Geological and mineralogical background of the megalithic and rock

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, 163-168.
GEOLOGICAL AND MINERALOGICAL BACKGROUND OF THE MEGALITHIC AND
ROCK-CUT SITES IN BULGARIA AND SOME OTHER EUROPEAN COUNTRIES
Ruslan I. Kostov
University of Mining and Geology “St. Ivan Rilski”, 1700 Sofia; [email protected]
ABSTRACT. The leading role of the geological and mineralogical, and not the geomorphological background has to be stressed in the distribution
of the megalithic and rock-cut monuments. Megalithic sites in Europe (in the cases of Bulgaria, Great Britain, France, Portugal and Spain) display a
tendency to be linked to a specific geological setting of the region. They are built mainly at places of distribution of quartz-bearing igneous (granites)
or metamorphic (gneisses) rocks. Usually their composition is of the same rock species, but in some cases the rock blocks have been transported
from remote areas. White vein quartz blocks are also considered of importance at such sites. Rock-cut trapezoidal niches on high vertical cliffs,
holes and graves in the Eastern Rhodopes in Bulgaria are related mainly to regions of distribution of volcanic (including volcanic tuff) or
sedimentary (limestone) rocks. Such a tendency may be observed in certain other places in Europe and worldwide. Other geological (geotectonic),
geographical features and physical (including acoustical) properties of the rocks are also to be considered important for interpretation of the
megalithic culture in future research.
circles, steps, borders, thrones, chambers, corridors, temples,
tunnels, labyrinths and other architectural forms (Kostov, 1993;
for an early classifcation of ring and cup marks c. Reader,
1891, 2-3; for their metrology including the “megalithic inch” –
Thom, Thom, 1978).
Introduction
The megalithic and rock-cut monuments are linked to the
development of human civilization since its origin. These
monuments have a key significance throughout the centuries in
different regions and countries around the world. For some of
them the discussion about their fuction, transport and
construction continues, as well as for their age and importance
for ancient civilizations. A lot of the ancient technologies are
not yet recognized by contemporary engineering and scientific
thought and some of them are considered even difficult or
impossible for the present technical possibilities of humankind.
Since prehistoric and ancient times two types of sacred
attitude towards the rock (stone) or the mountain can be
traced. The first one is as a lithic totem, where the rock or
stone is believed sacred and associated with a group or tribe,
and the second one is as lithic idol (amulet), where the sacred
object introduces a single individual (Kostov, 1993, 30-36). The
uniqueness of the object is regarded as some real or
imaginable important characteristic or property (morphology –
crystal habit or interesting mineral aggregate; physical property
– colour, hardness, transparency, lustre etc.; chemical
property; cut) or place and position in nature (mountain peak;
peculiar rock form; entrance of a cave; rock hit by lightning
etc.). The aesthetic view of humankind towards stones
(minerals and rocks) and bioobjects becomes the object of
study of gemmology (in the case of archaeological artefacts –
archaeogemmology).
The megalithic monuments are usually related to large rock
blocks which have been moved from their original location and
in most cases have been later partly of fully formed. Among the
megaliths can be listed a number of architectural forms as
menhirs (standing stones), dolmens (stone “table” or stone
“house”; usually a rectangular space formed by big rock slices
with or without an entrance passage and a barrow above),
cromlechs (stone circles), alignments (rows with large stones)
and cyclopic buildings (walls, temples, fortresses etc.).
Megalithic sculptures are represented by giant stone-cut
figures (for example the two quartzite statues 750 t each of
Amenhotep III transported at ~680 km distance in Ancient
Egypt, or the numerous elongated large volcanic ‘heads’ on the
Easter Island). Some giant rock blocks can be seen in the
ancient quarries even today – such are the cases in Baalbeck
in Lebanon and the Aswan quarry in Egypt (for examples see
also Kukal et al., 1989; Kostov, 1998).
