Khaled Beyaz

Carlos Vaca-Garcia

Emeline Vedrenne

Nabi La Haddadine

Ahmed Benaboura

Sophie Thiebaud-Roux

Graft copolymerization of hydroxyethyl cellulose with solketal acrylate: Preparation and characterization for moisture absorption applic ation

ln this work, we reported the preparation of a nove! biomaterial, by graft polymerization of 2-2-dimethyl-1-3-dioxolan-4-yl methyl acrylate (solketala crylate, DMDMA) on hydroxyethyl cellulose (HEO using KPS as initiator. Severa! experiments were performed to found the optimum conditions for the preparation of this biopolymer, by varying the time of the reaction as well as the initiator and the monomer ratio. Results showed that the high est grafting yield was 25%, obtained after 72 minutes at 65 °(, using THF as solvent. The structure of the grafted copolymer was confirmed by X-ray diffraction patterns which showed, besides the characteristic peaks of HEC at 20= 31.74 ° and 44.63 ° a new peak at 20= 30.72 ° related to an organ ized structure of the grafted polymer on the HEC backbone. The DSC ana lysis showed a single glass transition temperature Tg, intermediate between the corresponding values for HEC and neat poly(solketal acrylate). Moreover, the graftecl biomaterial presented two-fold more moisture absorption ability by comparison with HEC, making this new synthetic bio material highly promising for dryness applications. ln our knowledge, the synthesized monomer: 2-2-dimethyl-1-3-dioxolan-4-yl methyl acrylate, (sol ketal acrylate, DMDMA), has never been grafted on the HEC backbones before that is what makes the novelty of the present work.

Introduction

KEYWORDS Bio based acrylate; graft copolymerization; hydroxy ethylcellulose; synthetic biomaterials

Hydroxyl ethylcellulose, HEC, is a nonionic cellulosic derivative, with linear structure and high solubility either in aqueous or in several organic solvents. Moreover, HEC is used in particular applications as thickening, gelation, emulsifier, or lubricant agent, due to its specific properties suitable for paints, textiles, and cosmetics. 1 1 • 2 1 • During the last decades, there bas been a h ug e interest to the chemical modification of HEC to improve their bio-compatibility and expand the field of their applications. Grafting monomers on HEC remains a specific way to connect two dif ferent entities in a single macromolecule, with HEC as the main backbone and the side-chains consisting of oligomers that grow according to the synthesis conditions. The grafting method, In our previous work, 1 16 1 we reported a successful method to graft the pol ym erization of 2,2dimethyl-1,3-dioxolan-4-yl methyl acrylate (DMDMA, also called solketal acrylate), a derivative of glycerol and acrylic acid, on cellulose fibers. In this work, we grafted the same monomer DMDMA on the HEC fibers to improve the moisture adsorption properties, using the potassium persulfate (KPS) as initiator. The latter was chosen for its high efficiency, 1 17 1 and its high water solubility. 1 1 8 1 The obtained bio-copol ym ers, polyDMDMA-graft-HEC, were synthesized by varying several synthesis parameters, such as the initiator and the monomer concentrations and the dur ation of the reaction. The morphological properties were examined using SEM. The structural characterization was carried out by FTIR and DRX spectroscopies. The thermal properties were examined using TGA and DSC.

CONTACT

Experimental part

Materials and methods

Hydroxyethyl cellulose with 1.5 substitution degree, acryloyl chloride and 1,2-o-isopropylidene glycerol (solketal at 98% (100-79-81), potassium persulfate (99%), magnesium sulfate (97%), dichloromethane (99.8%), and the tetrahydrofurane (with free-radical inhibitor at 99.9%), were supplied by Sigma-Aldrich. Tri-ethylamine and sodium bicarbonate (99%) were supplied by Acros Organics. All reagents were used straightly without prior purification. DMDMA (2,2-dimethyl-1,3-dioxolan-4-yl methyl acrylate) was prepared by reacting solketal (racemic mixture) with acryloyl chloride and tri-ethylamine (Figure 1). The vinyl monomer obtained was purified by vacuum distillation as previously reported 1 16 1 In order to obtain neat homo-polymer for comparison purposes, DMDMA was radically polymerized (yielding poly-DMDMA) using solid KPS, without THF whose free-radical inhibitor would have acted negatively. 1 16 1 The pol yrn erization mechanism is similar to the one described in Figure 2.

DMDMA graft-copolymerization on hydroxyethyl cellulose

The graft-copol yrn erization of DMDMA on HEC was performed as follows. A quantity of 500mg of HEC ( 7 In order to evaluate the gr afting yield. we measured the weight gain (GP), defmed as follows:

( ) W 1-W o GP % =---.100 W o (1)
where W O and W 1 are the cellulosic solid material weight before and after the grafting process, respectively.

Characterization of the poly-DMDMA-graft-HEC

FTIR spectroscopy

The FTIR spectra of the poly-DMDMA-graft-HEC bio-materials were reco rded between 500 and 4000 cm 1 using a Perkin Elmer Spectrum with a resolution of 2 cm 1 and 64 scans. Dry powdered samples were mixed with spectroscopie KBrat a concentration of 5%. A back gr ound spectrum without any sample was subtracted from ail the spectra.

Differential scanning calorimetry (DSC)

The glass transition temperature (Tg) of the sample was measured with a TA Instrument 2010, DSC2 differential scanning calorimeter using a sample weight of 10 to 15 mg at a heating rate of 20 °C/min under nitrogen fl ow between 4-0 and 300 °C. The initial onset of the change of slope in the DSC trace during the second heating scan was identifi ed with the Tg.

Thermo-gravimetric analyses (TGA)

Thermo-gravimetric measurements were performed using a Mettler Toledo TGA (Stare system). About 10 mg of sample was heated in a platinum crucible from ambient temperature to 600 °C at a heating rate of 10 °C/min under nitrogen atmosphere.

X-Ray diffraction investigation

The structure of the biopol ym ers was investigated by X-ray powder diffraction (XRD). XRD pat terns were recorded by a X-ray diffractometer with graphite monochromatized Cul«< at scanning rate of 4 ° /min. The diffraction angle was ranged from 5 °to 4-0 ° (0.05 ° /min).

Scanning electron microscopy (SEM)

SEM images were recorded using a LEO 435VP scanning electron microscope. For SEM measure ment, a thin layer of the biopol ym ers were deposited on metal grids using an araldite epoxy resin. Surfaces were rendered conductive by silver layering of several nanometers thick with an Edwards Scanco SIX metalizing device.

Moisture adsorption measurements

Pristine HEC as well as the grafted materials were dried in an oven at 100 °C for about 12 h. Samples weighing 1 g, were placed into desiccators containing a sulfuric acid solution 18.5% v/v, introduced one day before at room temperature.r [START_REF] Wilson | Humi dity control by means of sulfuric acid solutions, with critical compilation of vapor pressure data[END_REF] where W i and Wr are the samples weights before and aftertheir input in the desiccators, respectively.

Results and discussion

In order to make clear the impact of each pertinent parameter on the graft-copolymerization of the DMDMA monomer onto HEC, a series of poly-DMDMA-gra. ft-HEC copol ym ers were pre pared varying the concentration of KPS between 0.94 and 15. 01 mmol/eq OH (Figure 3).

The increasing of KPS increases the grafting rate, up to a maximum value of 25. 2%, obtained when KPS = 7.51 mmol/eq OH. Higher amounts of KPS causes a fast decrease in the grafting rate. Such behavior can be explained by the fact that the increase in the KPS amount generates the creation of radicals also on the THF by radical transfer, at the expense of the graft reaction. f 16,21 1

The next parameter was studied by keeping the KPS amount at its optimum value (7.51 mmol/eq OH). The infl uence of the ration of monomer to HEC was then studied. Amount of KPS (mmol/eq OH of HEC) Amount of DMDMA (mol/eq OH HEC) Through this part, the amount of DMDMA was varied from 0.88 to 4.43 mol/eq OH (Figure 4). Subsequently, a graduai increase in the grafti ng yield is observed as the DMDMA amount increases from 0.88 to 2.66 mol/eq OH reaching a weight gain of 25.2%. Beyond 2.66 mol/eq OH, the grafting yield barely changes. --.---.---.---.---.---.---.---.---.---.---.---- The KPS and the DMDMA amounts were fi xed at 7. 51 mmol/eq (OH) and 2.66mol/eq(OH) for the study of the reaction time. Five reactions conducted under identical conditions were car ried out. Th ey were stopped at different durations going from 24 to 120minutes (Figure 5).

As shown in Figure 5, a graduai increase in the grafting rate is obtained as the reaction time increases. Beyond 72 minutes time, where the weight gain reaches 25.2%, the grafting yield reaches a plateau making fruitless the increasing of the reaction duration.

These experiments allowed us to conclude that an optimum grafting rate, equal to 25.2%, was obtained using a KPS concentration of 7.5lmmol/eq OH and 2.66mol/eq OH of DMDMA monomer, during 72 minutes of reaction time.

The comparison between the FTIR spectra of the pristine HEC and the grafted HEC (Figure 6) showed a new peak at 1735 cm 1 , corresponding to the stretching vibration of the C = 0 bond, which is related to the ester group grafted on the HEC chains.

The detailed examination of the pristine HEC FTIR spectrum, showed a large band centered at 3434 cm 1; related to the stretching vibration of the as sociated hydroxyl bond OH. This band became sharper after grafting. The stretching vibration of methyne and methylene Ch and CH 2 bonds appeared at 2933 cm 1 and 2881 cm 1 respectively. The band centered at 1648 cm 1, is related to the water H 2 0 absorption distortion vibration. The two bands centered at 1462 cm 1 and 1351 cm 1 respectively are related to the distortion vibration CH 2 and the CH bonds.

