Introduction
The period of the second half of the 4th–first half of the 6th century CE, when, according to Chinese dynastic chronicles, the Rouran Khaganate existed on the territory of modern Mongolia, and spread its influence to many nomadic tribes across the vast areas, is still one of the “blank spots” in the history of Central Asia (Barfield Reference Barfield2009, 199–204; Drobyshev Reference Drobyshev2019, 133–142; Golden Reference Golden1992, 76–79; Handsuren Reference Ts and Zoriktuev1993, 66–106; Kradin Reference Kradin2000, 80–94; Kychanov Reference Kychanov2010, 91–95; Sinor Reference Sinor1969, 97–100; Vorobyov Reference Vorobyov1994, 297–303; etc.). This time, which can be referred to as Rouran or pre-Turkic, is of fundamental importance for understanding the complex ethno-cultural and socio-political phenomena of the Great Migration Period (GMP), as well as for the reconstruction of the processes of formation of the early medieval nomadic communities. Archaeological sites that could be securely associated with the Rourans (as well as with other cultures) are virtually absent in the territory of modern Mongolia during this period (Kradin Reference Kradin2007, 147; Savinov Reference Savinov1984, 22). Only in recent decades have isolated burials been investigated that date from the second half of the 4th - first half of the 6th century CE in different parts of Mongolia (see review in Seregin and Matrenin, Reference Seregin2020). These burials have quite likely been left by representatives of the Rouran ethno-political association.
To date, the most representative corpus of well-attributed archaeological sources on the Rouran period originates from the territory of Altai and demonstrates the existence in the region in the second half of the 4th-5th century CE of the polyethnic Bulan-Koby Culture (a culture that spans the 2nd century BCE–5th century CE; Mamadakov 1990; Soenov Reference Soenov1997; Matrenin Reference Matrenin2005; Tishkin Reference Tishkin2007; Seregin and Matrenin Reference Seregin and Matrenin2016). Based on the available published and archival information, the studied complex of sites of this period consists of more than 130 burials (sites of Berel, Verkh-Elanda-II, Verkh-Uymon, Dyalyan, Katanda-I, Kok-Pash, Stepushka, Chendek, Ust-Biyke-III, Yaloman-II; Gavrilova Reference Gavrilova1965; Soenov and Ebel Reference Soenov and Ebel1992; Bobrov et al. Reference Bobrov, Vasjutin and Vasjutin2003; Tishkin and Gorbunov Reference Tishkin and Gorbunov2005; Seregin and Matrenin Reference Seregin and Matrenin2016; Tishkin et al. Reference Tishkin, Matrenin and Shmidt2018), rock paintings (Gorbunov Reference Gorbunov2003, 118), Kosh-Agach iron-melting furnaces (Bogdanov et al. Reference Bogdanov, Murakami, Soloviev, Grishin, Solovyova and Gnezdilova2018; Murakami et al. Reference Murakami, Soenov, Trifanova, Ebel, Bogdanov and Soloviev2019; Vodyasov and Zaitseva, Reference Vodyasov and Zaitseva2020, Reference Vodyasov and Zaitseva2021) and other site types (Kubarev Reference Kubarev2010). Research into these sites shows that dating remains a serious problem in their interpretation, which at the moment is based mainly on the typological analysis of objects, as well as radiocarbon (14C) dating of some individual complexes (Verkh-Uymon, Stepushka, Yaloman-II; Tishkin and Gorbunov Reference Tishkin and Gorbunov2005, 160–161; Tishkin Reference Tishkin2007, 175–179). Despite this, the accumulated data from available and unpublished new sources provides opportunities for detailing the time of appearance of specific sites. In particular, a systematic and detailed chronological study on the materials of the undisturbed burial ground of the Bulan-Koby Culture of Choburak-I in the Northern Altai, which has been completely excavated and contained numerous goods and various organic remains (anthropological and archaeozoological) is critical to understanding the social and chronological dynamics of this culture during the Rouran period (e.g. Seregin et al. Reference Seregin, Tishkin, Matrenin and Parshikova2022). The conclusions from such research would be fundamentally important for detailed chronological interpretation of the monuments of the Rouran period, both in Altai and other regions of Central Asia.
A similar analytical approach has recently been applied to another Altai site of the Bulan-Koby Culture—Karban-1 (Seregin et al. Reference Seregin, Svyatko, Barrett, Demin, Matrenin, Papin and Reimer2023), where compatibility between the newly obtained 14C dates and chronological indicators based on the analysis of artifactual complexes was presented and used to help clarify the chronology of monuments for this period in Altai.
