Characterization of archaeological obsidians from Lagartero, Chiapas Mexico by PIXE

Characterization of archaeological obsidians from Lagartero, Chiapas Mexico by PIXE

Journal of Archaeological Science 35 (2008) 3168–3171 Contents lists available at ScienceDirect Journal of Archaeological Science journal homepage: ...

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Journal of Archaeological Science 35 (2008) 3168–3171

Contents lists available at ScienceDirect

Journal of Archaeological Science journal homepage: http://www.elsevier.com/locate/jas

Characterization of archaeological obsidians from Lagartero, Chiapas Mexico by PIXE S. Rivero-Torres a, T. Calligaro b, D. Tenorio c, *, M. Jime´nez-Reyes c a

Instituto Nacional de Antropologı´a e Historia, Lic. Verdad No. 6, C.P. 06060 D. F. Mexico, Mexico Centre de Recherche et de Restauration des Muse´es de France, UMR 171, Palais du Louvre-Porte des Lions, 14, Quai François Mitterrand, 75001 Paris, France c ´n, Delg. Miguel Hidalgo, C.P. 11801 D.F. Mexico, Mexico Instituto Nacional de Investigaciones Nucleares, Apdo. Postal 18-1027, Col. Escando b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 7 February 2008 Received in revised form 24 June 2008 Accepted 29 June 2008

Obsidian samples from the archaeological site of Lagartero, Chiapas, Mexico and other samples from Mexican and Guatemalan sources were analyzed by proton induced X-ray emission. Statistical treatments such as principal-component analyses were applied to the data set. Obsidians from Lagartero were identified as coming from two obsidian sources in Guatemala and one in Mexico, thus indicating that there was contact between people of Lagartero and other Mayans or Mesoamericans. Ó 2008 Published by Elsevier Ltd.

Keywords: PIXE Obsidians Mesoamerica Lagartero Mexico

1. Introduction The archeological site of Lagartero (Fig.1) is a very important site for a knowledge of the cultural development in the Mayan area, especially because of its architectural remains, and the finding of characteristic lithic tools and ceramic pottery, which are intrinsically imprinted with the idiosyncratic stamp of their manufacturers (Rivero Torres, 1994– 1995,1990). The site is located in a small and privileged environment in the High Lands, thus presenting two main points of interest: archaeological and ecological. The area has been proposed as a National Park (Lagos de Colon), because it is the last surviving sector of the high subdeciduous jungle in this area. Lagartero, however, is a pre-Hispanic Mayan site offering a wide and worthy thorough range of possibilities for thorough research and having at the same time a pressing need to be protected from destruction. Lagartero is the largest archaeological site of the upper Grijalva river basin, having a characteristic architectural style that has so far been well preserved. According to the typology of the ceramic, this site was inhabited from the Protoclassical (100 B.C.) to the Early Postclassical (1200 A.C.) period. It is thus an ideal place for the study of the process of cultural changes that took place over a period of 1300 years, involving both ceremonial and domestic aspects.

* Corresponding author. E-mail address: [email protected] (D. Tenorio). 0305-4403/$ – see front matter Ó 2008 Published by Elsevier Ltd. doi:10.1016/j.jas.2008.06.026

The site is located on small islands surrounded by the Cristobal Colon lakes close to the community of the same name, which was established about 50 years ago by people from La Trinitaria, a municipality of the Chiapas State, Mexico. The Lagartero marsh is situated at the southwest of the Chiapas tableland at an altitude of 500–650 m and with an area of approximately 8.5 km2. Both the Lagartero and San Lucas rivers drain and flow into the Grijalva River. The Lagartero site is composed of eight islands and seven peninsulas of different sizes. The biggest island is called El Limonar, where most of the main and biggest structures have been found. During the first field work, the whole island was divided into 11 units. The Unit VII of Lagartero corresponds to the ballcourt area, which before being excavated looked only like two big parallel elongated mounds, one of which is 27.60 m long and 13.10 m wide and the other one 27 m long and 13 m wide, both of them being 2.70 m high. Later, these mounds, when excavated revealed two parallel structures, which form the ballcourt (Rivero Torres, 1996). The obsidian samples chosen for this research came from this zone and had been obtained by a surface search within an area of 2024 m2, before any specific deep excavation was carried out (Rivero Torres, 2005). Among the recovered pieces, the obsidian devices are of special interest because of the political and religious importance of this material for pre-Hispanic people. Obsidian, intensely exploited at that time, arrived at the regional markets by trade networks, which

