Archaeometric Characterization of Byzantine Pottery from Păcuiul Lui Soare Roxana Bugoi1* , Cristina Talmaţchi2, Constantin Haitaˇ3 and Daniele Ceccato4,5

Bugoi et al. Herit Sci (2019) 7:55 https://doi.org/10.1186/s40494-019-0298-2

RESEARCH ARTICLE Open Access Archaeometric characterization of Byzantine pottery from Păcuiul lui Soare Roxana Bugoi1* , Cristina Talmaţchi2, Constantin Haitaˇ3 and Daniele Ceccato4,5

Abstract Archaeometric investigations using OM (optical microscopy) and micro-PIXE (particle induced X-ray emission) were performed on 45 ceramic shards unearthed in archaeological excavations at Păcuiul lui Soare (southeastern Romania) and dated to the eleventh century AD. This study aimed to get clues about the raw materials and manufacturing techniques used by the potters from the Lower Danube area during the Byzantine period. The analyzed ceramic fragments were selected according to stylistic and archaeological criteria, trying to cover the entire palette of potteries discovered at this site. OM detailed the characteristics of the fabric (texture, microstructure and porosity), mineralogy, surface treatments and fring of the shards. Principal component analysis (PCA) of the PIXE data highlighted two main categories of shards with distinct compositional signatures, separated mainly by their aluminum and calcium content. Micro-PIXE maps of the interfaces between the glaze and the ceramic body showed that the green glaze is rich in lead oxide compared to the underlying ceramic body. The results of these investigations were compared to the ones previously obtained on coeval potteries from other Byzantine archaeological sites, i.e. Hârşova and Oltina, trying to get some hints about the consumption and circulation of pottery in the Lower Danube region at the beginning of the second millennium AD. Keywords: Byzantine, Ceramic, Păcuiul lui Soare, Micro-PIXE, Optical microscopy, Lead glaze

Introduction secure archaeological contexts; all of them were dated to Archaeometric investigations of Byzantine ceramics the eleventh century AD according to stratigraphic and are relatively scant, only the recent years witnessing an typological criteria. Te selected fragments can be con- increase in the number of the publications on this topic sidered as representative for all the ceramic fnds discov- [1–6 and references therein]. Tis statement also applies ered until now at this archaeological site. for the Byzantine pottery excavated on nowadays Roma- Trough this study, we try to answer the following nia’s territory [7–9]. questions: Are there any potteries diferent from the ones Until now, the studies dedicated to the ceramic trade positively identifed as local products on archaeological in Dobrudja were exclusively based on stylistic analo- grounds? Can we identify the ceramic vessels supposedly gies between similar fnds discovered at diferent sites imported to Păcuiul lui Soare based on mineralogical and [10–13]; however, these publications do not contain any chemical criteria Can we get any information about the analytical data. techniques and resources employed to manufacture these Tis research was conducted on an assemblage of 45 utilitarian products? ceramic shards excavated at the fortress from Păcuiul To reach these goals, OM was used to describe the fab- lui Soare (see Fig. 1) located on the eponymous island on ric and the mineralogy of the selected ceramic fragments, the Danube river (see Fig. 2). Te shards were found in while PIXE provided the compositional characterization of the shards. Te analytical information was used to get some hints about the raw materials and manufacturing *Correspondence: [email protected] techniques, trying to verify if the stylistic and typologi- 1 Horia Hulubei National Institute for Nuclear Physics and Engineering, cal diferences between the shards are also refected by 30 Reactorului Street, 077125 Maˇgurele, Romania Full list of author information is available at the end of the article distinctive morphological and physico-chemical features.

© The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Bugoi et al. Herit Sci (2019) 7:55 Page 2 of 16

Te ceramic material analyzed in this study comes from sealed contexts, as well as from the occupation layer. Te analyzed shards were dated between 1001 and 1094 AD. Tere are strong archaeological evidences indicating that ceramic vessels were produced at Păcuiul lui Soare during the frst half of the eleventh century AD. Tus, during the 1973 excavation campaign, a pottery kiln was discovered inside the fortress, close to the northern gate [17]—see Fig. 2. Inside this kiln, some ceramic vessels in fragmentary state and some refuses were found, suggesting that pots and cauldrons were produced here. In the flling of the access pit of the kiln, several amphorae fragments were also discovered. Te fnding of the amphorae shards nearby the kiln, as well as the discovery in 1971 of a bronze stamp for marking amphorae suggest the Fig. 1 Map showing the location of Păcuiul lui Soare, the production of this type of potteries at Păcuiul lui Soare archaeological site where the shards analyzed in this study were excavated. For comparison, Hârșova and Oltina are also indicated alongside with other types of vessels [18].