The DSC thermo-grams of the studied materials were recorded and gathered on Figure 7. The glass transition temperature of the grafted HEC showed a single glass transition Tg= 33 °C, which is intermediate between the Tg values of the poly-DMDMA (Tg= 14 °C) and the pristine HEC (Tg= 12 2 °C), respectively. This fi nding confirmed the grafting process of the DMDMA on the HEC resulting in a homo geneous biopol ym er. The Tg of the poly-DMDMA was found to be less than the ambient temperature. This result showed that this homo-pol ym er is supple and flexible.

The TGA thermo-grams of the homo-pol ym er poly-DMDMA and the HEC before and after the grafting process are presented in Figure 8. The deco mposition temperatures of HEC and the homo-pol ym er were found to be 350 °C and 40 0 °C, respectively (Table 1). Their thermal (2)

HEC

(1)

33 °c ---------�--- , ------( 2)

-PDMDMA (3)
(1)

(3) ------------------------ Temperature ( 0 C) HEC. Such difference in the thermal properties between pristine HEC and the grafted HEC con firms the chernical modificati on of the HEC backbone. Furthermore, the increasing in the weight loss at 600 °C in the case of the grafted material (Table 1) might be attributed to the griffons' emergence on the HEC pol ym er.

0 -+-
The study of the crystallinity of the polymers was investigated by XRD analyses. Figure 9 gath ers the XRD patterns of the PMDMA and the HEC before and after the grafting pro cess. The presence of a peak centered at 20.7 ° ei ther in the HEC or in the gr afted HEC was attributed to the crystallinity of both bi opolymers. A new peak appeared on the grafted HEC pattern at 30.7 °; The examination of the SEM images, shown in Figure 10, proved a pronounced morphological variation between the two materials. The image of these group was completely different from the one represented by the grafted HEC. Such variety is due to the input of poly-DMDMA on the HEC surface. Consequently, SEM images showed clearly the morphological change before and after the grafti ng process.

Finally, the moisture absorption properties of HEC and the grafted HEC materials were inves tigated and the corresponding values were gathered in Figure 11. As we can see, no significant difference in moisture absorption of HEC showed after 24 h and 48 h ( i.e., 9.8% and 10.5% respectively). On the other band, the grafted HEC moisture absorption was 18.4% and 25% after 24 h and 48 h. Such behavior can be explained by the fact that water molecules were accessible to

Conclusions

In this paper, we reported the grafting pol ym erization of 2,2-dimethyl-1,3-dioxolan-4-yl methyl acrylate on hydroxyethyl-cellulose by radical pol ym erization reaction using potassium persulfate as initiator. The experimental protocol allowed us to condude that in the optimum conditions the grafting rate was equal to 25.2%, using 7.51 mmol/eq OH of KPS and 2.66mol/eq OH of the monomer DMDMA, during 72minutes at 65 °C in the presence of THF. The SEM pictures showed a morphological modification of the HEC fibers. The obtained copolymer structure modi fication was confi rmed by FfIR and X-Ray diffraction (XRD) analyses. Furthermore, the water adsorption tests showed that the grafted HEC bas increased hydrophilic characteristics. Furthermore, results showed the grafted biomaterial presented two-fold more moisture absorption ability by comparison with HEC, making this new synthetic biomaterial highly promising for dry ness applications .

Figure 1 .

 1 Figure 1. Synthesis of DMDMA_l 161

Figure 2 .

 2 Figure 2. Synthetic mechanism ci poly DMDMA g,aft HEC.

  .9 meq OH), was dispersed in 20 ml of THF, in a 50 ml triple-neck fl ash glass equipped with nitrogen flow. After 3hours of magnetic stirring, KPS aqueous solution (25.2%) (amounts around 4ml to obtain between 0.94 and 15.01 meq ofKPS), and adequate quantities ofDMDMA (0.88 to 4.43 meq), have been added into the reaction vessel. The triple-neck fl ash glass was then introduced into a thermo-regulated that 65 °C. In these experiments, KPS and the monomer quantity varied between 0.94 and 15.01 mmol/eq OH and 1 to 5 ml (i.e. 0.88 to 4.43 mol/eq OH), respectively. The copol yrn erization time varied between 2 to 24 hours. The resulting mixture is kept under a nitrogen fl owall over the copol yrn erization reaction. The termination step of the copol yrn erization was performed by cooling the reaction fl ask into an ice-bath. The resulting graft-copolymerization reaction followed the chemical mechanism leaded to the poly-DMDMA graft-HEC, as shown in Figure 2. After a filtration and several washes with THF; the copol yrn er was dried at 50 °C for 12 hours and stored in desiccators until used.

I

  After one or two days respectively, the samples were removed and weighed again. The experi ment was repeated three times at least. The moisture absorption ability (%M abs ) was evaluated following the weight percentage equation: f201 W 1 -W;

  ----.--.--............. -.--............. -.--............. -.--............. -.--.............. -.--....

Figure 3 .

 3 Figure 3. Grafting yield (expressed as weight gain) evolution with the amount of KPS.

Figure 4 .

 4 Figure 4. Grafting yield (expressed as weight gain) evolution with the molar amount of DMDMA

Figure 5 .

 5 Figure 5. Grafting yield (expressed as weight gain) evolution with the reaction time.

Figure 6 .

 6 Figure 6. mR spectra of pristine HK, grafted HK and poly DMDMA.

Figure 7 .

 7 Figure 7. DSC thenno grarns (2nd scan) of samples of HK, grafted HK and poly DMDMA.

Figure 8 .

 8 Figure 8. TGA (A) and DTG (B) thermograms of the HEC, the graft HEC and the PDMDMA.

Table 1 .Figure 9 .

 19 Figure 9. ORX of HK and grafted HEC.

Figure 10 .Figure 11 .

 1011 Figure 10. MEB images of HK (left) and HEC graft PDMDMA (right). Upper row: magnification x 1000; lower row: x5000.


Antoine ; Zazzo
email: zazzo@mnhn.fr

Sébastien Lepetz

Jérôme Magail

Jamyian-Ombo Gantulga

High-precision dating of ceremonial activity around a large ritual complex in Late Bronze Age Mongolia

Keywords: Mongolia, Bronze Age, Radiocarbon dating, Bayesian modeling, Monument

High-precision dating of ceremonial activity around a large ritual complex in Late Bronze Age Mongolia

Antoine Zazzo, Sébastien Lepetz, Jérôme Magail, Jamyian-Ombo

Introduction

Most of the archaeological culture of the Eurasia's eastern steppes is apprehended through its rich monumental landscape. Among these, deer stones and khirgisuurs (DSK) complexes are iconic monuments that form the main components of a mortuary ceremonial system dating to the Late Bronze Age (ca. 1200-700 BCE). These monuments are part of the larger "kurgan" tradition of the Eurasian steppe and are found mostly in central and northern Mongolia, but also in northwestern China and southern Siberia (Allard & Erdenebaatar 2005;Amartuvshin 2007;[START_REF] Erdenebaatar | Burial materials related to the history of the Bronze Age on the territory of Mongolia[END_REF]. Khirgisuurs are composed of a central stone mound covering a stone burial chamber, usually containing the remains of a single human body. The central mound, which can reach an average diameter of about 10 m, is surrounded by a circular or quadrangular fence formed by an alignment of stones. Most of them also include external structures in the form of stone circles and stone mounds. Stone circles are made up of between seven and twelve stones and often contain the calcined bone elements of domestic animals (mostly caprines, but sometimes also bovines). Stone mounds consist of local rocks heaped to between 1 and 5 m in diameter, covering the head of a horse facing east together with the neck and hoof elements. Recent work has demonstrated that these horses also were domesticated and used for chariotry or mounted ridding, highlighting the importance of the horse in the development of mobile pastoralism during the Late Bronze Age [START_REF] Taylor | Horse demography and use in Bronze Age Mongolia Quaternary International[END_REF].

The archaeological context suggests that these remains are linked to a ritual practice but in the absence of decisive data to define the meaning of the gesture it is difficult to determine whether them come from sacrificed animals or if they are offerings. The number of associated peripheral structures varies from zero to several thousands and as a result, khirgisuurs range widely in size from 0.1 to 20 ha. However, the vast majority of khirigsuurs are of moderate size and very large monuments are rare. Deer stones are anthropomorphic stelae often covered with deer carvings [START_REF] Volkov | Olennye Kamni Mongolii, 2nd edition. Academy of Sciences, Moscow. Nauka, Ulaanbaatar. SQL Code for the Tsatsyn Outlier Model Plot() { Outlier_Model("Charcoal",T(5),U(0[END_REF][START_REF] Weber | Long-term occupation and seasonal mobility in Mongolia: a comparative study of two mobile pastoralist comunities[END_REF]Fitzhugh 2009a). Like khirgisuurs, they are often accompanied by peripheral stone mound and stone circle structures and indeed include the same sacrificial offerings of domestic animals.

The wide distribution of these elaborate burial mounds and stone monuments suggests shared knowledge between individuals and mobile communities across the eastern steppe and indicates a level of socio-political intensification and complexity previously unknown in this region. Despite the fact that khirgisuurs have been the focus of attention for several scholars over the past decade, many questions regarding their ritual and funerary role as well as their social and political function remain unanswered. Based on the analysis of form and architecture some authors suggested that their construction was planned and swiftly executed F o r P e e r R e v i e w 3 (Fitzhugh 2009b;Houle 2017) and regarded these monuments as evidence for the beginning of social inequality on the Mongolian plateau [START_REF] Honeychurch | Re-Writing Monumental Landscapes as Inner Asian Political Process, in Monuments, Metals, and Mobility: Trajectories of Complexity in the Late Prehistory of the Eurasian Steppe[END_REF]. Indeed, a significant amount of collective work was required to build them and variations in their number and size have been interpreted as reflecting differences in wealth between communities (Wright 2014) and/or in the social status of individuals [START_REF] Frohlich | Bronze age burial mounds (khirigsuurs) in the Khovsgol aimag, Mongolia: a reconstruction of biological and social histories[END_REF]. Joshua Wright also identified khirgisuurs which appear to have "accreted" over continual reuse (Wright 2014). He argued that khirgisuurs were living monuments that were built to be repeatedly visited and modified, highlighting their role at materializing communal cohesion through social interactions in an egalitarian society. The size of the community involved in the construction of these large monuments is also unknown. If we assume that large khirgisuurs are elaborated in an instant, then the animals slaughtered (sometimes more than a thousand of horses) must come from an area much larger than the local community and would be representative of social networks active over great distances (Houle 2017). On the contrary, repeated use over several decades would not necessarily require the involvement of very distant populations.

