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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, 83-92.

MINERALOGICAL PECULIARITIES OF THE HEAVY MINERAL FRACTION FROM SHERDS AND SEDIMENTS FROM THE ARCHAEOLOGICAL SITE “ADA TEPE”, KROUMOVGRAD DISTRICT George Ajdanlijsky1, George Nehrizov2, Elitza Ilieva1, Dimitar Zlatanov3

1University of Mining and Geology “St. Ivan Rilski”, 1700 Sofia; ajdansky@mgu.bg 2National Archaeological Institute and Museum, Bulgarian Academy of Sciences, 1000 Sofia

3”Hereward Venture Bulgaria” AD, 1164 Sofia

ABSTRACT. Despite that the analysis of the heavy mineral fraction from sediments and sedimentary rocks has wide practical application in the sedimentological, stratigraphical and paleogeographical investigations, it was only in recent years when this method found its place in archaeological studies. This paper reveals the initial results of the application of heavy mineral analysis to determinate the origin of the materials used for preparation of pottery found in a certain archaeological site. Through investigation and comparison of the mineral content of heavy mineral samples from sediments, sedimentary rocks and sherds found at the Thracian sanctuary “Ada Tepe” near the town of Kroumovgrad, SE Bulgaria, an attempt is made to identify the source (within the site or off-site) of the raw materials used for the pottery found during the archaeological investigations. 28 samples of heavy mineral fraction from sediments and sedimentary rocks and 161 samples from sherds, floor cover mortars and wall plasters, archaeological-stratigraphic levels, structure fills etc. were studied. Through the application of specialized mineralogical investigations and factor analysis the pottery samples are grouped according to the possible source of the raw material – as content and position. On the basis of pottery dating the duration of the raw material exploitation from the area was specified.

Introduction From the mid 1960s the Earth sciences find broader application in the examination of ceramics from archaeological sites – pottery, building materials (floor cover mortars, bricks, roof tiles etc.), especially in cases when the aim of the study is determination of the possible source of the raw material. Besides investigation of the specificity of the sediments suitable for ceramics production, studies of the mineralogical characteristics of the ceramics itself are also performed. Among the first methods, applied in such type of examinations are the investigations of pottery sections under a microscope (Orton et al., 1993) and the mineralogical characteristics of the heavy mineral fraction – HMF (Rapp, 2002). The mineralogical analysis of the HMF has a wide application in lithological, stratigraphical, facial and palaeogeographical investigations. It is successfully applied in the exploration of minerals that form placer deposits and in the identification of their source area. In many cases this method supports geological research and mapping in different scales. This study represents the results of a new application of this analysis – the opportunity to determine the origin of the materials used to make pottery that was found in a certain archaeological site – the Thracian sanctuary “Ada Tepe” near the town of Kroumovgrad, SE Bulgaria.

Geology of the area From geological point of view the investigated area is situated between Kroumovgrad and Dzebel-Zvezdel zones of the Momchilgrad depression of the Eastern Rhodopes structural zone, to the North of the Kesibir swell. As a whole

the studied area is built of Precambrian crystalline basement and Paleogene-Quaternary sedimentary and volcano-sedimentary cover (Fig. 1). The stratigraphical subdivision used in the present description follows Kozhoukharov et al. (1995а). The crystalline basement comprises Archean and Early Proterozoic diverse gneisses, shales and granite-gneisses interbedded by amphibolites, marbles and quartzites composing the Arda and Roupchovo Groups. This crystalline basement is discordantly overlaid by Paleocene red-brown coloured breccia-conglomerates, sandstones and clayey siltstones, united in Continental terrigenous-limestone complex (the Kroumovgrad Group). The Priabonian begins with the grey to yellowish polygenetic limy sandstones, conglomerates, clays and marls of the Coal-bearing-sandstone Formation, which overlay transgressively the rocks of the Kroumovgrad Group or the crystalline basement. In most of the cases the Coal-bearing-sandstone Formation is overlaid normally (with transition) by the light (white and light-gray) massive organogenic (reef) limestone of Marl-limestone Formation. Bands of dark-grey thin-bedded marls interbed this limestone. The Priabonian part of the section is completed by a band of intermediate tuffs, tuff-breccias, aleurolithic tuffs, tuffites, marls, sandstones and organogenic limestone belonging to Formation of the first intermediate volcanism.

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Fig. 1. Geological map of the studied area (after Kozhoukharov et al., 1995b) with the location of the samples from sediments and sedimentary rocks outside the area of the rescue archaeological investigations at the “Ada Tepe” archaeological site, Kroumovgrad district: Quaternary: 1 – alluvial deposits; Oligocene (2-5) Formation of second acid volcanism, 2 – organogenis (reef) limestones; Formation of the second intermediate volcanism (3-4), 3 – andesites, andesite-basalts, 4 – intermediate tuffs, tuffites, tuffo-breccias and organogenic reef limestones; Formation of the first acid volcanism, 5 – acid tuffs; Priabonian (6-8), Formation of the first intermediate volcanism, 6 – intermediate tuffs, tuffites, tuff-breccias, tuffo-sandstones, marls and organogenic limestones, 7 – Marl-limestone Formation, 8 – Coal-bearing-sandstone Formation; Paleocene, 9 – Continental terrigenous-limestone complex; Precambrian (10-11), 10 – alternation of diverse gneisses, shales, granite-geneisses, amphibolites and quartzites, 11 – marbles; 12 – fault; 13 – olistolith; 14 – location and number of a sedimentary sample

