Download Geomorphological survey of the area of archaeological site Bosilkovo

Geoarchaeology and Archaeomineralogy (Eds. R. I. Kostov, B. Gaydarska, M. Gurova). 2008.
Proceedings of the International Conference, 29-30 October 2008 Sofia, Publishing House “St. Ivan Rilski”, Sofia, 312-314.
GEOMORPHOLOGICAL SURVEY OF THE AREA OF ARCHAEOLOGICAL SITE
BOSILKOVO (BANITE MUNICIPALITY), SOUTH BULGARIA
Rossitsa Kenderova
University of Sofia “St. Kliment Ohridski”, 15 Tzar Osvoboditel Blvd., 1504 Sofia; [email protected]
ABSTRACT. The results from geomorphological study of the archaeological site Bosilkovo, situated in the Prespa Ridge, Middle Rhodopes are
resented. The function of the site was as a sanctuary and it was active from the Chalcolithic to the Iron Age. One profile and specific sediment
materials were described and sampled in order to specify their origin. Morphoscopic analysis of the pebble and full granulometric analysis of all the
horizons have been made. Attention is paid to the colour of the soil, referring to the differences in the anthropogenically influenced deposits and the
lowest horizons of the weathering curst.
stability they form bornhardts, rocky peaks and erosiontectonic valleys at many places. They have also built ridge and
slope bornhardts.
Geological and geomorphological setting
The archaeological site is defined as prehistoric sanctuary.
Several banks situated at different places are observed that
have different height and state of preservation. The highest
bank has average height of 1.5 m and it surrounds the North
site of the peak. It has West-East orientation. At the highest
part of the peak are situated two more banks, which look like
hills (they have a 5-3 and 3-2 m height).
Both rock types are stable to exogenic processes. Among
the gneisses small spots of volcanic rocks are exposed –
felsitic rhyolites with Paleogene age. There are also spots of
tuffs near the sanctuary. As they all are found over small
areas, they are not pointed on the Geological map of Bulgaria
in scale 1:100000. The volcanic rocks are situated to the West
of the peak and the peat-bog, which is formed on the
saddleback between the sanctuary and the slope (Fig. 1).
The date of the site is according to the pottery data. The
largest quantity of pottery is from the Late Chalcolithic,
followed by sherds from the Late Bronze Age (up to 1300 BC)
and there are several fragments from the Iron Age. It is
remarkable that the Chalcolithic is on the surface of the
outward bank. On the North slope the bank lies on a layer from
the Late Chalcolithic. Moreover, there are rounded and not
rounded ceramic pieces observed.
Because there are no special geology-tectonic studies of the
area, there is no more information about the Chukara peak.
Chukara peak, 1184,6 m; metamorphites
The sanctuary is situated on a relict hill. It is defined as slope
bornhardt, situated at the right site of Gloginsko Dere River,
which is a left tributary of the Davidkovska Arda River.
According to the geomorphological setting (Kanev, 1981;
Geography of Bulgaria, 1997), this area is part of the West
Rhodopes and the Prespa Ridge (with highest peak Prespa,
2000 m). Referring to some new ideas (Baltakov, 2003) this
territory belongs to the Middle Rhodopes. They are separated
from the Western Rhodopes by the gorge of Vatcha River to
Gorna Arda.
Peat-bog, high grunt water, transition from volcanic rocks to gneisses
Fig. 1. Schematic profile of the site
Material and methods
There is one described profile from the region. It is situated in
the central part of the site and it has the following coordinates:
41о42’00,1” N и 24о57’17,9” E. The structure of this profile is
shown on Fig. 2.
According to petrography the area is built of Gneissmigmatite complex of Precambrian age, present by migmatites
and migmatized double mica gneisses. Because of their
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Results and conclusions
The sanctuary is situated on bornhardt, which has a natural
special situation. It is defined by two main aspects:
▪ very good visibility along the slope and the valleys at the
bottom;
▪ very well separation of the bornhardt above the surrounding
relief.
Additional morphometric studies of the relief are needed
including horizontal and vertical unevenness and analysis of
the erosion set. Attention should be paid to the petrography
and the rocks should be marked on a large scaled map.
Special geological investigations of the region are also needed.
The conclusions from the granulometric analysis of the
deposits are the following (Table 1; Fig. 4-5):
▪ there are two types of fills in the horizons: clayish in the
“yellow clay” and the “trampled soil” and sandy-clayish in the
deposits below 30 cm;
▪ there is a huge difference between the natural layers and the
“trampled soil” and the “yellow clay”. This could be proved by
the quantity of the clay;
▪ there is a distinguished difference in the colour of the
horizons. This regards especially the natural deposits and the
anthropogenically influenced soil.