Choburak-I site
The funeral and memorial complex of Choburak-I is located in the Chemalsky District of the Altai Republic, south of the village of Elanda, on the right bank of the Katun River (Figure 1). A distinctive feature of this site is the presence of structures and objects of various chronological periods—from the Eneolithic (Afanasyevo Culture) to the early medieval period (Turk culture). In the northern part of this large complex, a necropolis of the Bulan-Koby Culture was identified, subsequently completely excavated by the Chemal archaeological expedition of Altai State University led by N.N. Seregin. This necropolis consisted of 12 burial mounds (kurgans), tightly arranged in a small area (Figure 2.1). These kurgans contained undisturbed burials, organised according to the ritual practice of what has been referred to as the Dyalyan tradition of the Bulan-Koby culture (a sub-group within the polyethnic Bulan-Koby Culture). These burials typically include a small stone mound with an oval crepidoma, shallow and narrow pit, positioning of the deceased stretched out on their back with their head to the western sector of the horizon with inclination to the north, and the accompanying burial of a horse at the deceased’s legs (Figure 2.2; Matrenin Reference Matrenin2005, 96–97; Seregin and Matrenin Reference Seregin and Matrenin2016, 161–162). Numerous accompanying items were found with the deceased (some of them are shown in Figure 2.3-11), among which various categories of weapons have been identified, as well as human equipment, horse ammunition, tools, household items and jewelry. Anthropological analysis identified seven men, three women, one teenager and a child among the deceased, which was also confirmed by the “typical” composition of the associated grave goods found with the individuals (Seregin and Matrenin Reference Seregin2020, 35–67). The analysed necropolis reflects the existence of a small, but at the same time very uniform, community and probably contains the burials of close relatives (ongoing DNA and anthropological analyses, Svetlana Tur, pers. comm.).
Location map of the Choburak-I archaeological site in the Altai region of Southern Siberia. The map is based on Shchukina (Reference Shchukina2005).
The materials obtained from Choburak-1 turned out to be informative for the implementation of chronological, ethno-cultural and social reconstructions. In particular, traumatic injuries without traces of healing documented on three male skeletons are indicative of armed violence inflicted mainly with a sword (decapitation, cutting off the hand, cut-chopped wounds on the bones), which suggest the involvement of these men in armed conflicts, reflecting the high level of social tension in Altai in the second quarter of the 1st mil. CE, including possible clashes with culturally/ethnically foreign populations (Tur et al. Reference Tur, Matrenin and Soenov2018).
From the available archaeological materials, the historical fate of the local population of the Bulan-Koby Culture, who buried their deceased at the Choburak-I burial ground, was closely connected with the Rouran Khaganate. In the second half of the 4th–beginning of the 5th century CE, being one of the groups bearing the so-called Dyalyan tradition of ritual practices, they became the local elite of the nomadic society of the Northern Altai (Seregin and Matrenin Reference Seregin2020). After the decline of the Rourans and the formation of the First Turkic Khaganate in the middle of the 6th century CE, the Dyalyan population was involved in the migration flow to the west; a manifestation of this can be observed in the appearance in the Eastern European steppes, during the second half of the 6th–7th century CE, of graves with a horse and individual parts of its carcass, laid in long pits with western and northwestern orientation and placed at the legs of the deceased at different levels (Mit’ko Reference Mit’ko2018, 38; Reference Mit’ko2019, 58). Another group of representatives of the Dyalyan tradition resettled in the northern foothills of Altai. This eventually led to the formation of one of the ethnic components, which later took part in the genesis of the Srostkinskaya Culture (second half of the 8th–12th century CE) in the Altai forest-steppe (Seregin et al. in press).
The presence of a variety of material culture, anthropological and archaeozoological remains discovered during the excavations of Choburak-I makes it possible to implement a program of comprehensive dating, including archaeological dating and AMS 14C dating; the results of this program are presented and discussed below. This methodological approach has been previously employed in the analysis of the Karban-1 monument of the Bulan-Koby Culture, also located on the territory of the Altai (Seregin et al. Reference Seregin, Svyatko, Barrett, Demin, Matrenin, Papin and Reimer2023).
Methods and materials
Archaeological dating
For the chronological interpretation of the grave goods from Choburak, we carried out typological analysis, comparing different categories of artifacts with relevant reference analogies from the Early Iron Age and Medieval sites of Central and East Asia (including the cemeteries of the Bulan-Koby Culture). This permitted identification of objects with an established initial period of existence elsewhere in Altai. After that, grading of dated types of objects was carried out, taking into account the previously accepted duration of their use in the region. The more detailed analysis of the objects is presented in Seregin and Matrenin (in press). Chronological indicators are considered to be objects dated sufficiently accurately during the cross-correlation of most abundant materials (Bazhan and Gay Reference Bazhan and Gay1992, 123).
