J. A. Birds — Geology of the Channel Islands. 85 



red sandstone with clayey and ferruginous bands. In Bouley Bay 

 this sandstone rests unconformably, and almost horizontally, upon 

 nearly vertical strata of the older sandstone or hornstone (/). Prof. 

 Ansted believes this latest sandstone to be " quite modern," and to 

 have been "deposited before" {7 shortly before), "or during the last 

 great elevation," * He does not, however, assign any reasons for his 

 belief. 



The age, indeed, of all these rocks is as yet a mystery. Not a 

 trace of fossils has been discovered either in the schist (e), or in the 

 sandstone portions of (/), or in the later sandstone (i) ; only among 

 the pebbles on the beach at Bouley Bay I found many containing 

 what certainly look like the remains of corals and portions of shells. 

 These have probably been derived from the newer conglomerate (h); 

 and if their organic character were determined, it might throw some 

 light on the age of the conglomerate. As yet, however, one cannot 

 even say whether the syenites are older or younger than the schist 

 (e), it not being known whether they ever enter and pierce the latter, 

 as in Cornwall the granites do the Devonian and Carboniferous rocks, 

 and are thereby proved to be younger than them. The direction of 

 the principal joints, nearly N. and S., is the same as that of the 

 granites in Cornwall, but, this being due to later causes, proves 

 nothing, of course, as to the age of the original formation of the rocks. 



It is easy enough to invent theories as to the age and history of 

 the various formations ; and, in the absence of further evidence, 

 this is about all that can be done. Dr. MacCulloch, in 1811, de- 

 scribed the schist as grauwacke,^ i.e. of Pre-Carboniferous age, and we 

 may perhaps pretty safely assume that it is of some Lower Silurian 

 period, coeval with the Silurian rocks of Normandy and Brittany. 

 (Llandeilo, Caradoc, or Lower Llandovery). 



Of the sandstone, and its accompanying felstone and cherty 

 porphyries, and conglomerate (/ and g), there is almost as little 

 evidence as to age. From their general appearance one might 

 imagine them to be of Old Bed Sandstone equally as well as of 

 Permian or Triassic age. Only at one point, just above Le Bourg, 

 did I discover the shale (e) and the felstone porphyry (/) in 

 contact, and here it seemed to me that the shale actually overlay 

 the porphyry. Of course this might have been due to a fault or 

 inversion of the strata. But I can hardly think so in this case. 

 Can the porphyries have been eruptive and pierced into the shale ? 



From the section it does not appear whether the shale is older or 

 younger than the sandstones and porphyries. Prof. Ansted con- 

 jectures, however, from the similarity of dip, that the newer Jersey 

 conglomerate (7t) and the Alderney sandstone may be of the same 

 age : and, if so, that the older conglomerate (g) may perhaps belong 

 to the Cherbourg grits (Bunter or Lower Trias). In this case the 

 underlying porphyries and sandstones (/) might be somewhat older, 

 or intermediate between the schist (e) and the conglomerate (g). 



1 The Channel Islands, p. 275. 



2 Account of the Geology of Guernsey and the other Channel Islands, Geol. 

 Trans. 1st series, vol. i. 1st paper. 



