The Edinburgh Geologist
The mud springs of Wootton Bassett, Wiltshire
by Bill Baird
The initial description of these mud springs was of three domed blisters some 10 m long by 5 m wide by 1 m high. There was a skin of vegetation containing a core of liquid mud which oozed from any fissure in the skin to a nearby brook called Hancock's Water. It is from Hancock's Water that most of the fine ammonites and other fossils have been collected. The technical explanation for the occurrence of the mud springs is that they are related to the local geology, in that they occupy sites in valley bottoms cut into the Ampthill Clay along synclinal axes. They seem to be driven by groundwater in the Coral Rag aquifer which crops out and is recharged beneath Wootton Bassett. From measurements taken in order to understand the mechanism of the springs, it seems that there are irregularly-shaped chambers underneath the mud domes which do not seem to be deeper than 20 m. It is probable, however, that there are further lateral and vertical fissures allowing movement of water and mud into these chambers.
The mud springs at Wootton Bassett have caused considerable interest amongst geologists and others. During recent site investigation, the British Geological Survey has provided support and assistance with seismic, stratigraphical, geochemical and hydrogeological input (Bristow et al., 2000). Fossil collectors have made available their collections for study to enable the stratigraphy of the source rock to be accurately defined. Further site searches in the general area have revealed similar springs near Greenham Common. Of course, no such site is free from the attentions of the well-meaning, if ill-advised, who wish to make it 'safe'. It was allegedly for this reason that approximately 100 tons of rubble were tipped into the most active spring in Wootton Bassett in 1990. The 100 tons of rubble disappeared without trace, except for the equivalent amount of mud which poured into Hancock's Water. This then had to be cleared from the brook by the long-suffering workmen of the local council.
It seems that, at present, activity is at a low level in the mud springs of Wootton Bassett. This is hardly surprising as they have been poked, jumped up and down on, dredged and sampled in various ways. However, what this site shows is how the mysteries of geology can occur on one's own door step. The mud springs of Wootton Bassett are a recognised part of the ancient town's social history, prompting a full-page write-up in the local guide Welcome to Wootton Bassett. They have also been the inspiration for some 50 papers in the literature and caused much argument and discussion amongst the scientific community.
C.R. et al., 2000 in 'The lithostratigraphy, biostratigraphy and hydrogeological
significance of the mud springs at Templar's Firs, Wootton Bassett, Wiltshire',
Proceedings of the Geologists' Association, volume 111, pp. 231-245.
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