AMS 14C dating and stable isotope analysis
AMS radiocarbon analysis was applied to all twelve excavated burial mounds of the Choburak-I complex. The detailed description of the burials is presented in Appendix 1. Sampling was carried out based on the degree of preservation of anthropological and paleozoological remains in particular burials. As a result, a series of 26 osteological specimens was selected, including 13 humans, 11 horses, and 2 ovicaprids (Table 1). Four samples were taken from burial mound 32 (two from the human and two from the horse) and 34a (two from the human, one from the horse, and one from the sheep), two (human and horse bones) from mounds 30, 31, 31a, 32a, 33, 34, and 38, one (human) from mounds 29 and 29a, and one horse and one ovicaprid from mound 30a. To date, this is a unique series for sites of the late stage of the Bulan-Koby Culture of Northern Altai, and also the most comprehensively radiocarbon dated site for the Rouran period.
AMS 14C dates, calibrated age ranges and stable C and N isotope values of human and animal bone samples from the Bulan-Koby Culture burials of the Choburak-I necropolis. Sex and age determinations for humans were provided by S. Tur
Radiocarbon dating was carried out in the 14CHRONO Centre for Climate, the Environment and Chronology of the Queen’s University Belfast (Northern Ireland). Bone collagen extraction was carried out following the ultrafiltration method (Brown et al. Reference Brown, Nelson, Vogel and Southon1988; Bronk Ramsey et al. Reference Bronk Ramsey, Higham, Bowles and Hedges2004) which included: a) bone demineralization in 2% HCl, followed by MilliQ® ultrapure water wash; b) 0.1M NaOH treatment for 15-30 mins, followed by MilliQ® ultrapure water wash; c) further treatment in 2% HCl for 15-30 mins, MilliQ® ultrapure water wash; d) gelatinization in pH=2 HCl at 58°C for 16 hours; e) filtration, using ceramic filter holders, glass filter flasks and 1.2 µm glass microfiber filters; f) ultrafiltration using Vivaspin® 15S ultrafilters with MWCO 30 kDa; 3000-3500 rpm for 30 min; and g) freeze-drying. The dried collagen was stored in a desiccator. Samples UBA-37792-40779 were combusted at 850°C in closed tubes with an excess of CuO. The CO2 was converted to graphite on an iron catalyst using a zinc reduction method (Slota et al. Reference Slota, Jull, Linick and Toolin1987). The pressed graphite target was then measured by 0.5 MeV National Electrostatics Compact AMS. The other samples were weighed into pre-cleaned tin capsules and combusted in oxygen with a helium carrier gas in an Elemental Analyser (Elementar Vario Isotope), and then transferred to the AGE3 automated graphite system where they were reduced to graphite using the hydrogen reduction method (Wacker et al. Reference Wacker, Němec and Bourquin2010). Graphite was pressed into vacuum cleaned aluminum holders (targets) using an automated hydraulic press, transferred to the magazine, and loaded into the MICADAS AMS together with suitable background (blank) samples (Hollis mammoth bone collagen).
The 14C/12C and 13C/12C ratios were measured with the MICADAS. The sample 14C/12C ratio was background corrected and normalised to the HOXII standard (SRM 4990C; National Institute of Standards and Technology). The 14C/12C ratio was corrected for isotope fractionation using the AMS measured 13C/12C ratio which accounts for both natural and machine fractionation. The dates were calibrated using Calib8.2 program (http://calib.org/calib/) and IntCal20 calibration curve (Reimer et al. Reference Reimer, Austin, Bard, Bayliss and Blackwell2020).
For carbon and nitrogen stable isotope measurements (including δ13C, δ15N, and C:Natomic ratios), a Thermo Delta V Isotope Ratio Mass Spectrometer was used. Collagen samples were measured in duplicate with a drift correction standard of certified isotopic composition bracketing every 10–12 samples. Reference materials with known isotopic compositions were also measured to create a two-point regression line, which is used to calibrate the sample data to the VPDB (carbon) and AIR (nitrogen) scales (detailed description of the analytical process is presented in Reimer et al. Reference Reimer, Hoper, Macdonald, Reimer and Thompson2015).
Bayesian modeling
Bayesian analysis and modeling were carried out using OxCal 4.4 (Bronk Ramsey Reference Bronk Ramsey2009a, the functions Phase, Sequence, First, Last were used) with the IntCal20 dataset (Reimer et al. Reference Reimer, Austin, Bard, Bayliss and Blackwell2020). Outlier analysis was performed using both χ2-tests (Ward and Wilson Reference Ward and Wilson1978) and the Outlier_Model function in OxCal 4.4 (Bronk-Ramsey Reference Bronk Ramsey2009b). For dates from the same samples that are in statistical agreement, weighted averages were carried out using the R_Combine function. A uniform phase model (distribution) is used as the underlying prior for sequences and phases (Bronk Ramsey Reference Bronk Ramsey2009a). It is important to emphasize that the most suitable underlying prior for the site is unknown and other distributions may be more appropriate. However, for this relatively short-lived site (based on calibrated dates alone), the use of a uniform phase model is considered acceptable as an interpretative/explorative tool. Additional archaeologically informed priors were as follows (see Figure 2 for points 2–4 below based on archaeological interpretation of kurgan stratigraphy):
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1. From typology of the burial artifacts the site would not be expected to pre-date the mid-4th c. CE. For modeling purposes a less rigid constraint of 325 ± 10 CE was used in the main model to provide a boundary after which activity commenced at the site. In the subsequent text this is referred to as an “artifactual boundary.”
