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New perspectives to save cultural heritage
Altan, M. Orhan

CIPA 2003 XIX 11 ' International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
Compared to the two cases discussed above, linear or curved
continuous signals are absent. The magnetograms seem to be
characterized mainly by “spot” localized anomalies. For the
correct interpretation of the signal the identification on field,
during the data collection, of an almost outcropping grave was
very helpful. Knowing its position in the surveyed area, it was
possible to recognize its correspondent anomaly, named A in
Figure 7a. This is a well-defined magnetic dipole normally
oriented. Therefore the useful signal in the surveyed area is
represented by dipolar anomalies whose maximum and
minimum values vary respectively from +16 to +34 nT and
from -10 nT to -5 nT. Some excavations were executed inside
areas 1 and 2 of Figure 6. The limits of two trenches, for
instance, are marked with a black line in Figures 7a and 7b
while the tombs brought to the light are shown in the
photographs of Figures 7c, 7d. The appropriate overlap of these
photos with the relative magnetograms points out the good
spatial correspondence and the likeness in shape between the
magnetic archaeological sources and the detected anomalies.
The tombs represent the magnetic sources as the filling material
of clayey composition has a greater magnetic susceptibility then
the surrounding grainstone. In the light of this archaeological
feedback all the spot anomalies detected especially in the
magnetograms 1 and 2 can be interpreted as buried graves and
the necropolis seems to be spread out all over the area.
In this study we also tried to make a synthetic model which
could reproduce the observed signal. In particular the F anomaly
whose sources have quite simple geometric features was
chosen. They were approximated with two prismatic structures
whose positions, dimensions and depth of burring were derived
by measurements executed on field (Figure 8a). The only
variable parameter was the intensity of magnetization; as the
material filling the graves is predominately a clayey soil, a
value of 0.26 A/m was assigned to it. Figure 8b shows the
finally synthetic anomaly. The likeness with the experimental
data is satisfactory in terms of dimension, location, shape and
a) b)
Figure 8. a) The black line shows on the magnetogram the
layout of the prismatic structures used to approximate the
sources of the F anomaly.
3.4 Coppa Nevigata (Italy)
.The settlement of Coppa Nevigata, located in the north of
Apulia, offers a complete sequence of the Bronze Age and
constitutes an important reference site for studying the recent
prehistoric era of southern Italy.
(http://antichita.let.uniromal.it/ricerca/ric_sect.htm). Since the
beginning of the last century the La Sapienza University of
Rome has been carrying on a systematic study on Coppa
Nevigata. It is not known yet if the first settlements of the
Bronze Age were fortified whereas the following phases after
the XVII century B.C. are characterized by the presence of
defensive boundary wall made of over 5 meter thick dry stones.
Currently the excavations have recovered more than 70 meters
of it. According to the framework of this kind of prehistoric
settlement, archaeologists initially supposed that a defensive
ditch strengthened with stone-made coverings should have
existed and surrounded the inhabited area just outside the
boundary walls.
!800 MOO 1000 *0 2C0cm
Figure 9. The five pseudosections arranged according to their
relative position point out the curved trend of the detected
anomalies and of their sources.
In 2000 a d.c. electric survey was performed to verify this
hypothesis. A detailed stratigraphic column of the ground
resulting from a shallow drilling in a nearby area, suggested the
presence of readable contrast of resistivity between the
calcareous stones which the archaeological structures could be
v made of and the surrounding material. The dipole-dipole
pseudosection technique was considered the most appropriate
method to detect the ditch. Five profiles, 18 m long were
executed along parallel lines 5 m apart. Their locations,
according to archaeologists’ suggestions, were chosen to
intersect the probable lay-out of the ditch.
The obtained pseudosections are visualized in Figure 9. The
computed apparent resistivity varies in the range of [3, 77]
Qxm. On the central-left part of the CpO pseudosection an area
with two sloping high-resistivity anomalies enclosing a
conductive one is well visible. This signal is still present in the
other pseudosections but it tends to disappear gradually. This
result may be explained by the fact that the buried sources
connected to these anomalies follows the curve of the defence
wall. An excavation close to the CpO pseudosection
subsequently brought to the light a stone made artifact ( in
correspondence to the first high resistivity value) characterized
by a visible slope (Figure 10a). This artifact (XIV B.C.) was
realized by an oblique cut made in the ground where a mixture
of soils and stones was afterwards laid upon. Archaeologists
also discovered (Figure 10b) another stone covering (the
second high resistivity value) realized two centuries later and
separated from the preceding one by a filling of earth (the
embedded conductive feature).