Upwards in the section follow alternating bands of acid and intermediate tuffs, tuffites, tuff-breccias, and organogenic (reef) limestones – all of them of Oligocene Age. Three formations were subdivided according to the volcanic composition: Formation of the first acid volcanism, Formation of the second intermediate volcanism and Formation of the second acid volcanism. Quaternary alluvial deposits are outcropping mainly along the valleys of the rivers Kroumovitza and Elbasandere. They formed the channels, the lower, middle and partly the high non-flooded river terraces (Dinkov et al., 1968f). Deluvial, colluvial and eluvial deposits are sporadically distributed and they are of little thickness. The archaeological site “Ada Tepe” is located at the highest point of the “Ada Tepe” hill ridge (altitude 492.4 m) about 3 km to the South of the town of Kroumovgrad. The area of the archaeological site is composed of the rocks of the Kroumovgrad Group.

Material and methods The present study is based on the investigation of total 197 heavy mineral fraction samples, from which: 29 are heavy min-eral samples from natural and artificial HMF from sediments and sedimentary rocks (including 7 samples from archaeologi-cal-stratigraphical levels (ASL) in the area of the site); 7 sam-ples are floor cover mortars and wall plasters from the area of the excavations; and 161 samples are artificial HMF and pot-tery (pottery) (Fig. 2).

Fig. 2. Sketch of the area of the rescue archaeological investigations of “Ada Tepe” archaeological site, Kroumov-grad District, with the location of the samples from sediments and pottery from the area of the site; archaeologi-cal-stratigraphical levels: a – Ada Tepe-I (incl. Ia and Ib); b – Ada Tepe-II; c – Ada Tepe-III; d – Ada Tepe-IV; archaeologi-cal structures (1-2) 1 – inner and outer stone-built wall of the oval-shape struc-ture; 2 – inner fill of the wall; 3 – the square number; archaeological and geological sampling: 4 – from the Late Iron Age; 5. – from the Iron Age; 6 – from the Early Iron Age; 7 – from the Late Bronze Age; 8 – sediments from the area of/near the site (characteristic ASL); 9 – fragments from floor and lute materials; 10 – fragments from portable fireplace

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The main part of the samples from sediments and sediment rocks (22 samples) are suitable for pottery production eluvial, deluvial and alluvial materials from and around the “Ada Tepe” archaeological site, from the valley bottom and the slopes of the Kesibir River, Elbasandere River and Kroumovka River (Fig. 1). Seven of the sedimentary samples characterize different archaeological-stratigraphical levels from the area of the rescue archaeological investigations of “Ada Tepe” – respectively Ada Tepe-I (including Ada Tepe-Ia and Ada Tepe-Ib) and Ada Tepe-II, connected to the period of construction of the massive structure of the periods Ada Tepe-III and Ada Tepe-IV. One of the samples represents material from the fill of the wall of the oval-shaped stone-built structure. The initial heavy mineral concentration of the sedimentary samples was made in the field by standard water pan washing. The obtained heavy mineral concentrate was dried and prepared for laboratory treatment. After a mechanical disintegration to release the mineral grains, controlled through a binocular stereomicroscope Carl Zeiss, the rock samples and the sherds and the samples from sediments were enriched in laboratory conditions by water pan washing and drying at room temperature till the formation of a dry concentrate. All obtained dry heavy mineral concentrates (field and lab) went through magnetic separation, heavy liquid (bromoform – CHBr3, relatively weight 2.89) separation, and electromagnetic separation (5A; 25V). After the heavy liquid separation every sample was cleaned with ethyl alcohol and dried at temperature of 35°C. As a final result magnetic (mf), electromagnetic (emf) and non-magnetic (nmf) heavy mineral fractions from every sample were obtained. The date of the studied pottery is based on the data obtained during the archaeological investigations. For the purposes of the mineralogical characteristics, part of the material from the magnetic HMF of each of the studied samples is mounted in polyester resin and polished sections were prepared and studied by polarization microscope Amplival Carl Zeiss. The precise mineralogical diagnostics was made using X-ray diffraction analysis (Cu-filter, 40 kV, 30 mA,

0.5°/min) and scanning electron microscope JEOL JMS 35 CF with X-ray microanalyser Tracorn TN-2000 (EDS-method in regime 20 keV, 2x10-9 A). The statistical calculation (cluster and factor analysis) of the results is made with the product Statistica 6.0 MS. The initial data base is the part of minerals (in volume %). In order to eliminate the antropogenic variations (for example the variation of electromagnetic characteristics that are result of thermal treatment) of the minerals (samples from the sherds, floor ma-terials, lute and from the infilling of the structure wall), the data for hematite, garnets, epidote and amphiboles from the elec-tromagnetic and nonmagnetic fractions are listed together. This allows the more accurate comparison of the results from the sediment and the pottery samples. The results of the analysis are represented as factor diagrams.