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2. Kurgan 33 precedes kurgan 29 and kurgan 29a.
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3. Kurgan 30 precedes kurgan 30a and kurgan 38.
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4. Kurgan 30a and kurgan 38 were stratigraphically contemporary.
Choburak-I necropolis: general plan of the mounds (1), funeral rite (2), selected finds (3) – iron bridle bits and psalia, (4) – iron clasp, (5–7) – iron arrowheads, (8) – bone comb, (9) – bronze earring, (10) – iron quiver hook, (11) – bone clasp).
Due to concerns over the sensitivity of the model to the 1st prior above, as well as the validity of the prior itself (i.e. using dates based on typological method from elsewhere to constrain similar artifact ages at Choburak-I) the robustness of the modeled results was examined for a range of artifactual boundary ages (from 260–340 CE), discussed below.
Results
Archaeological analysis
Based on the methodology described in Seregin et al. Reference Seregin, Svyatko, Barrett, Demin, Matrenin, Papin and Reimer2023, several groups of chronological indicators have been identified within the accompanying grave goods, which have varying importance for determining the time of use of the necropolis. Importantly, within the analyzed materials for Choburak-I there were no “classical” chronological markers with clearly established historical dates for the beginning of their manufacture (these usually include coins, Chinese mirrors, silk fabrics, lacquered items, “personalised” objects), which record the “terminus post quem” of closed archaeological complexes.
When determining the archaeological age of Choburak-I, we focused on the placement of funerary objects within the time interval, “… when all the components of the complex coexisted, i.e. between the beginning of the existence of the latest items and the end of the existence of the earliest” (Shchukin Reference Shchukin1978, 29–30). All analysed items presented in the paper (Figures 2 and 3) belong to the same chronological interval.
Chronologically indicative artifacts from the burials of the Choburak-I necropolis. 1 – iron swords; 2-4 – iron arrowheads; 5 – iron bridle buttons; 6 – leather headpiece strap with metal plates; 7 – iron bridle plate with pendant; 8 – bone horse hobble clasps; 9 – bone parts of the lash grip; 10 – bone edges of saddle bows; 11 – bronze earring See Table 2 for the individual burials containing the artifacts.
The most indicative group of chronological indicators has been represented by the youngest (i.e. latest) among the Bulan-Koby burials of Choburak-I artifacts, marking the lower chronological boundary of the Bulan-Koby burials at the necropolis as not earlier than the middle of the 4th century CE (Figure 3).
Among weaponry, these include iron single-bladed swords, iron armour-piercing three-bladed arrowheads with leaf-shaped and keeled body (Figure 3.1), as well as combat tetrahedral leaf-shaped arrowheads (Figure 3.3, 4), often equipped with an annular stopper and tiered trihedral three-bladed arrowheads with an annular stopper (Figure 3.2) (Gorbunov Reference Gorbunov2006, 39, 40, 59, 90, 111). Elements of horse harness are iron plaques, fixed with a false pin with a conical or hemispherical cap mounted into the body of a rounded quadrangular in cross-section plate (Figure 3.5); bronze bridle buttons with a hemispherical body of a rounded shape (Figure 3.6); iron plates with a hemispherical body of a rounded shape and a pendant in the form of a twisted eight-shaped loop (Figure 3.7; Belikova and Pletneva Reference Belikova and Pletneva1983, Figure 2.9 and 18.4; Egorov 1993, Figure 1.8; Yu Junyu Reference Junyu1997, Figure 3.6; Soenov Reference Soenov2000, Figure 10.1-5; Matrenin and Tishkin Reference Matrenin and Tishkin2016, 1.A1, B, B1, 3A-B; Matrenin Reference Matrenin2018, Figure 1.43-51; Yu Junyu Reference Junyu1997, Figure 3.6).