Addressing the debate on the timing of construction of large khirgisuurs is therefore essential if we are to better understand the social political structure of LBA societies. Houle (2017) pointed out that some of the structural elements like the position of the surrounding fence and the mounds closest to the fence outwards imply planning and simultaneous execution. But whether ritual features such as stone mounds and stone circles were built during a single ceremony or a prolonged period of time remains a matter of speculation, owing to the relatively small number of radiocarbon dates available so far (Allard & Erdenebaatar 2005;Fitzhugh & Bayarsaikhan 2009). For the same reason, the construction history of complexes in which deer stones and khirigsuurs appear together is also unclear at the site level, some viewing them as synchronous while others see deer stones as later intrusions in an already ritually sanctified ground (Fitzhugh 2009a;[START_REF] Weber | Long-term occupation and seasonal mobility in Mongolia: a comparative study of two mobile pastoralist comunities[END_REF].

To our knowledge, only two large khirgisuurs have more than two AMS dates: Urt Bulagyn and the B10 complex of Tsatsyn Ereg, both located in central Mongolia (Arkhangaï aimag). Urt Bulagyn is located in the Khanuy Valley. It covers about 15 ha and contains ca. 2700 peripheric structures out of which only four have been excavated and dated (Allard & Erdenebaatar 2005;Fitzhugh & Bayarsaikhan 2009). The calibrated dates suggest a possible outward growth for the satellite mound sector over a period of a few hundred years between the 11 th and the 7 th c BCE (Table S1 Fig S1). The B10 complex of Tsatsyn Ereg is located 50 km southeast of Urt Bulagyn in the Khoid Tamir Valley (Magail 2008a). This large khirgisuur 1). The radiocarbon dating of six ritual structures associated to the B10 complex suggests an extensive period of use for this khirgisuur from about the 11-10 th to the 4-2 nd c. BCE (Gantulga 2015). If confirmed, the prevalence of the same ceremonial activity over several centuries would be unprecedented archaeologically and raise questions regarding its significance and function. However, for reasons exposed in more detail in the SI Appendix we consider it likely that contamination of bone collagen with modern carbon affected the results.

Khirgisuurs were key features of the social and physical landscape of the Late Bronze Age. The debate about their significance regarding their date and construction histories has implications for wider understanding about demography, mobility, and regional networks: a) built at as a single event, drawing on large regional networks for people and animals; b) built across a human lifetime, with less necessity for regional resources/implications for local social and demographic organisation c) built over a century or more, and requiring still fewer regional resources and perhaps more localism.

It is therefore of uttermost importance to develop tight chronological control for these monuments of Central Mongolia with respect to sociopolitical development at this crucial time period. Bayesian modeling can be used to test these hypotheses, but they require large quantities of AMS dates on well-preserved samples, which can be challenging in the case of khirigisuurs becauses bones are shallowly buried and exposed to weathering. This article aims at providing the first high precision data of ceremonial activity that tie deer stone complexes together with a large and a small khirgisuur complex. We do so by dating a large number of horse and caprines deposited at the site of Tsatsyn Ereg and applying a Bayesian modeling treatment to the data. We also address the issue of bone contamination and its impact on radiocarbon dates and discuss the broader significance of our results for understanding of the Mongolian Bronze Age.

The Late Bronze Age monuments of the Khoid Tamir Valley

Since 2006, the joint Monaco-Mongolia archaeological mission carries out research at the Late Bronze Age to Early Iron Age site of Tsatsyn Ereg (Arkhangaï province, Khoid Tamir Valley) (Magail 2008b;Magail 2015). Within the surveyed area (ca. 150 km2) more than 2100 graves, over 110 deer stones and three thousands of petroglyphs have been documented so far (Fig. 2). The material included in this study derives from the excavation of F o r P e e r R e v i e w 5 three archaeological complexes located in the Khoid Tamir Valley: a small khirgisuur (KTS-01), a large khirgisuur (B10) and structures in close association with a deer stone (PAC38). A detailed description and analysis of each distinct ritual feature and its possible function in funerary or mortuary practice is beyond the scope of this article and will be the focus of a separate contribution (Lepetz et al., forthcoming). Briefly, KTS-01 presents seven peripheral structures which were all excavated in 2012 (Fig. 3). Six out of the seven mounds contained the remains of horses which were sampled for radiocarbon dating. The deer stone PAC38 is associated with 144 mounds, of which three were excavated in 2011 (Fig. 4). Each excavated mound contained the remains of a horse which was sampled for radiocarbon dating. The large khirgisuur B10 covers a surface of about 22 ha and contains 2361 peripheral structures, including 1116 mounds and 1245 circles (Fig. 5 and6). The size and architectural plan of this khirgisuur is very similar to that of Urt Bulagyn located ca. 50 km north-west (Allard & Erdenebaatar 2005). Between 2009 and 2016, a total of sixty structures were excavated including 22 circles and 38 mounds. The structures were selected in order to cover a wide topographical range. Twenty out of the 22 circles contained datable material, either calcined bone, charcoal or both, which were sampled for radiocarbon dating. While some mounds were empty (8/38), most of them provided one, sometimes two horse heads together with the neck and hoof elements. When two individuals were found in the same mound, both were sample.

Collagen was extracted from the horse bones and teeth from the three excavated complexes: KTS-01, B10 and PAC38. Two different collagen extraction methods were used, including ultrafiltration. The results are described and summarized in SI Appendix . The discussion below first examines the impact of diagenetic alteration on the radiocarbon dates. Then, carefully scrutinized samples are integrated into a high precision Bayesian model in order to precise the chronology of the LBA monuments.

Result and Discussion

Assessing the effect of diagenesis on radiocarbon ages

The ages measured in calcined bones and charcoal from the B10 complex cluster tightly between 2770±20 and 2910±25 BP. Pairs of calcined bone and charcoal dates were either very close or identical (SI Appendix, Fig. S2), indicating good preservation of the calcined bone apatite, in keeping with previous results obtained for this type of material [START_REF] Lanting | Dating of Cremated Bones Radiocarbon[END_REF][START_REF] Chatters | CALCINED BONE AS A RELIABLE MEDIUM FOR RADIOCARBON DATING: A TEST USING PAIRED NORTH AMERICAN SAMPLES[END_REF]). On the contrary, the ages measured in bone collagen samples from this khirgisuur appear more variable, ranging between 2630±25 and 2925±25 BP. The chemical integrity of the molecule was assessed independently of the F o r P e e r R e v i e w 6 measured age using collagen yield and C/N ratio as proxies (DeNiro 1985;Ambrose 1990;van Klinken 1999). All the samples fulfilled the conditions for well-preserved bones, with collagen yields above 1% and C/N ratios comprised between 2.9 and 3.6 (DeNiro 1985;Ambrose 1990;van Klinken 1999;Brock et al. 2010). But the correlation between the collagen C/N ratios and the 14 C ages observed at KTS01 (SI Appendix, Fig. S3) and at the B10 complex (SI Appendix, Fig. S4), together with the age difference between the high molecular weight (HMW) and the low molecular weight (LMW) fractions of the ultrafiltered bone collagen samples (Fig. S5) indicate that some of the bone collagen samples were contaminated by a young, 14 C-depleted source of carbon, probably coming from the soil.

Because the horse skulls were placed directly on, or just below the surface of the paleosol some 3000 years ago, they were continuously exposed to weathering and often had roots and fungi penetrating deep into them. This contamination could not have been detected solely on the quality control (QC) criteria routinely applied. In order to investigate whether ultrafiltration successfully removed this contamination, we compared the dates measured on the same samples treated with the two methods using the HMF results only for Method 2. The results are presented in the SI Appendix (Fig. S6) and show that there was no systematic difference between the 14 C age of bones treated with or without ultrafiltration. Only four ultrafiltered bones (in ST15, ST17, SAT533 and SAT 803) returned dates that were significantly (>50 14 C y) older than non-ultrafiltered bones, while the opposite situation was observed on two occasions (ST6 and ST8). On average, the 14 C dates measured on ultrafiltered collagen were slightly older and less variable than without ultrafiltration (2806±58 BP vs 2785±87 BP n= 15) but not significantly different (p= 0.41), thus suggesting that ultrafiltration is not the solution.

Our results strongly suggest that the QC criteria for collagen purity are not strict enough for accurately dating the B10 complex and associated structures and should be revised, at least for bones found in similar contexts (subsurface finds from mid-latitude sites). For this reason, only collagen samples with C/N ratios of 3.30 or below and extraction yields of 5% or above were considered not significantly contaminated. For ultrafiltered samples, we can only rely on the C/N ratio because lower collagen yields are typically obtained from poorly preserved samples [START_REF] Higham | AMS radiocarbon dating of ancient bone using ultrafiltration[END_REF]. This approach lead us to discard about half (34/65) of the samples for the large khirgisuur B10, 4/6 samples for STE01 and 0/3 samples for PAC38. It is noteworthy that most of the contaminated samples were from petrous bones, while most of the samples with well-preserved collagen were from tooth roots and dentine.

We postulate that the physical protection of dentine by tooth enamel probably explains this F o r P e e r R e v i e w 7 differential preservation within a single horse skull. Using these revised QC criteria, the radiocarbon age of the remaining collagen samples ranged from 2780±25 2915±25 BP and are undistinguishable from the circle dates. We tested the accuracy of the new QC criteria by comparing the 14 C age of samples that had been dated twice. This is the case in SAT 810 and ST 5 where collagen from the same individual bone was extracted using two different methods and in SAT 354 where two different bones were dated. In each case, the 14 C ages did not significantly differ (T-test, p<.001). We also show that once the revised QC criteria are applied, there is no more correlation between collagen age and either collagen yield (r2= 0.15) or C/N ratio (r2= 0.02). This gives us confidence in the fact that the samples that passed the new QC criteria are not significantly contaminated and that their 14 C age is reliable.