Results The correlation between the percentage of magnetic, electromagnetic and nonmagnetic HMF from the investigated sediments and pottery samples, floor lutes, portable fireplaces and sediment fill of the structure wall is represented on Fig. 3. As a whole, almost all of the samples have relatively low content of nonmagnetic HMF. In a small part of the samples, mostly from pottery from the Late Bronze and Early Iron Age, the magnetic HMF predominates. The rest of the samples can be subdivided into two groups: (1) samples with comparatively equal parts of magnetic and electromagnetic HMF; (2) samples predominated by electromagnetic HMF. The low percentage of the nonmagnetic HMF in the samples is well represented for data from sediment materials from or near by the site area, where in the basic part of the samples the quantity of that fraction is under 20%. Only in two samples from the bottom part of the North slope of Ada Tepe (АТ-716 and 718), the percentage of nonmagnetic HMF reaches 32-35%. The data from samples from floor cover mortars and wall plasters are similar, and only in two samples from fragments of floor cover mortars (АТ-774 and 853), belonging to level Ada Tepe-I, are observed increased quantities of nonmagnetic HMF – respectively 24% and 63%.

Fig. 3. МF-ЕМF-NМF diagram of sediments, floor cover mortars and wall plasters (а) and pottery samples (b) from the Ada Tepe area – archaeological-stratigra-phical levels to which the sample belongs: 1 – Ada Tepe-І (incl. Іа and Іb) and Ada Tepe-ІІ; 2 – Ada Tepe-ІІІ; 3 – Ada Tepe-ІV. Archaeological and geological sampling – pottery fragments (4-7): 4 – from the Late Iron Age; 5 – from the Iron Age; 6 – from the Early Iron Age; 7 – from the Late Bronze Age; Other fragments (8-9): 8 – fragments from floor cover mortar and wall plaster; 9 – fragment of portable fireplace; Sediment samples (10-11): 10 – fragments from the area of and near by the site (typical for ASL); 11 – sediments out of the archaeological area

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The part of the magnetic HMF varies in a very wide range. Among the samples from sediments dominated by magnetic HMF is the slick from eluvial materials directly Westwards and North-westwards of Kroumovgrad (АТ-721, 801, 802 and 803). On the contrary, in most of the samples from sediments from the site or its vicinity, the quality of magnetic HMF did not exceed 25-27%. Exceptions of this rule are three samples from the bottom part of the Northern slope of Ada Tepe (АТ-706, 716 and 718) and two samples from ASL Ada Tepe-ІІ (АТ-805 and 809), taken from the Northwest sector of the excavated area. In these samples the percentage of magnetic HMF is around 30-40%. Similar to them is the quality of magnetic HMF in the materials from the wall fill of the stone structure (sample АТ-710). Relatively high quantity of magnetic TMF have the samples from a fragment of portable fireplace (АТ-851), the fragments from floor cover mortar (АТ-774, 775 and 848) and fragments from wall plaster (АТ-852). The percentage of magnetic HMF in the slick from the samples of “burned soil” (АТ-849 and 850) and from floor cover mortar (АТ-853) is low. The quantity of magnetic fraction varies in wide range in the sherd samples – from nearly absolute absence to up to 95%. Between the samples in which the magnetic HMF is up to 50%, there is not any from the Late Bronze Age. During the microscope examination of the obtained HMF from each of the investigated samples, the following minerals were established: magnetite, ilmenite, specularite, limonite, chromite, garnet, amphibole, pyroxene, epidote, titanite, zircon, apatite, pyrolusite, pyrite, marcasite, cordierite, kyanite, as well as sillimanite, barite and gypsum. However, there are significant variations in the mineral quantity of the samples and in the percentage of the single minerals. The present study discusses only these peculiarities of the HMF from the examined samples that have direct relation to the identification of the source of the materials found during the excavations. Magnetic heavy mineral fraction Microscopically the quantity of magnetic HMF is relatively monotonous. The samples contain predominately magnetite and hematite and only in some cases single grains of marcasite and fossil nuclei of feroxides and hydroxides are established. During the microscope investigation of the materials the presence of pirrhotite, ilmenite, rutile, ulvıspinel, titanomagnetite and maghemite was established in the form of exsolutions, intergrowths and/or inclusions in magnetite and hematite grains and aggregates, or as alteration products in these grains and aggregates. As a whole in the magnetic HMF the detritic magnetite grains predominate. Medium to weakly rounded grains from fresh (not altered) magnetite. Comparatively rare, mostly in the grain periphery, alteration products are observed. Mostly this is hematite. In many of the cases the hematite is represented in a form of parallel to {111} lamellas, gradually becoming thinner inside the grain (Fig. 4c). Rarely such alters are observed inside the grains. In those cases the hematite lamellas are formed around cracks or pores. Only in two of the samples the hematitization is represented by stripes (Fig. 4e). The pyrrhotite comes as small inclusions in the grains of homogenous magnetite. The maghemite is established in several samples. In three of the samples that are a sediment material from the beddings at the site (АТ-806 from ASL Ada