Two opposite tendencies can be traced in describing rocks
and rock-cut monuments of culture – a “positive” and a
“negative”. The megaliths represent the first tendency with the
expression for building and constructing architectural forms
imitating the “holy” rock or mountain. In this case we see also
examples of building stone towers, columns, obelisks,
pyramids, walls and whole cities. The extreme case is the lithic
gigantism – cutting, transporting and using of giant rock blocks
or statues. The second tendency, as already discussed, is
related to the rock-cut monuments. This tendency is linked to
the primitive belief for finding shelter in nature (away from
The rock-cut monuments represent the “negative” approach
to the rock or stone – cutting and disintegration. Such
monuments are for example rock pits (cups), holes, niches,
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(Kostov, 1994; 1998 and the cited earlier literature; see also
Kostov, 2004; 2005; Fig. 1).
natural disasters, wild animals or enemies) – usually rock
shelters and caves. The extreme expression of this tendency
we find in the contemporary underground mines, military bases
and war shelters, as well as different kind of transport and
communication tunnels. In this respect is interesting to trace
the nature and distribution of the different troglodyte cultures
throughout the centuries (Reverski, 1996).
It has been observed that especially in the Sakar Mountain
region a lot of white quartz blocks were found around the
megaliths, which may have been used for some purpose in the
decoration or building the dolmens or on top of their barrows.
The dolmens are located in a course-grain granite region with
a lot of white granular quartz veins. It is well known that the
course-grain granite has a higher radioactivity background
compared to medium- or fine-grain granite.
Geological position of megalithic monuments
Bulgaria
The megalithic groups are located in the Sakar and Strandja
Mountains (megalithic sites are known also in Northern Greece
and the European part of Turkey). Some of the pioneers of
Bulgarian geology and archaeology have described mainly
dolmen sites in Bulgaria (Bontscheff, 1896; Bonchev, 1901;
Škorpil, 1925; Mikov, 1932; 1933; 1936; Velkoff, 1938). A
characteristic of the monuments is their beautiful landscape
setting, and it is pity that a lot of them have been destroyed
during the last century. Most scholars date the megalithic
monuments to the Iron Age (1200-500 BC) on the basis of
excavated finds (c. Thracian Monuments, 1976; 1981; Fol,
1993; 1997; 1998; 2000; 2007 and the cited earlier literature),
but there is a suspicion that some of the sites may well date to
an earlier period (Zacharieva, 1999; Kostov, 2004), perhaps
even to the Chalcolithic (5000-3500 BC) in Bulgaria. With the
closest megalithic group located in the Crimea Peninsula and
the Caucasus Mountains, the “Bulgarian” megalithic group is
unique to South-East Europe.
Some other dolmens and related structures are known also
in the Sredna Gora Mountain region (in granites; for example
Buzovgrad), the Hukhla Height (at Ostar Kamak, near the town
of Harmanli) South of the Maritsa River (in gneisses), the
Dervent Heights (in granites) near the Greek border, in the
Burgas region near the Black Sea (from the village of Rosen
on the North across Meden Rid to the South) and in the most
Southern part of the Eastern Rhodopes among the
metamorphic Precambrian complex (from the village of
Chernichevo on the West to the villages Zhelezino and
Pelevun to the East, near the Greek border; some dolmen sites
are known also on Greek territory in the same region of the
Rhodopes).
Other geological and geographic characteristics for the
location of the megalithic sites have been suggested to be
taken under consideration as: geotectonic setting; seismic
zoning; sunshine activity; climatic peculiarities; areas of
thunderbolts and hailstones; local background radioactivity
(related to the rocks) and geomorphological (landscape)
location and orientation (Kostov, 2005).