Bayesian modeling

The radiocarbon dates of the selected samples (31 bone collagen, 20 calcined bones and 6 charcoal from the B10 complex, 2 bone collagen from the KTS01 khirgisuur and 3 bone collagen from the deer stone PAC38) were used to generate a high resolution sequence using Bayesian modeling. The principle this modeling technique is to combine radiocarbon dates with prior information to produce a posterior density estimate which combines both sorts of evidence. A high overall agreement of the model (by convention, 60% or above) will indicate that the posterior distribution agrees well with the prior distribution and that the prior information and the radiocarbon dates are consistent. On the contrary, a low overall agreement for the model will indicate that both the standardized likelihood and prior belief have to be reassessed. In the case of a monument like the B10 complex, adding prior information is not trivial because the dated material comes from structures that are not linked by any stratigraphic relationship. For this reason, we used only weak or non-informative prior to estimate the onset, duration and end of use of the B10 complex. To assess the relationship of the B10 complex with the other two dated structures, we also modeled the onset, duration and end of use of PAC38 and KTSE01. We used the resulting sample of 62 dates, and produced a Bayesian model containing three phases corresponding to the three dated monuments with a uniform prior using the OxCal and the IntCal13 radiocarbon calibration curve (Bronk-Ramsey & Lee 2013). We then used the OxCal 'Order' function in order to test the chronological ordering between the different monuments. We repeated this analysis again with an outlier model which identifies and downweights anomalous measurements (Bronk Ramsey 2009). Details of the models can be found in the SI Appendix (S4.A). Both models produced similar results, but only results from the outlier model are reported here. The model Table 1. We then used the OxCal 'Order' function in order to test the chronological ordering between the different monuments.

The results provided an age model that precisely dated the onset, duration and end of use of the three monuments (Figure 7). The model suggested that the construction of the horse and caprine ritual structures in the B10 complex started during the second half of the 11 th c. BCE (1057-1007 cal. BCE, 95.4%) and ended during the first half of the 10 th c. BCE (1014-948 cal. BCE, 95.4%). The overall span of use of the B10 complex was comprised between 0-93 y (95.4%) with a median value of 41 y (Fig. 8). For PAC38, the results suggest that the construction of satellite features started 1337-945 cal. BCE and ended 1060-684 cal BCE (95.4%). The overall span is comprised between 0-113 y with a median value of 32 y. For KTS01, the results suggest that the construction of satellite features started 1532-1017 cal. BCEE (90.9%, median 1143) and ended 1122-619 cal BCEE (90.9%, median 998). The overall span is comprised between 0-103 y with a median value of 22 y. The test for the ordering of the three structures suggested that there was a high probability (98.2%) that the small khirgisuur KTS01 was constructed before the B10 complex and the deer stone PAC38 (79.8%) (Table 2). On the contrary, the start of the B10 complex and the PAC38 area cannot be chronologically differentiated, highlighting a probable connection between deer stones and large khirgisuurs, as already proposed (Fitzhugh 2009a;Taylor et al. 2017). It is noteworthy that the boundaries for the PAC38 and KTS01 are less precise than for the B10 complex due to the limited number of radiocarbon dates available for modeling.

Our results show with a high degree of confidence that the 2361 peripheral structures of the B10 complex were constructed over a fairly short period of time, probably within a generation. However what the model does not effectively distinguish is whether the B10 complex was built essentially in an instant -in a single event -or whether it was built over a longer period of time. Indeed, the 2-sigma confidence interval for the span of construction (0-93 yrs) includes 0 and additional simulation is required to address this question meaningfully.

To decipher the different scenarios, we built three models which used fictitious bone and charcoal dates, following [START_REF] Bayliss | Bayesian Buildings: An Introduction for the Numerically Challenged Vernacular Architecture[END_REF]. Details of the models can be found in the SI Appendix (S4.B-D). The three models show the calibrated dates integrated in a single phase to mimic the real dataset for the B10 complex. The dates have been simulated by a process of back calibration from samples whose real age is centered around 1000 cal BC as suggested by the results of the previous model. In the first model (Model 0), we hypothesized that all the peripheral structures were built in a single event and date from 1000 cal BC; in the second yrs, between 1025 and 975 cal BC; in the third model (Model 100), we hypothesized that the peripheral structures were constructed over 100 yrs, between 1050 and 950 cal BC. The results provided age models that precisely dated the onset, duration and end of use of the B10 complex Table 3. The comparison of the shape of the probability distribution for the real data (Fig 8) and the three simulations (Fig. 9) allow us to discard the single-event model (Model 0) because in this model, the highest probability is predicted for a span of 0 yrs (median 15 yrs).

We can also exclude Model 100 which does not include 0 in the modeled span. The best match is found with the intermediate simulation (Model 50) both in terms of model outputs (onset, duration and end of use) and in terms of the shape of the probability distribution of the span, suggesting that the B10 complex was built over a period of about 50 yrs.

Several functions have been attributed to large DSK complexes. While large monuments of the Mongolian Bronze Age are often presented as the earliest expression of elite power and inequality (Allard & Erdenebaatar 2005;Fitzhugh 2009a;[START_REF] Houle | Socially Integrative Facilities and the Emergence of Societal Complexity on the Mongolian Steppe[END_REF], others prefer to see them as instruments of trans-egalitarian interactions and invoke their importance as structuring elements of Bronze Age societies (Wright 2014). While the data and analysis presented here do not call into question the assumptions about the significance of large complexes, they are an essential anchor for the theoretical models proposed. For the first time, it also becomes possible to make some inference regarding the size of the population that built large DSK complexes such as that of Tsatsyn Ereg. In Mongolia today, households usually slaughter a horse per year, at the beginning of winter [START_REF] Marchina | The skull on the hill. Anthropological and osteological study of horse skull repositories among contemporary herders in Mongolia (Arkhangai province)[END_REF]. Modern ethnographic observations also show that in Central Mongolia, horse skulls are deposited annually on the top of ovoos [START_REF] Marchina | The skull on the hill. Anthropological and osteological study of horse skull repositories among contemporary herders in Mongolia (Arkhangai province)[END_REF]. Assuming a similar practice in the Late Bronze Age, we calculated that twenty-five family units/households would have been able to slaughter the ca. 1260 horses (corresponding to the 1116 and 144 mounds of B10 and PAC38, respectively) over the period of 50 years proposed based on our model. The different polygonal or linear arrangements of mounds observed at khirgisuur B10 include 10 to 15 mounds could then well represent these synchronous (possibly annual) events. Given the similarity between the number of stone mounds and stone circles, the deposition of burnt caprine bones could have occurred at the same rate, either at the same time as the deposition of the horse heads or at another time of the year. It is noteworthy that this figure of twentyfive family units/households is very similar to the paleodemographic estimates proposed for contemporary Bronze Age populations living in Arkhangaï (Houle 2010;cited in Houle 2017) or further north in the Hovsgol aimag [START_REF] Frohlich | Bronze age burial mounds (khirigsuurs) in the Khovsgol aimag, Mongolia: a reconstruction of biological and social histories[END_REF]. The Late Bronze Age is often presented as a period marked with major increases in people and animal mobility and our work also provides indirect insight into the question of the size of the regional networks at that time. Because animal remains were gradually deposited across a human lifetime around the khirgisuur, its construction did not require to draw on large regional networks and involve contributors from remote regions. Although this does not exclude the mobility of some individuals, our results suggest that the importance of local social and demographic organisation is perhaps underestimated. This is in partial disagreement with recent strontium isotopic evidence suggesting that Bronze Age horses from khirgisuurs located in the Khanuy Valley came from geographically distant locales and would be representative of social networks active over great distances [START_REF] Rodriguez | Isotopic evidence for ceremonial provisioning of Late Bronze age khirigsuurs with horses from diverse geographic locales Quaternary International[END_REF].

More work based on the comparison of the isotopic signature of horse teeth with isotope mapping of the distribution of local bioavailable strontium will be required to fully address this question.

.

Conclusion and perspective

New radiocarbon dating, involving the excavation of a large number of structures and Bayesian modeling of the results allow, for the first time, a high precision chronology for the construction of a DSK complex to be derived. Our findings place the beginning of the construction of the B10 complex during the second half of the 11 th c. BCE. They do not plead in favor of a single ceremony for the building of these features as suggested by some authors (Fitzhugh & Bayarsaikhan 2009;Fitzhugh 2017). They nevertheless strongly suggest that the time period required to construct the B10 complex was short, in the order of a human lifetime at the most. Bayesian modeling of the radiocarbon dates also demonstrated that ritual activities around the deer stones and the large khirgisuur complex are contemporary, highlighting a probable functional connection between the two types of monuments in agreement with (Fitzhugh 2009a;Taylor et al. 2017) shown to be completely unreliable. To a lesser extent, some of the new bone collagen dates presented here were also affected by contamination with modern carbon from the soil and required in-depth screening. We cannot dismiss the possibility that the contamination issue highlighted in this study could also apply to other sites where dated artifacts are heavily exposed to weathering. This would affect mostly shallowly buried finds like bones found in Bronze Age satellite features. In our study, contamination affected mostly bone but some teeth were also impacted. Only a careful selection under the microscope of the best preserved dentine and root fragment allowed to improve the collagen yield, C/N ratio and ultimately the radiocarbon results. Because most of the available radiocarbon dates published for the Mongolian Bronze Age lack QC information, their overall reliability should be reassessed.

We call for a widespread emulation of similar quality control measures in shallow burial contexts from across the Eurasian continent. As contamination adds modern carbon, making the dates look too young, this might bring into question earlier conclusions regarding the duration of the khirgisuur phenomenon, and the possible overlap with the slab-burial and the well-dated Arzhan culture in Mongolian Altai around 800 BCE (Taylor et al. 2017). Fully addressing these questions will require pursuing the research effort both in the field, with more in-depth excavation of key archaeological sites, and in the laboratory, by carefully selecting and directly dating the ritual structures implying domestic animals.