Tepe-І and АТ-804 and 808 from ASL Ada Tepe-ІІІ), well formed octahedral crystals were established. Single finds of absolutely identical crystals were found in three of the samples from the thick-wall (coarse) pottery (for example sample АТ-729). A special feature of magnetite in part of the samples is the presence of several types of exsolutions. Such are established in 29 pottery samples, three sediment samples (АТ-703, 708, 714 and 721) and three samples from the archaeological layers Ada Tepe-II (AT-805) and Ada Tepe-III (AT-804 and 808) from within the site or off-site (see Fig. 1b,c). The most widespread exsolutions are from the type magnetite-ilmenite, ulvıspinel-hematite and magnetite-ilmenite-hematite. Generally, the richer in iron phases are represented by thin lamellas orientated parallel to {111} (Fig. 4b, left part, and 4d). Rarely the lamellas are enriched by Ti phases. In these cases the pattern of exsolving is as equally orientated, relatively thick, lens-like lamellas of ulvıspinel (Fig. 4а) or ilmenite. The pottery samples have percentage of grains with exsolutions in the magnetic HMF between 10-15% and 30% and only in certain cases uplifts to 50-60%. This percentage in the samples from the archaeological layers is relatively constant (within the range of 15-20%). In most of the sediment samples with such exsolutions, the grains compose a half of the magnetic fraction volume and only in sample АТ-708 it is about 15%. In nine of the pottery samples and in single sediment sample (AT-708) the grains with exsolutions show corrosion in one of the phases (mostly the rich in Ti) in the grain periphery (Fig. 4d). In all of them the quantity of the grains is in the range of 15-20%. In most of the pottery samples, the samples from the archaeological layers within the site and off-site, the samples from fragments of floor cover mortar, wall plaster and portable fireplace are established grains that have marks of thermal transformation (melting). Very often the observed structure is fluidal and affects the periphery or the whole grain. Quite often relicts from non-altered material can be found. The parts with fluidal structure have relatively poor polishing. Another form of thermal alteration of the grains of the magnetic HMF is the “slag-like” structure. One of the varieties of these structures is represented by aggregates similar in structure as a deformed cell in which the bars are composed of stripes or a massive, homogenous mass with composition close to that of wüstite (Fig. 4f). The internal part of the so formed cells is partly or entirely filled with porous material of hematite or maghemite. Such structures can be observed in 16 pottery samples, 4 sediment samples from the archaeological layers from ASL Ada Tepe-ІІ (samples АТ-804 and 810) and Ada Tepe-ІІІ (samples АТ-805 and 809). The sediment samples are mostly from the Northwest part of the site (see Fig. 2b-c). Part of the “slag-like” grains in the magnetic fraction is under 20%. The pottery samples with such a grain structure belong from the Early to the Late Iron Age, as the percentage of the altered grains in the magnetic fraction varies from 5 to 45 %. To the group of “slag-like” grains belong the porous aggregates, composed of star-shaped phases linked with a fine netlike mass (Fir. 4g). The compound of these aggregates is wüstite. This structure is established in 26 samples of pottery fragments from the Early to the Late Iron Age. In many of the grains with “slag-like” structure are establishes pores, often with hematite crests on their walls.

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Fig. 4. Mineralogy of the magnetic heavy mineral fraction in the investigated heavy mineral samples: (а) exsolving of relatively thick, as well as very thin lens-like lamellas of ulvıspinel (yellowbrownish) in magnetite (ground mass); (b) magnetite-hematite-ilmenite exsolving as oriented parallel to the {111} planes lamellas; (c) surface alteration of magnetite (gray) into hematite (lightblue). The hematite is developed as thin lamellas, oriented parallel to the {111} planes; (d) exsolving of thin lamellas of magnetite (light yellowish) in ulvıspinel (pink-brownish) in three directions, parallel to the {111} planes. In the periphery of the grain the ulvıspinel phase is corroded; (e) zonal hematitization of magnetite grain (+ N); (f) aggregate with “slag-like” structure, build up by wüstite and maghemite; (g) porous aggregate with “slag-like” structure, build up mainly by wüstite; (h) aggregate with partially preserved fluidal structure (in the center) and strongly oxidized periphery

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Electromagnetic and nonmagnetic heavy mineral fraction The compound of the electromagnetic and nonmagnetic HMF is more variable than that of the magnetic fraction. Among the most widespread minerals are the amphiboles. They present in both the electromagnetic and the non-magnetic heavy mineral fraction. They were established in almost every sample from sediments, sedimentary rocks and ceramics. Their colour is mostly dark-green, rarely black and only in separated cases – blue. The quantity varies in a wide range from some percents to 50-60%. In two of the samples only (samples AT-674 and 847), the quantity of the electromagnetic amphibole is over 80% from the entire amount of HMF. Amphiboles are also established in the nonmagnetic HMF of the pottery samples (about 10% of all the investigated samples) where they are predominantly pale-grey to colourless and the grains are more fragile than those from the electromagnetic HMF. Their quantity varies in the range of 1-3% to 12-20% and rarely reaches 40% (for example in sample АТ-826). The garnets are represented as crumbled crystal fragments and rarely as preserved crystals. Garnets, like the amphiboles, present in both the electromagnetic and the non-magnetic heavy mineral fraction in almost all of the investigated samples. In the electromagnetic fraction they are represented by almandine and rarely spessartine. Red to pink and slightly rounded rhombic dodecahedron grains predominate. Rarely crumbled tetragontrioctahedron grains with pale orange colour can be found. In the nonmagnetic HMF whitish, transparent garnet is established – mostly uvarovite and rarely andradite and spessartine. Often in the andradite can be seen amphibole inclusions. The garnet quantity in the investigated heavy mineral samples is too variable. In spite of the considerable variations, as a rule, the quantity is greater in electromagnetic HMF, where it varies from 2-3% to 55% and in some cases to 68-70% (in pottery sample AT-671 and in sediment sample AT-713). According to the number of individuals the garnet presence in the nonmagnetic HMF is significantly limited. In a significant part of the samples garnets are not presented, and in the cases where they are present, their portion is in the range of 1-4% and only in two pottery samples (АТ-769 and 782) – up to 10-11%. Another mineral that presents in both the electromagnetic and the nonmagnetic HMF of the samples is the titanite. Unlike amphiboles and garnets, titanite has more limited presence in the investigated samples of pottery (hardly in ¾ of them), but it is established in almost all of the sediment samples. In the electromagnetic fraction it looks like yellow-brownish crystal fragments. The percentage varies between 2-5% and 10-20% and rarely reaches 30% (for example pottery samples АТ-662, 736 and 762). In the samples from the archaeologcal layers and floor cover mortars from the site area, the quantity of electromagnetic titanite decreases in samples up the section, and in ASL Ada Tepe-III and IV entirely is absent. In most of the off-site sediment samples, the quantity in that fraction is low too. For the nonmagnetic HMF, where the quantity of titanite is from 1-5% to 10-12%, envelope-like, pale to coppery-yellowish coloured forms are typical. In two of the pottery samples (АТ-649 and 669) the quantity of nonmagnetic titanite is over 20%.

