On the Overlap of the Upper Gault in England and on the “Red Chalk“ of the Eastern Counties

Abstract

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 Rook, 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 Greensand, 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 inflatus (Upper Gault).