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

Abstract

During the years 1918–19 we investigated the relations of the beds exposed in a remarkable section at Shenley Hill, north of Leighton Buzzard. Our conclusion that lenticles of limestone of basal varians-age are there overlain by a mass of Upper Gault showing an inverted order of zones provided an interesting glacial problem. This seemed to us of less importance, however, than the discovery that these transported masses had been deposited upon a, floor formed by a basement-bed of transgressive Upper Gault, which there rests immediately upon the local top of the Lower Greensand. The chief interest attaching to this example of glacial disturbance lay in the resulting disposition of particular beds in anomalous zonal relationships. Other striking instances of the glacial transportation of large masses of rock were known to occur in the tract of country to the north-east of this locality. The difference was chiefly one of degree, not of kind. We realized that the detection here of an overlap of the Upper Gault might prove to be a matter of greater moment, possessing, perhaps, a far-reaching stratigraphical significance. A study of the literature dealing with this formation, coupled with the examination of the Gault at a few localities in other counties where an overlap takes place, convinced us that a fuller investigation of the subject would prove fruitful in results.