Rutile also has steady presence in the electromagnetic and in the nonmagnetic HMF. It is established as prismatic grains of crystal fragments with red or orange-reddish colour. Rutile can be found in 2/3 of the electromagnetic samples, where its quantity is insignificant – 2-3%. An exception are the two pottery samples, where its quantity is significant – in sample AT-758 it is 15% and in sample AT-679 it reaches 30%. The last sample is characterised also by a high rutile quantity (24%) in the nonmagnetic fraction. Rutile is established in almost every sample from the nonmagnetic HMF, in the shape of well preserved crystals with red or the typical only for these samples orange colour. Its percentage varies from 1 to 15%. In some of the samples, for example АТ-654, 661 and 682, the rutile quantity is over 25%. Like the above-mentioned minerals, the epidote presents in both the electromagnetic and the nonmagnetic HMF. It is established in almost all of the electromagnetic HMF samples, where it looks like crumbled fragments and rarely like green coloured plate crystals. Its quantity varies in a wide range – from several to more than 25%, and in 7 samples (only one of them sedimentary – AT-720) its quantity is over 40% (in sample AT-680 it reaches to 61%). In the non-magnetic HMF epidote has blue color. It is presented relatively rare, only in pottery samples (36 samples). An exception of this rule is only one sample, representing fragment of floor cover mortar from ASL Ada Tepe-I (sample АТ-775), where the grey epidote content is 2%. The content of non-magnetic epidote is low – in the range from one to several percents. Only in four samples (АТ-693, 794, 797 and 839) it increases to 14-16%. Ilmenite and pyroxenes were established only in the electromagnetic HMF of the samples (only in half of them). Frequently its quantity is in the range of 1-4% and really rarely (in two samples – AT-804 and 807, and in three pottery samples – AT-649, 670 and 788) increases to 10%. The crumbled grains predominate. Well preserved crystals can be seen rarely. Relatively enriched of ilmenite samples are coming from the sediments from Ada Tepe. Pyroxenes are exclusively represented as fragmented crystals. Like as ilmenite, their quantiity varies in the range of some percents. The samples containing pyroxenes over 1% are from sediment samples, mainly from Ada Tepe slopes and only two (AT-703 and 704) have over 10%. Such more significant presence of pyroxenes (quantities to 13-24%) is found in five pottery samples – АТ-667, 702, 750, 855 and 856. The sulphide mineral presents only in one sample in quantities over 1%. Pyrite is predominantly established in electromagnetic and very rarely, as single grains in the nonmagnetic HMF. More significant is its presence in the sedimentary samples. In the electromagnetic fraction of nine samples, all from Ada Tepe slopes, its quantity is from 4 to 35% (sample AT-709). Pyrite also presents in the mechanical layers and floor cover mortars of the site (samples АТ-810 and 848), where its percentage is constant – 4%. In more significant quantity – 3%, it is established in only one pottery sample (АТ-762). Very significant presences in part of the samples have feroxide and hydroxide minerals. Limonite and hematite predominate among them. Hematite is established mainly in the samples from floor cover morters and sediments of archaeological layers samples from the site area. Usually it has