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2. Experimental The analyzed obsidian samples from Lagartero are described in Table 1. Samples of Mexican sources from Ucareo and Zinapecuaro (Michoacan) and one sample purchased in a workshop at Guaytan, Guatemala were analyzed as well. All these samples were carefully brushed in order to eliminate dust; later on after they had been washed by ultrasonic agitation using a solution of 10% EXTRAN (Merck Co.) in distilled water, they were dried at environmental temperature. PIXE analyses were carried out with an external micro-beam of the AGLAE facility of the Recherche et de Restauration des Muse´es de France. In this set-up, a 3-MeV proton beam passed to the air through a 0.1-mm thick Si3N4 foil and focused with a diameter of 30mm on the target with a triplet of magnetic quadrupole lenses. Two X-ray detectors were used to determine in a single run both bulk and trace-element composition. The first detector, equipped with an ultra-thin window and a flow of helium gas along the path from target to crystal, was used to measure low-Z elements, among which were the major constituents of obsidian (10 < Z < 27). The second detector with a 50-mm aluminum filter allowed us to measure high-Z elements (Z > 26) present at a trace concentration. The two detectors, oriented at 45 relative to the beam axis, had an active area of 10-mm2 and 50-mm2, yielding solid angles of 0.002Sr and 0.260-Sr, respectively. The samples were placed on a motorized sample-holder and analyzed at three spots. To avoid possible compositional heterogeneities when using a 30-mm diameter beam, the samples were mechanically moved; the beam covered a square area of 0.2  0.2-mm2. The beam intensity was 0.4-sA and the integrated electric charge was 0.2-mC. Quantitative analyses were obtained by processing two spectra, which were recorded at each spot with GUPIX software (Maxwell et al., 1995). This computer code can conveniently provide major and trace-element concentrations without measuring the integrated electric charge. The major constituents were extracted from the first spectrum only by normalizing the total oxide content to 100% without needing the dose of incident protons. The iron concentration delivered in the first step was subsequently used as an internal standard for the processing of the second spectrum to obtain the trace-element content. Chemical data were analyzed using the MURR procedures for statistical analysis of multivariate archaeometric data written in GAUSS language by Neff (2008). Fig. 1. Map of the Lagartero region. (1) Chiapas State Mexico. (2) Guatemala. (3) Michoaca´n State Mexico.

at times covered long distances, thus increasing, in great measure, the development of societies and their cultural exchanges. The characterization of the most important obsidian sources and the identification of the origin of the devices found at the archaeological sites have been essential in the reconstruction of the obsidian trade networks. Among the first and most detailed studies on Mexican obsidian sources were those carried out at the University of Missouri (Vogt et al., 1982; Cobean et al., 1991; Cobean, 2002). More recently, however, other studies have been reported on samples from these and other Mexican obsidian sources. All these results have been brought to light by an analysis of elements that identifies and classifies archaeological materials according to their original source; for these tasks neutron activation analysis has played a major role (Jime´nez-Reyes et al., 2001; Almaza´n-Torres et al., 2004). The aim of this research was to identify, by means of proton induced X-ray emission (PIXE) and statistical methods, the origin of 20 samples, which were 11 debitage pie`ces and nine prismatic blade fragments with unpolished surfaces. All these samples were collected at the Lagartero ballcourt.

3. Results The elements analyzed by PIXE were the following: Na, Mg, Al, Cl, K, Ca, Ti, V, Mn, Fe, Zn, Ga, Rb, Sr, Y, Zr, and Nb. Table 2 shows the results of these multielemental analyses. For statistical calculations a comparison was made with the literature data (Cobean et al., 1991; Braswell and Glascock, 1998; Jime´nez-Reyes et al., 2001; Cobean, 2002) of 30 obsidian sources. All these data were obtained by neutron activation analysis giving a total of 28 elements. In this research 17 elements were analyzed, not necessarily the same as those found in the literature; however, a good comparison was found for the concentration of coincident elements. Therefore, only the following elements were considered for statistical treatments: Na, Cl, K, Mn, Fe, Zn, Rb, and Zr. It is interesting to remark that the concentrations of Al, Mg, Si, Ca, Ti, Ga, Sr, Y, and Nb had not been previously reported for the obsidian samples of Zinapecuaro, Ucareo, El Chayal nor Ixtepeque Volcano. Two-dimensional plots of pairs of the measured elements were done in order to compare the artifacts to the obsidian sources. The pair Zr–Mn and particularly the pair Fe–Mn gave excellent discriminating results about the groups described afterwards. The principal-component diagram (Fig. 2) shows the evident discrimination between the obsidian samples; that means, three

