Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/128

90 90 S. V. WOOD, JUN., AND F. W. HA.RHER ON THE gritty marl which forms the light land of a large portion of North- western Norfolk. About 7 miles east of the last-mentioned valley, that of another small river, the Glaven, occurs. The high land out of which this valley is cut is for the most part crowned with the Middle Glacial, which sweeps boldly down into the valley, as in section XI. ; but in some places the Contorted Drift shows itself uncovered by the Middle Glacial on the highest points, proving that the Middle Glacial actually rests on the sides of the interglacial valleys which have been deepened postglacially, as described in the case of the North- Norfolk cliff- section. Fig. 11. — Section XL, across the Glaven Valley. (Length 3| miles. Vertical scale 17^ times the horizontal.) W.N.W. E.S.E. Brick-kiln Saxling- Saxlingham River of Holt ham. Heath. Glaven. church. J. The Chalk. 6. The Contorted Drift, 7. The Middle Glacial. 10. Postglacial valley-gravel and recent alluvium. The river next in consequence to the Yare in Norfolk is the Bure, the valley of which is of uniform structure throughout, being, near the sources of the river, cut out of the Contorted Drift only ; but as the valley deepens in its downward course it is first cut down through this Drift to the pebbly sands, and then to the Crag (where this exists) and the Chalk. About midway in the course of the river the Chalk disappears, and the base of the Con- torted Drift sinks below the water-line of the country. This is in consequence of the eastwardly dip of the Preglacial floor, the Chalk disappearing below the water-level to the east of a line drawn from a point about 4 miles east of Norwich to the coast near Mundesley*. The Crag and the Lower Glacial beds sinking with the Chalk are thus partially obscured in the lower course of the Bure, and the valley is now much below the level it possessed at a late stage in the Postglacial period, the Postglacial forest-grown land-surface having been found beneath the alluvial deposits. no doubt come on, as proved by the Yarmouth well-boi'ing ; but we have detected no traces of them at the surface, and the dip of the Chalk beneath them takes place, so far as we are aware, at some unknown point beneath the water-level of the country.
 * mile S.S.W.
 * Eastward of the point where the Chalk disappears, the Lower Tertiaries