Early Olmec obsidian trade and economic organization at San Lorenzo

Journal of Archaeological Science 40 (2013) 2784e2798

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Early Olmec obsidian trade and economic organization at San Lorenzo Kenneth Hirth a, *, Ann Cyphers b,1, Robert Cobean c, 2, Jason De León d, 3, Michael D. Glascock e, 4 a

Department of Anthropology, Penn State University, 409 Carpenter Building, University Park, PA 16802, USA Instituto de Investigaciones Antropológicas, Universidad Nacional Autónoma de México, Circuito Exterior C.U., México D.F. 04510, Mexico c Dirección de Estudios Arqueológicos, Instituto Nacional de Antropología e Historia, Lic. Verdad #3, Colonia Centro, México D.F. 06060, Mexico d Department of Anthropology, University of Michigan, Ann Arbor, MI 48109-1107, USA e University of Missouri Research Reactor, 1513 Research Park Drive, Columbia, MO 65211, USA b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 29 November 2012 Received in revised form 14 January 2013 Accepted 27 January 2013

The Olmec were the first complex society to develop in Mesoamerica between 1800 and 600 cal B.C. The earliest large Olmec center during this period was the archaeological site of San Lorenzo which emerged as Mesoamerica’s first large ritual and political center between 1400 and 1000 cal B.C. San Lorenzo’s growth as a prominent center included the development of long distance trade relationships with adjacent areas of Guatemala and highland Mexico. High precision chemical analysis of obsidian imported for use in the fabrication of cutting tools is used to reconstruct the growth, size and extent of San Lorenzo’s interregional exchange networks with areas of Mexico and Guatemala where obsidian occurs as raw material. A total of 852 obsidian artifacts were analyzed to reconstruct changes in obsidian procurement between 1800 and 800 cal B.C. This represents one of the largest samples of sourced obsidian from a Mesoamerican site and it provides a comprehensive picture for the development of interregional trade networks for Mesoamerica’s first large Olmec center. Ó 2013 Published by Elsevier Ltd.

Keywords: Olmec San Lorenzo Obsidian source analysis Trade Mesoamerica XRF

1. Introduction Research conducted over more than seven decades has established that the Olmec were Mesoamerica’s first great civilization (Coe and Diehl, 1980; Diehl, 2004; Pool, 2007). The Olmec were located in the humid coastal plains of Veracruz and Tabasco between 1800 and 400 cal B.C. Contact between the Olmec and their neighbors can be seen in the spread of religious iconography along with the movement of a range of trade goods into and out of the Olmec heartland. The earliest Olmec center is the archaeological site of San Lorenzo, Veracruz, which was occupied continuously between 1800 and 800 cal B.C. (Table 1) and developed into Mesoamerica’s first large ritual and political center between 1400 and 1000 cal BC (Fig.1). Complex society at San Lorenzo was supported by a highly diversified subsistence base tailored to its surrounding wetland environment. Despite a rich resource base, San Lorenzo lacked easy

* Corresponding author. Tel.: þ1 814 867 0005; fax: þ1 814 863 1474. E-mail addresses: [email protected] (K. Hirth), [email protected] (A. Cyphers), [email protected] (R. Cobean), [email protected] (J. De León), [email protected] (M.D. Glascock). 1 Tel.: þ55 5644 7822. 2 Tel.: þ55 5522 4446. 3 Tel.: þ1 734 764 7274. 4 Tel.: þ1 573 882 5270. 0305-4403/$ e see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.jas.2013.01.033

access to building stone and the lithic resources needed for both cutting and grinding tools. The San Lorenzo Olmec solved part of this problem by importing basalt from the Tuxtla Mountains located 60 km away which was used for grinding implements and large stone monuments so important for their public displays of religious and political ideology. Stone for cutting implements, however, was not locally available which they resolved by importing obsidian from distant sources. The focus of this study is this long distance obsidian procurement network and its implications for the development of early Olmec economic networks. The goal of this study is to provide a comprehensive view of the evolution of obsidian provisioning at San Lorenzo over a 1000 year period between 1800 and 800 cal BC. A total of 852 artifacts were analyzed using high precision neutron activation and X-ray fluorescence techniques which form the basis for reconstructing obsidian procurement networks. These artifacts were drawn from 50 different occupation contexts collected by the Proyecto Arqueológico San Lorenzo Tenochtitlan (PASLT) over six field seasons (Fig. 2). The large number of contexts available for study ensured that only artifacts from securely dated single component contexts were used in this analysis. These analyzes document the extent and diversity of San Lorenzo’s early economic obsidian networks and provide a glimpse into the complexity of economic interactions involved in the development of Mesoamerica’s first complex society.

K. Hirth et al. / Journal of Archaeological Science 40 (2013) 2784e2798 Table 1 San Lorenzo Chronology. Phase

Uncalibrated dates

Calibrated dates

Nacaste San Lorenzo B San Lorenzo A Chicharras Bajio Ojochi

850e700 BC 1000e850 BC 1150e1000 BC 1250e1150 BC 1350e1250 BC 1600e1350 BC

1000e800 cal B.C. 1200e1000 cal B.C. 1400e1200 cal B.C. 1500e1400 cal B.C. 1600e1500 cal B.C. 1800e1600 cal B.C.

Note: Uncalibrated dates based on Cyphers et al. 2008-2007: Fig. 3.

2. Previous studies of San Lorenzo obsidian procurement Obsidian source analysis has played an important role in reconstructing past economic systems in Mesoamerica for three reasons. First, obsidian is the only material resource that permits highly accurate reconstructions of raw material movement from its source to its final point of consumption. Furthermore, the reductive technology used to transform obsidian into usable tools is both well known and can be studied with a high level of analytical precision (Clark and Bryant, 1997; Collins, 1975, 1993; Hirth, 2003, 2006; Sheets, 1975). Second, obsidian was used for cutting tools in many areas of Mesoamerica where local silicates such as chert or rhyolite were unavailable. In these instances the control over the production and distribution of obsidian tools, particularly prismatic blades has been argued to have been a critical element in the rise of complex society in Mesoamerica (Clark, 1987) and the foundation of the early Teotihuacan state (Santley, 1984, 1989; Sanders and Santley, 1983; Spence, 1981, 1984). Third and finally, obsidian is one of the few materials that can withstand the highly corrosive effects of the Gulf Coast environment. Obsidian tools not only preserve, but they constitute more than 98% of the flaked stone tool inventory recovered at San Lorenzo. As such, they provide a comprehensive view of the procurement system for one indispensable material resource. San Lorenzo holds a special place in the history of obsidian research in Mesoamerica because two pioneering studies used San Lorenzo collections to test the feasibility of chemical characterization studies for the study of obsidian trade (Cobean et al., 1971, 1991). These studies made two very important contributions to obsidian research in Mesoamerica. First, they provided the chemical characterization of 25 major obsidian sources in Mexico and Guatemala (Fig. 1) using data from Robert Cobean’s (2002) systematic reconnaissance of obsidian source areas. In the process Cobean et al. (1991) demonstrated that archaeological quarries and outcrops should not be sampled as individual points but as components of large flow systems that often cover 100 sq km or more. The second important contribution of Cobean’s initial studies was that it demonstrated the feasibility of identifying the source provenance of archaeological artifacts. A sample of 65 obsidian artifacts was compared to 208 characterizations of 25 sources (Cobean et al., 1991:69). Chemical analyzes linked the obsidian artifacts recovered at San Lorenzo to ten geological obsidian sources: Guadalupe Victoria, Pico de Orizaba, Otumba, Paredon, Pachuca, Ucareo, Altotonga, and ZaragozaeOyameles, Mexico, as well as El Chayal and Ixtepeque, Guatemala (Footnote5). This

5 Subsequent analysis at Yale and MURR after the publication of Cobean et al. (1971) identified several of the sources for San Lorenzo artifacts which were originally reported as “Unknown”. These include Group A which is the Paredon source, Groups B/B0 which correspond to Ucareo-Zinapecuaro, Michoacan; and Groups C/C0 which correspond to ZaragozaeOyameles, Puebla (Cobean, 2002: 53,64,169). All artifacts in the 1971 report attributed to “El Paraiso, Queretaro” actually correspond to the Ucareo-Zinapecuaro source area. This identification error was caused by the inclusion in the initial Yale source analysis program of samples supposedly from El Paraiso that were not collected personally by our project (Cobean, 2002:71).

