ORIGINAL ARTICLES. 



On the Overlap of the Upper Gault in England and 

 on the "Red Chalk" of the Eastern Counties. 



By F. L. KiTCHiN, M.A., Ph.D., and J. Pringle, F.G.S. 



{Concluded from p. 166.) 

 III. The " Red Chalk ". 



Norfolk. — The so-called Red Chalk is visible in two quarries at 

 Snettisham, but the exposures there are less favourable for 

 investigation than the well-known section to be seen in the cliff 

 north of Hunstanton. The thin rock-bands there comprised under 

 this title have given rise to much discussion amongst geologists, 

 whose views have been summarized by Mr. W. Whitaker and by the 

 late A. J. Jukes-Browne.^ The Red Rock, not more than 4 feet thick 

 at this locality, has been variously referred by different authors to 

 the whole Gault formation, to the Upper Gault, to the Upper Green- 

 sand, and to the Lower Chalk. So long ago as 1869, the Rev. T. 

 Wiltshire published an illuminating paper in which he described the 

 characters of the three beds that can be recognized as composing 

 the red band.^ Chiefly on the basis of the fossils found in the two 

 lower beds he made a correlation with the Upper Gault of Folkestone. 

 The late Professor Judd and Professor C. Barrois emphasized the 

 fact that the Red Rock is unconformable with the underlying 

 Greensand, but conformable with the overlying Chalk. 

 Professor Barrois was so impressed by this fact and by the 

 unequivocal character of the fauna that he correlated the red beds 

 with his zone of Ammonites in/iatus (Upper Gault). 



Our examination of the Red Rock at Snettisham and Hunstanton, 

 amplified by a study of the collections of fossils at Cambridge and 

 elsewhere and by specimens of zonal value collected by ourselves, 

 convinces us that no horizon below the Upper Gault is represented. 

 All the ammonites we have seen are Upper Gault forms. The records 

 of " Ammonites interrujoius " from these beds, based upon the 

 erroneous identification of hoplitids of the Upper Gault with those of 

 the interruptus-zone, have proved misleading. We have found 

 Inocemmus salcatus in the lowest bed, only some 10 inches above 

 the base. 



We are of opinion that the top bed, 1 foot thick, which has not 

 yielded any Gaalt ammonites, should be regarded as forming the 

 base of the Lower Chalk. It is a reddened lower part of the overlying 

 " Sponge Bed ", which is not similarly stained. Except for the 



^ W. Whitaker, " On Things in General and the Red Chalk of Norfolk in 

 Particular " : Proc. Nonvich Geol Soc, vol. i, pt. vii, 1883, pp. 213-22.. 

 A. J. Jukes -Browne, The Cretaceous Rocks of Britain, vol. i {Mem. Geol. Sv.rv.), 

 1900, pp. 294, 296. 



* T. Wiltshire, " On the .Red Chalk of Hunstanton " : Quart. Journ. GeoL 

 Soc, vol. XXV, 1860, p. 185. 



