Humberside Geologist no 2
published 1977
Dr Paul Madgett, working under Dr Catt at Rothamsted, has recently put forward a new interpretation of the Hessle Till which will be of considerable interest to Humberside geologists (Nature, 10 January 1975, pp 105-7). The Hessle Till, the topmost member of the Devensian glacial sequence, has generally been regarded as a till sheet in its own right, with its own characteristic colour, texture and erratic content, and has been interpreted as the product of a Scottish ice stream which overrode the Pennine ice (Drab and Purple) to melt out at the top of the sequence in Holderness.
Dr Madgett now proposes quite a different explanation, based on a detailed mineralogical and pedological examination of the Holderness tills. He finds that although the Drab and Purple Tills are essentially uniform in texture and mineralogy throughout the area (though differing from one another), the Hessle Till undergoes a transition as one moves from the Wolds to the coast. This transition is shown in various ways (details of which are given in the paper quoted, with explanatory maps); but to be brief, the variations in mineralogy of the Hessle Till across Holderness are related to the characters of the till beneath, and the Hessle Till at any point can be adequately accounted for as the product of pedological processes acting on the till below. In other words, where the Hessle overlies Purple, it is weathered Purple; where it overlies Drab, it is weathered Drab; and where it overlies the feather edge of the Purple it is intermediate between the two, because the soil profile there embraces both Drab and Purple Tills.
No new theory should be accepted uncritically, and members will no doubt have Madgett's views in mind when they next examine an exposure of the "Hessle Till". Many will approve of the recognition of pedological processes in the formation of the till (cf. Fenton, E. Yorks. Field Studies, 1969, p 3), but some may find the question of erratics hard to swallow. Have we been wrong all these years in thinking that the Hessle Till had its own characteristic suite of erratics? Were we deceived by the preferential leaching of certain rocks into thinking that the assemblage was different from those of the Drab and Purple Tills? Or was there indeed a thin bed of Scottish till which is now wholly engulfed in the soil profile? Clearly the next thing to do is to make a thorough re-examination of the erratic content of the Holderness tills, rather as that stalwart of the Hull Geological Society, J.W. Stather, did in the nineteen-twenties; but this time against the background of modern knowledge and using methods which were perhaps not easily available in those days. Any offers?
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