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research established the value of obsidian source analysis for reconstructing prehistoric exchange networks in Mesoamerica (Pires-Ferreira, 1975, 1976). Unfortunately, these early studies did not report the complete source determinations of the archaeological sample examined from San Lorenzo. The research was structured as a qualitative study intended to identify the range of obsidian sources used at San Lorenzo rather than a quantitative study of phase-by-phase changes in the obsidian sources used over time. The artifacts analyzed were selected to sample “the widest possible differences in color and in surface appearance in the hopes of obtaining samples from most or all of the obsidian sources used” (Cobean et al., 1971:667). As a result, while this early study established the existence of extensive exchange networks at San Lorenzo, it did not identify changes in the frequency of obsidian sources used over time. Only 63 of the 65 analyzed artifacts could be identified to source (Cobean et al., 1991:84) which precluded a comprehensive view of obsidian exchange operating at San Lorenzo throughout the length of its occupation. Nevertheless, these analyzes identified that Guadalupe Victoria supplied 73% of the obsidian during the Chicharras and San Lorenzo phases, followed in turn by El Chayal (22%) and Otumba (5%) (Cobean et al., 1991: Fig. 5). 3. The analytical sample and research methodology The goal of the current study was to develop a comprehensive model for obsidian procurement at San Lorenzo between 1800 and 800 cal B.C. Obsidian samples used for source analysis rarely are constructed on the basis of technological and social variables that affected the quantity of material used from different sources. Instead, samples often are drawn from a small number of contexts and analyzed as if they were representative of the entire site. To avoid this problem a large multi-dimensional sample of 852 pieces of obsidian were analyzed from 50 components that spanned the six major occupations between 1800 and 800 cal B.C. The sample was stratified by production technology and artifacts were selected using non-redundant, unique elements analogous to the identification of minimum number of individuals (MNI) used in osteological studies. Table 2 summarizes the quantity of obsidian analyzed for each of the analytical contexts used in this study. Stratifying the sample by technology was designed to obtain a representative view of the obsidian sources used at San Lorenzo. Archaeologists have long recognized that the manufacture of pressure blades requires high quality obsidian with few impurities, while percussion flaking can utilize less pure obsidian. Since obsidian sources vary in the workability of the glass, it means that the obsidian used in percussion industries could come from different sources than those used in pressure blade production. Artifacts were selected for analysis using criteria analogous to the identification of MNIs to avoid redundant analysis (double-counting) of obsidian fragments from the same artifact. Lithic artifacts at San Lorenzo were never used as complete blades or flakes, but were broken into anywhere from 3 to 6 segments that were hafted or used as hand-held cutting tools. To avoid double representation of the same artifact in the study sample, proximal sections or striking platforms were used since they are both easily recognizable and occur as single elements on all flakes and blades. This insured that individual flakes and blades were the minimal unit of analysis. Excavation levels were regularly sampled as complete units to insure a representative sample of the obsidian consumed. The whole-level sampling of non-redundant artifacts often reduced the sample to only 1e2 artifacts per collection context. Archaeologists often select for diversity when choosing obsidian (e.g. Cobean et al., 1971) or do not specify the parameters used to select samples for analysis. This is unfortunate because it adds selection bias and

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Fig. 1. Location of San Lorenzo in Mesoamerica with obsidian sources.

Fig. 2. Location of all contexts sampled at San Lorenzo.

K. Hirth et al. / Journal of Archaeological Science 40 (2013) 2784e2798 Table 2 Contexts analyzed at San Lorenzo (SL), Loma de Zapote (LZ), Las Camelias, El Bajio and islote site of RSLT-116a. Contexts San Lorenzo SL: A4 Ilmenitas CHE SL: A4 Ilmenitas JZN SL: A4 Ilmenitas LGL SL: A4 Platos SL: B. Jobo CW SL: B. Jobo EHG SL: B. Jobo ESLE SL: B. Jobo MVG SL: C5-6 SL: C5-6, Sondeo 1 SL: D4 Plan SL: D4-7 SL: D4-22 SL: D5-9 SL: D5-9W SL: D5-31 SL: Grupo C, Col A SL: Grupo C, Col B SL: Grupo C, Col C SL: Grupo D, B3-5 SL: Grupo D, B3-11 SL: Grupo D, B3-17 SL: Grupo D, SL-30 SL: Grupo D, Sondeos SL: Grupo E, SL-14 SL: Grupo E, SL-73 SL: P. Camilo Dgz SL: P. M. Rosas, Col A SL: P. M. Rosas, Col F SL: P. M. Rosas, Col H SL: P. Perfecto Domínguez LO SL: P. Perfecto Domínguez TV SL: P. Simon HDZ DRH SL: P. Simon HDZ PS SL: SL-53 SL: SL-112 SL: Trans 1W, Sondeo 2 SL: Trans 1W, Sondeo 3 SL: Trans 2S, Sondeo 1 SL: Zanja La Mina Loma de Zapote LZ: Malpica U LZ: P. S. Salomon LZ: PN, S. Bernal LZ: PN, S. Diego Osorio LZ: PN, S Vasconcelos LZ: Represa Azuzul LZ: S. Aguilar Other regional sites El Bajio Las Camelias RSLT-116a Total N ¼ 50

Single component contexts

No. of pieces

4 2 2 1 3 3 1 2 3 1 2 1 1 1 1 1 4 2 1 2 2 2 3 1 3 2 3 2 1 2 4 1 1 2 4 2 1 1 1 1

14 20 10 4 20 24 18 10 24 3 26 1 16 9 4 13 29 5 1 8 40 31 25 1 49 16 27 3 2 19 61 50 19 11 89 16 2 1 2 7

1 2 2 1 1 1 3

19 16 7 4 11 4 12

1 1 1 91

26 14 9 852

diminishes the representativeness and interpretability of the results. Flakes and blades were selected for analysis in proportion to their occurrence within study levels. Because of their scarcity, all flake and blade cores were analyzed since they were the objects from which multiple flakes were produced. It is felt that high precision analysis of samples from a large number of contexts is essential for distinguishing the multiple paths through which raw material like obsidian could enter and circulate throughout a large multi-component site like San Lorenzo. All of the 852 obsidian artifacts discussed here were submitted to the Archaeometry Laboratory at the University of Missouri for analysis. During the course of this multi-year project, the analytical methods employed were changed to take advantage of