Materials and methods Materials Tis study is a stage of an ongoing archaeometric pro- To answer the above-mentioned questions, a set of 45 ject targeting the systematic multidisciplinary charac- ceramic shards excavated at Păcuiul lui Soare were terization of Byzantine ceramic dated to the eighth to selected for this archaeometric study; they are consid- twelfth centuries AD excavated in Dobrudja, the histori- ered representative for all potteries discovered until now cal province located in the south-eastern part of Romania at this site. Te ceramic fragments derived from diferent between Danube and the Black Sea—see Fig. 1. Based on types of vessels, being either manufactured from com- this information, this project attempts to produce analyt- mon clay or from “kaolinitic” clays, with fne or coarse ical evidences for the commercial exchanges between the paste, covered with olive-green glaze, golden engobe or centers from the Lower Danube region during the Byzan- with incised decorations, painted or not, originating from tine ruling. cooking or storage vessels, etc. In particular, the studied shards are fragments of cauldrons, jugs, pots with or Historical and archaeological background without handles, bowls, amphorae, and rush lights. For a Te fortress from Păcuiul lui Soare was raised by the more detailed description of the ceramic samples under Byzantines during the second half of the tenth century scrutiny, the reader is referred to Table 1 and Fig. 3. AD. Established as a naval basis [14], the fortress played Glazed shards represent 5% of the overall ceramics an important role in controlling the navigation on the fnds excavated until now at Păcuiul lui Soare. Te glaze Danube and protecting Dorostolon, the capital of the is olive-green, with hues varying from light to dark olive- Byzantine Teme Dristra/Paradunavon—nowadays Sil- green, sometimes with reddish refections. Te glaze istra. During the eleventh century AD, Păcuiul lui Soare is matte or shiny, being either uniformly or unevenly lost its military importance and turned into a civilian set- applied, mostly on the outer surface of the vessels. In tlement [15]. In 1094, a Cuman attack practically stopped most cases, the glaze was well preserved. Shard P2 from the habitation of the site for more than 100 years [16]. Fig. 3 is covered with a shining glaze without any exfo- Păcuiul lui Soare was situated on a well-known com- liation. However, the glaze is lacking from several small mercial route of the epoch, namely the Danube river, that zones of this shard. Tis partial absence of the external connects Central Europe with the Black Sea and the Mid- decoration is not an efect of the burial, but it can be dle East. Tis special location made Păcuiul lui Soare a explained by the fact that the glaze was not uniformly powerful commercial center during the eleventh century applied on the entire surface of the vessel, suggesting a AD. Commodities from Europe, Central Asia and Middle less careful manufacturing process. East arrived at this point, as demonstrated by the impres- An important category of ceramic fnds from Păcuiul sive archaeological discoveries and by the existence of a lui Soare is the one of potteries made of “whitish clays” harbor from which only a 42 m long quay survived until [14], a term cautiously used to describe the shards pre- today [16]. senting the visual characteristics of kaolinitic paste, i.e. Bugoi et al. Herit Sci (2019) 7:55 Page 3 of 16

Fig. 2 Left side—aerial view of the north-eastern part of Păcuiul lui Soare island, on which the part of the fortress still existing today is evidenced (Photo credits: Mircea Stoian); Right side—layout of the surviving Păcuiul lui Soare fortress (after [14], Fig. 3) on which the fnding place of the ceramic kiln is marked with a red dot

light grey, yellow, pale yellow with pinkish white and pink the mineralogical characterization, the thin sections hues and reddish rounded inclusions [19]. were analyzed using an Olympus BX 60 polarizing pet- Due to the fact that they were rare occurrences among rographic microscope at magnifcations varying from the ceramic fnds from Păcuiul lui Soare, it was presumed × 50 to × 500. Te microscopic description was made that the glazed shards and the ones with golden engobe following the guidelines of thin section analysis [20–22], represent imported potteries. based on the textural characteristics (granulometry, sorting, frequency and grain shapes), composition (nature Methods of mineral and organic constituents), microstructure, Optical microscopy porosity, fring and surface treatment [21]. In order to characterize the ceramic paste, the 45 ceramic samples were initially studied with a stereomicroscope PIXE with magnifcations of × 10...× 30. Tis preliminary PIXE measurements were performed on samples investigation showed that all the shards can be classifed extracted from all shards at AN2000 accelerator of into four types of ceramic paste. Subsequently, 15 shards LNL, INFN, Italy, with a 2 MeV proton beam [23], using 2 were selected to prepare thin sections that can be con- macro-beam settings (beam size ~ 3 × 3 mm ) and a sidered representative for the entire batch of 45 ceramic preset charge of 4 μC. Te IGLET-X™ HPGe detector fragments. To detail the types of paste and to perform from ORTEC® used for X-rays detection was covered Bugoi et al. Herit Sci (2019) 7:55 Page 4 of 16

Table 1 Archaeological description of the ceramic samples analyzed in this study Sample ID Type of clay Vessel External surface decoration OM type PCA group (archaeological criteria)

P1 Common clay Jug Olive-green glaze III II P2 Common clay Jug Olive-green glaze III II P3 Common clay Jug Olive-green glaze III II P4 Common clay Jug Olive-green glaze III II P5 Common clay Jug Olive-green glaze II II P6 Common clay Cup Olive-green glaze III II P7 Common clay Jug Olive-green glaze III II P8 Common clay Jug Golden micaceous engobe II II P9 Common clay Jug Golden micaceous engobe II II P10 Common clay Jug Golden micaceous engobe II II P11 Common clay Jug Golden micaceous engobe II II P12 Common clay Spheroidal amphora Bright yellow engobe II II P13 Common clay Spheroidal amphora Yellow cream engobe II II P14 Common clay Spheroidal amphora II I P15 Kaolinitic clay Bowl Red paint lines I I P16 Kaolinitic clay Bowl I I P17 Kaolinitic clay Bowl I I P18 Kaolinitic clay Pot I I P19 Kaolinitic clay Pot I I P20 Kaolinitic clay Pot I I P21 Kaolinitic clay Bowl I I P22 Kaolinitic clay Cauldron I I P23 Kaolinitic clay Pot I I P24 Kaolinitic clay Pot I I P25 Kaolinitic clay Pot I I P26 Kaolinitic clay Pot I I P27 Kaolinitic clay Pot I I P28 Kaolinitic clay Pot I I P29 Kaolinitic clay Pot I I P30 Kaolinitic clay Pot I I P31 Common clay Jug II II P32 Common clay Cauldron II II P33 Common clay Cauldron IV II P34 Common clay Rush-light IV II P35 Common clay Pot? IV II P36 Common clay Pot? III II P37 Common clay Pot IV II P38 Common clay Pot IV I P39 Common clay Pot III II P40 Common clay Pot IV II P41 Common clay Pot II II P42 Kaolinitic clay Pot I II P43 Common clay Pot? II II P44 Common clay Storage vessel II II P45 Common clay Storage vessel II II