Furthermore, within the horse-riding equipment, bone (antler) horse harness fasteners with an open and solid notch (Figure 3.8) are informative, related to typical objects of the late (Verkh-Uimon) stage of the Bulan-Koby Culture (second half of the 4th–first half of the 5th century CE; Matrenin Reference Matrenin2018, Figure 1.43-51). As a late chronological marker, bone (antler) edgings of unpreserved wooden saddle bows can also be considered (Figure 3.10; Seregin et al. Reference Seregin, Tishkin, Matrenin and Parshikova2021, 27–28; Tishkin and Mylnikov Reference Tishkin and Mylnikov2016, Figure 69.3-5). Among the ornaments, metal earrings with a lobe in the form of a closed ring and a detailed base in the form of a cylindrical spiral are of particular importance for dating (Figure 3.11; Gryaznov Reference Gryaznov1956, tab. XLV.−11, 25–27; Arslanova Reference Arslanova1975, tab. II.−11; Soenov Reference Soenov2000, Figure 7.9; Teterin Reference Teterin2005, Figure 2.29; Trifanova and Soenov Reference Trifanova and Soenov2019, 57). The series of products of the second half of the 4th–first half of the 5th century CE includes bone (horn) parts of lashes or riding crops in the form of massive tubes found in Choburak-I (Figure 3.-9; Teterin Reference Teterin2016, 91, Figure 2.1; Soenov Reference Soenov2017, 122, Figure 9.1; Tishkin et al. Reference Tishkin, Matrenin and Shmidt2018, tab. 39.3, 4). From our analysis of the indicated finds from different structures of the Choburak-I site (Table 2), we emphasize that the structures date to the period not earlier than the middle–second half of the 4th century CE, as confirmed by the discovery of similar items in other closed complexes of the Bulan-Koby Culture of Altai (Verkh-Uymon, Stepushka, Yaloman-II), the chronology of which was supported by 14C dating (Konstantinov et al. Reference Konstantinov, Soenov, Trifanova and Svyatko2018, tab. 1; Tishkin Reference Tishkin2017, 55–56; Tishkin et al. Reference Tishkin, Matrenin and Shmidt2018, 149–154).
Kurgans of the Bulan-Koby Culture of the Choburak-I necropolis, presence of chronological indicators, and calibrated age ranges for the dated samples. Numbers indicate types of chronologically indicative artifacts (see Figure 3)
In summary, the considered chronological indicators suggest the lower boundary (the start date) of the Choburak-I necropolis not earlier than middle of the 4th century CE. The upper boundary cannot be clearly determined based on material culture complex, as there are no solid grounds for documenting the duration of use of the specific groups of items (chronoindicators). From approximately the middle or second half of the 5th century a new—early Turk—population, formed on the basis of the local Bulan-Koby, and also a newly arrived populations appeared in Altai, replacing the Bulan-Koby Culture. Certain groups of the Bulan-Koby artifacts were still in use among the early Turk population (Seregin Reference Seregin2020, 124).
14C dating and stable isotope results
The calibrated radiocarbon results (Table 1) have good overlap with the expected dating of the site based on material culture, and they show a continuous use of the site, with the earliest date belonging to 130–380 cal CE (UBA-37794, kurgan 32) and the latest to 410–600 cal CE (UBA-37797, kurgan 33).
Bayesian analysis
A schematic of the relationship between dates used in the Bayesian modeling is presented in Figure 4. On the basis of outlier analysis samples UBA-37797 and UBA-37793 were removed from subsequent modeling. This does not exclude the possibility that those dates are valid only that those dates are not consistent with the model and priors employed here.
Schematic of Bayesian modeling for human and animal bone samples from the Bulan-Koby Culture burials of the Choburak-I. Solid blue line—bounds dates of same phase/subphase. Dashed red line—bounds dates that are combined (weighted average). Solid vertical lines—chronological ordering from top (earlier) to bottom (later). Boxes not connected to one another have no certain stratigraphical relationship to one another. Boxes with red line through them were identified as outliers for this particular model.
The Bayesian model results are presented in Figure 5, below. This is with the constraint (C_Date ‘Artifactual Boundary’) that activity is no earlier than 325 ± 10 years. The agreement indexes for the model are A model = 63.6% and A overall = 61.8%, both above the recommended 60% (Bronk Ramsey Reference Bronk Ramsey2009a).
Bayesian modeling results for human and animal bone samples from the Bulan-Koby Culture burials of Choburak-I. Multiple dates from individual kurgans are treated as being from the same phase. For consistency this has been maintained even for kurgans with a single date.
The modeled Start and End of activity as well as the duration of activity (Span) at the site are presented in Figure 6. This model provides an interpretation of the site commencing in 318–359 cal CE (95.4%) and concluding in 343–402 cal CE (95.4%) with a maximum duration of 66 years (95.4%).
Modeled Start, End and Span for human and animal bone samples from the Bulan-Koby Culture burials of Choburak-I.
A key consideration of modeling activity at Choburak-I is the validity and impact of the artifactual constraint on the modeled results. Typological analysis suggests earliest activity at the site of mid-4th century date, however this could be overly restrictive and exclude the possibility of some artifact types appearing earlier at Choburak-I than elsewhere. The effects this constraint has on the modeled Start, End and Span (Duration) of the site as well as the model agreement index, A model , are presented in Figure 7.
Exploration of the sensitivity of Bayesian modeling results to the artifactual boundary constraint. Top left—Agreement Index. Top right—Span/Duration of activity. Bottom left/right—variation of start/end boundaries. Solid red/blue lines mark upper/lower limits of the modeled ranges. For lower limits of artifactual boundary the Start/End boundaries are bi-modal until 275±10 cal. AD after which there is a single mode only (bounded with red lines).
