The results of the magnetic field gradient survey
are presented graphically as grayscale shaded maps. In the magnetic
survey maps, the light shades represent magnetic field gradient
(vertical component of the vector field) lows. The dark shades
represent magnetic field gradient highs.
The magnetic survey results are presented using
two images, one clipped at +- 0.5 standard deviations (Figure 1),
the other clipped at +- 3 standard deviations (Figure 2).
Figure 1 displays more subtle magnetic anomalies, while Figure 2
is intended to display and emphasize extremely high amplitude
large-scale anomalies. Anomalies of interest are outlined in Figure 1.
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Figure 1
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Figure 2
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1. A high-amplitude, large wavelength bipolar anomaly
centered at 18N, 27E is outlined in red. This anomaly has strong
positive and negative components (+280, -220 nT) aligned with
magnetic north. The anomaly has a relatively large wavelength
in profile, indicative of a greater depth below surface for the
anomaly source. The characteristics of this anomaly make it a
strong candidate for a large, iron rich, in-situ buried thermo-remanent
archaeological feature such as a blast furnace. Note: this anomaly
is more readily visible in Figure 2.
2. A large high amplitude anomaly, centered at 25N,
35E is outlined in yellow. This anomalous region is fan shaped,
approximately 30 meters wide in the east-west direction and 15
meters in the north-south direction. Magnetic field gradient values
range from approximately +225 to -100 nT. The source of this anomaly
is likely the slag and charcoal deposit identified during previous
investigations at 44CF7 (MacCord, 1964; Higgins, 1995). Note:
The high amplitude anomaly centered at 13N, 43E is a modern drainage
culvert that runs underneath the access road.
3. Two low-amplitude, large wavelength bipolar anomalies
(centered at 34N, 54E and 46N, 84E) are outlined in light blue.
They have positive and negative components that are aligned with
magnetic north, a relatively strong positive component (+ 30 to
50 nT) to the south and a relatively weak negative component to
the north (- 8 to 10 nT). Both anomalies have a large wavelength
in profile, making them appear "diffuse". Larger wavelengths
are often indicative of a greater depth below surface for the
anomaly source. The characteristics of these anomalies make them
strong candidates for smaller buried in-situ thermo-remanent archaeological
features (bloomeries, chaferies, kilns etc).
4. Two linear magnetic field gradient highs centered
at 29N, 72E and 45N, 72E are outlined in dark blue. The southern
anomaly is a set of parallel linear features separated by 1-2
meters. These anomalies have maximum amplitudes of approximately
15-20 nT. The source of these anomalous regions may be linear
archaeological features (walls, trenches, etc).
5. Numerous high-amplitude, short wavelength bipolar
anomalies are outlined in green. These anomalies are aligned to
magnetic north and have strong positive and negative components
(+-50 to 100 nT). The high amplitude and short wavelength of these
anomalies indicate they are probably caused by ferrous iron objects
at or close to the ground surface, however their north-south orientation
suggests that they might be caused by in-situ thermo-remanent
archaeological features.
6. Many other high amplitude bipolar anomalies are
present in the magnetic data which appear to be randomly oriented,
and high amplitude anomalies which seem to lack bipolarity. Many
of these are due to modern iron objects, many of which were observed
on the surface. It is possible, however, that some of these are
due to archaeological features which have been disturbed, or iron
objects associated with the 1619-1622 iron works.