The paste types resulting from OM, as well as the compositional categories resulting from PCA of the PIXE data are also in indicated in the last two columns Bugoi et al. Herit Sci (2019) 7:55 Page 5 of 16

Fig. 3 Photos of some ceramic fnds from Păcuiul lui Soare

with a 100 μm thick Al funny flter (0.7%) that enabled Basalt BHVO-2 Certifed Reference Material (CRM) the reduction of the intense peaks of low-Z elements in was used to assess the accuracy of the quantitative the characteristic X-ray spectra. An example of a PIXE results. Te overall uncertainties were estimated to spectrum is given in Fig. 4. around 5% for the major elements, varying from 10% up Using an agate mortar, small ceramic fragments to 30% for the minor elements and trace-elements. broken from each shard were transformed into pow- Te detection limits of the employed experimental ders that were subsequently pelletized. Te interfaces set-up for a ceramic target are given in Table 2, while between the glaze layers and the underlying ceramic the results of the PIXE analyses—chemical composition bodies were measured with the micro-beam (beam size of the ceramic body and green glaze—are presented in 2 2 ~ 4 × 4 μm ), by scanning 750 × 750 μm areas on the Tables 3 and 4, respectively. shards as such. To obtain the glaze composition, small zones on the decorated surface of shards were bom- barded with the proton beam without any preparation. Results and discussion To obtain quantitative results, PIXE spectra were Results treated with GUPIXWIN software (version 2.2.4) [24], Optical microscopy considering all the detected elements (Mg, Al, Si, P, S, Using OM, four main types of ceramic paste were iden- Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, tifed for the Păcuiul lui Soare shards. Teir description Pb, Sb) as oxides (except for Cl), and normalizing the is given in the lines below; their assignation to a certain concentrations to 100 mass%. type of paste is summarized in Table 1. Bugoi et al. Herit Sci (2019) 7:55 Page 6 of 16

