432 



P. B. BRODIE ON CERTAIN QUARTZITE AND SANDSTONE 



which must have had a different origin. Yery likely the altered 

 Llandovery Sandstone (quartz rock) of the Lickey contributed many 

 of the pebbles in this Drift, though it would be almost impos- 

 sible to determine the source of all the quartz pebbles in the latter ; 

 I have, however, not yet detected a single well-defined Llandovery 

 species in any of them in this district; and a very considerable num- 

 ber, if not a majority of the fossils in the pebbles I have obtained are 

 decidedly of Lower Silurian origin ; so that in a direction south of 

 Birmingham and towards Warwick and Stratford-OD-Avon the 

 tendency evidently seems to be that pebbles of lower palaeozoic age 

 predominate; and the lithological and zoological resemblance which 

 they bear to the pebbles of this date at Budleigh is sufficiently close 

 to lead to the conclusion that they are in all respects identical and 

 were derived from some Old Silurian rocks at a greater or less dis- 

 tance, and so far had a common origin. Originally, of course, they 

 must have come from their parent palaeozoic rock wherever it was, 

 by the wear and tear of which, by the action of waves and currents 

 and other processes of denudation, in the course of ages they became 

 pebbles, and may have been in the first instance, perhaps, washed 

 into the Bunter and have helped to form a portion, greater or less as 

 the case might be, of its conglomerates in certain places. When this 

 was in its turn fractured and denuded, some of these pebbles may 

 have been afterwards redeposited in the New Bed Sandstone, not 

 everywhere, but locally, as at Budleigh in Devonshire, and parts of 

 Warwickshire*. When the latter was also largely denuded, these 

 Old Silurian bouldered remnants were finally scattered about and 

 mingled with the Drift. If not derived from the Bunter or the New 

 Bed Sandstone they must have come directly from the relics of some 

 ancient Silurian formation which was still in existence, and was 

 finally but partially broken up at a more or less distant period, 

 thus helping to add largely to the widely accumulating, often sifted 

 and re-formed Drift. 



In a redistributed and miscellaneous superficial deposit of pebbles 

 and other debris, like that of the Midland Counties in the districts 

 referred to, it would, I think, be incorrect (at least we have not 

 sufficient evidence as yet) to infer that most of the quartzite and 

 other pebbles are derived from the Bunter. A large majority of 

 these are more or less consolidated quartzite ; and I have one pebble 

 of quartz with an obscure impression of a shell, which reminds me 

 of the Cornish Lower Silurian rock at Caerhayes. The most abun- 

 dant are grey and brown, more or less striated, consolidated sand- 

 stone boulders, varying in size and sometimes of a deep red colour ; 

 and these agree lithologically with the Budleigh pebbles containing 



* Although, with the exception of the Lower Keuper sandstone at Budleigh, 

 there are no pebbles elsewhere found in situ in the New Bed Sandstone, there 

 is no reason why they should not have occurred in certain places in other di- 

 rections in the same formation, either in the Upper or Lower Keuper. In the 

 Midland Counties the upper division has here and there undergone very ex- 

 tensive denudation ; or possibly pebble-beds may still exist in the New Eed which 

 have not yet been discovered. 



