A HISTORY OF NORFOLK some iron-ore was obtained at one time near Ash Wicken and Wormegay. The Lower Greensand has been proved to occur beneath the Chalk as far eastwards as Holkham. GAULT AND RED CHALK The Lower Greensand is succeeded by the Gault and Red Chalk, which practically replace one another as we pass from the southern out- crop near West Dereham northwards to Dersingham. There is no representative of the Upper Greensand in Norfolk, although specimens supposed to indicate it were identified in the deep boring which penetrated the Chalk at Norwich.' It is, however, generally admitted that in other parts of England the Gault and Upper Greensand form one group to which the name Selbornian, from Selborne in Hampshire, has been applied by Mr. A. J. Jukes-Browne. In some tracts, as in Devonshire, the formation is almost wholly sand ; in others, as in East Kent, it is almost wholly clay ; in the intermediate tracts there is an upper division of sand and a lower division of clay. In the Gault and Red Chalk of Norfolk we have represented in time the Sel- bornian of other tracts. The Norfolk Gault is more calcareous in character than it is else- where. It is a bluish-grey marly clay, which on drying appears of a greyish-white colour ; while the Red Chalk is in reality a chalky deposit, and locally marks the incoming of Chalk conditions earlier than in more southern counties. Moreover, it has yielded some species of fossils not elsewhere known to occur below the White Chalk. The Gault is from 20 to 60 feet thick, and contains at its base a layer of phosphatic nodules, or ' coprolites,' which have been worked at West Dereham — a locality where phosphatic nodules also occur in less abundance in the upper part of the Lower Greensand. The Gault extends through Shouldham and Gayton northwards as far as Dersing- ham, where, according to Mr. Jukes-Browne and Mr. William Hill, it passes down into a brown and red marly clay about 4 feet thick, and is finally replaced northwards by the Red Chalk.* The fossils of the Gault include fishes, such as Beryx, also Ammonites interruptus, A. rostratus, A. lautus, Belemnites minimus^ Inoceramus sulcatus, etc. Copious springs are here and there thrown out at the junction of the Chalk and Gault, for the lower portions of the Chalk in Norfolk are not impervious. The Red Chalk, or Hunstanton limestone, has attracted much attention from geologists, as it forms a very conspicuous band in the cliff at Hunstanton, at the base of the White Chalk and above the brown Carstone.' It is in reality a limestone containing from 80 to 83 per
- C. B. Rose, Proc. Geol. Assoc, vol. i. p. 226 ; F. Kitton, Trans. Norf. Nat. Soc, vol. i.
pp.81.
- Quart, yourn. Geol. Soc, vol. xliii. p. 544.
' The literature is fully dealt with by Mr. Whitaker, Proc Norwich Geol. Soc, vol. i. p. 212. 6