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improvements in equipment and technology. The first 50 samples were analyzed by neutron activation analysis (NAA) using a shortirradiation procedure described by Glascock et al. (1994). This method measures seven elements (Al, Ba, Cl, Dy, K, Mn, and Na) and is very powerful but has the disadvantage of being destructive. The remaining 802 samples were analyzed non-destructively by X-ray fluorescence (XRF) which measures a different suite of elements (the best of which are Rb, Sr, Y, Zr, and Nb). Two different spectrometers operating at 40 kV and 17 microamps were used for XRF. A table-top Elva-X spectrometer with tungsten anode was used for 594 samples and a handheld portable Bruker IIIeV spectrometer with a rhodium anode and copper filter was used on the remaining 208 samples. All of the NAA and XRF results were compared to chemical data for obsidian sources from Mexico and Guatemala previously analyzed in the Archaeometry Laboratory (Cobean et al., 1991; Glascock et al., 1988, 1998; Glascock, 2010). Two of the obsidian samples analyzed by XRF did not agree with the source data and were further tested by the destructive NAA procedure. One of these (SL-482) could not be matched to a known source while the other (SL-509) was identified as Ucareo, Michoacan. 4. Trade network reconstructions by phase 4.1. The Ojochi phase (1800e1600 cal BC) This was the initial occupation phase at San Lorenzo. The Ojochi population occupied and initiated landscape modification across the San Lorenzo landform that consisting of filling, leveling and initial terracing. The site’s early occupation was identified across the central site area and on some terraces. San Lorenzo was a large village community and the primary settlement in a 3-tier settlement hierarchy (see Symonds et al., 2002: Figure 4.1). Its inhabitants also built small earthen platforms known as islotes in the wetlands to assist in exploiting wetland resources (Cyphers and Zurita-Noguera, 2012). Differentially fired ceramics, often considered an Olmec hallmark, are present at this time. No public architecture or monumental sculpture has been identified at the site, although one elite area (SL-53) was excavated. The presence of obsidian at San Lorenzo, together with jade and other imported resources identified at the nearby site of El Manati (Ortiz and del Carmen Rodriguez, 2000) indicate that interregional exchange networks were already well established and functioning by 1800 cal B.C. Fifty obsidian artifacts were analyzed from the five Ojochi phase deposits identified at San Lorenzo (Fig. 3b) which consisted of 49 percussion flakes and one percussion flake core. Kenneth Hirth’s analysis of the complete obsidian assemblage reveals that an expedient flake industry predominated. Obsidian was brought into the site as irregular fist-sized nodules which were used to produce razor sharp flakes that were broken into small sections or employed “as is” in cutting tasks. Analyzes reveal that 92% of the obsidian at San Lorenzo during this phase originated from Guadalupe Victoria source located 312 km northwest of San Lorenzo on the western slope of the Orizaba volcano (Fig. 1, Table 3). At this source small irregular nodules are exposed in ravines and gullies in a 20 km radius around the modern town of Guadalupe Victoria (Cobean, 2002). These data confirm the earlier identification of this source as a major supplier of obsidian for the early percussion industries at San Lorenzo (Cobean et al., 1971, 1991). Two other sources also were identified in small amounts. These include the Pico de Orizaba source (6%) located in the Ixtetal Valley (Cobean, 2002) on the northern slope of the Orizaba volcano, and the important source of El Chayal (2%) in the highlands of Guatemala (Table 4).

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Fig. 3. Obsidian distributions at San Lorenzo. A) The location of San Lorenzo, B) The Ojochi phase obsidian distribution, C) The Bajío phase obsidian distribution, D) The Chicharras phase obsidian distribution.

The presence of El Chayal obsidian in even small amounts is important because it demonstrates that obsidian was already moving over 613 km across the Isthmus of Tehuantepec to reach San Lorenzo (Tables 3 and 4). The SL: D4-Plan excavation area is the only context where obsidian from all three sources was recovered together.

4.2. The Bajío phase (1600e1500 cal BC) San Lorenzo grew during this phase and expanded beyond the plateau to include settlement along the site’s periphery. Monumental construction in the form of landscape modification was initiated on the summit of the natural landform. These

K. Hirth et al. / Journal of Archaeological Science 40 (2013) 2784e2798 Table 3 Distance to obsidian sources used at San Lorenzo. Obsidian source

Distance from San Lorenzo (km)a

Phases present at San Lorenzo

El Chayal, Guatemala

577

Guadalupe Victoria, Puebla

320

Ixtepeque, Guatemala Otumba, Mexico

656 464

Paredon, Puebla

440

Pico de Orizaba, Veracruz

303

Pachuca, Hidalgo Ucareo, Michoacan

490 669

Zacualtipan, Hidalgo ZaragozaeOyameles, Puebla

521 370

Zinapecuaro, Michoacan

681

Ojochi, Bajio, Chicharras, SL-A, SL-B, Nacaste Ojochi, Bajio, Chicharras, SL-A, SL-B, Nacaste SL-A, SL-B, Nacaste Chicharras, SL-A, SL-B, Nacaste Chicharras, SL-A, SL-B, Nacaste Ojochi, Bajio, Chicharras, SL-A, SL-B SL-B, Nacaste Chicharras, SL-A, SL-B, Nacaste SL-A, SL-B Chicharras, SL-A, SL-B, Nacaste Nacaste

a

Note: Distances are in direct air kilometers. Actual travel distances would be much further under prehispanic conditions.

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This sample consists of 64 percussion flakes, five worked nodules, three flake cores, and six flake tools. Source analysis reveals that the same sources used in the Ojochi phase continued to be exploited throughout the Bajío phase. Obsidian from Guadalupe Victoria again dominated the assemblage representing 71% of the material entering the site (Table 4). Nevertheless, several important trends are noticeable during this phase. The first is an increase in obsidian from the Pico de Orizaba and El Chayal sources. El Chayal obsidian represents 11.5% of the collections and now is as prevalent as material from Pico de Orizaba even though it is 321 km further away (Table 3). Second, there is greater variability in the distribution of these sources within San Lorenzo. For example, SL: D4-Plan is the only site area sampled where all three obsidian sources were recovered. This is the same pattern observed for the Ojochi phase, although the obsidian at SL: D4-Plan from Pico de Orizaba and El Chayal is now as prevalent as that from Guadalupe Victoria. The variability in obsidian sources between the different areas of San Lorenzo suggests the operation of multiple independent sources of supply rather than a single centralized procurement mechanism. 4.3. The Chicharras phase (1500e1400 cal BC)

architectural modifications formed the first construction phase of what was to become the largest public earth work constructed in Mesoamerica during the Early Formative period (Cyphers, 1996:70; Cyphers et al. 2008-2007). Increasing intra-site social differentiation is suggested by the presence of two elite areas, one containing a low earthen stepped platform (Coe and Diehl, 1980: I: 105). Differentiation in regional settlement patterning suggests that San Lorenzo exerted its influence over its surrounding population (Cyphers, 2012). It is during the Bajío phase that hollow figurines and decorative motifs in the Olmec style appear in local ceramic assemblages and San Lorenzo became the major source of Olmec influence in Mesoamerica. Obsidian continued to be imported into the site as irregular nodules that were manufactured into usable flakes using percussion techniques. Seventy-eight pieces of obsidian were analyzed for this phase and were drawn from eight Bajío phase contexts (Fig. 3c). Table 4 Ojochi and Bajio obsidian source determinations. Area

Guadalupe Victoria

Pico de Orizaba

El Chayal, Guat

Total

No.

No.

No.

No.

0 2 0 0 1 3 6

0 1 0 0 0 1 2

1 11 5 1 32 50 100%

Ojochi phase percussion, N ¼ 50 SL: A4 Ilmenitas CHE 1 SL: D4 Plan 8 SL: Grupo C, Col A 5 SL: Grupo C, Col B 1 SL: SL-53 31 Total 46 Percent 92 Area

Guadalupe Victoria, Ver

Pico de Orizaba, Ver

El Chayal, Guat

Total

No.

