Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East
Sussex
NGR: 532938 104787
(TQ 32938 04787)
Scheduled Ancient Monument: 1010929
ASE Project No: P106
ASE Report No. 2014165
By John Cook BSc (Hons) AIFA
May 2014
The Whitehawk Community Archaeology Project
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
Abstract
Archaeology South East along with Brighton and Hove Archaeological Society
undertook a detailed fluxgate gradiometer survey on Whitehawk Camp, Brighton,
East Sussex. The survey took place between Monday 28th April and Friday 2nd May
2014.
Despite the magnetic ‘noise’ encountered the magnetic survey at Whitehawk Camp
has successfully indicated possible archaeological features. The most significant
features noted in the survey were possible ditches and linear areas of magnetic
debris that corresponded to the causewayed enclosure. The magnetic debris and
disturbance relating to the previous use of much of the site as both allotments and a
dumping ground has served to potentially obscure any archaeology. However, the
more modern magnetic material has also highlighted the lines of the causewayed
enclosure. Two linear areas of magnetic debris in the north of the race course and a
linear positive anomaly in the south west of the survey may relate to further circuits
of the enclosure. However, these anomalies may also relate to features associated
with track maintenance and the previous use of the site as allotments.
Statement of Indemnity
Geophysical survey is the collection of data that relate to subtle variations in the form
and nature of soil and which relies on there being a measurable difference between
buried archaeological features and the natural geology. Geophysical techniques do
not specifically target archaeological features and anomalies noted in the
interpretation do not necessarily relate to buried archaeological features. As a result,
magnetic and earth resistance detail survey may not always detect sub-surface
archaeological features. This is particularly true when considering earlier periods of
human activity, for example those periods that are not characterised by sedentary
social activity.
© Archaeology South-East UCL
i
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
CONTENTS
1.0
INTRODUCTION
2.0
SURVEY METHODOLOGY
3.0
GEOPHYSICAL SURVEY RESULTS
4.0
CONCLUSIONS
Bibliography
Acknowledgements
Appendix 1: Raw survey data (CD)
Appendix 2: Section 42 License
HER Summary sheet
OASIS Form
Figures
Figure 1:
Figure 2:
Figure 3:
Figure 4:
Figure 5:
Figure 6:
Figure 7:
Figure 8:
Figure 9:
Site location
Plan showing areas of magnetometer survey
Raw data southern viewport
Raw data northern viewport
Processed data southern viewport
Processed data northern viewport
Interpretation southern viewport
Interpretation northern viewport
Plan showing geophysics interpretation over previous work
© Archaeology South-East UCL
ii
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
1.0
INTRODUCTION
1.1
Site background
1.1.1
Archaeology South-East, with the assistance of members of the Brighton
and Hove Archaeological Society (BHAS), conducted a Magnetometer
survey on a site totalling approximately 8 hectares on land at Whitehawk
Camp, East Sussex hitherto referred to as ‘the site’ (NGR.TQ 32938
04787; Fig.1). The work was undertaken as part of the wider 'Whitehawk
Community Archaeology Project' funded by an 'Our Heritage' grant from
the Heritage Lottery Fund (HLF).
1.1.2
Permission for the work was given by Paul Roberts, Inspector of Ancient
Monuments, English Heritage under a Section 42 License to use a metal
detector and/or geophysical survey, as defined by the Ancient
Monuments and Archaeological Areas Act 1979. A copy of the licence is
attached to this document in Appendix 2.
1.1.3
Permission to undertake the work was also given by the landowner
Brighton and Hove City Council via Robert Walker, Head of Operations,
City Parks.
1.2
Geology and topography
1.2.1
According to the British Geological Survey (2014) the site lies
predominately over bedrock geology of Newhaven Chalk Formation. No
superficial deposits are recorded.
1.3
Aims of Geophysical Investigation
1.3.1
The purpose of the geophysical survey was to detect any buried
archaeological anomalies that might provide a measurable magnetic
response. The specific aims of the project were to investigate whether
the Neolithic causewayed enclosure of Whitehawk Camp extends
beyond the known extent and to assess the site for further work to be
carried out as a part of the HLF funded scheme.