S1 Previous radiocarbon dating of Urt Bulagyn (Khanuy Valley) and the Tsatsyn Ereg monuments (Khoid Tamir Valley) discussed in this paper

To date, only two large khirgisuurs have multiple dates: Urt Bulagyn and the B10 complex both located in central Mongolia (Arkhangaï aimag). Urt Bulagyn (Khanuy Valley) covers about 15 ha and contains ca. 2700 peripheric structures out of which only four have been excavated and dated (Allard & Erdenebaatar 2005;Fitzhugh & Bayarsaikhan 2009). The calibrated dates suggest a possible outward growth for the satellite mound sector over a period of a few hundred years between the 11 th and the 7 th c BCE (Table S1 Fig S1). The DSK complex of Tsatsyn Ereg is located 50 km southeast of Urt Bulagyn in the Khoid Tamir Valley. It contains several deer stones and a large khirgisuur (B10) covering about 22 ha and containing 2361 peripheral structures (Magail 2008). This monument is part of the area surveyed and excavated since 2007 by the Monaco-Mongolia mission in Mongolia under the patronage of H.S.H. Prince Albert II and the aegis of UNESCO. Two mounds associated with a deer stone (PAC38) were dated and returned 14 C ages of 2580±30 and 2660±30 BP, covering a period comprised between the 9 th and the 6 th c. BCE (Gantulga 2015). The dates obtained on six peripheral structures associated with the B10 complex vary between 2160±30 BP and 2800±30 BP (Table S1, Figure S1). The calcined bones found in the circles returned the oldest ages. Two mounds (532 and 803) contained two horse heads each, which were both dated yet which returned very different 14 C ages (Table S1, Figure S1). The results obtained at Tsatsyn Ereg are somewhat problematic for several reasons. First, they could suggest that circles from the B10 complex were constructed several centuries before the mounds. This is rather counter intuitive from a geometric point of view since the circles surround the mounds and form the outer ring of the structure. Second, the age difference between the two individual horses found in the same mound is difficult to explain. This result would suggest either two distinct interventions in a single mound separated by several centuries, or the deposition of a weathered horse skull together with a freshly killed horse head, something undocumented archaeologically. Finally, the wide large age range would argue for an extensive period of use for this khirgisuur from about the 11-10 th c BCE to the 4-2 nd c. BCE. If confirmed, the prevalence of the same ceremonial activity over several centuries would be unprecedented archaeologically and raise questions regarding its significance and function.

For the reasons mentioned above, we consider it likely that serious doubts must be attached to the vast majority of the radiocarbon dates performed at Tsatsyn Ereg. The collagen dates in particular seemed doubtful and invite us to revisit the dating of the site. Collagen is usually considered the material of choice for radiocarbon dating as it allows direct dating of the bone remains. The chemical integrity of the molecule can be assessed independently of the measured age, using collagen yield and C/N ratio as proxies (DeNiro 1985;Ambrose 1990;van Klinken 1999). The vast majority of the samples dated in Mongolia, including the ones mentioned above (but see (Taylor et al. 2017)), were processed by Beta Analytics, a private company which provides very little detail about its analytical procedures and which did not include, until very recently, the classical quality control indicators of collagen yield and C/N ratio.

F o r P e e r R e v i e w 3

S.2. Methods

Calcined bone

Calcined bones were sonicated in distilled water and oven-dried. Only the whitest fragments were selected with 1-2 g being powdered (<100 µm). The powder was then pretreated in acetic acid (1N) under a weak vacuum for 20 h to remove diagenetic carbonates, rinsed in distilled water and oven-dried. Yields were calculated and carbon isotope values were measured using a Kiel interfaced with a Thermo DeltaPlus Advantage mass spectrometer. All samples had δ 13 C values below -20‰ indicating that recrystallization was complete (Zazzo et al. 2012;Hüls et al. 2010). A total of 0.5-1.0 g was hydrolyzed in orthophosphoric acid under a vacuum for 20 min. The evolved CO2 was cleaned using Sulfix then introduced in a semiautomated graphitization unit.

Charcoal

Charcoal was pretreated using the classical acid-alkali-acid method. First immersed in HCl 1N for 1h, rinsed to neutrality then immersed in NaOH 0.1 N for 1-20 min depending on the degree of decoloration, rinsed to neutrality, then immersed in HCl 1N again for 1 h. Finally, the samples were rinsed and oven-dried overnight at 50°C. Yields were calculated and only samples with yields above 50% were dated. These samples (1-3 mg) were then wrapped in ultra-light tin capsules, combusted and graphitized in the automated AGE 3 device.

Bone and tooth collagen

Each mound that provided a horse remain was sampled for radiocarbon dating. When two horses were deposited in the same mound, both were sampled. When possible, bone and teeth from the same individual were also sampled. We selected the petrous bone as this bone is considered to be denser and therefore the favorite support for DNA and collagen extraction (Pinhasi et al. 2015). Bone and teeth were rinsed in an ultrasonic bath then oven-dried overnight. They were crushed in a mortar and pestle, then sieved and the 0.3-0.7 mm fraction was kept for analysis. For teeth, we selectively removed the enamel and cement fractions under the microscope and only kept the better looking dentine and/or root fraction. Two methods of collagen extraction were used. The first method was our in-house protocol [START_REF] Bocherens | Isotopic biogeochemistry (13C,15N) of fossil vertebrate collagen: application to the study of a past food web including Neandertal man[END_REF]. Coarse bone powder (0.3-0.7 mm) was immersed in 1 N HCl for 20 min under continuous stirring. The solution was filtered on a 5.0 µm pore size mixed cellulose The resulting alkali-insoluble residue was subsequently immersed in 0.01 N HCl and gelatinized at 100 °C for 17 h. The final solution was then filtered on the cellulose membrane and the gelatinized collagen freeze-dried. Most of the collagen samples had a creamy to beige color, suggesting incomplete decontamination. For eighteen samples, we added an ultrafiltration step to further purify the extracted collagen. The ultrafilters (Vivaspin® 15)

were cleaned following (Brock et al. 2013). The solubilized collagen was spun for 20 min at 3000 rpm and the remaining volume was checked. This operation was repeated until only 0.5-1 mL remained in the upper part of the filter. Both fractions were collected and freeze-dried.

About 2.5 mg of collagen was wrapped in an ultra-light tin capsule, and combusted in the elemental analyzer (EA) of an AGE 3 automated compact graphitization system (Wacker et al.

2010

). The quality control parameters (%C, %N and C/N ratios) were measured in the EA prior to graphitization. The CO2 was then transferred to the graphitization unit where reduction was performed in seven quartz reactors, each containing 5 mg of iron catalyst. In order to reduce the risk of memory effects in the graphite reactors, a sample of similar expected age (a VIRI F collagen sample of about 2525±69 BP, or an aliquot of the same sample) was combusted prior to each sample to be dated. Graphite samples were then pressed into targets within a few days. Two oxalic acid II standards and two phtalic anhydride blanks were processed together with the unknowns every ten samples (Synal et al. 2007).

Graphite targets were dated using the compact AMS ECHoMICADAS at Gif-sur-Yvette

S.3. Results

Radiocarbon dating of the circles

Calcined bones and charcoal from twenty circles within the B10 complex were analyzed and the results are summarized in the SI Appendix (Table S2 and Fig. S2). Calcined bone δ 13 C values ranged between -19.7 and -25.4 ‰ and are typical of well-calcined bones. Their radiocarbon age range was between 2770±20 and 2860±20 BP (average 2827±6 BP, n= 20).

There was no correlation between calcined bone age and carbon isotope value, indicating that the bone samples had not been significantly affected by contamination from soil carbonate (r2= 0.07). The charcoal radiocarbon age range was between 2780±20 and 2910±25 BP (average 2839±18 BP, n= 7). Overall, charcoal and calcined bone radiocarbon ages did not differ significantly (T-test, p= 0.41). In six circles, pairs of calcined bone and charcoal were dated (SI Appendix, Fig. S2). Four pairs of dates (circles C107, 111, 113 and 117) passed the Chi2 test (T<3.84), while the remaining two did not. In one case (C103), charcoal was 75 14 C years younger than the calcined bone, possibly suggesting possible contamination of the charcoal by roots; in the case of C102, the charcoal was 75 14 C years older, possibly highlighting an old wood effect. For these six pairs, the 14 C dates from charcoal were more variable than from the calcined bones but the average values were not significantly different (2840±53 BP vs 2842±24 BP, n= 15) (p= 0.94).

Radiocarbon dating of the mounds

Collagen was extracted from the horse bones and teeth from the three excavated complexes: KTS-01, B10 and PAC38. The results are summarized in SI Appendix (Table S2).

Because the chronological relationships between the three complexes cannot be assessed independently, the results are described separately. All the bones and teeth were treated using Method 1 [START_REF] Bocherens | Isotopic biogeochemistry (13C,15N) of fossil vertebrate collagen: application to the study of a past food web including Neandertal man[END_REF]. For a subset of 18 samples the collagen underwent an extra step of ultrafiltration (Method 2). The results obtained using the two methods are presented below.

Method 1

Khirgisuur KTS-01: The seven mounds associated with the khirgisuur KTS-01 were excavated and six of them provided datable material. Collagen was extracted from four petrous bones and two teeth. Collagen contents ranged from 4.7 to 14.9%, higher than the cutoff value of 1% used by radiocarbon labs (van Klinken 1999; Brock et al. 2010). Higher 8 yields were measured in tooth samples (11.9 and 14.9%) than in petrous bones (4.7-8.7%).

C/N ratios ranged from 3.23 to 3.51, within the 2.9-3.6 range of uncontaminated collagen (DeNiro 1985;Ambrose 1990). C/N ratios were lower in teeth (3.23 and 3.24) than in bones (3.30-3.51). Radiocarbon ages ranged between 2785 and 2890 BP. A positive correlation was found between the collagen yield and the 14 C age (r2= 0.94), and a negative correlation was found between the C/N ratio and the 14 C age (r2= 0.86) (SI Appendix, Fig.

