The geotechnical characteristics of the till deposits of Holderness

The glacial deposits of Holderness are well displayed along the coast of Humberside from Bridlington to Spurn Head. These deposits consist primarily of tills which may contain chalky debris and include pockets and lenses of sands and gravel. They have been subdivided in the past into four units the Basement, Drab, Purple and Hessle Boulder Clays. This has been re-interpreted as three tills (the Basement, Skipsea and Withernsea Tills) below a composite weathered unit of Skipsea and Withernsea Till. The dominant clay minerals in all the clays are kaolinite and illite. In addition, the clay fraction usually constitutes up to 30% of the deposit. Accordingly the clays have a low plasticity. However, because the Basement Till contains a larger content of fines it does have higher consistency limits. The geotechnical data confirm the interpretation of the “Hessle Clay” as a weathered product of the Skipsea and Withernsea Tills