This sensitivity testing demonstrates that the model fails (A model < 60%) if the site is constrained to occur after 330 CE. For earlier constraints, the Agreement Index is relatively stable. For best compatibility between the quality of the model and dating based on typological method (suggesting mid-4th c.) the constraint of 325 ± 10 CE was used in the main model presented above (the uncertainty on this constraint was selected to allow some additional flexibility on the model while remaining within the order of a generation).
The sensitivity testing also shows that while a shift of 80 years in the artifactual constraint results in a reduction in the modeled duration of the site from approximately 85 years to 55 years, the effect on the modeled start and end of the site (at least considering the single dominant mode in the probability distributions) is more modest. In particular, constraining the site to any period after 280–340 CE results in changes in the modeled start and end boundaries of the order of only 5–20 years typically. As such, the main modeled results above are considered relatively robust for providing generational scale interpretations of the start, end and duration of the site.
Discussion
Chronological indicators represented by the youngest/latest grave good items (Figure 3) provide the basis for the earliest date of the formation of the Bulan-Koby necropolis of Choburak-I as mid-second half of the 4th century CE, which corresponds to the beginning of the Rouran period in the history of the Altai.
Calibrated AMS 14C dates for ten graves of Choburak-I span the second half of the 3rd–beginning of the 5th century CE. However, with Bayesian modeling the chronology of the site can be further refined to suggest a continuous but relatively short-lived period from approximately 318–359 cal CE (95.4%) to 343–402 cal CE (95.4%) with a maximum duration of 66 years (95.4%). Sensitivity tests of the model also support the site being in use before 350 cal CE as well as demonstrating that the modeled start and end of the site is relatively robust with respect to earlier constraints based on typology method on when the site was first used. These ranges broadly agree with the typological analysis albeit allowing for a slightly earlier commencement to the site than would be expected from the chronological indicators alone.
The correlation of the 14C dates for humans and the associated herbivores (from the same graves) suggests the absence of reservoir offsets in the majority of human remains, with the exception of two individuals—kurgans 32 and 33. The 14C dates of humans from these graves are older than the dates from the associated horses. However, for kurgan 33 it was the horse bone (UBA-37797) that was identified as an outlier in the Bayesian model, appearing too early relative to the overall chronology. As it has been mentioned previously, all burials of the Choburak-I cemetery were undisturbed, which eliminates the possibility of asynchronicity of the burials/samples. One of the explanations for any difference in the 14C dates could be the freshwater reservoir effect on human samples. The effect is usually associated with the presence of freshwater fish in the diet of people, which results in their older 14C dates as compared to purely terrestrial samples. However, the δ15N values of these individuals do not clearly indicate the consumption of fish by these individuals or any of those analyzed from the group, with human δ15N varying between 9.8 and 10.4‰, unless the consumed fish had δ15N values indistinctive from herbivore protein. As such, unless strongly identified as an outlier during Bayesian modeling, dates were retained in the analysis.
The radiocarbon dates and Bayesian modeling provide strong support for the observation that the burials of the Bulan-Koby Culture in Choburak-I were made within a short period of time. Additional arguments for the short (probably within several generations) interval of functioning of this cemetery is a small number of burials, a highly uniform funeral rite and accompanying objects, as well as—circumstantially—the violent (weapon-based) death of three out of seven men.
Among the known sites of the Bulan-Koby Culture, the Choburak-I burial ground bears most similarity, by virtue of the recorded features of ritual practice (the design and shape of the mounds, inhumation with a horse at the feet and on top of the deceased with the northwest orientation, etc.) and accompanying goods, with the Rouran period complex of Dyalyan, also located in the Northern Altai (Kalinin and Teterin Reference Kalinin and Teterin1991; Mit’ko Reference Mit’ko2018, Reference Mit’ko2019; Teterin Reference Teterin1991). Taking into account the striking similarity of the specified indicators, it is possible to assume the approximate synchronicity of these burial grounds, and to suggest that they were left by related local groups of nomads within the 2nd quarter to end of the 4th century CE.
Considering the intensity of the processes during the Rouran time, it appears reasonable now to use these latest radiocarbon results to further examine the chronology of the funerary complexes within the late stage of the Bulan-Koby Culture. However, within the body of material data of the second half of the 4th–first half of the 5th century CE assembled to date, no fundamentally significant differences in the accompanying goods have yet been identified to confidently distinguish the early and late funerary structures. The results of the radiocarbon dating thus only suggest that the Choburak-I burial ground belongs to the beginning of the late (Verkh-Uimon) stage of the Bulan-Koby Culture.
