Preliminary Report 2006
2006 Geophysical Survey Report
Assoc. Prof. D.Burcu Erciyas, Tuna Kalaycı
Introduction
Geophysical survey was conducted in September 2006 by a small group and lasted for 2 weeks.
The work was carried out in two major areas; Hamamtepe and Bula.
Geophysical survey was conducted in a field just to the north of Hamamtepe in order to understand the
possible extension of the buildings to the surrounding flat areas. The surface of this area was perfect
for conducting geophysical survey since it was a flat empty field. A small road passes between the field and the Tepe,
and it was observed that the density of pottery distribution was higher towards Hamamtepe.
Geophysical survey was also conducted in the fields between Kılıçlı and Bula villages.
Initial geophysical research has started in 2005 with gradiometer and electrical resistivity survey around the pool,
and the study area was broadened in 2006. Illegal excavations have revealed a structure just to the east of the pool.
The study in 2006 was basically conducted around the these pits in order to document the partially destroyed structure.
The survey was then moved 40m towards the west, skipping the possibly man made hill separating the two fields.
This field was characterized by significant pottery scatter.
Methodology
Geophysical survey was conducted by a FM36 Fluxgate Gradiometer. Geoplot v1.2 was used as the software.
The version of the software created numerous problems during both processing and visualization.
The work was carried out in 20mx20m grids. A total number of 56 grids were surveyed which covered an area of 2.25 hectares.
The positions of the grids are provided in Figure 1.
Traverse interval was set to 1m and 0.25m of sample interval was used. Grid Traverse Mode was selected as ‘Parallel’
in order to obtain better data. The surveying direction was to the North.
Resolution of the gradiometer was set to be 1nT while initializing, and 0.1 nT while surveying.
Work
During the first half of the study period, the field to the north of the mound was investigated.
The remaining 5 days were devoted to the study at Bula.
The grids were suitable to work on in terms of topography. On the other hand, there are significant differences in the output grids.
This case is more obvious at Hamamtepe. There are two reasons for this.
First one is the lack of experience of the surveyors. A stable handling of the machine is critical while surveying,
and this needs quite attention and experience. Secondly, survey is conducted with numerous people
in order to equalize the amount of experience for future research. However,
this situation has resulted in a variety of grids due to the physical differences of the surveyors,
namely different arm lengths, and various other variances.
Hamamtepe
A total of 25 grids were surveyed. No evidence of the continuity of the mound was detected.
The most significant anomaly in the data is 4 circular accumulations in various parts of the study zone.
Another characteristic of the data is the existence of linear features due to ploughing.
Circular anomalies can be grouped into 2 categories: First group is comprised of higher readings at the centre and lower readings around (blue mark),
and second group is formed by less significant circular features with no lower readings around.
In its very basic form, the first group can be interpreted as a pit with stones around.
The other group can be interpreted as an ordinary pit, but this categorization is highly speculative.
Red ellipsoid indicates the linear features (Fig.1). The one, at the north-west corner is a water channel dug into the ground,
which is clearly visible on the surface. Another linear feature on the north is less visible,
and most probably is an older water channel dug before the time of the investigation.
The surveyors observed that the villagers continously dig new channels, a common practice in the area.
There is one final line on the south side, which appears to be artificial however because it curves smoothly on the east,
it might be compared to the other linear features.
Another interesting set of anomalies was observed on the north-west side of the data set. High readings,
which make up a discrete line of readings are, most probably, not natural (Green line). Although not as strong,
another similar group encloses the circular anomalies which were discussed before (Blue line).
The linear features lying diagonally in northeast-southwest direction were not so visible, and most probably they are ploughing marks.
Bula
The study area in Bula was divided into two zones by an artificial ridge. On the east side, the survey was conducted in a smaller area.
It was composed of 8 grids, and on the west side our study focused around the area with looter’s trenches.
On the eastern section, the plough marks are clearly seen (Fig.3). Those can be divided in 3 different groups.
The first very obvious ones are also clearly seen on the surface, and are used for terracing, and field marking.
Another group, which is not seen on the surface, is most probably the older plough marks.
The most interesting group is comprised of features which are parallel to the other marks,
but more visible than older plough marks, and they can be interpreted as ancient terracing efforts.
On the northwestern corner of this small area, a group of high readings were obtained. Although there were no marks on the surface,
the different soil type and vegetation could have been the cause of this rather unexpected occurrence.
The main survey area, located towards the west, can be divided into two in terms of the quality of the data.
This difference is evident on the surface with an artificial bump at the center, and different pottery density on the south side.
This situation results in a homogeneity, in terms of the distribution of the data on the north.
The study at Bula reveals some anomalies which are far from natural occurrences.
One of the most significant observations is the existence of circular features of various sizes distributed all over the area (Figure 4).
Two of them are significantly larger than the others, and most probably contains burnt material inside.
On the other hand, it is better to treat them as different entities.
According to the information obtained from the illegally dug pits, there are walls under the soil,
and they are close to the surface. The dimension of the walls suggest the presence of a large scale structure.
On the other hand, this is not visible in the geophysical data, but the linear features (red ellipsoids) are most probably
the walls and they are cut by other linear features (purple ellipsoid) which are visible on the surface as well.
If this deduction is true then the walls form a rectangular structure. Moreover,
if the geophysical data of the vicinity of the pit is examined a fuzzy area can be observed.
This fuzziness is also evident in the hypothetical rectangular structure,
so it can be concluded that although the walls around the pit are not clear in the geophysical data,
a structure does exist in the region.