In Bulgaria the main distribution of described dolmens (only a
few new sites have been excavated and published) has been
related to two main regions – in the Sakar and the Strandja
Mountain. In both cases the host rocks are mainly granites and
in some cases – gneisses (both are quartz-bearing rocks)
Fig. 1. Geological map and dominant localization of megalithic (mainly dolmen) sites in the Sakar and Strandja Mountain in SE Bulgaria in regions with
quartz-bearing rocks (granites and gneisses) (Kostov, 1994; 1998): 1 – Quaternary, alluvial sediments; 2 – Neogene and Paleogene, sedimentary rocks; 3 –
Upper Cretaceous, sedimentary rocks; 4 – Upper Cretaceous, igneous rocks; 5 – Jurrasic and Triassic, sedimentary rocks; 6 – Paleozoic, sedimentary
rocks; 7 – Paleozoic, granites; 8 – Precambrian, metamorphosed granites; 9 – Precambrian, gneisses, schists, amphibolites and quartzites; 10 – one or
more megalithic sites; 11 – Black Sea; 12 – border with Turkey
164
Other European countries
Similar pattern of distribution of the megalithic sites and the
host local geological setting (granites or gneisses) has been
described for Great Britain and Ireland (geological setting from
Atlas géologique, 1980; megalithic sites after Chippindale,
1983; see Kostov, 1995; 1998). In the Cornwell Peninsula,
there is a very good match between the location of megaliths
and granitoid rocks (Fig. 2). In Scotland megaliths are
represented mainly in areas with granites and metamorphic
rocks (gneisses) and in Ireland – in areas with granites or
sandstones. White quartz blocks have been inserted in the
solar “window” of the Newgrange megalithic site in Ireland (the
passage and chamber are illuminated by the winter solstice
sunrise) – they are brought from the Wicklow Mountains 40 km
to the South, and the rock igneous and metamorphic slabs –
from the Newry Complex ~25 km to the North (O’Kelly, 1982).
In Scotland there is a lot of data for the possible use of white
quartz pebbles in megalithic sites in some sort of a Moon ritual
(Welfare, Fairley, 1980, 145). The same authors mention the
presence of “strange discs of shining white quartz” found after
excavations among some cromlechs in Northeast Scotland.
The observation of distribution of megalithic sites on the map
of France shows that they are grouped mainly to the West in
Brittany along the sea coast and spread to the Southeast in the
mountain areas at the Mediterranean coast (Bily, 1999). The
region around Carnac in Brittany (Bretagne) is famous with
menhirs, a lot of dolmens and a number of unique stone
alignments (Mereaux, 1992; Briard, 2000; Strong, 2001). The
main rocks are granites and the megaliths have been built
mainly from granite slabs (c. Migon, 2006, 328-330). In the
Carnac area the orientations of the dolmens (average 116o)
coincide with the orientation of the fault lines (average 117o)
and certain suggestions have been made linking the megalithic
structures with seismic activity, electric, magnetic and
gravitation anomalies (Mereaux, 1992, 49; Strong, 2001, 5).
The geological map of France (Carte Géologique, 1996)
clearly displays that the North-West to South-East diagonal
distribution of the megaliths is under the “control” of acid
intrusions of other quartz-bearing rocks (Fig. 3). Almost no
megaliths are to be found in the vast territories of the Paris
basin to the North-East or of the Aquitaine basin to the SouthWest. In the corridor of the dolmen passage on the Island of
Gavrinus two blocks of pure quartz have been used with very
faint traces of carving and brought from a distance of 10 km
(Mereaux, 1992, 169; Strong, 2001).
Portugal is also famous with a lot of megalithic monuments
which have been grouped on the corresponding map of their
distribution in several fields – Evora, the Viseu area, South of
Chaves, the extreme North-West, Sintra and Sagres (Bily,
1997). Comparing the megalithic sites with the geological
setting of Portugal (Atlas géologique, 1980) one can find a
tendency for overlapping distribution of megaliths and acid
intrusive (granite, granodiorite, tonalite) or other quartz-bearing
rocks (Fig. 4).
Fig. 2. Distribution of megalithic sites on the British isles (Chippindale,
1983); examples of clustering at the Cornwell Peninsula, Island of Arran,
Eastern Scotland and Northern Ireland – areas of granite and other
quartz-bearing rock outcrops
Fig. 3. Distribution of
megalithic monuments (left)
in France and location of
acid intrusive (granite) or
metamorphic
(mainly
gneiss) rocks (right)
165
Acoustic properties can be found at the perimeter of the
chambers of the dolmens, which were measured for a number
of the Caucasus megaliths, revealing three main groups: 472
cm, 720 cm (largest group) and 1035 cm, corresponding to
resonance frequencies of 35, 23 and 16 Hz near the ultrasonic
region (in which certain internal and brain effects can appear
when such low frequencies are applied to human beings;
Furdui, 2005, 158-159, Fig. 22).
