Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/140

102 102 S. V. WOOD, JUN., AND F. W. HARMER ON THE inland of these cliffs which are shown in the sketch map as stretch- ing westward on the north side of Blyth, consist of the Pebbly sands for the most part resting on the Chillesford beds, though in the neighbourhood of Halesworth and Henham they have taken the place of these latter and lie up against a low cliff or foreshore of the Chillesford Clay in the condition of thick masses of beached shingle — a feature which we regard as due to the conversion of that clay together with the Crag into land between the close of the Crag and the commencement of the Glacial periods. Everywhere along the outcrop of these pebbly sands, the Contorted Drift seems to have been removed, the only remnants that we discovered between the Waveney and the Aide being at Sotteiiey brick-kiln (yielding traces of Mactra ovalis and Tellina balthica), and a doubtful one at the north end of Easton Cliff, which is also exposed in a pit a short way inland near Covehithe church. Along the south side of the Blyth, from a point a little east of Halesworth to the sea, we could detect no signs of the Lower Glacial pebbly sands, or of the Chillesford Clay, and the Middle Glacial seems to go down to the water-level, indi- cating, as it appears to us, another space of interglacial denudation ; and from this neighbourhood southwards we lose trace of any thing that can be identified with the Lower Glacial sands; indeed the masses of shingle around Halesworth and Henham, into which these sands change, coupled with their highly oblique bedding, seem to show that the southern shore-line of the sea depositing such sands passed somewhere near those places. Along the coast-section southwards also we lose all trace of the Contorted Drift ; but inland we found what seemed to be an immense and deep excavation in it at Blaxhall, on the tableland between the rivers Aide and Deben. Unfortunately this excavation, though dry to the bottom, was mostly overgrown, and the section obscured ; but a mass of marl imbedded in red brick-earth exactly resembling that of the Contorted Drift in the Norfolk cliff, was exposed at one part, and a short way off was a small pit in another mass of marl, while good sections of the Upper resting on the Middle Glacial occurred within half a mile. Had this exposure stood alone, we should have hesitated to call it a protrasion of the Contorted Drift through this tableland ; but the discovery of several such protrusions which, in our opinion, are free from all question, many miles to the south, on the tableland dividing the Deben from the Orwell, leaves no doubt in our minds that the Contorted Drift overlapped the pebbly sands, and stretched southwards in considerable thickness at least as far as the extremity of Suffolk. This Blaxhall protrusion, like those north-west of Lowestoft, through one of which the line of section XVI. (p. 97) is carried, and those at Woodbridge and Kesgrave (sections XX. and XXI. pp. 104, 105), indicates, as it seems to us, that the tableland dividing the Aide from the Deben is underlain by the Contorted Drift, and that the valleys of both these rivers have been excavated out of it. Indeed, if we are right in this, a line of section drawn through the Blaxhall protrusion from the valley of the Deben to that of the Aide would in all respects, save that the tableland would be capped throughout