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cherry-coloured to grey, uneven or oval aggregates and the even crystals, which are rarely found, usually have dark-gray colour. A special feature of these samples is the increase of hematite percentage in the heavy mineral fraction from the bottom upwards in the section. As for the samples from ASL Ada Tepe-I, the quantity varies from 25 to 40-45%, in levels Ada Tepe-III and IV it decreases to 7-12%. The quantity of the hematite (over 40%) from the reddish-orange fill of the wall is high (sample AT-710). Hematite is mainly found in the electromagnetic fraction. In the nonmagnetic fraction, it is established in single samples as its percentage is 1-2%. The significant presence of microscaled specularite should be mentioned in most of the samples from the archaeological layers of the site, in the fragments from the floor cover mortars, wall plasters and from the red coloured part of the fill of the wall structure. The electromagnetic fractions of four sedimentary samples (АТ-708, 709, 715 and 719) also have increased quantity of hematite – 9-11%. Only in a single sample (АТ-719) it takes part in the nonmagnetic compound with percentage of almost 4 %. In the pottery samples hematite is weakly represented and in most of the cases it is less than 1%. Only in two samples (АТ-743 and 835) hematite takes a significant part and in the second sample its percentage reaches 26% (18% of all are from the nonmagnetic fraction). Like hematite, limonite presents only in the electromagnetic HMF from the fragments of floor cover mortar and archaeological layers, as well as in separate samples from the slopes of Ada Tepe. Its quantity in the archaeological layers decreases upwards in the section – from 6-9% in the bottom level to 2-4% in Ada Tepe-III. In the sedimentary samples it is in the range of 2-4% (samples АТ-704, 706 and 707) and rarely has significant quantities (for ex. АТ-709 – 17%, or АТ-715 – 27%). Besides detritus grains and aggregates, hematite and limonite are part of the established in 4 sedimentary (АТ-705, 711, 717 and 721) and 14 pottery (АТ-651, 660, 666, 671, 688, 690, 729, 738, 739, 743, 474, 760, 825 and 832) samples, mainly from the Late Iron Age. The microfossil remains belong to three groups – foraminifers, gastropods and bivalves. In the present investigation the presence of microfossil remains is used only for the purpose of the heavy-mineral correlation. The pyrolusite, like ilmenite and pyroxene, is established only in the electromagnetic HMF. It is represented by uneven, crumbled, sooty aggregates that are extremely crumbly. It is found in some pottery samples and its quantity does not exceed 4%. In significant part of the nonmagnetic heavy mineral fraction zircon is established. It is represented mostly by even crystal forms, frequently with rounded edges. Usually it is colourless or yellowish. In the samples from the archaeological layers and floor cover mortars, as well as in most of the off-site sedimentary samples, the quantity of the zircon is in the range of 1-2%. Zircon is absolutely absent from the samples in the area to the West of Kroumovgrad and to the East of Kroumovka River. Increased quantities (5-17%) are established in the samples from the Southern and the Northern slopes of Ada Tepe (samples АТ-713, 714, 716 and 718). The distribution of the zircon in the pottery samples is very uneven. In most of the samples where it is established, its quantity is 1-

6%. Only in six samples, these values are between 10 and 20% – samples АТ-727, 742, 752, 756, 759 and 834. The apatite is found only in the nonmagnetic HMF. It is represented by prismatic crystals or mineral fragments. Usually is transparent or mat with yellowish colour. Apatite is found in 2/3 of the samples from the sediments and in 35% of the pottery samples. Like the zircon, it is absolutely absent from the samples from the area to the West of Kroumovgrad and to the East from Kroumovka River. In most of the sedimentary samples its quantity is in the range 1-3% and in a single sample (eluvial material from the Northern slope of Ada Tepe (sample АТ-718), it is 12%. The quantity of apatite in the pottery samples varies from 1% to 7% and rarely exceeds it: in samples АТ-642 (14%), АТ-660 (17%) and АТ-758 (15%). A few in number are the samples with presence of gypsum. It is established in the nonmagnetic HMF only in 28 samples from ceramics, as well as in the samples from the floor cover mortars at the site area. Gypsum entirely absents from the off-site sedimentary simples. Its quantity in the sediments and in most of the sherd samples is 1-4%. Only in small part of the pottery (samples АТ-758, 761, 764, 765 and 781) it is significant, but does not exceed 20%. Specific distribution in the samples has the barite. In the sedimentary samples it is found in quantities of 2-5% in alluvial samples from the lowermost parts of the valleys of Kesibir River and Elbasandere River (for example АТ-705, 707 and 720) and in single samples from the Northern slope of Ada Tepe, where its highest quantity in sediments is established – 12% in АТ-718. In the sediments and floor mortars within the site it absolutely absents. Barite is found in 44 samples from pottery where its quantity is in the range from 2 to over 27%. In the investigated samples were established cordierite, kyanite, sillimanite, tourmaline and chromite. However, their presence is very sporadic and their quantity is rarely over 1%. Among the nonmagnetic HMF of some samples from pottery were established single grains of a metal phase (sample AT-725) with close to the wüstite composition. The factor analysis of the results from the mineralogical investigations of the heavy mineral fraction can be divided into four well differentiated groups with specific mineralogical HMF characteristics (Fig. 5): ▪ sediments and fragments of floor cover mortar from the area of the rescue excavtions, that characterise different ASL of the archaeological site “Ada Tepe”. These are: sediments - sample АТ-806 from ASL Ada Tepe-І; samples АТ-805, 807 and 809 from ASL Ada Tepe-ІІ; samples АТ-804, 808 and 810 from ASL Ada Tepe-ІІІ; sediment from the fill of the wall structure (sample АТ-710); fragments from floor cover mortar – samples АТ-774, 775, 848, 849, and 850 from ASL Ada Tepe-І; sample АТ-852 from ASL Ada Tepe-ІІ and sample АТ-851 from ASL Ada Tepe-ІV. To this group belong the samples from eluvial and deluvial sediments from the North and Southeast slopes of Ada Tepe (samples АТ-709, 713, 714, 716, 717 and 718), part of them, situated in the immediate vicinity of the archaeological site. Close to this group are four more sedimentary samples from the North slope of Ada Tepe – samples АТ-703 and 706. For most of the samples in the group is typical a comparatively high percentage for the electromagnetic fraction;

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▪ eluvial and proluvial materials from the area to the West of Kroumovgrad – in the area of lyulkino Tepe (sample АТ-721) and to the North of the Traikovtzi hamlet (samples АТ-801, 802 and 803). A significant quantity of the magnetic HMF is typical for the group, that varies in the range of 0.6 to 1.2 %. With the exception of magnetite, high quantities over a percent are found also for amphibole (2-7%), epidote (2-8%) and hematite (5-8%);