Similar research at Neolithic sites around the British Isles has
revealed striking similarities in some of their acoustical
properties with key examples being the huge passage tomb of
Newgrange and the burial mound known as Cairn L at
Loughcrew (both in Ireland). These sites contain passageways
leading to large circular chambers, and have a resonant
frequency (at which sounds naturally echo and reverberate) of
about 110 Hz, probably inducing physiological and
psychological changes in people during chanting, singing or
drumming (Pilkington, 2003; for earlier studies of acoustic
properties of megalithic sites see Watson, Keating, 1999;
Devereux, 2001).
Fig. 4. Distribution of megalithic monuments (left) in Portugal and
localization of acid igneous intrusive (granite, granodiorite, tonalite) and
volcanic rocks (right)
Similar is the location of megalithic sites in Spain with
clustering of such sites mainly in the North-West part of the
country (Fig. 5). At the Alberite dolmen in Andalusia (Cadiz
Region) in Southern Spain a large up to 20 cm rock crystal has
been found with suggested magic functions (Domínguez-Bella,
Morata, 1996; similar quartz prismatic crystals have been
found in other dolmen sites in the country).
The observed tendency of linking megaliths to the quartzbearing (mainly granite or gneiss) geological background has
to be carefully applied in remote places where different cultural
influences may have taken place, including South East Asia or
the Pacific Region (Lansing, 1987). The distribution of
megaliths (mainly dolmens) in Korea (the whole Korean
Peninsula as well as the Shandong Peninsula in China and for
the South of Japan – the Eastern part of Kyushu Island; Byon,
2000) confirms the main idea for their location mainly on a
granite type quartz-bearing background.
A second geological problem in the study of megalithic
monuments is the precise mineralogical and petrographical
determination of the type of rock blocks or pieces used in such
constructions. Usually there is a concurrence between their
composition and the local geology, but in a number of cases
some or all of them have been transported from distant
quarries. A classical example in this respect is the Stonehenge
megalithic site in England with a number of different large rock
species, some of them being brought as far as the Preseli
Mountain in Southern Wales (for review see Green, 1995).
Fig. 5. Distribution of the larger megalithic areas (a single black dot
corresponds to a large number of megalithic sites) in Spain – mainly in
NW Spain (Galicia and Asturias) and NE Spain (Cataluna), linked to a
granite geological setting
Geological position of the rock-cut monuments
The rock-cut “concave” (negative) stone monuments are
reviewed as typical in their distribution for regions with volcanic
and sedimentary rocks with a lot of examples in the Eastern
Rhodopes in Bulgaria (rock-cut cups, niches, rock tombs, as
well as other architectural types). Famous for Bulgaria are the
“Madara Horseman” rock bas-relief on vertical limestone cliffs
in North-East Bulgaria (UNESCO heritage site) or the Aladja
Rock Monastery in a limestone near the town of Varna.
In the Crimea Peninsula and the Caucasus Region
(Markovin, 1978; 1997; 2000) there is also a geologically linked
tendency for the distribution of dolmens (part of them is
granite-controlled – for example in the Maikop area or to the
North of Sukhumi in Abkhazia) (Kostov, 1994; 1998). In the
rest of the cases probably the dolmens are built by
sedimentary rocks as in the case of the Zhane Valley – quartz
sandstones with a high quartz content (two types: light
yellowish in colour with 20-30% quartz composition and hard,
dark grey with quartz composition more then 50%; personal
communication by Dr. V. Trifonov – St. Petersburg, Russia; c.
Markovin, 1978, Fig. 20). It has also been discovered that the
main group of dolmens in the Western Caucasus is linked in
most cases to large faults (Furdui, 2005, Fig. 23).
Some of the most famous rock-cut temples in India (Ajanta;
Elora; Elephanta) have been cut in hard volcanic rocks (see
other examples in Kostov, 1998). The occurrence of volcanic
rocks and the lack of acid intrusive rocks on the main part of
the Apennines (without areas in the most Southern parts) or
along the Adriatic coast of the Balkans in Europe explain the
lack of megalithic type structures in such geological setting (an
opposite tendency one can observe on the near-by islands of
166
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and Phrygians: Problems of Parallelism. Proc. Intern.
