The Petrology of some Yorkshire Boulder Clays

Abstract

One of the most imposing and best known exposures of glacial deposits in the north of England is the line of high cliffs along the Yorkshire coast, between Patrington and Withernsea, the highest point of the cliffs being at Dimlington Beacon. Here 140 feet of glacial material is exposed in the cliff face and the foreshore is entirely of boulder clay, the base of the deposits being a long way below sea-level. The work of this paper relates to the clays and sands in this cliff exposure. The deposits are easily distinguished as being of three varieties; at the base and along the foreshore, a dark leaden grey to black, tough boulder clay, including lenticles of sand frequently containing shell fragments; this is succeeded by a thick clay of rich purple or red colour, with noticeably more contained boulders, and near the top, much included sand in lenticles, passing into a bed of pure sand; the highest part of the cliff is of earthy clay, foxy red in colour, and with relatively few boulders. These are respectively the Basement clay, the Purple clay, and the Hessle clay. Between the Basement clay and the Purple, and at the top of the Purple clay, there are beds of sand a few feet thick; these are not to be seen at all parts of the coast, but are generally present in the highest sections. Fig. 1 is a vertical section of the Dimlington cliff, and the Roman numerals indicate the specimens petrologically examined.