Broom Farm, Soberton
Preliminary Report of a Geophysical survey
(18th – 19th July 2014)
By Carl Raven
Liss Archaeological Group
(edited by Nick Stoodley)
Introduction
Liss Archaeological Group were asked by the Meon Valley Saxons Project to
carry out a geophysical survey using both magnetometry and resistivity at
Broom Farm, Soberton, Hampshire. The survey was carried out in a field lying
immediately west of woodland (Bottom Copse). Some years previously a
Roman building had been discovered in this wood and the area was designated
a Scheduled Ancient Monument (SAM 1001848) (Fig. 2). A recent visit to the
field revealed a series of
earthworks and a
geophysical survey was
organised to try to identify
the nature of these
features and to reveal any
underlying archaeology.
Magnetometry
Twelve 20 x 20 m grid
squares, covering an area
of 4800 m², were surveyed
giving 19200 readings. The
results show a number of
linear features which are
probable ditches filled with
debris containing either
burnt or metallic material
or both (Fig. 1). A number
of sub-circular anomalies, measuring roughly 6-7 metres across, were
identified in the centre and northern part of the site. In the southern most
grids (A1 and B1) an area of high magnetic readings was recorded, probably
resulting from large concentrations of ferrous (iron) material. Concentrations
of metal often build up around stone features due to fragments of metal
breaking off as the plough comes into contact with buried stonework. It may
be significant that this area is relatively close to the site of the known building
(Fig. 2).
Resistivity
Nine 20 x 20 m grid squares, covering an area of 3600 m² were surveyed and a
total of 14400 readings were taken. A low battery voltage caused by flat
batteries resulted in readings that were ‘over-range’ (above 31.5Ω) and are
displayed as white blocks in the linear plot (Fig. 3). When the results are
displayed in the relief plot the effect of the over-range readings are less
apparent (Fig. 4 & 6). The data in this area should however still be regarded as
corrupt and invalid. Despite this problem, the overall results show a range of
linear features some of which were also identified by magnetometry and thus
confirm the accuracy of the survey.
Interpretation of anomalies (Fig. 5)
A – D linear features, probable ditches containing material also detectable
with magnetometer.
E – I Linear features, possible walls or ditches not detectable with
magnetometer.
J – L Area of disturbed ground possible occupation also detectable with
magnetometer.
M – N Sub-circular features, 6 -7m diameter, possible building base also
detectable with magnetometer.
O – Q High resistance anomalies also detectable with magnetometer.
Summary
The geophysical survey successfully identified a complex range of features,
mainly consisting of ditches, walls and boundaries that are probably related to
the known Roman site. Anomalies E - I appear to act as a barrier containing
the areas of disturbance J - L; these two groups are therefore probably
contemporary and in all likelihood form part of the villa. Features A - D
probably indicate various phases of enclosure ditches and may have
demarcated fields that were farmed by the occupants on the villa. High
resistance features P and Q are possible pits filled with debris. The sub-circular
anomalies (M and N) do not appear to respect E - I and may reflect a different
phase of activity on the site. The recovery of a 6th-century Saxon saucer
brooch from a location a short distance to the west of the site suggests
possible activity in the centuries following the Roman period but it is uncertain
whether features M and N are post-Roman in date.
Acknowledgements
We would like to thank Tom Parker for granting access to the site. The
Soberton volunteers are thanked for their assistance, enthusiasm and hard
work and we are grateful to Duncan Colin-Jones and David Salmon for
arranging the surveys. The Meon Valley Saxons Project are indebted to Liss
Archaeological Group for carrying out the geophysical surveys and John
Whittaker, Jeff Slingsby and John McNee for providing tuition on metal
detecting.