Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/129

LATER TERTIARY GEOLOGY OF EAST ANGLIA. 91 Although the structure of the Bure valley throughout is repugnant to any Preglacial origin, it affords but slight evidence of interglacial excavation. This is partly owing to the paucity of sections along it, and partly to the difficulty of distinguishing between the Middle and the Lower Glacial sands where the one rests on the other. A section, however, of what we feel little doubt is the Middle Glacial sand, occurs at a large excavation about half a mile N.N.W. of Wroxham bridge, in the midst of the valley where the Lower Glacial sands are easily distinguishable, either from their being fossiliferous or from containing their characteristic seams of rolled pebbles ; and we therefore give a line of section (No. XII) across the Bure valley at this point. Fig. 12. — Section XII., across the Bure Valley. (Length 4 miles. Vertical scale 17| times the horizontal.) e.s.w. N.N.E. N. Pits land H mile W. of Salhouse church. River Bure. Great pit 3± furl. N.N.W. of Wroxham bridge. Pits 4 and 8 furl. S.W. of Tinstead church. 1. The Chalk-floor dipping north-eastward. 4. Kemnants of the Chillesford beds (well exposed, with No. 5 over them on both sides of the river, near to, but not in, the line of section). 5, 6, 7, and 11 as in fig. 5. N.B. The sands rise high up on the south side of the valley above the line of junction of 5 and 6 ; and where this is the case there can be no doubt that they belong to No. 7 ; but when, lower down, they rest below the level of No. 6, there is a difficulty in distinguishing between them and No. 5. Not more than 2 furlongs from the great excavation in the Middle Glacial last referred to, and between it and Wroxham bridge, an extensive excavation in the Chillesford Clay, capped by the Lower Glacial sand, occurs at about the same level, show- ing the plunge into the valley which the Middle Glacial here makes. This excavation lies two furlongs out of the line of section XII. The next river is the Ant, which falls into the Bure. The valley of this river is, in its lower part, similar to that of the Bure, as shown in the last section, the Chalk being concealed beneath the water-level, owing to the Postglacial depression before alluded to ; and the original valley is now largely filled up with the alluvium that covers the Postglacial forest-grown surface. The upper part of the Ant valley, however, being cut out of higher ground formed by the Contorted Drift, which has here been left by the interglacial