Fig. 4 PIXE spectrum of sample P31

Table 2 Detection limits (expressed in ppm) I. Fine paste with silty clay matrix, oriented micro- of the employed experimental set-up for a ceramic matrix structure and micro-fssures: P15, P16, P17, P18, Oxide/element DL (ppm) P19, P20, P21, P22, P23, P24, P25, P26, P27, P28, P29, P30, P42. MgO 740 Al2O3 435 Fine, homogeneous paste with fne silty clay matrix SiO2 250 with rare (5–10%) silt grains, 10–50 μm, and more P2O5 550 frequent (10–15%) fne sand grains, 100–250 μm, SO3 445 rarely medium sand, 300–500 μm, and accidental Cl 77 coarse grains, 1.0–1.4 mm; mono- and polycrys- K2O 50 talline (for coarse sand fraction) quartz and feld- CaO 190 spar, frequent amorphous ferruginous stains and TiO2 55 concretions, 10–30 μm, and rarely (1–2%) much Cr2O3 40 larger, i.e. 100–300 μm. Low porosity (5–15%), MnO 30 with fne isolated pores, 100–300 μm, and more Fe2O3 65 frequent micro-fssures, 0.5–3.0 mm. Te clay is NiO 15 birefringent, the sand grains are sub-rounded and CuO 13 rounded, being intentionally added to the silty clay ZnO 7 matrix. Tis paste shows a good to moderate sort- Ga2O3 7 ing; mica fakes are absent (Fig. 5a). Tese vessels Rb2O 11 were fred in oxidizing conditions, complete or SrO 7 incomplete (“banded” structure). In some cases, Y2O3 17 secondary fring is present, as some of these shards ZrO2 28 were fragments of cooking pots or because some PbO 25 fragments were discovered in burned dwellings. Bugoi et al. Herit Sci (2019) 7:55 Page 7 of 16 84 919 910 637 864 339 912 524 640 980 941 725 337 122 351 180 141 326 225 327 206 252 627 318 120 304 180 255 MnO (ppm) 3742 1277 1057 1335 1074 1026 1158 O (ppm) 0 2 85 93 Cr 216 311 224 183 165 224 454 208 168 158 274 160 215 160 463 399 124 118 204 153 217 266 146 118 149 225 163 122 184 241 176 166 (mass%) 2 TiO 0.9 1.0 0.9 0.9 0.8 0.9 0.6 1.0 0.7 1.0 0.9 1.0 1.0 0.9 1.1 1.0 1.0 1.1 1.0 1.1 1.1 1.3 1.1 1.3 1.7 1.2 1.2 1.4 1.3 1.3 1.2 1.3 1.3 1.2 1.1 CaO (mass%) CaO 2.5 1.3 3.3 5.7 2.8 1.4 3.7 1.3 0.8 2.6 3.3 6.3 6.8 8.7 6.9 7.9 7.0 0.8 0.5 0.7 0.6 1.7 1.2 0.8 1.0 1.1 1.3 0.6 1.1 1.2 0.5 0.6 1.2 1.6 2.3 O (mass%) 2 K 2.5 3.1 3.2 2.9 2.5 2.4 4.6 2.9 4.5 2.8 3.1 3.4 2.9 2.8 3.1 3.2 3.7 1.3 2.2 1.3 1.4 1.6 1.4 1.3 1.7 1.3 1.2 1.4 1.3 1.7 1.8 1.3 1.0 1.3 3.0 0 0 0 0 0 0 0 0 0 0 0 0 0 244 179 266 209 189 571 283 395 505 176 179 702 226 746 217 927 270 106 308 202 320 Cl (ppm) Cl 1276 (ppm) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 935 922 784 593 521 837 697 885 867 727 684 SO 1556 2506 1088 (mass%) 5 O 2 P 0 0.4 0.5 0.9 0.5 0.4 0.3 0.0 0.2 0.5 0.4 0.4 0.6 0.7 1.0 0.4 0.5 0.5 0.1 0.4 0.1 0.2 0.5 0.6 0.5 0.3 0.6 0.2 0.4 0.9 0.1 0.3 0.5 0.6 2.5 (mass%) 2 66.3 67.9 64.2 SiO 63.7 70.2 70.9 61.9 69.4 63.8 67.5 65.4 58.0 63.3 63.7 60.8 57.2 58.1 69.8 68.3 69.6 71.2 62.0 65.7 59.2 63.0 67.3 67.3 69.4 55.7 61.9 68.5 64.2 60.3 65.1 63.4 (mass%) 3 O 2 18.4 18.3 Al 17.9 17.1 15.0 16.8 17.2 17.5 17.4 17.3 18.2 19.8 17.1 16.2 17.6 18.1 18.2 23.2 25.0 23.5 22.5 26.0 26.6 28.6 22.9 24.0 24.6 22.7 28.6 26.7 21.3 26.2 27.4 24.5 17.3 Chemical composition data determined by PIXE determined data Chemical composition for ceramic in mass% body expressed for major and minor and ppm elements means for traces (“0” 2.7 2.0 MgO (mass%) 2.9 2.7 2.7 2.0 3.1 2.4 3.2 2.2 2.6 3.6 2.6 1.9 3.2 4.9 4.3 1.1 0.9 1.2 1.2 1.3 1.1 0.9 1.2 1.0 1.1 1.3 1.1 1.0 1.3 1.3 1.1 1.1 1.9 3 Table below the detection limits) P1 P2 P32 P3 P33 P4 P34 P5 P35 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 P29 P30 P31 Bugoi et al. Herit Sci (2019) 7:55 Page 8 of 16 0 0 0 0 0 55 86 54 43 21 27 27 31 40 33 51 50 249 484 107 888 415 993 PbO (ppm) PbO 2645 1628 1102 3918 MnO (ppm) 1145 1353 1125 1702 1342 O (ppm) (ppm) 2 2 0 Cr 237 229 201 208 239 152 291 246 234 232 314 400 307 243 180 456 171 300 276 195 141 279 271 276 269 168 469 317 313 584 576 ZrO (mass%) 2 (ppm) 3 TiO 0.9 0.9 1.0 1.0 0.8 1.0 0.8 0.6 1.0 1.1 O 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Y 57 39 58 37 29 36 50 34 CaO (mass%) CaO 5.5 4.6 1.2 4.9 4.2 3.9 3.9 3.2 1.5 1.7 47 86 51 57 69 97 SrO (ppm) 164 110 173 109 125 156 148 179 209 341 268 214 180 111 154 118 O (mass%) 2 O (ppm) K 5.8 2.9 1.1 3.1 2.7 3.1 2.7 3.9 3.5 3.3 2 0 90 84 84 62 69 73 57 37 40 80 Rb 147 103 124 113 144 160 124 153 121 135 105 0 0 610 292 248 444 381 835 234 Cl (ppm) Cl 2754 (ppm) 3 O 2 0 0 0 Ga 27 32 24 23 23 21 17 26 31 28 33 32 26 31 26 45 29 53 49 (ppm) 0 0 0 0 3 810 2739 SO 1196 1291 1206 1481 93 57 35 47 39 53 73 36 65 (mass%) ZnO (ppm) 109 106 164 112 100 132 220 136 106 179 146 144 115 5 O 2 P 0.7 1.3 0.7 1.0 1.0 0.9 0.6 0.6 0.5 0.6 0 0 0 0 (mass%) CuO (ppm) CuO 25 49 33 43 46 47 29 38 34 58 64 14 13 13 23 16 36 21 2 60.6 SiO 63.8 65.0 63.8 58.7 59.7 62.7 59.5 61.9 65.4 91 59 89 59 59 78 61 67 67 26 19 12 20 18 35 21 39 23 NiO (ppm) 152 110 254 216 (mass%) 3 O 2 Al 16.8 17.1 24.7 16.9 19.7 18.6 18.8 17.1 19.3 17.3 (mass%) 3 O 2 5.6 5.7 5.5 4.8 5.2 5.2 5.7 7.1 5.3 4.5 5.9 7.1 7.0 5.7 1.8 1.9 2.0 1.9 7.1 2.3 7.8 3.4 Fe (continued) MgO (mass%) 2.2 2.5 1.6 2.5 6.2 2.9 3.8 5.3 3.7 1.9 3 Table P36 P1 P37 P38 P2 P39 P40 P3 P41 P42 P4 P43 P5 P44 P45 P6 P7 P8 P9 P10 P11 P12 P13 P18 P17 P16 P15 P14 P20 P19 P21 P22 Bugoi et al. Herit Sci (2019) 7:55 Page 9 of 16 0 35 36 38 54 40 51 30 42 58 90 36 50 55 59 49 63 96 106 101 104 180 160 PbO (ppm) PbO (ppm) 2 94 357 470 420 354 383 452 437 455 260 330 342 102 492 354 401 454 217 257 350 121 544 ZrO 1713 (ppm) 3 O 2 0 0 0 0 0 Y 25 62 36 36 58 28 27 53 53 36 45 35 56 46 29 45 53 85 69 SrO (ppm) 101 106 193 157 196 166 172 312 244 202 144 139 229 363 100 304 203 356 200 191 201 195 O (ppm) 2 61 55 68 82 59 65 63 Rb 100 124 121 174 124 199 238 237 154 138 177 232 178 287 189 200 (ppm) 3 O 2 32 Ga 47 54 40 45 45 42 34 30 28 23 33 32 29 24 55 29 46 31 57 59 40 37 58 65 96 77 75 80 60 61 ZnO (ppm) 119 209 166 142 172 192 250 182 168 200 251 200 201 201 488 0 CuO (ppm) CuO 29 26 28 31 17 26 26 60 52 39 35 47 82 64 72 54 86 75 92 71 91 57 0 0 28 36 41 42 33 37 37 57 74 89 87 84 88 58 78 58 42 NiO (ppm) 110 100 166 107 (mass%) 3 O 2 2.3 2.8 5.1 5.1 4.5 7.0 4.4 8.0 6.7 5.3 8.4 9.1 6.9 6.5 4.5 6.4 6.3 9.5 6.2 9.2 7.8 8.3 Fe 10.3 (continued) 3 Table 2 Table the detection limits—see in the table means below values “0” 100%; to normalized Results were P23 P24 P25 P26 P27 P28 P29 P30 P31 P32 P33 P34 P35 P36 P37 P38 P39 P40 P41 P42 P43 P44 P45 Bugoi et al. Herit Sci (2019) 7:55 Page 10 of 16 60.6 65.9 50.4 65.3 65.4 75.7 65.4 PbO PbO (mass%)