1.4
Scope of report
1.4.1
The scope of this report is to report on the findings of the survey. The
project was conducted by John Cook and John Hurst with assistance
during fieldwork from BHAS members Jon Baczkowski, John Funnell,
Joan MacGregor, John Skelton, Eddie Start, Peter Tolhurst and
volunteers. The Maria Gardiner and the fieldwork volunteers also took
part in an office based training course on processing geophysical survey
data following the completion of fieldwork. The project was managed by
Jon Sygrave.
© Archaeology South-East UCL
1
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
2.0
SURVEY METHODOLOGY
2.1
Geophysical survey
2.1.1
A fluxgate gradiometer (magnetometry) survey was undertaken in the
areas depicted in Figure 2 (NGR 532938 104787).
2.1.2
The field work was undertaken between Monday 28th April and Friday 2nd
May 2014 when the weather was warm and dry.
2.2
Applied geophysical instrumentation
2.2.1
The Fluxgate Gradiometer employed was the Bartington Instrumentation
Grad 601-2. The Grad 601-2 has an internal memory and a data logger
that store the survey data. This data is downloaded into a PC and is then
processed in a suitable software package.
2.2.2
30m x 30m grids were set out using a GPS (see below). Each grid was
surveyed with 1m traverses; samples were taken every 0.25m.
2.2.3
Data was collected along north-south traverses in a zigzag pattern
beginning in the south-west corner of each grid.
2.3
Instrumentation used for setting out the survey grid
2.3.1
The survey grid for the site was geo-referenced using a Leica Viva
Smartrover. The GPS receiver collects satellite data to determine its
position and uses the mobile phone networks to receive corrections,
transmitting them to the RTK Rover via Bluetooth to provide a sub
centimetre Ordnance Survey position and height. Each surveyed grid
point has an Ordnance Survey position; therefore the geophysical survey
can be directly referenced to the Ordnance Survey National Grid.
2.4
Data processing
2.4.1
All of the geophysical data processing was carried out using
TerraSurveyor published by DW Consulting. Minimally processed data
was produced using the following schedule of processing. Due to the
very high positive readings of some of the magnetic disturbance the
values were replaced with a dummy value so as to avoid detrimentally
affecting the dataset when further processed. The first process carried
out upon the data was to apply a DESPIKE to the data set which
removes the random ‘iron spikes’ that occur within fluxgate gradiometer
survey data. A ZERO MEAN TRAVERSE was then applied to survey
data. This removes stripe effects within grids and ensures that the survey
grid edges match. Figures 5 and 6 display the processed survey data.
2.5
Data presentation
2.5.1
Data is presented using images exported from TerraSurveyor into
Autocad software and inserted into the geo-referenced site grid. Data is
presented (Figures 3-6) as raw data and processed data greyscale plots.
© Archaeology South-East UCL
2
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
3.0
GEOPHYSICAL SURVEY RESULTS (Figures 7-9)
3.1
Description of site
3.1.1
The survey area consisted of approximately eight hectares currently
used as public amenity land and a race course.
3.2
Survey limitations
3.2.1
There were a number of physical obstructions encountered on site.
Including metal fences, footpaths and significant amounts of fly tipped
waste. Obstructions are noted in the results. Areas where physical
obstructions form a barrier to survey, or a health and safety issue, have
been omitted.
3.2.2
In addition to the physical limitations of the survey, the effectiveness of
magnetometer surveys depends on a contrast between the absolute
magnetic susceptibility of the topsoil to the underlying subsoil (Clark
1996). Features may also be difficult to detect where there has been
significant primary silting.
3.3
Introduction to results
3.3.1
The results should be read in conjunction with the figures at the end of
this report. The types of features likely to be identified are discussed
below.
3.3.2
Positive Magnetic Anomalies
Positive anomalies generally represent cut features that have been infilled with magnetically enhanced material.
3.3.3
Negative Magnetic anomalies
Negative anomalies generally represent buried features such as banks or
compacted ground that have a lower magnetic signature in comparison
to the background geology.
3.3.4
Magnetic Disturbance
Magnetic disturbance is generally associated with interference caused by
modern ferrous features such as fences and service pipes or cables.
3.3.5
Magnetic Debris
Low amplitude magnetic debris consists of a number of dipolar
responses spread over an area and is indicative of ground disturbance.
3.3.6
Dipolar Anomalies
Dipolar anomalies are positive anomalies with an associated negative
response. These anomalies are usually associated with discreet ferrous
objects or may represent buried kilns or ovens.
