Sourcing mudsprings using integrated palaeontological analyses: an example from Wootton Bassett, Wiltshire, England

This paper presents comprehensive macro‐ and micropalaeontological analyses of taxa recovered from mud and stream lags disgorged from mudsprings at Wootton Bassett, Wiltshire, England. These mudsprings are unusual as they are found in a stable intraplate tectonic setting, but the techniques and provisos employed in this investigation can equally well be employed to source the material venting from other mudsprings, including those found in compressional tectonic settings. The Wootton Bassett mudsprings Site of Special Scientific Interest at Templars Firs (Wiltshire, England), has become renowned through considerable media coverage over the past few years, largely on account of the well preserved fossils exhumed in the outpourings of mud from a series of springs. However, it is emphasized that care must be exercised when undertaking sourcing investigations to ensure that the possibilities of contamination are minimized. Thus micropalaeontological analysis of freshly disgorged mud samples is shown to be a more accurate method of obtaining biostratigraphic information than the use of macrofossil material from stream lags. The erupted material contains biostratigraphically diagnosed microfossil species from several Later Jurassic ammonite zones, indicating sourcing from more than one subsurface stratigraphical horizon. Integrating this information with the local lithostratigraphy described herein, the source material for the mud can therefore be identified as the local Ampthill and Kimmeridge clays immediately underlying the site at a depth of around 10 m. Copyright © 2000 John Wiley & Sons, Ltd.