GEOLOGY In West Norfolk the most notable deposit is the Nar Valley brick- earth, to which attention was drawn by C. B. Rose in 1835. It is an estuarine deposit of blue clay containing remains of Elephas (mammoth), Rbinoceros antiquitatis and red deer ; also Aporrhais pes-pelicani, Turritella terebra, Scrobkularia plana, T'ellina balthka and Ostrea edulis. It occurs in places as much as fifty feet above the level of the marshes, beneath layers of valley gravel, and it extends down to the marsh level, indicating former submergence and subsequent upheaval. The clay was at one time worked for brick-making, and the shelly beds were put on the land as ' marl.' An interesting deposit of freshwater marl and silt also occurs at Gayton Thorpe. In the valleys of the Waveney, Yare, Wensum and Bure there are here and there tracts of valley gravel, as near Thorpe Station, Norwich. On the whole but few organic remains have been obtained from these accumulations. Remains of mammoth and other extinct mammalia have been recorded from some localities, but it is not clear that all the valley gravels are of an age to yield the mammoth. At Mundesley an old river-bed of Pleistocene age was described by Lyell and Prestwich. It comprises deposits of gravel with an inter- calated bed of peaty loam, altogether 45 feet thick. In the loam plant remains, shells such as Hydrobia margtnata, and elytra of beetles have been obtained. Remains also of Elephas antiquus, Cervus [Megaceros) giganteus and Emys orbicularis have also been found. ^ The occurrence of the freshwater tortoise is remarkable, as remains of that reptile were previously discovered in a peat bog at East Wretham, where the deposits would naturally be regarded as far more recent than those at Mun- desley." On this subject further light is needed, although Professor A. Newton has observed that remains of the tortoise have been found in peaty deposits in Denmark and Sweden. The depth of the alluvial deposits in some of the old valleys shows that they are now much below the sea-level, so that the land in these comparatively recent times must have been much higher. Thus at Norwich the depth was proved to be 42 feet, at Potter Heigham 56 feet, and at Wroxham 72 feet. It seems probable that the land was higher in Pleistocene times, for the Dogger Bank is a remnant of old Pleistocene deposits ; as Mr. Reid suggests, a re-extension of the old Rhine estuary. It is a shoal under 10 fathoms, and about 120 miles north- north-east of Cromer. Many mammalian remains dredged up by fisher- men have been obtained from this bank, and they indicate in general a deposit of the age of the Thames Valley gravels.' It must however be remembered that specimens from various geological horizons and from different portions of the North Sea bed are dredged up, and
- E. T. Newton, ' Note on some Fossil Remains ot Emys lutaria from the Norfolk
Coast,' Geol. Mag., Dec. ii. vol. vi., 1879, p. 304.
- A. Newton, ' On the Zoology of Ancient Europe,' Proc. Cambridge Phil. Soc, 1862 ;
and Ann. Nat. Hist., ser. 3, vol. x., 1862, p. 224. ' Reid, Geo/ogy of Cromer, p. 122 ; W. Davies, Geol. Mag., Dec. ii., vol. v. pp. 97, 443- 23