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Table 1 Description of archaeological obsidian samples from the archeological site of Lagartero Chiapas, Mexico Sample

Description

Color

Source name

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Debitage pie`ce Debitage pie`ce Debitage pie`ce Debitage pie`ce Blade fragment, medial-part Blade fragment, distal-part Debitage pie`ce Debitage pie`ce Blade fragment, proximal-part Blade fragment, proximal-part Debitage pie`ce Blade fragment medial-part Debitage pie`ce Blade fragment medial-part Debitage pie`ce Debitage pie`ce Debitage pie`ce Blade fragment distal-part Blade fragment medial-part Blade fragment medial-part

Dark gray Dark gray Opaque gray Dark gray Back Opaque light gray Opaque striped light gray Light gray Striped dark gray Striped dark gray Translucent rosy gray Striped dark gray Striped dark gray Striped light gray Gray with dark/light stripes Translucent light gray Translucent striped gray Opaque dark gray Striped light gray Translucent striped light gray

El Chayala El Chayala El Chayala El Chayala El Chayala El Chayala El Chayala El Chayala Zinapecuaro-Ucareo Michoacanb El Chayala Ixtepeque Volcanoa El Chayala El Chayala Ixtepeque Volcanoa El Chayala Ixtepeque Volcanoa El Chayala El Chayala El Chayala El Chayala

a b

Guatemala. Mexico.

origins for the obsidian samples coming from Lagartero. One of these sources is from Ucareo–Zinapecuaro area in Michoacan, Mexico and two are Guatemalan: El Chayal and Ixtepeque Volcano. Data for Ucareo (UM) and Zinapecuaro (ZM) sources were obtained of the present research (Table 2) and those of Guatemalan sources and others of Zinapecuaro (ZM(l)) and Ucareo (UM(l)) were taken from Cobean et al. (1991) and Cobean (2002). The clusters of Fig. 2 are the following: (1) sample 9, Ucareo and Zinapecuaro, (Michoacan, Mexico); (2) samples 1, 2, 4–7, 10, 12, 13, 17–19, one purchased in a workshop of Guaytan and El Chayal (Guatemala); and (3) samples 11, 14, 16, and Ixtepeque Volcano (Guatemala). The elemental analyses of samples 3, 8 and 20 (Table 2) are similar to those of the cluster number 2; however, their chlorine content is higher. According to Table 2, the chemical composition of sample 9 is quite similar to the sample of Ucareo and differences are observed regarding the sample of Zinapecuaro, mainly for the chlorine and titanium contents. On the other hand, Healan (1997) reported that Ucareo and Zinapecuaro sources have different chemical compositions. Therefore, even if sample 9 is

in the cluster of Ucareo–Zinapecuaro area (Fig. 2), this sample was probably coming from the Ucareo source, which had a considerably great magnitude of exploitation and a truly panMesoamerican importance in pre-Hispanic times. This source is located at 1100 km from Lagartero and it was probably reached by traveling along the Pacific coast, as it was suggested as well for the obsidian found in Lower Rio Verde Valley, Oaxaca (Joyce et al., 1995). Cobean et al. (1991) describe the Guatemalan sources at El Chayal as an enormous flow, being the most important obsidian source of Lowland Maya centers during the Classical Period; the Ixtepeque Volcano source is even larger than El Chayal, its obsidian having been widely traded all over southern Mesoamerica and lower Central America. The results of the present research indicate that 65% of the analyzed samples of Lagartero came from El Chayal. This result is different of that found with an obsidian collection of artifacts of Chichen Itza; in that case, the majority of them came from distant geological sources located in central and west Mexico and only 10% came from El Chayal and 12% from Ixtepeque (Braswell and Glascock, 2002).

