IV.—On a Displaced Mass of Chalk on the Foreshore of Speeton Cliffs, Flamborough Head

Abstract

When revisiting Speeton on the 6th of April, 1905, I was surprised to find that the exposures of Bed (Hunstanton) Chalk on the beach at the locality (about 500 yards east of the mouth of Speeton Beck) where the excellent vertical section described by Mr. W. Hill occurs were almost invisible owing to the accumulation of boulders of white chalk by which they were covered. At length I found a small exposure of Eed Chalk near low water mark and, within 3 or 4 yards to north of it, that is, seawards, I came across a reef of chalk in well-defined beds, each perhaps 6 or 8 inches thick, weathered to a brownish or drab tint. This chalk, when freshly fractured, was hard and white, quite unlike the true Red Chalk, although practically at the same level. The prevailing dip of the white chalk of the reef was from 25° to 28° to W. 40° S. mg. (= W. 57° S. true), and the length of the exposure along the strike, so far as the limited time at my disposal would allow me to observe, was 65 paces (say 55 yards), the width in the direction of dip being 16 paces (say 13½ yards). So far as I have been able to gather, this reef of white chalk to seaward of, and apparently dipping beneath, the Red Chalk has not been described. Four possible explanations of its occurrence may be suggested.