Fig. 5. Diagram with the results of the factor analysis of the mineral content of the HMF of samples from: (1) sediments and sedimentary rocks outside the area of the rescue archaeological investigations; (2) sediments from ASL within the site; (3) floor cover mortars, wall plasters from the site or fills of the wall structure; (4) mobile hearth. Archaeological-stratigraphical levels: (5) Ada Tepe-ІV; (6) Ada Tepe-ІІІ; (7) Ada Tepe-І (including Іа and Іb) and Ada Tepe-ІІ

▪ eluvial materials and fresh sediment rocks from the Coal-bearing-sandstone Formation, that forms the Eastern slope of Kroumovka River near Kroumovgrad, and the Western slope of that river in the area near the the Kesibir River – samples АТ-711 and 712. Most typical for the group is the presence of a significant quantity of microfossil cores and shells; fluvial sedi-ments from the overbank area of the Kesibir River valley, situ-ated in the interval between South of the archaeological object and to the area of Kroumovka River – samples АТ-704, 705. A distinguished mark for this group is the relatively poor mineral variability. The remaining six samples – alluvial (АТ-707, 720 and 800) and proluvial (АТ-708, 715 and 719) sediments do not form a distinguished group. The factor analysis of all of the investigated samples (Fig. 6) show the presence of three types of groups: (i) small in volume groups from ceramics, formed around one sedimentary sample (F and A); (ii) multiple groups of samples from ceramics, one of which is formed around the samples from ASL from the site and the sediment revealing next to it (AT-1 and AT-2); (iii) Some not large, relatively “non compact” groups of samples, one of them uniting samples mainly from ASL and floor mortars from the site and eluvial sediments from the near by area. The most numerous group of samples is “Ada Tepe-1” (AT-1, Fig. 6). The specimens from the group are characteristic by a variability according to material type. The group consists of 64 ceramics samples, 9 sedimentary samples (one of them is from archaeological layer fwithinthe site – AT-809), 5 samples from floor cover mortars from the site (АТ-774, 775, 848, 849 and 852) and a single sample from fragments of portable fire-place (sample АТ-851). The off-site sedimentary samples, rep-

resent materials from the Northern and Eastern slopes of Ada Tepe (samples АТ-706, 716 and 718), and also sediments from the area to the West of Kroumovgrad (АТ-720, 721, 801, 802 and 803). Typical for the samples from that group is the high quantity of garnet, rutile, pyrite, zircon and apatite. To this group belongs the largest number of samples with high quan-tity of gypsum and barite. At the same time, also typical is the very low quantity of epidote, amphibole and titanite, as the last two minerals present mainly in the nonmagnetic HMF. From an archaeological point of view, the pottery samples that belong to that group represent equally (as a number of samples) the Early and Late Iron Age. With very similar mineralogical characteristics to group AT-1 is also a variable to material type cumulation of 29 specimens – “Ada Tepe-2” (AT-2, Fig. 6). It consists of 19 pottery samples (representing equal in number samples from the Early and Late Iron Age), 9 sedimentary samples (two of which are from the archaeological layers from the site – АТ-808 and 810) and a sample from floor cover mortar (АТ-849). Among the sedimentary samples is АТ-710 that is “burned soil” from the fill of the wall structure. In three of the samples fossil micro fauna is found. In this group there are no samples from the Late Bronze Age. While repeating the main characteristics of group AT-1, group AT-2 shows some differences such as increased quantities of titanite, epidote and more limited presence of rutile, gypsum and barite. A composition of 10 specimens, half of that is from sediments from archaeological layers (АТ-805, 806 and 807) and fragments from floor cover mortar (АТ-850 and 853), show some similarities with the above described two groups. In that group are included two pottery and three sedimentary samples from the Southern and Northern slope (АТ-709, 715 and 719). Three other groups are compact but not numerous. The first is formed around two of the sedimentary samples (АТ-711 and 712), that contain microfossil fauna – “fossiliferous” or “Polkovnik Zheliazkovska” formation (F; Fig. 6). The heavy mineral fraction in the group is dominated of electromagnetic HMF, composed mainly of amphiboles, garnets and epitot. The percentage of the magnetic HMF is relatively low and varies in the range of 2-19%.

Fig. 6. Diagram with the results of the factor analysis of the mineral content of the HMF of samples from sherds, sediments and sedimentary rocks within and outside the area of the rescue archaeological excavations; symbols – see Fig. 3