5 O 2 0 0 0 0 0 0.6 1.3 Sb (mass%) 0 87 190 123 506 162 140 ZnO (ppm) 759 443 537 596 4059 1127 1351 CuO CuO (ppm) 1745 1974 1548 1855 1894 2228 1847 NiO (ppm)

3 O 2 2.5 1.7 1.9 2.1 2.2 3.2 2.5 Fe (mass%) 0 0 0 238 633 451 456 MnO (ppm)

2 0.3 0.2 0.3 0.4 0.2 0.3 0.3 TiO (mass%) 2.3 1.1 2.1 3.4 0.9 1.9 12.8 CaO CaO (mass%) O 2 1.2 1.5 1.3 1.2 0.6 0.5 0.5 (mass%) K

2 24.8 24.0 25.3 23.0 20.3 12.5 20.4 (mass%) SiO

3 O 2 6.5 4.4 5.5 4.8 4.8 3.6 5.7 Al (mass%) Chemical composition data determined by PIXE determined data Chemical composition for the green in mass% expressed glaze for major and minor and ppm elements means for traces (“0” 4 1.1 0.7 1.6 0.8 2.2 1.1 1.4 MgO (mass%) P7 P6 P5 P4 P3 P2 P1 Table below the detection limits) 2 Table the detection limits—see in the table means below values “0” 100%; to normalized Results were Bugoi et al. Herit Sci (2019) 7:55 Page 11 of 16

Fig. 5 OM micrographs of thin sections considered as representative for the main paste types. All images are in cross polarized light. a Fine silty clay oriented paste, with medium sand grains of quartz and feldspar (scale bar: 200 μm). b Fine silty porphyritic paste, with fne sand grains and muscovite fakes (scale bar: 200 μm). c Fine carbonate porphyritic paste, with fne sand grains and muscovite fakes (scale bar: 200 μm). d Medium granular porphyritic paste, with fne muscovite fakes and medium to coarse sand grains (scale bar: 200 μm)

