Quartsose Conglo7ne7xite at Caldon Low, Staffordshire. 81 



others, except in the bands which are largely composed of vein- 

 quartz. The metamorphic quartzites are relatively subordinate. 

 Many of the quartzite pebbles appear to be derived from local 

 rocks of Pendleside, Millstone Grit, and, possibly, Lower Coal- 

 measures age, while the limestone fragments, according to the 

 fossil contents, are derived from beds ranging from the Caldon Low 

 limestones to D^ rocks. 



On an average the amount of calcium carbonate in the 

 conglomerate does not exceed 20 per cent, and of this at least half 

 belongs to the crystalline matrix. Hence the amount of primary 

 detrital limestone is less than 10 per cent, compared with 85-95 per 

 cent in the normal Caldon Low limestone. The cherts possibly 

 originated in the deposits of that material in the Dg and Pendleside 

 Beds of Derbyshire. An almost identical lithological assemblage is 

 found in the Bunter beds Avhich occur at a height of 814 feet above 

 O.D. at High Shutt, about 4 miles to the south-west. 



The Weaver Savd-pits. — An examination of the sand- and clay- 

 pit south of Ribden Mine, about 1 mile from Caldon Low, gives much 

 help in elucidating the problem of the Caldon Low conglomerate. 

 This large, open pit, which is about 900 feet above O.D., is worked 

 for sand and clay, the former being predominant. It contains 

 pockets of uncemented pebbles, similar in character to those at 

 Caldon Low, but here and there consolidation has occurred, and we 

 find hard masses of quartzose conglomerate like grea;t sarsens, 

 and very similar lithologically to the infilling at Caldon Low. 

 Nowhere are the limestone sides of the pocket to be seen, but the 

 limestone outcrops all round the deposit. In the pit fairly large 

 pebbles, 2 to 3 inches in diameter, are to be seen, and these are 

 typically pitted like the Bunter pebbles. We have observed similar 

 pebbles at the former clay-pit at Caldon Low and in the Derbyshire 

 sand-pits near Newhaven. Moreover, the lithological assemblage 

 at Ribden is essentially Bunter, and very similar to the deposits 

 of the latter at High Shutt. 



The sand deposits at Ribden and elsewhere and the conglomerate 

 at Caldon Low have thus many points in common : (a) There is 

 a close lithological similarity between the constituent materials ; 

 (b) each contain a local concentration of vein-quartz pebbles of 

 intermediate size ; (c) each contain deposits of fine sand ; (r/) in 

 each case the latter shows well-developed secondary outgrowths 

 on the quartz crystals ; (e) the relative amounts of such materials 

 as Lydian stone are similar. The chief points of difference are the 

 presence of calcareous cement at Caldon Low as compared with 

 the generally unconsolidated nature of the material at Ribden, 

 and the substitution of the large quartzose pebbles at Ribden 

 by the limestone fragments at Caldon Low. The larger blocks have 

 not been transported any great distance, and it is probable that 

 they represent material which has fallen from the sides and roof of 

 the pits ; in the one case the sandstone blocks from now denuded 



VOL. LVII. — NO. II. 6 