3.3.7
Bipolar Anomalies
Bipolar anomalies consist of alternating responses of positive and
negative magnetic signatures. Interpretation will depend on the strength
© Archaeology South-East UCL
3
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
of these responses; modern pipelines and cables typically produce
strong bipolar responses.
3.3.8
Thermoremanence
Thermoremanence is most commonly encountered through the
magnetizing of clay through the firing process although stones and soils
can also acquire thermoremanence.
3.4
Interpretation of fluxgate gradiometer results (Figures 7 and 8)
3.4.1
The survey area assigned for geophysical survey was situated on the
crest of a southward running spur of down land ranging from gentle
slopes to steep undulating ground with the road of Manor Hill running
through the site.
3.4.2
Evidence for possible archaeological features in the form of discrete
moderate positive anomalies representing possible cut features are
noted in a small number of places. However, due to the ‘noise’ created
by modern ferrous material the possibility of discrete features being
obscured is not discounted. In addition to these, linear moderate positive
anomalies (A1) indicating possible ditches are noted. Several of these
appear to align with the upstanding remains of the causewayed
enclosure. Additionally, a linear anomaly is observed running across the
southern section of the race course (A2) which may represent land
division prior to the current race course.
3.4.3
The most significant anomalies noted within the survey data are of areas
of magnetic debris. It is likely that most of these anomalies relate to
modern material in the near surface caused by ground disturbance or
dumping of waste material. However, some linear areas of magnetic
debris (A3) were observed to correspond with the causewayed
enclosure. It is likely that these anomalies represent where the
monument ditches have filled with more modern material and does the
most to highlight the form of the monument within the data. Other linear
areas of magnetic debris were noted crossing the racecourse in the
northern extent of the survey (A6).
3.4.4
A possible thermoremanent anomaly (A4) is observed in the south of the
race course. This anomaly may be indicative of kilns, furnaces, ovens or
other heating activity. However, the anomaly noted here correspond to a
section of the causewayed enclosure previously excavated and therefore
may relate to the process of backfilling.
3.4.5
Bipolar anomalies with associated magnetic disturbance (A5) are
observed both across the race course and in the south east of the
monument. These anomalies correspond to below ground services such
as a pipes and cables.
3.4.6
A scattering of dipolar anomalies across the area may represent
archaeological features such as kilns or ovens, but more likely they
indicate discrete ferrous objects. These anomalies are not individually
marked due to number.
© Archaeology South-East UCL
4
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
4.0
CONCLUSION
4.1
Discussion
4.1.1
Despite the magnetic ‘noise’ encountered, the magnetic survey at
Whitehawk Camp has successfully indicated possible archaeological
features. The most significant features noted in the survey were possible
ditches and linear areas of magnetic debris that corresponded to the
causewayed enclosure. The magnetic debris and disturbance relating to
the previous use of much of the site as both allotments and a dumping
ground has served to potentially obscure any archaeology. However, the
more modern magnetic material has also highlighted the lines of the
causewayed enclosure. Two linear areas of magnetic debris (A6) in the
north of the race course and a linear positive anomaly in the south west
of the survey may relate to further circuits of the enclosure. However,
these anomalies may also relate to features associated with track
maintenance and the use of the site as allotments. Magnetometry does
not specifically target archaeological features and anomalies noted in the
interpretation do not necessarily relate to buried archaeological features.
The technique may not always detect sub-surface archaeological
features. This is particularly true when considering earlier periods of
human activity. Therefore, areas where archaeology may not have been
interpreted may also need to be ground truthed.
Acknowledgements
Archaeology South-East would like to thank the Heritage Lottery Fund for funding the
work, Brighton Racecourse for access and use of facilities, Brighton and Hove City
Council for agreeing to the survey and all the volunteers from Brighton and Hove
Archaeological Society who helped.
© Archaeology South-East UCL
5
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
Bibliography
BGS 2014 British Geological Survey, Geology of Britain Viewer, accessed
12.05.2014. http://mapapps.bgs.ac.uk/geologyofbritain/home.html
Clark, A. 1996. Seeing Beneath the Soil. (2nd edition). London: Routledge.
© Archaeology South-East UCL
6
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
SMR Summary Form
Site Code
Identification Name
and Address
County, District &/or
Borough
OS Grid Refs.