Conclusions
Dating of the archaeological, anthropological and archaeozoological materials of the Bulan-Koby Culture cemetery of Choburak-I makes it possible to determine the period of its functioning within the 2nd quarter to end of the 4th c. CE, which broadly corresponds to the beginning of the Rouran period in the history of Altai. From the available materials, this complex is close in time (perhaps synchronous?) to the Dyalyan burial ground in the Northern Altai, with which it reveals a striking similarity in the majority of features. The results of archaeological dating are supported by the largest set of AMS 14C dates for the Bulan-Koby Culture, which, aided by Bayesian analysis, demonstrates the likely continuous existence of the necropolis between 318–402 cal CE (95.4% probability). The small number of burials, the rare uniformity of the funeral rite and accompanying goods, as well as the presence of lethal combat injuries, provide grounds for assuming a short interval in the existence of this cemetery (probably no more than several generations); modeling of the site suggest a maximum duration of 66 years (95.4%). The relative chronology (sequence of construction) of individual burials of the necropolis still remains open, although it could be suggested that the kurgans that went beyond the “straight” line of structures within the rows of mounds were the later ones. The presented results make it possible to consider the fully excavated Bulan-Koby Culture necropolis of Choburak-I as a chronologically defining monument of the Rouran period of the Northern Altai. The associated burial artifacts will permit a new level of relative and absolute chronological reconstructions for archaeological sites of this region and adjacent territories at the turn of late antiquity and early Middle Ages; this includes the reconstruction of various aspects of ethno-cultural and social history. We hope that the new data introduced will contribute to more intensive scientific research aimed at identifying the phases within the late stage of the Bulan-Koby Culture based on the extensive 14C dating of both already known and new funerary monuments in different regions of the Altai mountainous country.
Acknowledgments
The study was supported by the Leverhulme Trust grant RPB-2019-372. We are grateful to the anonymous reviewers of the manuscript of this paper.
Appendix 1. Burials of the Bulan-Koby Culture in the Choburak-I necropolis
Kurgan 29 . Small oval-shaped mound of medium and small stones. The undisturbed grave contained the skeleton of a 9–11-y.o. child in anatomical order, extended on the back with the head to the northwest. Sparse accompanying goods included three iron tanged and one bone arrowheads, a fragment of iron knife and iron belt buckle.
Kurgan 29a. Oval-shaped stone mound with a crepidoma laying-out. The grave contained the skeleton of a 13–15-y.o. male in a wooden chamber. The deceased was lying extended on his back with his head to the northwest. A number of accompanying items included a bow with horn plates, seven iron arrowheads, two belt buckles, distributor, knife, fragment of a lash handle, comb, and horn clasps.
Kurgan 30 . The largest structure of the complex. In the northwestern half of the grave, the remains of a wooden log were recorded, and the burial of a 30–35-y.o. male, extended on his back with his head to the northwest. The grave goods included weaponry (bow with horn plates, more than 40 iron arrowheads, sword, two combat knives), equipment (composite belt with numerous iron elements, fasteners), tools (short-bladed knife), and a metal ornament (tube-bead). In the southeastern part of the grave, there was a burial place of a horse with its head oriented to the northwest. Next to the horse, there were iron bits, bridle buckles, four plaques, bet clip, two fasteners, and a pair of bone horse hobble clasps.
Kurgan 30a. Oval mound with poorly preserved crepidoma laying-out. In the northwestern half of the grave, a decay of a wooden chamber (box or frame?) around a skeleton of a 30–40-y.o. male, positioned extended on the back with his head to the northwest, has been preserved. The deceased was accompanied by numerous implements (bow with horn plates, iron sword in a scabbard, five iron and three bone arrowheads, iron elements of a composite belt, bone saddle edging, horse hobble clasp, and an element of a lash). In the south-eastern part of the grave pit, there was a burial of a riding horse, laid almost perpendicular to the male, with its head to the northwest. In animal’s jaws, iron bits with psalia were preserved, as well as, in different places, metal parts of the bridle (two buckles, fragments of a mane piece, seven plates-badges, and a bone (horn) girth buckle.
Kurgan 31. Oval stone mound with a crepidoma laying-out. In the northwestern half of the grave, the inhumation of ca. 40-y.o. male was recorded, lying stretched out on his back with his head to the northwest. On different parts of the postcranial skeleton, incised and chopped wounds, inflicted by sword, without traces of healing, were observed. Weapons (a bow with horn pads, four iron arrowheads), military equipment (composite belt with a large number of garnitures), tools (iron knife, bone arrowhead, and a part of lash handle) were found with the male. In the southeastern part of the pit, there was a burial of a horse with its head to the northwest. The skeleton of the animal overlaid the human femora to the middle. A series of articles related to horseback riding (iron bits, bone girth buckle, three horse hobble clasps, clasp, part of a lash) has been found.
Kurgan 31а. Stone mound with oval crepidoma laying-out. In the northwestern half of the grave, the skeleton of an elderly (over 55 y.o.) male was found in anatomical order–extended out on his back, with his head to the northwest. A relatively limited assemblage of grave goods was recovered: bow with horn pads, iron arrowhead, composite belt with iron sets, quiver hook-clasp, fasteners, and four bone arrowheads. Under the pelvis of the deceased, there were sheep vertebrae—the remains of ritual meat food. In the southeastern half of the pit, there was a riding horse, with its head oriented to the same direction as the male. The skeleton of the animal overlaid the human body up to the middle of the thigh bones. Iron bits, bridle and girth buckles, five plaques, belt clip, three plates (possibly belt tips) were found with the horse.