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A distinguished mark of this group is that its samples have the highest quantities (in the entire heavy mineral fraction and in the nonmagnetic fraction) of amphibole which in some samples reaches 90%. The low quantity of rutile is typical for the group (it entirely absents from the non magnetic fraction), ilmenite, zircon and apatite. The content of hematite is very low. To that group belong 17 sherd samples, most of which are suggested as dated to the Early Bronze Age. Another two less numerous pottery groups are formed around sedimentary samples from the flood-plain of the lower course of the Kesibir River: i) sedimentary sample АТ-704 and 8 sherds; ii) sedimentary sample АТ-704 and 10 pottery samples, predominately from the Iron Age. Because of the closeness of their mineralogical characteristics these two groups can be combined into one – “alluvial (Kesibir)” group (А-1, Fig. 6). Typical for this group is the high content of titanite – in the heavy mineral fraction as a whole (in the range of 20-30%) and in part of the nonmagnetic HMF (reaches up to 35-39%), as well as that of epidote – 32-59% from the heavy mineral fraction volume. Relatively low are the contents of rutile and zircon, while apatite is absolutely absent. Pyrite (1-4%) is established only in the electromagnetic HMF of the sedimentary samples. A quite non-compact group of 17 pottery samples, predominately dated to the Early Iron Age, is formed around sedimentary sample AT-800, representing alluvial materials from the flood-plain of Kroumovka River, to the Southeast of district “Izgrev”, Kroumovgrad and according to that is marked as “alluvial (Kroumovo)” formation (А-2, Fig. 6). Typical for the samples belonging to this group is: i) relatively poor (in mineralogical ponit of view) heavy mineral fraction compound; ii) certain enreachment of pale grey amphibole in the pottery samples. The connection between the above described groups of samples with factor 2 on the diagram of Fig. 6 shows differentiation in two larger groups. In one of them are the samples from groups AT-1 and AT-2 that have negative values towards this factor. To the other group belong the samples from groups F, А-1 and А-2 for which the values of factor 2 are positive. Between the two groups a compact group of 21 pottery samples is identified mainly dated to the Early Iron Age. Only sherds fall in this group that accordingly is marked as “ceramic” group (K, Fig. 6). The mineral composition of the group is relatively balanced without dominant minerals. Only in some samples significant presence of gypsum and barite can be pointed out.

Discussion and conclusion The specialized mineralogical investigations of the heavy mineral fraction extracted from pottery and floor cover mortars found in the Thracian sanctuary “Ada Tepe”, near Kroumovgrad, SE Bulgaria, confirmed the good suitability of part of the minerals from the HMF to be used as an indicator for the origin of the raw material used for pottery production. Among the most useful minerals in that respect are amphiboles, garnets, titanite, rutile, epidote, zircon, apatite, gypsum and barite. Gypsum, apatite and zircon can be pointed out as minerals that indicate the use of material for pottery that comes from within or near the site. Gypsum is typical only for

the materials from the site area. On the other hand, barite presents almost in every pottery sample and its origin is connected to the alluvial materials from the flood-plain of Kroumovka River and these from the lower courses of Kesibir River and Elbasandere River. On the contrary, because of the relatively even distribution in the specimens, minerals such as ilmenite and pyroxene are not so suitable for the purposes of the present investigation. Although pyrite is typical for certain samples only, because of its low resistance during heat treatment, it does not present in the pottery heavy mineral fraction. Another direction of the application of the HMF minerals during archaeological research is their application for identification of different events. Such example is the enrichment with limonite and hematite from specimens of ASL, floor cover mortar and fillis from the wall structure and the significant presence of finegrained specularite in the samples from ASL within the site on which fire marks are determined. It is presumed that such enrichment is connected to oxidational alteration of the iron bearing materials in result of cataclysm (for ex. fire) or regular anthropogenic activity inside the structure. From the off-ste sedimentary samples, increased contents of hematite have only these in which significant pyrite contents is established (f. e. samples AT-709 and 719) where most likely the hematite is oxidational product of pyrite. In support of such a claim is the similarity of the mineral contents of the heavy mineral fraction from samples of ASL from within the site with the samples from off-site sediments (f. e. samples АТ-713, 714, 717 and 718), and compared to those from inside the site, where there are no fire marks. The results received during this study gave explicit enough evidence for the wide use of local materials (from the vicinity of the site) for pottery production. These are mostly sediments from the site area, from the nearby region and sediments from the river valleys of Kroumovka and Kesibir Rivers, immediately to the West of the town of Kroumovgrad. The most numerous group of fragments (81 samples) are from pottery made of raw materials that can be found within the site, near the site or in the region to the West of the town of Kroumovgard – samples from group АТ-1 and АТ-2. In that group are established both fine and coarse pottery. On basis of pottery dating it can be accepted that the use of materials for pottery production from these areas has continued over the whole period of the existence of the site – from the Late Bronze Age (established by five pottery samples) to the Late Iron Age with maximum during the Early Iron Age. The pottery fragments from this period are 54% of all the sherds in the group, while the fragments from the Late Iron Age are twice less. In confirmation of the above mentioned, are data for the contents of the unaltered by heating part from the magnetic HMF for a greater part in the ceramics from that group where homogenous magnetite grains can be find, and those with hematite, ilmenite or ulvıspinel exsolutions are present in a subordinate quantity. According to Grigsby (1990) such composition of the mineral contents of HMF is typical mainly for medium-acidic volcanic materials. The sedimentary specimens where the presence of this type of exsolutions of magnetite grains is established are situated in the lower part of the Southern and Eastern slope of Ada Tepe.

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The limited geographical area of the sediments in the composition of which are present magnetic detritus grains with such type of exsolutions is a very useful indicator for determination of the origin of materials used for pottery preparing. Such exsolutions in magnetite are established in 29 pottery fragments, mainly from АТ-1, АТ-2 and К groups, mainly from the Early Iron and Iron Age. Much more limited is the presence of Late Iron Age pottery in the groups therefore it is accepted that the used material derives from another area – the fossil-bearing group F and alluvial groups “Kesibir” and “Kroumovka” (respectively A-1 and А-2). The data from the pottery group F shows that the sources of material (sediments) for production of that group, were probably used only in the Early Iron Age.

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