II. Fine silty paste with porphyritic microstructure: III. Fine carbonate paste with porphyritic microstruc- P5, P8, P9, P10, P11, P12, P13, P14, P31, P32, P41, ture: P1, P2, P3, P4, P6, P7, P36, P39. P43, P44, P45. Fine, homogeneous paste with fne carbonate Fine, homogeneous paste with fne grained silty matrix, with frequent (10–15%) fne silty grains, matrix, well sorted, with frequent (15–25%) grains 10–50 μm, rare fne sand, 50–200 μm, and very of fne sand; mono- and polycrystalline quartz and rare (2–3%) medium to coarse sand grains, 400– feldspar, 50–100 μm, rarely 150–200 μm and fre- 750 μm; sand fraction with mono- and polycrys- quent mica (predominant muscovite), 50–200 μm, talline quartz and feldspars, rare (5%) fne fakes of frequent fne vegetal debris, 20–150 μm, ferrugi- mica, 50–150 μm, rare calcite grains, 100–200 μm nous stains and concretions, 50–150 μm, rare fne and opaque grains, 50–100 μm (Fig. 5c). Tis carbonate grains, 100–400 μm, and accidental shell paste includes areas of calcite recrystallization on fragments. Fine porosity (5–10%), with frequent voids and fne cracks. Low porosity (5–10%), with isolated and rounded voids, 50–200 μm, very rarely fne circular voids, 50–300 μm, and rare mm-size up to 1 mm. Rare elongated voids originating from micro-fssures are visible. Tis paste was made vegetal temper are present. Tis paste was most from carbonated sediments (unconsolidated marl probably made from alluvial sediments, well sorted type), featuring a well-sorted matrix, with possible silt with fne sand and clay; sand grains are sub- mixture of fne sand with medium to coarse sand rounded and rounded (Fig. 5b). Tese shards were grains, that are generally sub-rounded and rounded. fred in complete or incomplete (with dark organic Te shards were fred in oxidizing conditions, fea- “core”) oxidizing conditions. turing a banded structure and an organic “core”. Bugoi et al. Herit Sci (2019) 7:55 Page 12 of 16

IV. Medium granular paste with porphyritic micro- oriented and birefringent clay, possibly kaolinitic, such as structure: P33, P34, P35, P37, P38, P40. the one identifed in the two aforementioned sites. Semi-fne, homogeneous paste, with silty clay with Te silty paste with porphyritic structure (type II) fne sand matrix, moderately to poorly sorted; rare is made of fne alluvial sediments. As in the other two silty grains (5%), 20–50 μm, and frequent very fne archaeological sites studied until now (Hârşova and Olt- sand (10–20%), 50–200 μm. It includes rare coarse ina) this is indicated by the good sorting of the sedimen- sand grains (1–5%), 500–1500 μm. Tis paste is tary matrix, the presence of the vegetal debris (partially similar with the fne silty paste (type II), with fre- decayed fragments of wood), and accidentally, of the shell quent fne mica fakes, 50–200 μm, but with fre- fragments. quent quartz and quartzite sand inclusions, with Te fne carbonate paste (type III) is most probably heterogeneous appearance (Fig. 5d). Fine poros- made of fne alluvial sediments deposited in low energy ity, 10–15%, isolated voids, 50–200 μm, circu- sedimentary environments, such as marshy areas or lar and elongated, irregular, and micro-fssures, lakes. 100–300 μm, rarely 0.5–1.5 mm. Te sand grains Te medium granular paste (type IV) is made of silty are sub-angular, sub-rounded and rounded. Tese fne sands with clay, very probably alluvial, mixed with shards were fred in reducing conditions, with an coarse alluvial sands with variable granulometry. organic “core”, being oxidized at the exterior. PIXE Te four main types of ceramic paste identifed for the To get a clear picture about the possible grouping of the ceramic fragments from Păcuiul lui Soare are similar to ceramic shards according to their composition, taking the ones evidenced for the coeval potteries discovered in into account the relatively large number of samples and the nearby archaeological sites Hârșova and Oltina that variables, PCA (Principal Components Analysis) of the were previously analysed in the frame of the on-going standardized PIXE data—Mg, Al, K, Ca, Ti, Cr, Fe, Ni, project mentioned in “Introduction” section [7, 8]. Cu, Zn, Ga, Rb, Sr and Zr oxides—was performed using Te fne paste with silty clay matrix (type I) is made STATISTICA software (version 8.0). Figure 6 shows the from a mixture of sediments, silty clay and fne sand, with result of this analysis indicating the separation of the

Fig. 6 Bi-plot of the frst and second principal components—PCA performed on standardized oxide concentrations for Mg, Al, K, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Ga, Rb, Sr and Zr—PIXE data for the ceramic paste Bugoi et al. Herit Sci (2019) 7:55 Page 13 of 16