No.

No.

No.

0 0 4 4 0 0 1 0 9 11.5%

0 0 4 0 4 1 0 0 9 11.5%

1 2 15 11 4 5 20 20 78 100%

Bajio phase percussion industry, N ¼ 78 SL: A4 Ilmenitas CHE 1 SL: A4 Ilmenitas LGL 2 SL: D4 Plan 7 SL: Grupo C, Col A 7 SL: Grupo C, Col B 0 SL: Grupo B, B3-5 4 SL: P. Perfecto Dominguez LO 19 SL-53 20 Total 60 Percent 71%

During this phase there was intensified development at San Lorenzo. Large scale terrace and earthwork construction continued across the plateau. We know that the entire upper plateau was probably occupied and the initial stages of the elite GD-1 structure (known as the Red Palace) in Group D were built. Whatever the internal structure, the site’s political and religious institutions were centered on the elite who claimed to be descendants of deified ancestors (Clark, 2007:41; Cyphers, 1997b:233). Evidence for long distance trade increased and included the importation of greenstone, iron ore mirrors, and mica into the site. The complete obsidian analysis indicates that the majority of the obsidian cutting edge at San Lorenzo was again supplied by expedient flakes produced from small irregular nodules. It was during this phase, however, that obsidian pressure blades began to appear in low frequencies, often as single artifacts in Chicharras phase deposits. A total of 100 pieces of obsidian was selected for analysis from 15 separate deposits (Fig. 3d). These included 93 percussion artifacts (78 flakes, five worked cobbles and flake cores, 10 flake tools) and seven obsidian prismatic pressure blades. Chemical analysis reveals widening trade relationships with obsidian from four new source areas arriving at the site for the first time (Table 5). Percussion flaking continued to dominate the Chicharras phase assemblage with obsidian from Guadalupe Victoria supplying 74% of the raw material used. The Guatemalan source of El Chayal was the second most commonly used source providing 20% of the obsidian used for quotidian activities. The Pico de Orizaba source which supplied 6e12% of raw material during the Ojochi and Bajío phases all but disappeared, supplying little more than 2% of the obsidian used in percussion flaking. Notably obsidian nodules from two new highland sources (Ucareo and Paredon) appeared at San Lorenzo in trace amounts for the first time (Table 5). Prismatic pressure blades are little more than 2% of the total obsidian assemblage. The seven blades (Table 5) are an opportunistic sample analyzed to obtain a preliminary identification of the sources exploited. Although the number analyzed is small, a notable diversity was observed in the sources used to manufacture obsidian blades. The sources represented include the three Mexican sources of Paredon (N ¼ 3), Otumba (N ¼ 1) and ZaragozaeOyameles (N ¼ 1), along with El Chayal, Guatamala (N ¼ 2). There is no evidence for onsite manufacture of obsidian blades (sensu De León et al., 2009) so it is likely that these materials reached San Lorenzo as a result of trade in finished blades (Jackson and Love, 1991).

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Table 5 Chicharras phase obsidian source determinations. Area

Guad. Victoria

Chicharras phase percussion (N [ 93) SL: A4 Ilmenitas CHE 1 SL: B. Jobo CW 0 SL: B. Jobo EHG 1 SL: B. Jobo MVG 2 SL: C5-6 2 SL: Grupo C, Col A 5 SL: Grupo C, Col C 0 SL: Grupo D, B3-5 1 SL: Grupo D, SL-30 13 SL: Grupo D, Sondeos 0 SL: Grupo E, SL-73 0 SL: P. Perfecto Domínguez LO 10 SL: Simon Hdz DRH 15 SL: P. Simon Hdz PS 1 SL: SL-53 18 Total Percussion 69 Percentage of Percussion 74.2% Pressure Blades SL: B. Jobo MVG 0 SL: Grupo D, B3-5 0 SL: Grupo D, Sondeos 0 SL: P. Simon Hdz DRH 0 SL: SL-53 0 Total Pressure Blades 0 Total Obsidian 69

Pico de Orizaba

El Chayal, Guat

Ucareo, Mich

Paredon, Mex

Otumba, Mex

Zaragoza, Pue

Total

0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 2 2.15%

0 3 0 4 2 1 0 0 3 0 1 2 3 0 0 19 20.4%

0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1.1%

0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 2 2.15%

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0%

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0%

1 4 1 6 4 6 1 1 17 0 1 13 18 1 19 93 100%

0 0 0 0 0 0 2

1 0 0 1 0 2 21

0 0 0 0 0 0 1

0 2 1 0 0 3 5

0 0 0 0 1 1 1

0 0 0 0 1 1 1

1 2 1 1 2 7 100

4.4. The San Lorenzo A phase (1400e1200 cal BC) San Lorenzo emerged as the largest site in Mesoamerica during this phase growing to more than 690 ha (Cyphers, 1996:70; Lunagómez Reyes, 1995; Cyphers et al. 2008-2007). It is now and during the following San Lorenzo B phase that the site reached the height of its cultural development. Massive filling operations created a monumental construction in the shape of a terraced earthen plateau. Large public buildings were constructed and there were sculpture workshops in the central plateau that produced colossal heads and medium sized stone monuments used in ritual displays and to reinforce the dynastic authority of San Lorenzo rulers (Cyphers, 1997b, 2012). San Lorenzo was the most influential center in the southern Gulf Coast and its location on the ancient Coatzalcoalcos river system provided a locational advantage for participation in regional and interregional trade. Both Loma de Zapote and Laguna de los Cerros developed into secondary centers (Cyphers, 2012; Symonds et al., 2002) and household inventories reveal differences in wealth indicative of status differences both at San Lorenzo and throughout sites in the surrounding region (Cyphers, 1996, 1997a). The complete lithic analysis shows that percussion flaking of blocky nodules continued to supply most of the cutting edge used at San Lorenzo. Nevertheless, there was a clear increase in the number of prismatic pressure blades used in both domestic and non-domestic contexts across the site. A total of 193 pieces of obsidian were sourced that consisted of 156 percussion flakes and flake tools and 37 prismatic pressure blades (Table 6). This sample was drawn from 19 well preserved San Lorenzo phase A deposits (Fig. 4). Chemical analysis reveals that exchange intensified along the trade routes established during the Chicharras phase and two new areas were exploited which raised the number of sources used at San Lorenzo to nine (Table 6). The bulk of obsidian exchange remained focused on the procurement of small irregular and blocky nodules for the production of usable flakes. Eight sources supplied these nodules with Guadalupe Victoria providing 71.2% of the flakes, cores, and flake tools