Table 2 Elemental concentration of obsidian (O) samples collected at Lagartero Chiapas, Mexico

Na (%) Mg Al (%) Si (%) Cl K (%) Ca (%) Ti Mn Fe (%) Zn Ga Rb Sr Y Zr Nb

O9 (Z–U)

Ucareo

Zinapecuaro

IG group n ¼ 3a

CG group n ¼ 14b

Sample G

O20

O3

O8

2.3 503 6.6 36.1 499 4.1 0.4 524 198 0.9 42 23 201 19 22 156 19

2.3  0.2 350  47 6.7  0.02 35.92  0.08 586  64 4.2  0.2 0.4  0.01 581  60 205  10 1  0.1 43  4 19  2 192  16 21  2 28  7 150  19 18  6

2.7  0.2 439  63 6.63  0.04 36  0.06 831  59 4  0.1 0.39 360  34 213  26 0.8  0.1 47  9 23  2 237  21 72 35  6 123  15 21  5

31 1701  72 7.4  0.2 34  1 804  55 3.9  0.6 0.87  0.06 1565  39 527  10 1.04  0.04 35  4 17  2 114  5 171  16 20  7 188  12 12  6

2.7  0.5 1468  298 7.1  0.1 35.2  0.8 794  103 3.6  0.5 0.8  0.07 1141  76 665  62 0.75  0.09 41  3 17  2 146  16 184  25 17  4 121  12 10  4

2.75  0.04 2203  644 7.1  0.06 35.22  0.03 892  110 4.2  0.2 0.8  0.1 1346  378 638  139 0.9  0.3 41  4 17  2 144  41 162  0.6 18  4 135  33 18  6

2.9 1134 7 35.1 2796 3.6 0.8 1180 800 0.73 49 20 175 164 7 118 13

3.2 1348 7.3 34.7 1729 3.1 1.1 1013 498 0.59 37 17 112 307 15 103 10

4.3 1026 6.6 32.9 1232 3.3 0.7 1039 697 0.63 38 15 154 157 22 108 7

The concentrations are in mg/g unless otherwise indicated. Individual data are grouped according to PC diagram and CG: El Chayal, IG: Ixtepeque Volcano, and G: Guayta´n, Guatemala. Z–U: Ucareo and Zinapecuaro, Michoacan Mexico. a Samples: 11, 14, and 16. b Samples: 1, 2, 4–7, 10, 12, 13, 15, 17–19, and G.

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0.04

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01 2CG

0.02

02 05 06 018 019

04 013

0.00

08

El Chayal samples Ucareo/Zinapecuaro samples 07 UM(I)

010 01

PC03

015 G

ZM

-0.02

017

09 UM ZM (1)

03 IG 020

-0.06

-0.04

014 016

-0.10

-0.06

-0.02

Ixtepeque

011 samples

0.02

0.06

0.10

0.14

PC01 Fig. 2. Principal-component diagram for 20 obsidian samples from Lagartero Chiapas Mexico, one purchased in Guayta´n Guatemala (G) and the following sources: UM: Ucareo Michoacan, Mexico; ZM: Zinape´cuaro Michoacan, Mexico. Data for CG: El Chayal, Guatemala; IG: Ixtepeque Volcano, UM(l) and ZM(l) were taken from Cobean et al. (1991) and Cobean (2002). The confidence interval for ellipses is 0.85.

4. Conclusions

References

Since the archaeological site of Lagartero is situated on a Mesozoic limestone substratum there are no igneous or metamorphic stones to be found anywhere in the vicinity. Their nearest obsidian flows are located in Guatemala, and thanks to this study it was possible to define the origin of the obsidian samples. Obsidians were able to be identified as coming from two Guatemalan sources: El Chayal, and the Ixtepeque Volcano; which are at a distance no farther than 200-km from Lagartero as the crow flies. Therefore, the discovery in Lagartero of obsidian coming from these sources is certainly due to the relative proximity. The raw material probably arrived by commerce or by the barter of other goods or services. It was probably brought to the site in nodules because of the evidence found concerning the whole production process of several types of obsidian tools. Taking into consideration the blade fragment identified as coming from the Ucareo area, the exchange over a long distance is evidenced even though on a minor scale. The distance from Lagartero to Ucareo is 1100-km. That implies a long sweep of both distance and time. Due to the small quantity found at the site, these materials probably did not arrive directly but passed through different hands and over several chronological periods. Our results lead us to conclude that people of Lagartero certainly had contact with other Mayan and Mesoamerican people.