Geology
Arch. South-East
Project Number
Type of Fieldwork
Type of Site
Dates of Fieldwork
Sponsor/Client
Project Manager
Project Supervisor
Period Summary
-
Whitehawk Camp, Brighton, East Sussex
Brighton, East Sussex
532938 104787
Newhaven Chalk Formation
P106
Eval.
Excav.
Green
Field
Eval.
Shallow
Urban
Excav.
HLF
Jon Sygrave
John Cook
Palaeo.
Meso.
AS
MED
Watching
Brief
Deep
Urban
WB.
Standing
Structure
Other
Neo.
PM
BA
Other
Modern
Survey
Other
5th – 9th May 2014
IA
RB
100 Word Summary.
Archaeology South East along with Brighton and Hove Archaeological Society undertook a
detailed fluxgate gradiometer survey on Whitehawk Camp, Brighton, East Sussex. The survey
took place between Monday 28th April and Friday 2nd May 2014. Despite the magnetic ‘noise’
encountered the magnetic survey at Whitehawk Camp has successfully indicated possible
archaeological features. The most significant features noted in the survey were possible ditches
and linear areas of magnetic debris that corresponded to the causewayed enclosure. The
magnetic debris and disturbance relating to the previous use of much of the site as both
allotments and a dumping ground has served to potentially obscure any archaeology.
© Archaeology South-East UCL
7
Archaeology South-East
Detailed Magnetometer Survey at Whitehawk Camp, Brighton, East Sussex
ASE Report No:2014165
Appendix 1
Included on C.D
1.
2.
Raw Magnetometry Data
Positive and negative trace plots
© Archaeology South-East UCL
8
N
106000
105000
The Site
104000
Contains Ordnance Survey data
Crown copyright and database right 2014
© Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
534000
533000
0.5km
532000
0
103000
Whitehawk Camp
Site location
Fig. 1
N
533170, 104930
Ma
no
rH
ill R
oa
d
533170, 104640
532820, 104440
533070, 104440
Reproduced by permission of Ordnance Survey on behalf of HMSO.
Ordnance Survey Licence no. AL 503 10 A
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
Whitehawk Camp
Fig. 2
Plan showing areas of magnetometer survey
N
10nT
0nT
-3SD
mean
0
3SD
50 m
-10nT
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
Whitehawk Camp
Fig.3
Geophysics raw data southern viewport
N
10nT
0nT
-3SD
mean
0
3SD
50 m
-10nT
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
Whitehawk Camp
Fig.4
Geophysics raw data northern viewport
N
7nT
0nT
-3SD
mean
0
3SD
50 m
-7nT
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
Whitehawk Camp
Fig.5
Geophysics processed data (south)
N
7nT
0nT
-3SD
mean
0
3SD
50 m
-7nT
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
Whitehawk Camp
Fig.6
Geophysics processed data northern viewport
N
A3
A1
A5
A5
A3
A3
A2
A5
A5
A4
A5
A1
A5
A5
Moderate positive anomaly (Possible archaeology)
Weak positive anomaly (Possible archaeology)
Moderate negative anomaly
Weak negative anomaly
Magnetic disturbance
Magnetic debris
Dipolar/Bipolar anomaly (Modern)
Thermoremanent anomaly
Linear anomaly land drain/former field boundary
Linear positive anomaly possible agricultural origin
Area positive anomaly possible agricultural origin
A1
0
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
50 m
Whitehawk Camp
Fig.7
Geophysics interpretation southern viewport
N
A6
A5
A1
A3
A1
A5
A5
A3
A3
A2
A5
A5
Moderate positive anomaly (Possible archaeology)
Weak positive anomaly (Possible archaeology)
Moderate negative anomaly
Weak negative anomaly
Magnetic disturbance
Magnetic debris
Dipolar/Bipolar anomaly (Modern)
Thermoremanent anomaly
Linear anomaly land drain/former field boundary
Linear positive anomaly possible agricultural origin
Area positive anomaly possible agricultural origin
A4
A1
A5
0
50 m
A5
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
A5
Whitehawk Camp
Fig.8
Geophysics interpretation northern viewport
N
533170, 104930
Ma
no
rH
ill R
oa
d
533170, 104640
532820, 104440
533070, 104440
Archaeology South-East
Project Ref: P106
Report Ref: 2014165
May 2014
Drawn by: JC
Whitehawk Camp
Fig. 9
Plan showing geophysics interpretation over previous work
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