Something strange at Nunney

Over the years I have seen a number of references to a strange deposit at Nunney, a small village in Somerset which lies due west of Stonehenge.  The above map shows Geoff Kellaway's reconstructed glacial route, showing the Irish Sea Glacier passing over Nunney on its way to Stonehenge.  leaviung aside for the moment the queestion of whether the ice actually did reach Stonehenge, what is the deposit at Nunney?  Rodney Castleden describes it as a "drift deposit" -- a reddish-brown sandy clay containing both chalk and flint fragments, which means it is not directly related to the underlying bedrock.  Castleden suggests that the deposit has come from the EAST -- from the chalk escarpment -- and that the material was transported in mudflows during the cold phases of the Ice Age.  Hmm -- that sounds a bit strange to me.  On the other hand, Kellaway's explanation is equally difficult, since he thinks that the chalk and flint blocks have come from some chalk outcrop at an unknown location to the north or west.

In his famous (infamous?) Nature article in 1971, Kellaway described the Nunney deposit in some detail.  Actually, it is at Holwell, just outside the village at grid ref ST72554523, where there are large limestone quarries.  The deposit was observed when the land was being cleared for one of the quarries.  The reddish clay was seen to be up to 1m thick, resting on Inferior Oolite (Jurassic) limestone.  It was thin and patchy, and was partly decalcified, but the deeper pockets contained rounded and subangular fragments of white chalk (thought to be from the Middle Chalk), flint, chert, quartzite, Carboniferous and Jurassic limestone.  Kellaway thought that this deposit was related to other glacial deposits on the limestone uplands on the eastern margins of the Mendips, at an altitude of c 152m.  He also thought that at one time the ice extended at least as far east as the "western approaches of the vale of Pewsey."

What are we to make of the Nunney (Holwell) deposit?  Well, it so happens that my son and his family live in Nunney -- next time I go to see them, I am minded to pop over to those quarries and to see if any of that strange reddish deposit is still to be seen, forty years after Kellaway.......

It might well be a till, incorporating fragments from relict weathering deposits or residuals which accumulated to the west during a long process of denudation.  Another possibility is that the deposit incorporates gash breccia material which has come from the Nunney Fault.  Watch this space....