analyzed samples into two main compositional groups. layers. A clear change in the chemical composition A column in Table 1 also indicates to which of these two were observed for this type of decoration characterized groups each sample belongs. by a large lead content (~ 64.4 mass% PbO on average, One of these groups (conventionally indicated with PbO content ranging from 50.4 to 76.8 mass%) com- “I” in Fig. 6) is made out of 18 samples with relatively pared to the ceramic body (~ 0.1 mass% PbO on aver- high Al2O3 (~ 24.9 mass% on average) and low CaO age)—see Fig. 7 and Tables 3 and 4. (~ 1.0 mass% on average) contents. Tis frst group sep- Tere are two ways of producing a Pb glazing: either arates quite well from the rest of the other 27 ceramic by applying a Pb compound (e.g. litharge) as a sus- fragments that cluster in a second group (marked with pension in water or by applying a mixture of PbO and “II” in the same fgure), regardless of their characteristics quartz. In the former case, the glaze forms through (decoration, granulation, fring etc.). Tis second group direct reaction of PbO with the clay body; in the lat- is characterized by relatively low Al 2O3 (~ 17.7 mass% ter, the two components of the suspension react dur- on average) and high CaO (~ 4.0 mass% on average) con- ing fring, form a glaze that interacts with the body, and centrations. As also visible from the loading plots shown certain chemical elements (Al, Ca, Fe, Na, Mg) difuse in Fig. 6, the higher contents of Al are correlated with from the body into the glaze. Tese two glazing meth- higher concentrations of Ti (group I), while the higher ods can be distinguished by subtracting the PbO con- contents of Ca are correlated with higher concentrations tent from the glaze composition and renormalizing of Mg, K and Sr (group II). the recipe to 100% and subsequently comparing this Te frst compositional group superposes relatively adjusted glaze composition with the one of the body well with type I resulting from the petrographic analysis, [25–27]. Figure 8 shows that the Al2O3 content in the except for sample P14 (containing 23.2 mass% Al2O3), recast glaze composition is roughly the same as in the attributed to type II from OM and sample P38 (with corresponding ceramic body, indicating that glazing 24.6 mass% Al2O3) that belongs to type IV resulting from was made through the application of lead oxide onto a OM. Other discrepancy appears in the case of sample non-calcareous ceramic body. P42 (18.8 mass% Al 2O3) that belongs to type I resulting Te micro-PIXE Pb Lα maps were used to estimate the from OM, and, at the same time, pertains to compo- thickness of the green glaze layer that turned out to range sitional cluster II, the one made out of the low-Al sam- from 50 μm up to 300 μm. Some shards feature decora- ples. Explanations for these discrepancies are still sought, tive layers with variable thickness. but in any case, there seems to be a pattern that can be Relatively small amounts of CuO (~ 1270 ppm on aver- recognized from the analysis of the data obtained using age) were found in the green glaze—see Table 4. Te most these two diferent analytical techniques. Tus, paste I likely explanation for the olive-green hues of the glaze is resulting from OM superposes quite well with the sam- that they were induced by iron ions in reducing state [3, 4, ples attributed to group I resulting from PCA; more or 26, 28]. It must be mentioned here that certain amounts less, this refects the use of a distinct type of clay that of Sb were determined in the composition of the green was chosen on purpose—most likely, to obtain vessels glaze covering samples P1 and P2—see Table 4. How- with diferent properties. On the other hand, the samples ever, these particular two samples do not exhibit yellow belonging to group II resulting from the PCA of PIXE hues, color that might have resulted from the presence of data correspond to three types of paste (II, III and IV) lead antimonate [3]; they are also olive-green, similar to revealed by OM. Te most plausible explanation for this the other fve glazed samples analyzed in this study. Te fnding is that the shards belonging to these groups con- relatively small amounts of Sb from these two particular tain more or less the same minerals/compounds, hence samples did not lead to any change in the appearance/col- the compositional similarity of the pellets (see also PIXE oring of their decorations. A possible explanation for the section). Te diferences between types II, III and IV of presence of Sb in the glaze is that this chemical element is paste mainly consist in textural parameters, homogeneity a contaminant of the raw materials employed for making and porosity, etc., and do not result from geochemistry. the glaze (in particular, of the lead compound). A similar sub-division of potteries into two large Te micro-PIXE scans of the interfaces did not pro- groups, mainly separated by their Al and Ca contents, vide any hint about what causes the shining of the golden was also evidenced in the case of previously analyzed engobe. However, the explanation was provided by OM: coeval ceramics from Hârșova and Oltina [7, 8]. fne fakes of muscovite embedded in the slip produce the Micro-PIXE scans of the interfaces between the deco- glittering golden shine of these shards. Tis decoration is rated surfaces and the ceramic bodies were performed the result of a diferent preparation manner and it did not to identify the compound(s) responsible for the green imply the use of other raw materials. glaze, as well as to estimate the thickness of these Bugoi et al. Herit Sci (2019) 7:55 Page 14 of 16

Fig. 7 Micro-PIXE Pb L map (750 750 μm2) on glazed ceramic fragment no. 1—scan of a small area on the interface between the green glaze α × decoration and the underlying ceramic body

above-mentioned deposits, marly clays of Barremian age, sands and clays of Albian age, Ypresian clayey sands, quartz sands and clays of Tortonian age, greenish and brown clays and diatomites of Sarmatian age, gray and yellowish ferruginous sands, of the Dacian, and Levan- tine quartz sands with red sands intercalations can be encountered [29]. Summarizing, Southern Dobrudja region ofers a wide range of raw materials that can be used for pottery making. Te archaeometric analyses indicated that the Byzan- tine craftsmen from Păcuiul lui Soare chose in a natural way local sedimentary clays to produce ceramic vessels. Kaolinitic clays were used in Dobrudja starting from the Roman period, as indicated by the discovery at Castelu of a kiln for pottery making and of some pits con- Fig. 8 Plot of the Al2O3 concentrations in the recast glaze composition and body composition—the points fall relatively close taining ceramic refuses [30]. Kaolinitic clays have been to the bisector, indicating that the glazing was made through the also employed during the Byzantine period from the application of lead oxide onto the ceramic body ninth century AD onwards, but mostly during the tenth to eleventh centuries AD [31]. In Southern Dobrudja, important deposits of kaolinitic clays are known in the area of Medgidia, Cuza Vodă, Satu Discussions Nou, Ţibrinu, and Tortoman, in the Carasu Valley, as well From geological point of view, Păcuiul lui Soare area is as on small tributaries, such as Agi Cabul and Adânca characterized by the presence of Holocene clayey and Valley. Tese deposits are in the form of lenticular layers sandy sediments, terrace deposits and Upper Pleistocene separated by sand layers; this complex of Aptian age is sit- loessoid deposits [29]. uated above a layer of thick sands and below the Sarma- Going south along the main valleys in the South- tian lumachelic limestones [32]. Tese clays are formed ern Dobrudja area, beside consolidated rocks and the by the kaolinisation of detrital feldspathic material in a Bugoi et al. Herit Sci (2019) 7:55 Page 15 of 16