in the sample. El Chayal, Guatemala (18.6%) and Paredon, Mexico (4.5%) were the next most used sources, following the pattern established in the previous Chicharras phase. The remaining sources exploited (Pico de Orizaba, Ucareo, ZaragozaeOyameles, Zacualtipan, and Ixtepeque) occur in trace amounts of only 0.6e 1.9%. Two new sources were exploited at this time: Zacualtipan, Hidalgo, situated 555 km northwest of San Lorenzo and Ixtepeque, Guatemala, located 647 km to the southeast (Table 3). The appearance of these new sources is significant because they reflect the continued broadening of trade connections with San Lorenzo. Prismatic pressure blades were manufactured from six different sources and comprise 6% of the obsidian recovered during this phase. Nearly 90% of these blades come from the four highland Mexican sources of Paredon (27.1%), Otumba (21.6%), Ucareo (21.6%) and ZaragozaeOyameles (18.9%). The other two sources used were El Chayal, Guatemala (8.1%) and Guadalupe Victoria (2.7%). That Guadalupe Victoria obsidian also was used to manufacture pressure blades is surprising given its high level of inclusions which impede blade removal. Particularly striking is the variable consumption of obsidian blades across the site. Blades comprise 80% of the obsidian sample from the non-elite residential area of P. Camilo Domínguez (N ¼ 11) and 37% of the samples from the GD-1 or Red Palace structure (areas SL:B3-11 and SL:B3-17) in Group D. Conversely, blade consumption is low at both monuments SL: SL-53 (6%) and in SL: Grupo E, SL-14 (8%). All indications are that pressure blades reached San Lorenzo through blade trade (De León et al., 2009). 4.5. The San Lorenzo B phase (1200e1000 cal BC) San Lorenzo reached its maximum size and influence during this phase. Regional population grew to its maximum size and there is the possibility that large sites like Laguna de los Cerros became more independent, eventually competing with San Lorenzo (Borstein, 2001, 2008; Cyphers, 2012). Many of the public monuments found at San Lorenzo date to this phase and it is likely that there were changes in the site’s ruling dynasty. Evidence for monument recycling suggests that either rulers were losing the

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Table 6 San Lorenzo A phase obsidian source determinations. Area Percussion SL: A4 Ilmenitas CHE SL: A4 Ilmenitas JZN SL: A4 Ilmenitas LGL SL: B. Jobo CW SL: B. Jobo EHG SL: C5-6 SL: Grupo C, Col A SL: Grupo D, B3-11 SL: Grupo D, B3-17 SL: Grupo D, SL-30 SL: Grupo E, SL-14 SL: Grupo E, SL-73 LZ: PN, S. Bernal LZ: S. Aguilar SL: P. Camilo Domínguez SL: P. Miguel Rosas SL: P. Perfecto Domínguez LO SL: SL-112 SL: SL-53 Total Percussion Percentage of Percussion

Guad. Victoria

Pico de Orizaba

El Chayal, Guat

Ucareo, Mich

Paredon, Mex

Otumba, Mex

Zaragoza, Pue

Zacualtipan, Hid

Ixtepeque, Guat

Total

10 0 7 8 12 2 5 7 6 1 19 3 0 0 2 0 8 6 15 111 71.2

1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 1.9

0 1 0 2 0 1 2 3 1 0 4 1 2 0 0 1 7 4 0 29 18.6

0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0.6

0 0 0 1 1 0 0 1 1 0 0 0 0 0 0 0 0 3 0 7 4.5

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0

0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0.6

0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0.6

0 0 0 0 0 0 0 0 0 0 1 2 0 0 0 0 0 0 0 3 1.9

11 1 8 11 14 3 7 12 8 1 24 8 2 0 2 1 15 13 15 156 99.9

Area

Guad. Victoria

El Chayal, Guat

Ucareo, Mich

Paredon, Mex

Otumba, Mex

Zaragoza, Pue

Total

Pressure blades SL: B. Jobo CW SL: Grupo D, B3-11 SL: Grupo D, B3-17 SL: Grupo E, SL-14 SL: Grupo E, SL-73 LZ: PN, S. Bernal LZ: S. Aguilar SL: P. Camilo Domínguez SL: SL-112 SL: SL-53 Total Pressure Blades Percentage of Pressure Blades

0 0 0 1 0 0 0 0 0 0 1 2.7

0 2 0 0 1 0 0 0 0 0 3 8.1

0 2 2 0 0 0 1 3 0 0 8 21.6

1 0 3 1 1 1 0 2 1 0 10 27.1

0 1 2 0 0 1 0 2 1 1 8 21.6

0 0 0 0 5 0 0 2 0 0 7 18.9

1 5 7 2 7 2 1 9 2 1 37 100

ability to command the labor necessary to import large basalt blocks from the Tuxtla mountains and/or older monuments were defaced and recycled to remove the images of earlier rulers from public spaces. The quantity and diversity of imported goods indicate that San Lorenzo was at the center of an extensive trade network that included green stone, ilmenite, mica and polished magnetite mirrors. The massive deposits of drilled ilmenite blocks date to this phase and indicate both high levels of interregional trade and the on-site manufacture of exotic craft goods (Cyphers, 1996; Di Castro Stringher, 1997). A significant change also occurred in the organization of San Lorenzo lithic assemblages. While percussion flakes still accounted for most of the lithic artifacts recovered (68.6%), obsidian pressure blades rose sharply in popularity accounting for 31.4% of all the obsidian artifacts recovered at San Lorenzo. This was a transitional period for blade use at San Lorenzo with blade frequencies soaring from 6% during the preceding phase. Of course, 31.4% is the average level of blade consumption for the entire phase. Since blades represent only 6% at the start of this phase, usage rates would have had to be very high by the end of San Lorenzo phase B to produce an average usage rate of 31% for the entire phase. A total of 331 obsidian artifacts were chemically analyzed which were drawn from 34 well preserved deposits at San Lorenzo and the nearby sites of Loma de Zapote and El Bajío (Figs. 2 and 5). This sample was composed of 177 percussion flakes, cores and flake tools, and 154 pressure blades (Table 7). Obsidian continued to move into the site along previously established trade routes. Obsidian from the Sierra de Pachuca is recovered in collections for

the first time and represents the only new source exploited during this phase. Procurement networks were remarkably stable from the preceding phase with the same eight sources supplying raw material for the percussion industry. The nearby source of Guadalupe Victoria supplied the bulk of this material (58.7%) although in lower amounts than during the preceding phase. El Chayal (19.2%), Paredon (10.2%) and Ucareo (7.9%) also provided significant amounts of nodular material. The remaining four sources (Pico de Orizaba, Otumba, ZaragozaeOyameles, Ixtepeque) contributed only trace amounts of obsidian in the range of 0.6e1.1% for percussion flaking. The increase in nodular material from Ucareo and Paredon from previous phases was very likely a side product of the large number of pressure blades entering the region from these sources. Prismatic blades occur in obsidian from nine different sources. Three sources supplied over 80% of these blades. The most important of these was Ucareo (37.6%) followed by Paredon (27.3%) and Otumba (16.2%). The sources of ZaragozaeOyameles (6.5%) and El Chayal (5.2%) also supplied a small but important quantity of blades. Blades also appeared for the first time from three new sources in trace amounts: Ixtepeque (3.2%), Zacualtipan (1.3%) and Sierra de Pachuca (0.7%). 4.6. The Nacaste phase (1000e800 cal BC) The Nacaste phase witnessed the waning of San Lorenzo as a major center in the Gulf Coast. Its political influence declined sharply along with its on-site population. A dispersed population

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Fig. 4. San Lorenzo A phase obsidian distribution.