Kurgan 32. Oval-shaped stone mound with crepidoma laying-out. In the northwestern half of the grave, a wooden bed was found, with the skeleton of a 25–30-y.o. male extended on his back, with his head to the northwest. Different categories of weapons (bow with horn pads, four iron arrowheads, combat knife), equipment (composite belt, quiver hook-clasp, fasteners) and tools (bone part of a lash, knife) were placed with the deceased. In the southeastern half of the pit, there was an accompanying burial of a horse with its head oriented to the same side as the male. Elements of horse ammunition (iron bits, bridle buckle, bone girth buckle, pair of clasps, end edging of two saddle bows) were found on different parts of the horse skeleton.
Kurgan 32а. Oval mound with larger stones along the contour. In the northwestern half of the pit, the skeleton of a 40–50-y.o. female was found, lying on her back with her legs slightly bent, and her head oriented to the northwest. Six bronze sewn-on plates from a headdress, two earrings, stone spinning wheel, iron elements of a belt, awl, and a pendant made of maral tooth were found. In addition, the accumulation of sheep bones, representing the remains of ritual meat food, was recorded within the grave. In the southeastern half, there was a burial of a riding horse with its head pointing to the same direction as the woman. With the animal, various items of equipment were found (iron bits, bridle buckle, belt clip, plates, bone girth buckles, and edgings from two saddle bows).
Kurgan 33. Oval-shaped mound with central part built of small and medium-sized stones and larger ones around the contour. The grave contained massive wooden poles, and a wooden log in the northwestern half. Inside the chamber, there was the skeleton of a 20–25-y.o. female, laid on her back in extended position, with her head to the northwest. A bronze earring, iron armor plate, short-bladed knife, awl, badge-plate, pendant, fragment of a tool, and an ornament made of maral tooth were found with the deceased. In the southeastern half of the pit, there was a burial of a riding horse with its head oriented to the northwest. The jaws of the animal were holding iron bits with ringed psalia. Numerous iron elements of the bridle (buckle, badge-plates, tips, distributors, belt clip and other items) were found on different parts of its skull.
Kurgan 34. The mound with larger stones along the outer lane, which formed an oval crepidoma laying-out. In the northwestern half of the grave, the decay of a wooden burial chamber was traced, which contained a skeleton of a 30–35-y.o. female, laid extended on her back with her head to the northwest. A number of decorative items related to headdress (rounded plaque made of precious metal, eight sewn-on plates made of non-ferrous metal, braid piece, earrings) and outerwear (four bronze bell-shaped sewn-on plaques, two oval-shaped sewn-on plaques, pendant made of a maral tooth), as well as items for other functional purposes (iron belt buckles, knife, stone spinning wheel, bone hygienic brush) were found. In the southeastern half of the pit, there was a burial of a horse with its head oriented to the northwest, with numerous items made of iron (bits with psalia, three bridle and one girth buckles, 23 plates, fastenings) and bone (girth buckle).
Kurgan 34а. Oval-shaped stone mound with crepidoma laying-out on the outer line. In the northwestern half of the grave, there was a skeleton of a 30–35-y.o. male on his back with his legs extended. In place of the head of the deceased, there was a skull of young ram, mounted on a base and thus imitating a single whole with the postcranial skeleton of the male. Incised injuries without signs of healing were recorded on some of the bones of the male. A bow with horn plates, at least ten iron arrowheads, quiver hook-clasp, two short-bladed knives, awl, and fasteners were found with the deceased. An unusual find was the iron round-bottomed cauldron. In the southeastern part of the pit, there was a horse burial, oriented with its head to the northwest, which almost half covered the skeleton of the male. Items of equipment made of iron (bits, bridle buckles, two plates, fasteners) and bone (horn) (girth buckle, clasp, edging from the bow of a saddle) were found with the animal.
Kurgan 38 . Oval-shaped stone mound with a crepidoma laying-out. In the northwestern half of the grave, there were skeletal remains of a 25–30-y.o. male, laid extended on his back with his head to the northwest. The grave goods included a bow with horn plates, nine iron arrowheads, two long-bladed knives, sword, composite belt with diverse iron set, fasteners, seven bone arrowheads, two knives, awl, bone parts of lashes, and a bronze plate. In addition, the remains of ritual meat food in the form of sheep bones have been recorded. The south-eastern part of the grave pit was occupied by the burial of a riding horse with its neck twisted in the northwestern direction. Various pieces of equipment were found with the animal (iron bits, bridle buckle, fastening, seven bridle plates, bone edging from the bow of the saddle).
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