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



III. — Geology of the Channel Islands. 

 By J. A. Birds, B.A., F.G.S. 

 (Continued from p. 86.) 

 Fart II. — Post-Pliocene Geology. 



FEOM the sandstone [i), which Professor Ansted asserts, though 

 without giving his reasons, to be " no doubt modern," and to 

 have been "deposited before" [just before?] "or during the last 

 great elevation," down to the superficial clays and sands, there is 

 not a scrap of any other Secondary or Tertiary rock in situ to be 

 found on any of these islands. We leap at once from this sandstone 

 to clays and sands of Post-Tertiary date. Mr. Duncan, in his 

 History of Guernsey (edit. 1841, p. 513), says that "flint and chert 

 nodules, containing impressions of shells, etc., are frequently dis- 

 covered beneath the soil in places which preclude the probable 

 transport by the hand of man." 



" This," he adds, " is especially the case on the denuded summit 

 of the gneiss of the South of Guernsey." I conclude he means 

 in the brick-clays and sands covering the S.E. corner of the 

 island. I have myself traced these clays, etc., from near the 

 Doyle Column on Jerbourg Point, round by St. Martin's and 

 St. Andrew's Churches, to the Foulon Cemetery, and the Amherst 

 Road above St. John's Church, in St. Peter's Town ; and I found 

 two or three small specimens of chalk flints in the clay associated 

 with pebbles and fragments of gneiss, granital, quartz, and other 

 rocks of the neighbourhood. The island of Sark, in the same 

 manner, is covered at various points with a coating of clay con- 

 taining stones, generally derived from the underlying rocks ; but, at 

 the old mine-heaps in Little Sark, I found, beside these, a fi-agment 

 of amygdaloid, and another almost perfectly hexagonal fragment of 

 basalt, not, so far as I know, derived from any of these islands. 

 Aldemey, again, is said to contain almost inexhaustible supplies of 

 brick-clay, which has probably a similar derivation. 



Jersey, also, is covered in many places with brick-clay and sand, 

 especially around St. Helier's ; but no chalk flints have been found 

 in these deposits. Upon the shores, however, of all the islands, 

 without exception, chalk flints occur, and in some places very 

 abundantly. Dr. MacCulloch in 1811 says that he "picked up flints 

 upon the beach at Alderney," and Professor Ansted calls attention to 

 a singular profusion of chalk flints often of large size in Port-Saie, 

 on the N.E. of Jersey ; and also on the beach at Grouville Bay ; 

 and he appears to think, from their being found chiefly in the 

 neighbourhood of the newer conglomerate (k), that they may 

 possibly have been derived from it. They have not, however, he 

 admits, ever been seen in situ in the conglomerate itself. I can add 

 that the flints are to be found, though not in equal abundance, in St. 

 Clement's Bay and the Greve d'Azette on the south, and in Bouley 

 Bay on the north — in fact, on all the shores of the eastern half of 

 Jersey. They are wanting, Professor Ansted says, on the western 