Deer stone PAC38: Three mounds associated with the deer stone PAC38 were excavated and collagen was extracted from three horse teeth. High collagen contents (15-16%), and low C/N ratios (3.21 to 3.24) were measured. The radiocarbon ages cluster tightly and range between 2840 and 2860 BP. No correlation was found between the collagen yield, the C/N ratio and the 14 C age.

Khirgisuur B10: From the B10 complex, thirty out of the 38 excavated mounds provided datable material (either bones or teeth) which was sampled for radiocarbon dating. In some of the structures, both bones and teeth from the same individual were dated. Collagen contents ranged from 2.3 to 18.3%, above the accepted cutoff value of 1% (van Klinken 1999;Brock et al. 2010). C/N ratios ranged from 3.07 to 3.53, within the accepted 2.9-3.6 range (DeNiro 1985; Ambrose 1990). Average collagen content was twice as high in teeth (9.6±3.4%, n= 27) than in bone (4.5±2.4%, n= 20). On average, the C/N ratio was lower in teeth (3.26±0.06, n= 27), than in bones (3.36±0.13 n= 20). Radiocarbon ages ranged between 2630±25 and 2925±25 BP. On average, radiocarbon ages were lower in bones (2777±82 BP) BP than in teeth (2835±45 BP). A negative correlation was found between the C/N ratio and the 14 C age (r2= 0.68). No correlation was found between the collagen yield and the 14 C age (r2= 0.17), but the youngest ages were found in samples with less than 5% collagen (SI Appendix, Fig.

S4).

Method 2

A selection of 18 bone collagen extracts from the B10 complex was ultrafiltered. Results are summarized in the SI Appendix (Table S2 and Fig. S5). For five samples, both the highmolecular weight (HMW, > 30 KDa) and the low-molecular weight (LMW, < 30 KDa) fractions were dated. For the remaining 13 samples, only the HMW fraction was dated. The C/N ratios in HMW fractions ranged from 3.23 to 3.46 (3.34±0.07 on average), within the accepted range of 2.9-3.6. The C/N ratio in LMW fractions were significantly higher, ranging F o r P e e r R e v i e w

S.4. Modeling

S4.A. Tsatsyn model

The model used only weak or non informative prior to estimate the onset, duration and end of use of the B10 complex, PAC38 and KTS01. We used the resulting sample of 62 dates to produce a Bayesian model containing three phases corresponding to the three dated monuments, with a uniform prior using the OxCal and the IntCal13 radiocarbon calibration curve (Bronk-Ramsey & Lee 2013). We then used the OxCal 'Order' function in order to test the chronological ordering between the different monuments. We repeated this analysis once with an outlier model which identifies and downweights anomalous measurements (Bronk Ramsey 2009). Two different outlier models were used for the charcoal and bones, respectively. The outlier-model used for the charcoal ("Charcoal") was a Normal "t" outlier-analysis model postulating an a priori outlier probability of 5% for every sample following (Bronk Ramsey 2009). We used this outlier-model because we could not exclude that the charcoal was either too old due to an old-wood effect or too young due to contamination. The outlier-model used for calcined bone and bone collagen ("Bone") is a negative exponential model postulating an a priori outlier probability of 100% for every sample. We used this model because we postulated that bones were all in a primary position and could only be too young due to contamination with modern carbon. Both models produced similar results, but only results from the outlier model are reported here. The model was run five times to assess its reproducibility and the data from one of the runs are shown in Table 1

S4.B. Model 0

The model uses fifty fictitious radiocarbon dates to estimate the onset, span and end of use of the B10 complex. Here we postulate that the B10 complex was constructed in an instant. The radiocarbon distributions have been simulated by a process of back-calibration from samples whose real age is 1000 cal BC. All the dates are grouped in a single phase to produce the Bayesian model, with a uniform prior using the OxCal and the IntCal13 radiocarbon calibration curve (Bronk-Ramsey & Lee 2013). The model was run five times to assess its reproducibility and the data from one of the runs are shown in Table 3. The model uses fifty fictitious radiocarbon dates to estimate the onset, span and end of use of the B10 complex. Here we postulate that the B10 complex was constructed over fifty years. The radiocarbon distributions have been simulated by a process of back-calibration from samples whose real age range between 1025 and 976 cal BC. All the dates are grouped in a single phase to produce the Bayesian model, with a uniform prior using the OxCal and the IntCal13 radiocarbon calibration curve (Bronk-Ramsey & Lee 2013). The model was run five times to assess its reproducibility and the data from one of the runs are shown in Table 3. The model uses fifty fictitious radiocarbon dates to estimate the onset, span and end of use of the B10 complex. Here we postulate that the B10 complex was constructed over a hundred years. The radiocarbon distributions have been simulated by a process of back-calibration from samples whose real age range between 1050 and 950 cal BC. All the dates are grouped in a single phase to produce the Bayesian model, with a uniform prior using the OxCal and the IntCal13 radiocarbon calibration curve (Bronk-Ramsey & Lee 2013). The model was run five times to assess its reproducibility and the data from one of the runs are shown in Table 3.

  ha and contains 2361 peripheral structures (Fig.

  times to assess its reproducibility and the data from one of the runs are shown in

  50), we hypothesized that the peripheral structures were constructed over 50

  contra[START_REF] Weber | Long-term occupation and seasonal mobility in Mongolia: a comparative study of two mobile pastoralist comunities[END_REF]. This work highlights the importance of large monuments as structuring elements of Bronze Age societies, at a time of intense socio-political transformations of a scope hardly before seen in this region of Eastern Eurasia. This work has also broader implications as it invites us to question the validity of previous chronologies proposed for the monumental cultures of central Asia based on the direct dating of bone collagen artifacts. Previous dates obtained at Tsatsyn Ereg have been

  . 2014. Landscapes of Inequality? A Critique of Monumental Hierarchy in the Mongolian Bronze Age Asian Perspectives 51: 139-63.

Figure Legends : Fig. 1 .Fig. 2 .

 :12 Figure Legends: Fig. 1. Localization map of Tsatsyn Ereg and of the three dated monuments Fig. 2. The large khirgisuur B10 at Tsatsyn Ereg, Mongolia.

Fig. 3 .Fig. 4 .Fig. 5 .Fig. 6 .

 3456 Fig. 3. Plan of the khirgisuur KTS01 and the excavated peripheric structures Fig. 4. Plan of the deer stone PAC 38 and the excavated peripheric structures Fig. 5. Plan of the khirgisuur B10 and the excavated peripheric structures Fig. 6. Ritual features at the B10 khirgisuur. Top panel: Mound ST 1 containing at its center the heads of two horses. Bottom panel: Circle ST 114 containing at its center (whitish area) calcined bones of caprines.

Fig. 7 .

 7 Fig. 7. Modeled start and end dates for the large khirgisuur B10, the deer stone PAC38 and the small khirgisuur KTS01 from the site of Tsatsyn Ereg.

Fig. 8 .

 8 Fig. 8. Modeled span for the large khirgisuur B10.

Fig. 9 .

 9 Fig. 9. Modeled spans for Model 0 (a) Model 50 (b) and Model 100 (c). The calibrated dates have been simulated from 50 samples which either all date to 1000 cal BC (Model 0), or range from 1025 to 975 cal BC (Model 50), or range from 1050 to 950 cal BC (Model 100).

  Fig. 1.

  then rinsed. After which the acid insoluble residue was immersed in 0.1 N NaOH for 20 h. The solution was then filtered again on the cellulose membrane and rinsed.

(

  France). Data reduction was performed using BATS software (version 4.07)(Wacker et al. 2010). The first couple of scans were discarded to account for possible surface contamination of the target due to contact with ambient air between the graphitization and the AMS measurement. Measurement parameters such as 12C current and 13CH current were checked. Time and isobar corrections were made prior to validation. Normalization, correction for fractionation and background corrections were applied for each individual run by measuring the oxalic acid II NIST standard and the phthalic anhydride blanks.

  from 3.41 to 3.62 (3.53±0.08, on average) with one sample exceeding the accepted range (a petrous bone from ST2, C/N= 3.62). Intra-individual differences in the C/N ratio between the LMW fraction ranged from 0.07 to 0.23 (average difference 0.13±0.06, n=5).The radiocarbon ages of the HMW samples ranged from 2665±25 to 2905±25 BP (2805±58, on average, n= 18). The radiocarbon ages of the LMW samples were significantly lower and ranged from 2515±25 to 2720±25 BP (2629±83, on average, n= 5). Intra-individual differences in radiocarbon age between the HMW and the LMW fraction ranged from 80 to 185 14 C yr BP (average difference 126±46 14 C yr BP, n=5).

Figure S6 .

 S6 Figure S6. Left panel: Comparison of radiocarbon dates of collagen samples prepared using Method 1 (no ultrafiltration) and Method 2 (ultrafiltration, HMW fraction). Right panel: Radiocarbon age (average ± SD, n= 15) for each method.

Table 1 .

 1 Results of the Tsatsyn Phase Model using the IntCal13 calibration curve

				IntCal 13
		Number of	68.2% (y cal BCE)	95.4 (y cal BCE)
		dates in the
	Boundary	Model
			From	To	From	To	Median
	B10
	Start	57	-1037	-1014	-1057	-1007	-1027
	End		-1003	-972	-1014	-948	-986
	Span		13	63	0	93	41
	PAC38 Start End	F 3 o -1104 r -1024	-996 -919	-1337 -1060	-945 -684	-1054 -965
	Span KTS01 Start End Span Results obtained using the Outlier approach 0 P e 2 -1226 -1034 53 e -1106 -914 r e -1749 0 -1122 0 42 0 R	113 -1017 -379 103	32 -1143 -998 22
					v
					i e
					w
							23

Table 2 .