continental-lacustrine sedimentation environment. Te nearby Păcuiul lui Soare. PCA of the PIXE data sin- color of the kaolinitic clay varies greatly from white to gled out two compositionally distinct groups. Te frst yellow, pink, and even bluish, depending on the amount one is made of the shards produced from Al-rich clays, and nature of the impurities (e.g. iron and manganese possibly taken from a relatively nearby location from hydroxides) [32]. Tese deposits are situated on the Dan- Dobrudja. Te geology of the region and the archaeo- ube valley, the closest to Păcuiul lui Soare (approximately logical discoveries indicated a possible source of kao- 50 km away) being the one nearby Cernavodă [33]. linitic clays located approximately 50 km north-east Other kaolinitic clay deposits are encountered as small from Păcuiul lui Soare, source exploited starting with outcrops in the form of lenses on Gîrliţa valley, Oltina the Roman period. Te second compositional group valley and southwest from Rasova, at distances between is composed of shards produced from several types of 12 and 35 km from Păcuiul lui Soare [29]. Tey contain sedimentary raw materials that were locally available— small clay lenses, along with sands, pebbles and quartzitic most likely alluvial deposits of Danube and/or nearby micro-conglomerates, with intercalations of sands and lakes, as suggested by the petrographic data. limestone. However, the use of these deposits for pot- Te Pb-rich green glaze was manufactured through tery making during the Byzantine period remains to be the application of lead oxide onto a non-calcareous clay demonstrated. body, technology often encountered during the Roman Byzantine kaolinitic clay vessels discovered in Dobrudja and the Byzantine periods. Te mica fakes present in are characterized by an increased mechanical resist- the yellow engobe indicate that this type of decoration ance—i.e. it is harder to break them compared to other was produced by covering the vessels with a slip made potteries found at the same archaeological sites. of silty alluvial clay containing muscovite. It seems that the potters from Păcuiul lui Soare knew Te results of this study demonstrated that the elev- about the kaolinitic clay deposits situated some tens of enth century AD pottery from Păcuiul lui Soare, with km from their settlement and they used this type of raw various appearances and playing diferent roles, was materials to make pots with good mechanical resistance. most likely locally manufactured using distinct raw Tus, they could produce vessels not only diferent in materials, preparation and decoration techniques. appearance, as demonstrated by the diferent light hues of Tis research showed a marked similarity between the paste, but mostly with better mechanical properties, the potteries from Păcuiul lui Soare and the ones exca- hence justifying the efort of collecting some raw materi- vated in the nearby Byzantine sites Hârșova and Oltina, als that were not readily available nearby their settlement. indicating that during the eleventh century AD ceramic Shards P1…P7 (the green glazed shards from the stud- manufacturing in Dobrudja involved mostly the use of ied assemblage) and P8…P11 (the ones with golden common local clays, but also of some pure, birefringent engobe) belong to types II and III of paste resulting from (possibly kaolinitic) clays from specifc deposits, that OM analysis, i.e. potteries made from fne alluvial sedi- were prepared using various recipes and techniques. ments. Compositionally, they belong to group II emerg- Te archaeometric characterization performed using ing from PCA. At this stage of research, we do not have OM and PIXE did not provide any argument to suggest any analytical argument to support the idea that these the presence of imported potteries among the analyzed shards represent imported potteries, as they are similar ceramics from Păcuiul lui Soare. in chemical compositional and mineralogy to the ceramic Te data reported in this paper contribute to the vessels that were locally produced from raw materials understanding of the way pottery was made during the available nearby the settlement. eleventh century AD in the Lower Danube region, a topic little tackled until recently, and certainly of inter- Conclusions est for the scholars involved in the study of the Byzan- Tis paper describes the OM and micro-PIXE investiga- tine period. tions on 45 ceramic shards dated to the eleventh century Acknowledgements AD and in discovered in well-defned archaeological con- Leonardo La Torre is gratefully acknowledged for his skilled technical contribu- tion in realizing the LNL experiment. The authors would like to express their texts at Păcuiul lui Soare, Romania, in a trial to identify gratitude to Dr. Oana Damian from Institutul de Arheologie “Vasile Pârvan”, the raw materials and working techniques employed for Bucureşti, for providing the ceramic fragments discovered at Păcuiul lui Soare the manufacturing of these potteries, as well as to check investigated in this study. some provenance hypotheses. Authors’ contributions OM led to the identifcation of four types of pastes, CT initiated this study and selected the archaeological material. CH realized similar to the ones evidenced for the coeval ceram- the OM studies. RB and DC performed the PIXE analyses and interpreted the compositional data. All authors contributed to the discussions of the results. ics from Hârșova and Oltina, two archaeological sites All authors read and approved the fnal manuscript. located on the bank of the Danube River, relatively Bugoi et al. Herit Sci (2019) 7:55 Page 16 of 16

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