continued to live on the plateau but there is no evidence for major architectural construction across the plateau either in the form or terracing or the construction of monumental public buildings. Nevertheless, San Lorenzo shared ceramic and figurine styles with other sites in the Gulf Coast (Coe and Diehl, 1980:188; Lowe, 1989:53e57) even though it was eclipsed by La Venta and other sites in the Gulf Coast after 1000 cal BC. Despite changes in the internal organization of San Lorenzo, the total obsidian analysis indicates that blades continued to increase in frequency, constituting almost one-half of the lithic assemblage (47.5%) compared to percussion flakes and flake tools (52.5%). Although the frequency of blades to flakes was about equal, flakes were smaller than they were during all previous phases. It is likely that prismatic blades provided the majority of the cutting edge used at San Lorenzo at this time. A sample of 100 pieces of obsidian was chemically analyzed for this phase that consisted of 38 percussion flakes and 62 pressure blades (Table 8). This sample was collected from nine Nacaste phase contexts at San Lorenzo (Fig. 6). The major source for obsidian blades was the highland source of Otumba, Mexico (40.3%). Other important sources used for blades were Ucareo-Zinapecuaro (29%), Paredon (11.3%), ZaragozaeOyameles (8.1%), and El Chayal (8.1%). Blades were also identified in trace amounts from the Ixtepeque (1.6%) and Pachuca (1.6%) sources. The disappearance of obsidian from Pico de Orizaba and Zacualtipan reflects a slight shrinkage in procurement patterns. Zinapecuaro obsidian appeared in trace amounts for the first time and probably entered the site through the same channels as material from its neighboring source of Ucareo. Changes can be observed in the procurement networks that supplied small nodules for percussion flaking. There was a sharp

decrease in the quantity of material from Guadalupe Victoria from nearly 59% during the preceding phase to only 36.9% during Nacaste. The decrease in Guadalupe Victoria obsidian was offset by increases in raw material from both El Chayal (34.2%) and Paredon (15.8%). Obsidian from Ucareo (7.9%), Otumba (2.6%) and Zaragozae Oyameles (2.6%) supplied the remainder of nodular raw material used at the site. 5. Discussion The results of this study expand on the pioneering investigations conducted of obsidian procurement at San Lorenzo (Cobean et al., 1971, 1991). This investigation confirms that the obsidian used at San Lorenzo came from a large number of sources. Furthermore, it adds new information by analyzing a large sample of obsidian artifacts from each of the six phases of site development from 1800 to 800 cal B.C. The results allow us to identify the structure of obsidian procurement networks by recognizing which sources supplied raw material and finished goods in different quantities over the life of the site. Eleven obsidian sources were identified that are distributed across the greater breadth of Mesoamerica (Fig. 1, Table 8). San Lorenzo had access to, and drew material from, most of the major obsidian source areas in the Mexican and Guatemalan highlands before 1000 cal BC. This has important implications for understanding the structure of early trade and procurement networks that need to be explored in greater depth in future studies. Obsidian supplied the primary cutting edge at San Lorenzo and had to be transported long distances to reach the site. The inhabitants of San Lorenzo had established contact with two major source regions by 1800 cal BC. These were: 1) the slopes of the

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Fig. 5. San Lorenzo B phase obsidian distribution.

Orizaba volcano where the Guadalupe Victoria and Pico de Orizaba sources were located, and 2) the Valley of Guatemala with its important obsidian source at El Chayal (Fig. 1). Guadalupe Victoria and Pico de Orizaba are the closest sources to San Lorenzo. Located 300 km northwest of San Lorenzo, these sources supplied the majority of the hand-sized obsidian nodules used to produce flakes at the site. The earliest use of Orizaba obsidian is an obsidian projectile point recovered from El Riego phase deposits in the Tehuacan Valley (Cobean et al., 1971:668) which predates its appearance at San Lorenzo by nearly 4000 years. This underscores the early importance of obsidian and its movement over long distances to supply quotidian cutting tasks. What is more surprising is that obsidian from El Chayal, Guatemala, occurs at San Lorenzo during the Ojochi and Bajío phases. El Chayal is more than 600 km from San Lorenzo, fully twice the distance of the two sources near the Orizaba volcano. While El Chayal obsidian is a higher quality of glass than obsidian from Guadalupe Victoria, it provides no real technological advantages for expedient percussion flaking. All three sources provide razor sharp flakes suitable for hand-held cutting tasks. The greater distance to the El Chayal source should have precluded its use at San Lorenzo because of its higher transportation costs (Drennan, 1984; Hassig, 1985). Clearly resource provisioning was not structured purely in energetic terms. Instead, resource procurement more likely operated through multiple, nested interregional social networks that moved material over space irrespective of the distances involved. Interregional procurement networks operating during the Ojochi and Bajío phases expanded dramatically during the Chicharras phase around 1500 cal BC. Two important developments occurred at this time. First, the quantity of obsidian moving through the

Guatemalan source network increased substantially, indicating an expansion and intensification of long distance relationships through the Isthmus of Tehuantepec and into the Guatemalan highlands (sensu Zeitlin, 1982). Second, there is the expansion of source networks north and west into the Mexican highlands reaching as far west as the Cuitzeo Basin in eastern Michoacan. This highland Mexican route represents a third procurement network that provided obsidian from four new sources. These new sources included: ZaragozaeOyameles in the eastern Puebla highlands, Otumba and El Paredon in the northeastern Basin of Mexico, and Ucareo in the Cuitzeo Basin of Michoacan. The direct line distances to these sources range from 360 km to ZaragozaeOyameles to over 660 km to Ucareo (Table 3). The obsidian that moved through this new highland network was small in quantity and relatively insignificant in terms of provisioning San Lorenzo residents with usable cutting edge. The importance of the obsidian data is that it documents the creation of network relationships that linked San Lorenzo to highland Mexico. These contacts provided the linkages for the reciprocal movement of people, ideology, technology and material goods. It was along this corridor and at least a century later that Gulf Coast ceramics moved into the Basin of Mexico (Blomster et al., 2005; Neff et al., 2006) and West Mexico. Likewise it was through this network that highland goods including obsidian blade technology reached the Gulf Coast. Obsidian pressure blades manufactured from Otumba, Paredon, and ZaragozaeOyameles obsidian reached San Lorenzo during the Chicharras phase. Although Ucareo obsidian moved across the highland route as small nodules, blades and other goods appear to have followed this network as trade expanded after 1400 cal BC.

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Table 7 San Lorenzo B phase obsidian source determinations. Area Percussion SL: A4 Ilmenitas JZN SL: A4 Platos SL: B. Jobo CW SL: B. Jobo EHG SL: B. Jobo MVG SL: C5-6 SL: D4-22 SL: D5-9 SL: D5-9W SL: D5-31 SL: Grupo D, B3-11 SL: Grupo D, B3-17 SL: Grupo D, SL-30 SL: Grupo E, SL-14 Las Camelias LZ: Malpica U LZ: P. S. Salomon LZ: PN, S. Diego Osorio LZ: S. Aguilar SL: P. Camilo Domínguez SL: P. M. Rosas, Col A SL: P. M. Rosas, Col F SL: P. Perfecto Domínguez LO SL: Perfecto Domínguez TV RSLT-116a SL: Trans 1W, Sondeo 2 SL: Trans 2S, Sondeo 1 SL: Zanja La Mina El Bajio Total Percussion Percentage of Percussion Area Pressure blades SL: A4 Ilmenitas JZN SL: A4 Platos SL: B. Jobo EHG SL: B. Jobo MVG SL: C5-6 SL: C5-6, Sondeo 1 SL: D4-22 SL: D4-7 SL: D5-9 SL: D5-9W SL: D5-31 SL: Grupo D, B3-11 SL: Grupo D, B3-17 SL: Grupo D, SL-30 Las Camelias LZ: Malpica U LZ: P. S. Salomon LZ: PN, Diego Osorio LZ: Represa Azuzul LZ S. Aguilar P Camilo DGZ SL: P. M. Rosas, Col F SL: P. M. Rosas, Col H SL: P. Perfecto Domínguez LO SL: P. Perfecto Domínguez TV SL: SL-112 SL: Trans 1W, Sondeo 3 SL: Trans 2S, Sondeo 1 SL: Zanja La Mina El Bajio Total Pressure Blades Percentage of Pressure Blades

