Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/283

 1869.] WILTSHIKE — ^HUNSTANTON RED CHALK. 189 the beginning, the pebbles are of larger size, and in which, after- wards, the sandy particles are so loosely held together as to present a strong contrast to the massive nature of the white and red beds above. Covered by the Carstone and adjoining it is a bed of clay marked Z in the section. Throughout the space of more than 30 feet below the base of the Red Chalk no fossils have been hitherto found at Hunstanton in the Carstone, but beyond that distance, and just above the clay (Z), there is a line of nodules (y) in which are numerous specimens of Ammo- nites Des7im/esi, and occasionally of A. Cornuelianus ; close to these nodules are others of ironstone, very similar to the masses found in the Lower Greensand of Blackgang and Shanklin, in the Isle of Wight, containing casts of fossils, of which I give the following list, the species having been determined by Mr. Etheridge. Fossils from Nodules in hase of Carstone. Wood. Trigonia, sp. Leda, sp. Pecten striato-punctatus, Bcemer. Lucina crassa, Sow. Isocardia angulata, Phil, Nucula planata, Desk. Avicula macroptera. Pecten orbicularis, Sow. Cardium subhillanum, Leym. Pleurotomaria gigantea. Ammonites Cornuelianus, If Orb. Dentalium. Pectunculus. Terebratula biplicata, Broc. Dianchora. From this part of the Carstone I have obtained Perna Mulleti, Ancyloceras gigcis, Pleurotomaria — fossils which, viewed in connexion with the presence of Ammonites Deshayesl, &c., correlate the portion of the Carstone immediately above the Clay (Z) with the base of the English Lower Greensand. By a reference to the section it will be seen that the Hunstanton Red Chalk is, in position, lower than the Chalk Marl (a) and higher than the Lower Greensand (X, Y) ; the fossils also, it will be ob- served, recorded in the hst as common to the bed, present a mixture of what are generally considered Lower Chalk, Upper Greensand, and Gault forms. The mingling together of these species, no less than the peculiar aspect of the stratum, has long caused the Red Chalk to be a fertile field for discussion in reference to its proper position in the geological scale, various writers offering various opinions, Mr. C. B. Rose* inclining to its being the equivalent of the Gault, Mr. H. Seeley t to its being Upper Greensand, and Mr. Judd J to its combining both formations. If, however, the very fine section of the Gault at Folkestone (where the succession of the beds and their fossils can be examined in situ) be taken as typical of the English Gault, then it wiU become evident that the " Red Chalk " is the representative of the upper division of that formation ; for at t " Notice of Opinions on the Stratigraphical Position of the Ked Lime- stone," Ann. Mag. Nat. Hist. 1861, vol. vii. p. 240. I " Strata which form the base of the Lincolnshire Wolds," Quart. Journ. Geol. Soc. Tol. xxii. p. 249, 18G7.
 * " On the aeology of West Norfolk," Phil. Mag. 1835, vol. vii. p. 180.