Fig. 2. Field description of profile М1: 0-5 cm; soil; 5-30 cm; humus with
gravel; inclusions of pebble, clayish-sandy fill; 30-42 cm; more grayish
and clayish than the upper layer; clayish fill; 42-55 cm; weathering curst
with inclusions of large non-rounded brown pieces
All the described horizons have been sampled for laboratory
analyses. At the bottom of the outer bank there are different
types of deposits with anthropogenic origin (Fig. 3). The first
one is named “trampled soil”, because it is more compact than
the other materials and does not contain large inclusions. The
second one is named “yellow soil” because the colour is very
different from all other deposits and the content is much more
clayish. The “yellow soil” is situated above the “trampled soil” in
the outer bank of the site.
The profile M1 is characteristic for eluvium deposits, e.g. they
are formed as a result from weathering (destruction) of
gneisses. These rocks are building the bornhardt and they are
more stable than the other rocks in the area. The obtained
results show that there are two main layers: upper – up to 30
cm and lower – up to 55 cm. The upper one is formed by
eluvial-soil formation processes. The Chalcolithic pottery was
found in it. Probably the anthropogenic influence during the
Chalcolithic developed in this part of the soil when it was in the
beginning of its formation, e.g. transformation of eluvium into
soil when the stage of humification had started.
The “trampled soil” is close to the upper two horizons
according to mechanical content. This layer is not spread over
the whole site and it is assumed as anthropogenically
influenced weathering curst. Probably it was formed when the
terrain was trampled by people at some places (for example
paths or gathering places).
Table 1
Generalized results from the granulometric analysis
Fig. 3. The “trampled” soil and the “yellow clay”
Morphoscopic analysis of the pebble and full granulometric
analysis of the horizons were made. The granulometry was
performed by sieve analysis. A special attention was paid to
the colour of the soil, since there are differences in the
“trampled soil”, the “yellow clay” and the lowest horizons of the
weathering curst. The mechanism of sampling was consulted
with the archaeologists.
Layer
(cm)
5-30
Pebble
Gravel
Sand
Clay
54.98
7.99
35.5
1.5
30-42
10.69
6.67
36.8
45.9
42-55
7.33
14.93
30.9
46.8
“Yellow
soil”
“Tramplin
g soil”
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Colour
(Munsell charts)
2.5Y 3/2 very dark
grayish brown
2.5Y 4/3 olive
brown
2.5Y 4/4 olive
brown
10YR 7/4 very
pale brown
2.5Y 5/3 light olive
brown
5-30 cm
54,98
7,99
35,5
1,5
pebble
30-42 cm
10,69
6,67
36,8
gravel
45,9
sand
clay
7,33
42-55 cm
0
14,93
30,9
20
46,8
40
60
80
100
120
%
Fig. 4. Distribution of the fractions in the horizons of the profile
120,00
%
100,00
80,00
5-30 cm
30-42 cm
60,00
42-55 cm
40,00
20,00
0,00
>0,02
0,1
0,5
2
5
10
mm
Fig. 5. Cumulative curves of the layers of the profile
The colour and the mechanical contain of the “yellow soil”
characterise other kind of deposition. Without very detailed
analyses we assume that this is weathering material taken
from the near volcanic tuffs. This material was maybe brought
at the site by people. More detailed analyses for the yellow soil
are needed in order to find more information.
Baltakov, G., R. Kenderova, E. Fitova. 1999. System of
geological and geomorphological methods and mapping,
related with archaeological investigations. – Mining Affair
and Geology, 54, 6-7, 56-59 (in Bulgarian).
Baltakov, G., R. Kenderova, A. Sarafov. 2002. Methods for
palaeogeographical research in the archaeological
investigations. – Symposium Kiten-2000, 39-46 (in
Bulgarian).
Geological Map of Bulgaria 1:100000, Part Davidkovo.
Explanation Notes. 1995. Geological Institute, BAS, Sofia
(in Bulgarian).
Kanev, D. 1993. Geomorphology of Bulgaria. University Publ.
House “St. Kliment Ohridski”, Sofia, 322 p. (in Bulgarian)
Kenderova, R. B. Borislavov, A. Sarafov, G. Baltakov. 2002.
Soil and geomorphological researches related to
investigation of archaeological objects. – In: Development
and State of the Environment. Papers of Scientific
Conference in Memory of Prof. D. Jaranov, Varna-2002.
Bulgarian Academy of Sciences, Sofia (in Bulgarian).
During the Bronze Age the anthropogenic influence affects
deeper horizons and reaches the bedrock. The older culture
layers are on the surface and the younger ones are in depth.
This could be in connection with the sanctuary activity and/or
the manner of its activity.
References
Baltakov, G. 2003. Neogene and Quaternary Exogenic
Geomorphogenesis of the Eastern Parts of the Balkan
Peninsula. DSc Dissertation, Sofia (in Bulgarian).
Baltakov, G., R. Kenderova. 2003. Quaternary
Palaeogeography. Maleo-63, Sofia, 324 p. (in Bulgarian)
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