Guad. Victoria

Pico de Orizaba

El Chayal, Guat

Ucareo, Mich

Paredon, Mex

Otumba, Mex

Zaragoza, Pue

Ixtepeque, Guat

Unknown

Total

1 0 3 6 1 6 1 3 1 5 6 2 1 7 0 0 2 0 1 3 1 1 2 27 9 2 1 2 10 104 58.7

0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 2 1.1

10 0 0 2 0 1 2 0 0 1 5 1 4 0 0 0 0 1 0 0 1 0 1 4 0 0 0 0 1 34 19.2

0 0 0 0 0 0 0 0 0 0 1 0 0 0 2 7 0 0 0 0 0 0 0 0 0 0 0 0 4 14 7.9

1 1 1 0 0 2 1 0 0 5 0 3 0 0 1 0 0 0 0 0 0 0 0 3 0 0 0 0 0 18 10.2

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0.6

0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 1.1

0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0.6

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0.6

12 1 4 8 1 9 5 3 1 11 12 7 5 8 4 7 3 1 1 3 2 1 4 34 9 2 1 2 16 177 100%

Guad. Victoria

El Chayal, Guat

Ucareo, Mich

Paredon, Mex

Otumba, Mex

Zaragoza, Pue

Zacualtipan, Hid

Ixtepeque, Guat

Pachuca, Hid

Unknown

Total

0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 1.3

1 1 0 0 0 0 0 1 0 0 0 2 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 8 5.2

1 0 0 0 0 0 4 0 4 0 0 3 5 1 5 10 2 1 1 0 1 1 1 4 7 1 0 0 2 4 58 37.6

5 0 1 1 4 3 2 0 0 1 1 3 2 0 1 0 2 0 1 2 1 0 1 2 6 0 1 1 1 0 42 27.3

0 1 0 1 4 0 3 0 2 2 1 0 1 1 1 0 1 1 2 0 0 0 0 0 1 0 0 0 1 2 25 16.2

0 0 0 0 0 0 1 0 0 0 0 1 1 0 1 0 0 1 0 0 0 0 0 3 1 0 0 0 1 0 10 6.5

0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 1.3

0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 2 5 3.2

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0.7

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0.7

7 3 1 2 8 3 11 1 6 3 2 11 9 2 10 12 5 3 4 2 2 1 3 9 16 1 1 1 5 10 154 100%

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Table 8 Nacaste phase obsidian source determinations. Area

Guad. Victoria

El Chayal, Guat

Ucareo, Mich

Paredon, Mex

Otumba, Mex

Zaragoza, Pue

Total

Percussion SL: B. Jobo ESLE SL: Grupo E, SL-14 LZ: P. S. Salomon LZ: PN, S. Bernal LZ: PN, S. Vasconcelos LZ: S. Aguilar SL: P. Camilo Domínguez SL: P. M. Rosas SL: P. Simon Hdz PS Total percussion obsidian Percentage percussion obsidian

3 5 0 0 1 2 1 0 2 14 36.9

1 2 0 0 7 1 1 0 1 13 34.2

1 1 0 0 0 0 0 1 0 3 7.9

2 1 1 1 0 1 0 0 0 6 15.8

0 0 0 0 0 0 0 0 1 1 2.6

0 0 0 0 0 0 0 1 0 1 2.6

7 9 1 1 8 4 2 2 4 38 100%

Area Pressure blades SL: B. Jobo ESLE SL: Grupo E, SL-14 LZ: P. S. Salomon LZ: PN, S. Bernal LZ: PN, S. Vasconcelos LZ: S. Aguilar SL: P. Camilo Domínguez SL: P. M. Rosas SL: P. Simon Hdz PS Total Pressure Blades Percentage of Pressure Blades

El Chayal, Guat

Ucareo, Mich

Paredon, Mex

Otumba, Mex

Zaragoza, Pue

Ixtepeque, Guat

Pachuca, Hid

Zinapecuaro, Mich

Total

2 0 0 0 0 0 3 0 0 5 8.1

4 2 5 0 0 0 4 2 0 17 27.4

3 0 1 0 0 2 1 0 0 7 11.3

0 1 1 2 2 1 0 12 6 25 40.3

1 2 0 0 0 1 1 0 0 5 8.1

1 0 0 0 0 0 0 0 0 1 1.6

0 0 0 0 1 0 0 0 0 1 1.6

0 1 0 0 0 0 0 0 0 1 1.6

11 6 7 2 3 4 9 14 6 62 100%

Fig. 6. Nacaste phase obsidian distribution.

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San Lorenzo reached its cultural apogee during San Lorenzo phases A and B. Between 1400 and 1000 cal BC it was the primary Olmec center and a source of cultural influences throughout the Gulf coast and possibly beyond (Footnote6). The obsidian information indicates an increased volume of raw material and finished blades moving along trade circuits across Guatemala and the Mexican highlands. The same also was true for ceramic and other goods (Blomster et al., 2005; Herrera et al., 1999; Neff et al., 2006; Pires-Ferreira, 1975). Most notably the increased consumption of obsidian blades at the beginning of the San Lorenzo A phase continued well into its decline during the Nacaste phase. Blades constituted 6% of the obsidian assemblage during the San Lorenzo A phase, 31% during the San Lorenzo B phase, and nearly one-half of the assemblage (47.5%) during the Nacaste phase. During these three phases fully 90% of all blades consumed at San Lorenzo were produced from obsidian from highland sources (Footnote7). Four new highland sources (Zacualtipan, Ixtepeque, Pachuca, Zinapecuaro) were added during these three phases, all of which occur as prismatic blades by the San Lorenzo B or Nacaste phase. It is important that the frequency of obsidian blades continued to increase unabated into the Nacaste phase. Blade use in domestic contexts continued to rise to 47.5% throughout the Nacaste phase despite San Lorenzo’s political decline and the decreased importance of the site elite. This high level of blade use differs from that reported near La Venta where pressure blades constitute only 28% of the obsidian assemblage at the Middle Formative site of San Andres (Doering, 2002:72; see also Raab et al., 2000). Clearly economic systems operated independently of the political events that engulfed San Lorenzo during its decline. The economic needs of San Lorenzo domestic units were too important to have political disruptions interfere with them. Obsidian blades reached Nacaste phase households well after the elite had departed or declined in regional importance at San Lorenzo. Clark (1987) has suggested that blade technology spread throughout Mesoamerica as a direct result of elite action. This proposed involvement took two forms: 1) the procurement of obsidian cores from distant sources, and 2) sponsorship of the artisans with specialized skills to produce obsidian blades (Clark, 1987:278). Elite involvement is assumed to be motivated by the control over unique or preferred goods that they could selectively distribute to individuals for elite political advantage (sensu Brumfiel and Earle, 1987; Clark, 1987:280). The San Lorenzo data expands our understanding of obsidian procurement in two ways. First, obsidian was the dominant material used for cutting tools during the Ojochi phase indicating that it moved readily through interregional exchange networks by 1800 cal BC. This obsidian moved into San Lorenzo in nodular form and probably reached the site through the same type of reciprocal,

