484 SUBMERGED LAND-SURFACES AT BARRY. [Aug. 1 896, 



in place and abundant land-shells. The same sort of evidence, in a 

 scarcely less striking degree, is presented by every layer from the 

 bottom to the very top of the series. There is, in fact, no part of 

 it that could be formed with the land at its present level. 



It will be noticed that the Cadoxton River flows for much of its 

 course over Keuper Marls and the conglomerate or limestone which 

 form the base of that series, but that at the coast it traverses the 

 .Carboniferous Limestone. In the softer rock its valley is broad and 

 occupied by the alluvial flat, of which the Sully and Cadoxton 

 Moors form part, but in the Carboniferous Limestone it narrows 

 down to about 100 yards. It was in this broad area of obstructed 

 drainage that the deposits described above accumulated, and no 

 doubt the regularity with which they were laid down, and the 

 gentleness with which estuarine influence was occasionally in- 

 sinuated, was largely due to the narrowness of the outlet. At the 

 time of the earliest land-surface, when the land stood not less than 

 55 feet higher than at present, the sea must have been still farther 

 removed, but how much farther it is not possible to say. Though 

 the Carboniferous Limestone would waste with extreme slowness, 

 ^here may have been extensive post-Glacial deposits outside Barry 

 Island, of which the Bristol Channel tides would make short work, 

 so that it is doubtful how far the contours of the present sea-bottom 

 are those of a submerged land-surface, or to what extent they have 

 been modified by marine erosion. It is worth noticing tltat the only 

 part of the Bristol Channel, south and east of Barry, which exceeds 

 60 feet in depth is a rather narrow trough about 2 miles south of 

 the Welsh coast. 



At any rate, we may suppose that the alluvial flat of the Sully 

 and Cadoxton Moors occupies what was a generally freshwater 

 estuary, occasionally dry enough to support a forest-growth on its 

 margins, but as a rule swampy and densely overgrown with sedges, 

 etc. By a more or less continuous sinking of the land the swamp 

 tended to become a shallow lake, nearly but not wholly beyond the 

 reach of the tide, until the subsidence admitted the sea by the gap 

 east of Barry, thus separating that island from the mainland, and 

 burying the estuarine series under true marine and tidal muds. 

 The occurrence of the fragment of a polished flint-implement in the 

 uppermost peat proves that the subsidence was in progress in 

 Neolithic times, but had not yet sufficed to insulate Barry Island. 



In conclusion, I should mention that there is a copious literature 

 on both submerged forests and raised beaches in the Bristol Channel. 

 The re-survey of the district, however, by the Geological Survey 

 being in progress, I hope that much fresh information will be forth- 

 coming, and I have confined myself to a description of the one section 

 that I have had an opportunity of examining, more especially as 

 that section seemed unusually complete in itself. In dealing with 

 the subject generally, both the earlier upward movement implied by 

 the raised beaches, and the later downward movement proved by 

 the submerged land-surfaces, I shall hope to do full justice to my 

 numerous predecessors. 