 2 Probability that the start of Event 1 (left column) precedes Event 2 (top row) using

	OxCal 'Order' function
			Event 2
			B10	PAC38	KTS01
	Event 1	B10	-	27.73%	1.76%
		PAC38	72.27% -	20.16%
		KTS01	98.24%	79.84% -

Table 3 .

 3 Results of the Model 0, 50 and 100 using the IntCal13 calibration curve

	IntCal 13

Table of contents S.1. Previous radiocarbon dating of Urt Bulagyn (Khanuy Valley) and the Tsatsyn Ereg monuments (Khoid Tamir Valley) discussed in this paper

	S.2. Methods
	S 3. Results
	S.4. Modeling
	Tables and Figures

Table S1 .

 S1 Previous radiocarbon dates from Urt Bulagyn (Khanuy Valley, Arkhangaï aimag) the B10 complex and deer stone PAC 38 (Khoid Tamir Valley, Arkhangaï aimag)

Table S2 .

 S2 Results of the 100 AMS-radiocarbon analyses performed on charcoal (7), calcined bone (20) and bone and tooth collagen (73) from the B10 complex, the deer stone PAC38, and the khirgisuur KTS01.

	F o r
	P e
	e r
	R e
	v
	i e Figure S5. Top panel: comparison of radiocarbon dates of high molecular weight (HMW, > 30KDa) and low molecular weight (LMW, < 30 KDa) fractions of six ultrafiltered collagen samples prepared using Method 2 (see Table S2 for details). Bottom panel: comparison of C/N ratios of high molecular w
	weight (HMW, > 30KDa) and low molecular weight (LMW, < 30 KDa) fractions of six ultrafiltered
	collagen samples prepared using Method 2.
	Figure S6. Left panel: Comparison of radiocarbon dates of collagen samples prepared using Method 1
	(no ultrafiltration) and Method 2 (ultrafiltration, HMW fraction). Right panel: Radiocarbon age
	(average ± SD, n= 15) for each method.
	2

Figure S1. Previous calibrated dates from Urt Bulagyn (Khanuy Valley) and the Khoid Tamir Valley monuments discussed in this paper (see Table S1 for details) Figure S2. Left panel: comparison of radiocarbon dates of charcoal and calcined bones in six circles from the B10 complex. Right panel: radiocarbon age (average ± SD, n= 6) for charcoal (black circle) and calcined bone (open circle).

Figure

S3

. Top panel: relationship between bone and tooth collagen radiocarbon age and C/N ratio at KTS01. Bottom panel: relationship between bone and tooth collagen radiocarbon age and collagen yield at KTS01. Collagen was extracted using Method 1. Figure

S4

. Top panel: relationship between bone and tooth collagen radiocarbon age and C/N ratio at the B10 complex. Bottom panel: relationship between bone and tooth collagen radiocarbon age and yield at the B10 complex. Collagen was extracted using Method 1.

Table S1 .

 S1 Previous radiocarbon dates from Urt Bulagyn (Khanuy Valley, Arkhangaï aimag) the B10 complex and deer stone PAC 38 (Khoid Tamir Valley, Arkhangaï aimag) Previous calibrated dates from Urt Bulagyn (Khanuy Valley) and the Khoid Tamir Valley monuments discussed in this paper (see Table S1 for details)

									Calibrated range
	Structure type	Feature	Sample material	Sample detail	Target #	14 C age error	(IntCal13, 2σ)	Reference
									From	To
	Khirgisuur B10 (Khoid Tamir Valley)
		C531		calcined bone	-	B-290938	2790	30	-1011	-846	Gantulga 2015
	Circles	C531		calcined bone	-	B-290945	2760	30	-992	-830	Gantulga 2015
		C1162		calcined bone	-	B-290943	2800	30	-1027	-848	Gantulga 2015
		SAT 528		indet.		B-323801	2590	30	-820	-595	Gantulga 2015
		SAT 532		bone fragment	Horse B	B-290941	2270	40	-403	-206	Gantulga 2015
	Mounds	SAT 532 SAT 803 SAT 803 SAT 811 F tooth fragment bone fragment petrous bone indet. o r F o r	Horse A Horse B Horse A	B-290940 B-290936 B-290935 B-323804	2610 2160 2310 2340	40 30 40 30	-894 -358 -482 -507	-590 -108 -209 -366	Gantulga 2015 Gantulga 2015 Gantulga 2015 Gantulga 2015
	Deer Stone PAC38 (Khoid Tamir Valley) Mounds PAC38-1 PAC38-95 Khirgisuur Urt Bulagyn (Khanuy Valley) KYR1-9	Horse bone Horse bone P e P e Horse tooth e ---r e r	B-323806 B-323808 B-159598	2660 2580 2810	30 30 40	-895 -814 -1073	-794 -590 -843	Gantulga 2015 Gantulga 2015 Allard and Erdenebatar 2005
	Mounds	KYR1-17 KYR1-21 KYR1-22		Horse tooth Horse tooth Horse tooth	---R e R e v B-170749 B-222532 B-222533 v	2680 2780 2790	70 50 40	-1015 -1049 -1042	-597 -820 -836	Allard and Erdenebatar 2005 Fitzhugh and Bayarsaikhan 2009 Fitzhugh and Bayarsaikhan 2009
						i e i e
						w w
									5

4 Figure S1.

  Left panel: comparison of radiocarbon dates of charcoal and calcined bones in six circles from the B10 complex. Right panel: radiocarbon age (average ± SD, n= 6) for charcoal (black circle) and calcined bone (open circle). Top panel: relationship between bone and tooth collagen radiocarbon age and C/N ratio at KTS01. Bottom panel: relationship between bone and tooth collagen radiocarbon age and collagen yield at KTS01. Collagen was extracted using Method 1. Top panel: relationship between bone and tooth collagen radiocarbon age and C/N ratio at the B10 complex. Bottom panel: relationship between bone and tooth collagen radiocarbon age and yield at the B10 complex. Collagen was extracted using Method 1. Top panel: comparison of radiocarbon dates of high molecular weight (HMW, > 30KDa) and low molecular weight (LMW, < 30 KDa) fractions of six ultrafiltered collagen samples prepared using Method 2 (see TableS2for details). Bottom panel: comparison of C/N ratios of high molecular weight (HMW, > 30KDa) and low molecular weight (LMW, < 30 KDa) fractions of six ultrafiltered collagen samples prepared using Method 2.