Almaza´n-Torres, M.G., Jime´nez-Reyes, M., Monroy-Guzma´n, F., Tenorio, D., AguirreMartı´nez, P.I., 2004. Determination of the provenance of obsidian samples collected in the archaeological site of San Miguel Ixtapan, Mexico State, Mexico by means of neutron activation analysis. Journal of Radioanalytical and Nuclear Chemistry 260 (3), 533–542. Braswell, G.E., Glascock, M.D., 1998. Interpreting intrasource variation in the composition of obsidian: the geoarchaeology of San Martin Jilotepeque, Guatemala. Latin American Antiquity 9 (4), 353–369. Braswell, G.E., Glascock, M.D., 2002. The emergence of market economies in the ancient Maya World: obsidian exchange in the Terminal Classic, Yucatan, Mexico. In: Glascock, M.D. (Ed.), Geochemical Evidence for Long-distance Exchange. Bergin and Garvey, Westport & London, pp. 33–52. Cobean, R.H., Vogt, J.R., Glascock, M.D., Stocker, T.L., 1991. High-precision characterization of major meso-American obsidian sources and further analysis of artifacts from San Lorenzo Tenochtitlan, Mexico. Latin American Antiquity 2 (1), 69–91. Cobean, R.H., 2002. A World of Obsidian: The Mining and Trade of Volcanic Glass in Ancient Mesoamerica. The University of Pittsburgh Press and INAH. Healan, D.M., 1997. Pre-Hispanic quarrying in the Ucareo–Zinapecuaro obsidian source area. Ancient Mesoamerica 8, 77–100. Jime´nez-Reyes, M., Tenorio, D., Esparza-Lo´pez, J.R., Cruz-Jime´nez, R.L., Mandujano, C., Elizalde, S., 2001. Neutron activation analysis of obsidian from quarries of the central quaternary trans-Mexican Volcanic Axis. Journal of Radioanalytical and Nuclear Chemistry 250 (3), 465–471. Joyce, A.A., Elam M, J., Glascock, M.D., Neff, H., Winter, M.C., 1995. Exchange implications of obsidian source analysis from the Lower Rio Verde Valley, Oaxaca, Mexico. Latin American Antiquity 6 (1), 3–15. Maxwell, J.A., Teesdale, W.J., Campbell, T.L., 1995. The GUPIX PIXE software package II. Nuclear Instruments and Methods in Physics Research B95, 407–421. Neff, H., 2008. GAUSS Language Routines for Statistical Analysis of Multivariate Archaeometric Data Available from: http://archaeometry.missouri.edu. Rivero Torres, S., 1990. La cera´mica y lı´tica de Lagartero Chiapas, procedente del Limonar, Unidad I. Informe de la primera temporada de campo del proyecto Lagartero Chiapas. Archivo del Consejo de Arqueologı´a del INAH, Me´xico. Rivero Torres, S., 1994–1995. Informe de las temporadas de campo del proyecto Lagartero, Municipio la Trinitaria, Chiapas. Entregado al Consejo de Arqueologı´a del INAH. Rivero Torres, S., 1996. ‘‘El Juego de Pelota del sitio Lagartero, Chiapas’’, Quinto Foro de Arqueologı´a de Chiapas. Serie Memorias. Gobierno del Edo. De Chiapas, UNICACH y Centro de Estudios Superiores de Me´xico y Centro Ame´rica, pp. 39–52. Rivero Torres, S., 2005. Artefactos lı´ticos del Montı´culo no. 5 de Lagartero, Chiapas. Revista de la Coordinacio´n Nacional de Arqueologı´a, segunda e´poca, INAH, 165–182. Vogt, J.R., Graham, C.C., Glascock, M.D., Cobean, R.H., 1982. A study of Mesoamerican obsidian sources using activation analysis. Journal of Radioanalytical and Nuclear Chemistry 69, 271–289.

Acknowledgments This research is a part of the project ‘‘Characterization of archeological pieces from Lagartero Chiapas Mexico’’ financed by IAEA, project number: 13070/RO. Technical assistance of Mr. Jesu´s ˜ oz Lujano is also much appreciated. Mun Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:doi:10.1016/j.jas.2008.06.026