Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/149

Rh LATER TERTIARY GEOLOGY OF EAST ANGELA. Ill responds with the level at which the clay was reached in the well at the railway-station, it seems to us that this bed of chalky clay and overlying brick-earth may probably be similar to that occurring in the Yare valley, marked a in Sections V. and VI., and of inter- glacial age ; and if so, the beds at Copford, from which the late Mr. John Brown obtained an extensive collection of the remains of Vertebrata and of land and freshwater Mollusca, may possibly be of similar age. We are informed by Mr. Whitaker that the pits at ApixLeford Bridge were closed when the members of the Geological Survey examined the district, but that they found brick-earth in the same part of the valley, not far off, which yielded remains of fresh- water Mollusca, and which they regarded as of Postglacial age. In the face of this we feel more hesitation than we otherwise should in identifying the bed at Appleford Bridge with that in the Yare valley ; for the evidence available to guide us to an opinion as to its precise age (whatever we regard that as being) is, it must be con- fessed, obscure. Section XXIII. represents the appearance presented by the section when we examined it. Fig. 24. — Section XXIII., at Appleford Bridge, near Witham. a. Blue Clay with rolled Chalk, identical in appearance with the Upper Glacial of the neighbourhood. b. Sandy Brick-earth passing down imperceptibly into a. c. Red sandy gravel passing downwards into yellow sand. d. Gravelly wash and humus. e. Water. /. Talus &c. It was pointed out by one of us * that the highest elevation to which the Middle Glacial attained in East Anglia was about 360 feet, at Danbury in Essex, the usual limit being between 200 and 250 feet, the Upper Glacial overlapping it above these elevations and resting on the older formation direct ; and in Middlesex, at Einchley, it underlies the Upper Glacial at an elevation somewhat exceeding 300 feet. Mr. Penning f has made this limit in elevation and this overlap the basis of an argument to prove that the submergence was, during the deposit of the Middle Glacial, confined to something like the altitude to which this formation ranges. The not unfre- quent absence of the deposit, however, at low elevations within the area over which it usually occurs, and its absence over a wide area, embracing most of the counties of Cambridge, Lincoln, Northampton, Leicester, Rutland, Huntingdon, and Bedford, at elevations far below t Quart. Journ. Geol. Soc. vol. xxxii. p. 194.
 * Geol. Mag. Feb. 1870.