	ST116 ST117 ST 117 ST118 C476 C531 C1162 ST 1 ST 1 ST 1 ST 2 ST 2 ST 2 ST 3 ST 3 ST 5 ST 5 ST 5 ST 6 ST 6 ST 8 ST 8 ST 8 ST 8 ST 8 ST 8 ST 8 ST 8 ST 9 ST 10 ST 11 ST11 ST12 ST 14 ST 14 ST 15 ST 15 right petrous bone calcined bone calcined bone charcoal calcined bone calcined bone calcined bone calcined bone left petrous bone left petrous bone left petrous bone M1 sup G left petrous bone left petrous bone left petrous bone left petrous bone left lower P2 left lower P2 left petrous bone tooth indet tooth indet left petrous bone M1 sup D uper right third molar left petrous bone left petrous bone uper right third molar left petrous bone left petrous bone left petrous bone lower premolar upper tooth cervical bone left third premolar lower right first molar lower left P2 lower left P2 ST 15 right petrous bone ST 15 right petrous bone ST 16 left petrous bone ST 16 upper left P2 ST 17 left second molar ST 17 left second molar ST 18 left petrous bone ST 18 lower right P/M SAT 354 upper right P/M SAT 354 lower right M SAT 397 upper left P2 SAT 415 upper right P2 SAT 416 upper right P/M SAT 528 tooth indet SAT 528 tooth indet SAT 532 bone indet SAT 532 bone indet SAT 533 bone indet SAT 533 bone indet SAT 533 bone indet SAT 666 M sup D SAT 732 left dP3 SAT 799 P/M sup G SAT 799 petrous bone SAT 803 tooth indet S6 petrous bone Deer stone PAC38 Mounds Mounds PAC38-1 P2 inf G PAC38-27 tooth indet PAC38-95 P2 sup D 2650 2750 2800 2850 2900 Radiocarbon age (BP) 2700 2750 2800 2850 2900 Radiocarbon age (BP) 2950 2950 3000 SAT 803 tooth indet SAT 810 tooth indet SAT 810 tooth indet SAT 811 petrous bone SAT 811 tooth indet SAT 811 petrous bone SAT 811 tooth indet SAT 1023 P2sup G SAT 1023 M2 sup D Khirgisuur KTS01 Mounds S1 petrous bone S2 M sup S3 petrous bone S4 petrous bone S5 M sup 3.50 3.60 F o horse A ---------------horse A horse B --horse A horse A horse A F o r P e e r R e v i e w -24.8 16377 ECHo 1486 -88.2 --24.1 16378 ECHo 1482 -87.6 --16350 ECHo 1437 -78.5 42.0 -25.4 16379 ECHo 1470 -88.1 --21.0 17017 ECHo 1481 -89.3 --22.6 17018 ECHo 1472 -86.1 --21.6 17019 ECHo 1473 -86.7 -16322 ECHo 1416 1 6.4 16322 A ECHo 1687.1.1 2 (HMW) --16322 B ECHo 1687.1.2 2 (LMW) --17266 ECHo 1804.1.1 1 15.1 -16323A ECHo 1673.1.1 2 (HMW) --16323B ECHo 1673.1.2 2 (LMW) --16324 ECHo 1418 1 5.1 -16324B ECHo 1688.1.2 2 (LMW) --16327 ECHo 1439 1 12.5 -16327A Echo 1684.1.1 2 (HMW) -16326 ECHo 1438 1 8.4 --16328 ECHo 1420 1 3.3 --16328A ECHo 1675.1.1 2 (HMW) ---16325 ECHo 1419 1 3.7 --17267 ECHo 1805.1.1 1 8.9 --17021 ECHo 1491 1 4.5 -horse A -16325A ECHo 1689.1.1 2 (HMW) --horse A -16325B ECHo 1689.1.2 2 (LMW) --horse A -17021A ECHo 1678.1.1 2 (HMW) --horse B -16329 ECHo 1421 1 4.6 -horse B -16329A ECHo 1676.1.1 2 (HMW) ---16330A ECHo 1677.1.1 2 (HMW) ---16331 ECHo 1422 1 8.6 --16332 ECHo 1441 1 8.8 --16333A ECHo 1685.1.1 2 (HMW) --16334 ECHo 1424 1 8.7 --16335 ECHo 1442 1 4.9 --17268 ECHo 1806.1.1 1 18.3 --17269 ECHo 1807.1.1 1 9.9 --16336 ECHo 1425 1 4.7 --16336B ECHo 1674.1.2 2 (LMW) ---16336A Echo 1674.1.1 2 (HMW) ---16337 ECHo 1426 1 2.9 --17270 ECHo 1808.1.1 1 9.8 --16338 ECHo 1415 1 12.1 --16338A ECHo 2 (HMW) -F o r P e e r R e v i e w 1686.1.1 -16339 ECHo 1427 1 5.1 --17271 ECHo 1809.1.1 1 8.6 --17260 ECHo 1798.1.1 1 14.8 --14429 SacA39453 1 7.9 --17261 ECHo 1799.1.1 1 13.2 --17262 ECHo 1800.1.1 1 12.2 --17263 ECHo 1801.1.1 1 10.1 --17022 ECHo 1492 1 11.8 --17022A ECHo 1679.1.1 2 (HMW) ---17023 ECHo 1493 1 3.7 --17023A ECHo 1690.1.1 2 (HMW) ---17024 ECHo 1494 1 3.1 --17024A ECHo 1693.1.1 2 (HMW) ---17024B ECHo 1693.1.2 2 (LMW) ---17264 ECHo 1802.1.1 1 7.7 --14430 SacA39454 1 6.8 --17265 ECHo 1803.1.1 1 11.8 --17025 ECHo 1495 1 2.5 --17026 ECHo 1496 1 10.7 ---17277 ECHo 1815.1.1 1 4.7 ---17278 1816.1.1 1 15 ---17279 ECHo 1817.1.1 1 15.4 ---17280 ECHo 1818.1.1 1 16 -v i e w v i e w y = 10.609x + 2743.8 R 2 = 0.9356 v i e w w e i v ECHo R e R e R e e R F o r P e e r R e v i e w -17026A ECHo 1680.1.1 2 (HMW) ---17027 ECHo 1497 1 7.3 --17027A ECHo 1681.1.1 2 (HMW) -horse A -17028 ECHo 1498 1 5.0 -horse B -17029 ECHo 1499 1 7.4 -horse A -17028A ECHo 1682.1.1 2 (HMW) --horse B -17029A ECHo 1683.1.1 2 (HMW) --horse A -17258 ECHo 1796.1.1 1 5.6 -horse B -17259 ECHo 1797.1.1 1 9.5 ---17272 ECHo 1810.1.1 1 4.9 ---17273 ECHo 1811.1.1 1 11.9 ---17274 ECHo 1812.1.1 1 8.7 ---17275 ECHo 1813.1.1 1 6 ---17276 ECHo 1814.1.1 1 14.9 -e r e r C/N ratio e r 3.00 3.10 3.20 3.30 3.40 C/N ratio r e r P e Figure S2. 2700 2750 2800 2850 2900 2950 3000 Radiocarbon age (BP) charcoal calcined bone ST 102 ST 103 ST 107 ST 111 ST 113 ST 117 2700 2750 2800 2850 2900 2950 3000 2840 ± 53 2842 ± 24 F o r P e Figure S3. y = -366.97x + 4065.3 R 2700 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.55 P e 2550 2600 tooth e P bone 2 = 0.859 2750 2800 2850 2900 2950 F o r 2650 2700 2750 2800 2850 2900 Radiocarbon age (BP) F r o Radiocarbon age (BP) R 2 = 0.6808 2950 3000 Figure S4. y = -616.92x + 4841.3 Figure S5.	-------3.19 3.34 3.41 3.27 3.39 3.62 3.23 3.40 3.21 3.23 3.16 3.07 3.36 3.52 3.28 3.32 3.46 3.60 3.32 3.30 3.41 3.30 3.25 3.30 3.28 3.15 3.33 3.23 3.25 3.46 3.50 3.40 3.46 3.27 3.29 3.29 3.41 3.24 3.22 -3.24 3.25 3.23 3.32 3.29 3.42 3.37 3.53 3.43 3.54 3.27 3.25 3.25 3.49 3.32 3.51 3.23 3.24 3.21 3.31 3.27 3.24 3.36 3.30 3.30 3.26 3.22 3.25 3.41 3.23 3.30 3.44 3.24	2805 2850 2815 2770 2830 2840 2855 2810 2800 2720 2845 2770 2585 2915 2735 2840 2870 2850 2925 2790 2715 2850 2820 2665 2515 2850 2915 2810 2840 2780 2745 2805 2835 2755 2855 2875 2645 2695 2775 2685 2825 2805 2905 2790 2860 2880 2845 2900 2840 2865 2790 2815 2685 2710 2630 2765 2630 2820 2885 2845 2720 2745 2785 2860 2840 2840 2800 2835 2850 2815 2805 2865 2835 2865 2840 2785 2880 2845 2820 2890	20 -1006 20 -1107 25 -1015 20 -978 20 -1044 20 -1053 20 -1110 25 -1025 25 -1016 25 -911 25 -1107 25 -994 25 -811 25 -1207 -1021 -904 -929 -911 -842 -922 -924 -935 -901 -858 -815 -923 -840 -761 25 -926 -821 25 -1085 -918 25 -1121 -940 25 -1109 -928 25 -1214 -1037 25 -1009 -851 25 -908 -813 25 -1109 -928 25 -1042 -910 25 -895 -797 25 -791 -543 25 -1109 -928 25 -1207 -1021 25 -1025 -901 25 -1085 -918 25 -1002 25 -970 -826 25 -1023 -897 20 -1047 -925 25 -974 -831 25 -1111 -934 25 -1126 -941 20 -831 -796 25 -900 -807 25 -996 -845 25 -896 -804 25 -1047 -913 25 25 -1195 -1011 20 -1006 -859 25 -1115 -935 25 -1188 -946 30 -1110 -921 25 -1193 -1008 25 -1085 -918 30 -1118 -937 25 -1009 -851 25 -1028 -905 25 -896 -804 25 -905 -811 25 -830 -789 25 -978 -836 25 -830 -789 25 -1042 -910 30 -1193 -946 30 -1110 -921 20 -906 -820 25 -970 -826 25 -1006 -847 25 -1115 -935 25 -1085 -918 25 -1085 -918 25 -1016 -858 25 -1071 -913 25 -1109 -928 25 -1028 -905 20 -1008 -907 25 -1118 -937 25 -1071 -913 25 -1118 -937 25 -1085 -918 25 -1006 -847 25 -1188 -946 25 -1107 -923 25 -1042 -910 25 -1193 -998	11 Bone Bone Charcoal Bone Bone Bone Bone Bone excluded from model excluded from model Bone excluded from model excluded from model Bone excluded from model Bone Bone Bone excluded from model excluded from model excluded from model Bone excluded 12 from model excluded from model excluded from model excluded from model excluded from model excluded from model Bone Bone Bone Bone Bone excluded from model Bone Bone excluded from model excluded from model excluded from model excluded from model Bone Bone Bone 13 excluded from model Bone Bone Bone Bone Bone Bone excluded from model Bone excluded from model excluded from model excluded from model excluded from model excluded Bone Bone Bone excluded from model excluded from model 14 excluded from model Bone Bone Bone from model excluded from model Bone Bone excluded from model Bone Bone Bone Bone Bone excluded from model Bone excluded from model from model Bone excluded
	2700 2600	0	2	4	6	8	10	12	14	bone tooth	16
	2550				Collagen yield (%)
	0		5			10		15			20
					Collagen yield (%)
											15 16 17 18

  .

	Sequence ("KTS01")	Interval("Duration PAC38");
	{	Sum("Sum PAC38");
	Boundary ("Start KTS01");	};
	Phase("KTS01")	Boundary ("End PAC38");
	{
	R_Date("ECHo 1811 KTS01-S2", 2880, 25){Outlier("Bone",
	1);color="red";};
	R_Date("ECHo 1817 KTS01-S5", 2890, 25){Outlier("Bone",
	1);color="red";};
	Span("Span KTS01");
	Interval("Duration KTS01");
	Sum("Sum KTS01");
	};
	Boundary ("End KTS01");
	};
	};
	Order()
	{
	Prior("Start B10","0Start_B10.prior");
	Prior("Start PAC38","0Start_PAC38.prior");
	Prior("Start KTS01","0Start_KTS01.prior");
	};
	F o r F o r F o r
	P e P e P e
	e r e r e r
	R e R e R e
		v v v
		i e i e i e
		w w w
		22 23

Acknowledgments

We thank all the members of the Monaco-Mongolia Archaeological Mission. We are particularly thankful to the members of the 2016 mission who excavated a large number of the dated structures. We thank D. Fiorillo (SSMIM, Paris), M. Massault (GEOPS, Orsay), C. Gauthier, N. Tisnérat and F. Thil (LSCE, Gif-sur-Yvette) for their help with isotopic analysis, graphitization and radiocarbon dating, respectively. We also thank J. Cucchi for English editing, R. Witcher and the two anonymous reviewers for insightful comments. Fieldwork was supported by the Monaco-Mongolia Archaeological Mission (dir. J. Magail) and the French archaeological mission in Mongolia (CNRS, MNHN, MAEDI, dir. S. Lepetz). The analyses were supported by the LabEx BCDiv and the CNRS.

F o r P e e r R e v i e w 10 Table S2. Results of the 100 AMS-radiocarbon analyses performed on charcoal (7), calcined bone (20) and bone and tooth collagen (73) from the B10 complex, the deer stone PAC38, and the khirgisuur KTS01.