6 For the broader debate on the role of the Olmec in Mesoamerica prehistory the reader can consult: Blomster et al. (2005) Clark (1997), Cyphers (2012), Flannery and Marcus (2000), Grove (1993), Neff et al. (2006), Pool (2007), and Wilk (2004). 7 Blades recovered at San Lorenzo were predominantly manufactured from obsidian sources in the Mexican highlands. Exact percentages of the blade assemblage manufactured from Mexican obsidian sources were 89.2% during the San Lorenzo A phase, 90.3% during San Lorenzo B, and 90.3% during the Nacaste phase. This contrasts with analysis of obsidian from the Tuxtla region where ZaragozaeOyameles was identified as the only highland Mexican source entering the region during the Early Formative period (Santley et al., 2001). Zaragozae Oyameles was also the only highland obsidian identified at Tres Zapotes during the Early Formative period (Pool et al., 2010:99e100) although this conclusion rests primarily on visual identification. These differences demonstrate the type of variation found in site-oriented procurement networks during the Early Formative. Unfortunately the Tuxtla study lacks the chronological precision and assemblage separation into percussion and pressure industries necessary for an exact comparison with obsidian procurement at San Lorenzo.

down-the-line exchange networks through which obsidian nodules had moved across Mesoamerican since the Archaic period (Clark and Lee, 1984:241; Nelson and Voorhies, 1980; Voorhies, 1976). Second, if the spread of obsidian blade technology and the distribution of prismatic pressure blades was a political process as Clark (1987) suggests, then the frequency of blades should have decreased during the Nacaste phase with the decrease in elites and their influence over a reduced population. This is not what happened. Rather blade consumption at San Lorenzo continued to rise into the Nacaste phase. What these data imply is that neither the procurement of obsidian, nor the production of blades, depended completely upon the presence of elite. Instead the first obsidian blades probably arrived as trade goods moving through the same networks as obsidian nodules (De León, 2008). This study has examined the obsidian imported and consumed at San Lorenzo from 1800 to 800 cal BC. It was not designed to reconstruct the network of economic relationships through which it moved. Nevertheless the data are suggestive. They imply that during the Early Formative period obsidian moved through a network of decentralized domestic exchanges. Domestic trade networks often operated through trade partner relationships (Heider, 1969) with resources moving from household to household as gifts or reciprocal exchanges (Wiessner, 1982; Yan, 2005). Because these networks are household centered, they produce a matrix of independent and overlapping connections through which resources move. The result is a greater diversity in the type and distribution of the resources moving through household networks compared to centralized systems. Winter and Pires-Ferreira (1976) have demonstrated that domestic exchange networks were the principal conduits for obsidian provisioning in the Valley of Oaxaca during the Tierras Largas phase 1150e1400 BC. Diversity in the distribution of obsidian from different sources is found across San Lorenzo during all phases of site occupation. During the Ojochi and Bajío phases the SL: D4-Plan area displays greater variation in the sources of nodular obsidian used than do areas SL-53 or Perfecto Dominguez LO (Table 4). These differences became exaggerated once obsidian blades increased in popularity. During San Lorenzo B, variation in blade occurrence was pronounced. Blades ranged from 10 to 11% of lithic materials recovered from ritual and domestic areas at C5-6 and D5-31, to 48% of the domestic assemblage in the residence of D4-22 (De León, 2008: Tables 6.14e6.43). This variation continued into the Nacaste phase where Otumba obsidian dominated blade assemblages at SL: P. Miguel Rosas and SL: P. Simon Hdz in contrast to SL: B. Jobo ESLE and LZ: P. S. Salomon where Ucareo, Paredon and El Chayal obsidian predominated (Table 8). 6. Conclusions This study has developed a comprehensive model for obsidian procurement and exchange at San Lorenzo between 1800 and 800 cal B.C. Chemical analysis of 852 obsidian artifacts reveals that obsidian moved over distances of 300e600 km as early as 1800 cal BC. Furthermore, the results document that San Lorenzo was provisioned from 11 different obsidian sources over the length of its occupation. This investigation examined the procurement requirements of two different production technologies: the production of obsidian percussion flakes from obsidian nodules and the obsidian manufactured into prismatic blades. The high percentage of blades manufactured from highland Mexico obsidian is very likely a function of the early development of craft specialization in this area and the early trade in finished blades by the specialists who produced them (Boksenbaum, 1978; Boksenbaum et al., 1987; De León et al., 2009). Nevertheless, it appears that obsidian nodules and finished blades from most Mexican and Guatemalan sources

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probably moved together through interregional procurement networks. Most of the discussion of Early Formative Gulf Coast culture focuses on the San Lorenzo period from 1400 to 1000 cal BC. This was the period of rulers, palaces and impressive stone monuments. It was also when San Lorenzo reached its maximum size and importance and an array of exotic goods reached the site through extensive interregional trade. This is the Olmec story as we have come to know it. Obsidian, however, supplies a different perspective. Obsidian analysis illustrates that by 1800 cal BC San Lorenzo was involved in two long distance procurement networks, one extending north into central Veracruz and the Orizaba region, and the other extending south across the Isthmus of Tehuantepec and into Guatemala. A significant moment in Olmec development appears to have been the Chicharras phase (1500e1400 cal B.C.). Not only were strong leaders and the foundations of Olmec society emerging at San Lorenzo, but also the site extended its procurement networks deep into the Mexican highlands as far as the Ucareo obsidian source in West Mexico. It is likely that most if not all of the obsidian moved along these routes through down-lineexchange. What is important for Olmec development is that trading networks stretching from Guatemala to West Mexico were already established and operating by 1400 cal BC, at the beginning of San Lorenzo’s rapid growth and development. This framework served as the foundation for expanded interregional exchange by both Olmec and non-Olmec groups and it was through these networks that both resources and ideologies moved across the greater breadth of Mesoamerica (Blomster et al., 2005; Coe, 1989). Obsidian does not provide all the answers to questions about resource procurement, trade and exchange during prehispanic times. What it does supply, however, is a solid empirical foundation for reconstructing the structure of exchange networks between source areas and points of consumption like San Lorenzo. What are needed now are data from other sites on the landscape so that a fuller reconstruction of trade relationships is possible for the areas that were directly or indirectly liked to San Lorenzo and the obsidian sources that they used. Acknowledgments We are grateful to the Dirección General de Asuntos del Personal Académico-Universidad Nacional Autónoma de México for providing the financing for this project. Our special thanks to Michael Coe who worked with Cobean and Glascock in the original Yale and Missouri obsidian projects. We acknowledge the National Science Foundation for grants BCS-0802757 and BCS-1110793 supporting the Archaeometry Laboratory at MURR. We also thank Greg Luna for drafting the accompanying maps. References Blomster, J.P., Neff, H., Glascock, M.D., 2005. Olmec pottery production and export in ancient Mexico determined through elemental analysis. Science 5712, 1068e 1071. Boksenbaum, M.W., 1978. Lithic Technology in the Basin of Mexico During the Early and Middle Preclassic. Department of Anthropology, City University of New York. Boksenbaum, M.W., Tolstoy, P., Harbottle, G., Kimberlin, J., Neivens, M., 1987. Obsidian industries and cultural evolution in the Basin of Mexico Before 500 B.C. Journal of Field Archaeology 14, 65e75. Borstein, J., 2001. Tripping Over Colossal Heads: Settlement Patterns and Population Development in the Upland Olmec Heartland. Department of Anthropology, The Pennsylvania State University, University Park. Borstein, J., 2008. El Papel de Laguna de los Cerros en el Mundo Olmeca. In: Hirth, K., Cyphers, A. (Eds.), Sociedad e Ideología en el periodo Formativo. Instituto de Investigaciones Antropológicas, Universidad Nacional Autónoma de México, Mexico, D.F, pp. 153e176.

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