr. C. B. Wedd 3 

 have described sections in the eastern part of the Midland area 

 which afford evidence of local earth-movement and erosion in Upper 

 Carboniferous Limestone times. One section is near Youlgreave, the 

 other at Darley Bridge. The limestones in these sections are 

 regarded as representing a high level in the Zonsdalia-subzone, and 

 in both cases black shales, presumably of Pendleside age, clearly 

 overstep their denuded edges, thus causing local unconformity. It 

 is not improbable that the formation of the shell and limestone- 

 pebble conglomerate of Castleton and other places was contem- 

 poraneous with the earth-movement and erosion which produced these 

 unconformities. 



In addition to the main unconformity near Youlgreave, Dr. Sibly 

 also points out the probability of further contemporaneous elevation 

 and erosion during the formation of the Upper Zonsdalia-be&s, as in 

 the lower part of the section the truncated edges of a series of 

 limestone-beds form a surface upon which rests another series of 

 beds, less steeply inclined. 



In the North Wales sequence Dr. Wheelton Hind and Mr. J. T. 

 Stobbs have described a similar phenomenon to that of Youlgreave in 

 the upper beds of the Carboniferous Limestone seen in Waenbrodlas 

 Quarry, Halkyn Mountain (Flintshire). 4 At or about the same 

 horizon (D2) in other localities in North "Wales the same authors 

 record the occurrence of a conglomerate with quartz-pebbles 

 succeeding a Productus gigantens-\>e&. 



The absence of sections at Cauldon renders it difficult to ascertain 

 the relationship of the quartzose conglomerate to the limestones 

 containing a fauna typical of the Brachiopod-beds of Castleton. 

 Consequently, at the moment, it is not possible to correlate with 

 absolute certainty this conglomerate with that of Castleton and 

 other places. The contained fauna seems to suggest that it may be 

 contemporaneous, and if so there appears to be a considerable gap 

 between it and the ITutnerosus-he&s of Caldon Low. The age of the 

 latter beds is a subject upon which some difference of opinion 

 prevails. Dr. Sibly, in 1908, 5 regarded them as probably belonging 

 to the upper part of D 1? while others, including Dr. Wheelton Hind, 

 are inclined to place them much lower in the sequence, viz. C— Sj. 6 

 In this connexion it will be of some interest to record the discovery 

 by one of the writers (J. "W. J.) of an interesting coral recently in 



1 Elizabeth Dale, The Scenery and Geology of the Peak of Derbyshire, 

 1900, p. 17. 

 a Op. cit., 1908, p. 63, and fig. 5 (p. 62). 



3 Discussion of Dr. Sibly's paper, op. cit., p. 81, and Mem. Geol. Surv., 

 The Geology of the Northern Part of the Derbyshire Coalfield and Bordering 

 Tracts, London, 1913, p. 35. 



4 Geol. Mag., n.s., Dec. V, Vol. Ill, p. 396, PI. XXII, 1906. 



5 Q.J.G.S., vol. lxiv, p. 44, 1908. 



6 Geol. Mag., Dec. VI, Vol. V, p. 480, October, 1918. 