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Fol, V. 2000. Megalithic and Rock-Cut Monuments in Ancient
Thrace. University Publishing House “St. Kliment Ohridski”,
Sofia, 159 p. (in Bulgarian)
Fol, V. 2007. Rock Topoi of Faith in the Eastern Mediterranean
and in Asia Minor during the Antiquity. Studia Thracica 10,
Sofia, 479 p. (in Bulgarian with an English summary)
Furdui, R. S. 2005. The Fascination of Secret. Ripol Classic,
Moscow, 447 p. (in Russian)
Green, C. P. 1995. Stonehenge: geology and prehistory. –
Proc. Geologists’ Association, 108, 1-10.
Kostov, R. I. 1993. Mythological Gemmology. Precious
Minerals Throughout the Centuries. Nauka i Izkustvo,
Sofia, 213 p. (in Bulgarian)
Kostov, R. I. 1994. On the geological and mineralogical basis
of the megalithic culture in Bulgaria. – Spisanie na BAN
(Journal of the Bulgarian Academy of Sciences), 40, 5-6,
60-67 (in Bulgarian).
Kostov, R. I. 1995. Geology beyond nature: symmetry cases in
culture. – Symmetry: Culture and Science, 6, 2, 312-315.
Kostov, R. I. 1998. The Quartz Enigma. Litera Prima, Sofia,
159 p. (in Bulgarian)
Kostov, R. I. 2001. Geology and morphology of the rock niches
from the Eastern Rhodopes. – In: Perperek I. Perperek and
Its Close Microregion. Complex Study of a Millennial
Multireligeous Centre in the Eastern Rhodopes (Ed. V.
Fol). New Bulgarian University, Sofia, 206-217 (in
Bulgarian).
Kostov, R. I. 2004. Megalithic monuments in Bulgaria. –
Universe, Science and Technology, 9, 29-36 (in Bulgarian).
Kostov, R. I. 2005. Ancient stone circles in Bulgaria. –
Universe, Science and Technology, 10, 3, 34-37 (in
Bulgarian).
Kukal, Z., J. Malina, R. Malinova, H. Tesarová. 1989. Man &
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Corsica or Sardinia – in the second case with its Nuragi stonebuilding culture).
An example of the tendency for relation of rock-cut
monuments to sedimentary and volcanic rocks are the
enigmatic trapezoidal niches, known in hundreds of numbers
cut high on vertical cliffs in the Kurdjali and Haskovo Regions
in Southern Bulgaria (with no analogue of the shape in the
Balkans or elsewhere in Europe). Their function has been also
under discussion (“places for votive objects for the dead”?), but
their geological background is linked dominantly to certain
places along rivers with a geological setting by hard to very
soft volcanic rocks and tuffs, and in places – limestones (one
exception is known near the town of Ardino in the Central
Rhodope – the “Eagle’s Rocks” site is located in metamorphic
rocks) (for all the hypotheses and size description see: Kostov,
2001).
Conclusion
The leading role of the geological and mineralogical, and not
the geomorphological background has to be stressed in the
distribution of the megalithic and rock-cut monuments. In each
case these rock monuments have to be related to a certain
population. Most of the megaliths in Europe (in the cases of
Bulgaria, Great Britain, France and Portugal) show a tendency
to be linked to the geological setting of the region. They are
built on the place of distribution of quartz-bearing igneous
(granites) or metamorphic (gneisses) rocks. Usually their
composition is of the same rock species, but in some cases
rock blocks have been transported from remote areas.
Rock-cut niches, holes, rock-cut graves and a whole rock-cut
ancient town (Perperek) in the Eastern Rhodopes in Bulgaria
are all related mainly to regions of distribution of volcanic or
sedimentary rocks. Such a tendency can be observed in other
places in Europe and worldwide.
The ‘hidden’ plutonic (usually quartz-bearing granite) rocks
are raised and hipped on the Earth’s surface, and on the
contrary, the erupted on the Earth’s surface volcanic rocks
(usually of a darker colour, because of the content of mafic
minerals) have been cut and disintegrated. This dualism of updown, Sky-Earth, white-black, light-dark, in-out, day-night and
similar oppositions have to be considered in the cosmogonic
and other mythological systems of thinking among the ancient
population with its lost heritage – the hidden “rock philosophy”.
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