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Journal of Archaeological Science 40 (2013) 2784e2798

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Journal of Archaeological Science

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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

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

a r t i c l e i n f o

Article history:Received 29 November 2012Received in revised form14 January 2013Accepted 27 January 2013

Keywords:OlmecSan LorenzoObsidian source analysisTradeMesoamericaXRF

* Corresponding author. Tel.: þ1 814 867 0005; faxE-mail addresses: [email protected] (K. Hirth), cyph

[email protected] (R. Cobean), jasonpatrLeón), [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.

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a b s t r a c t

The Olmec were the first complex society to develop in Mesoamerica between 1800 and 600 cal B.C. Theearliest large Olmec center during this period was the archaeological site of San Lorenzo which emergedas Mesoamerica’s first large ritual and political center between 1400 and 1000 cal B.C. San Lorenzo’sgrowth as a prominent center included the development of long distance trade relationships withadjacent areas of Guatemala and highland Mexico. High precision chemical analysis of obsidian importedfor use in the fabrication of cutting tools is used to reconstruct the growth, size and extent of San Lor-enzo’s interregional exchange networks with areas of Mexico and Guatemala where obsidian occurs asraw material. A total of 852 obsidian artifacts were analyzed to reconstruct changes in obsidian pro-curement between 1800 and 800 cal B.C. This represents one of the largest samples of sourced obsidianfrom a Mesoamerican site and it provides a comprehensive picture for the development of interregionaltrade networks for Mesoamerica’s first large Olmec center.

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1. Introduction

Research conducted over more than seven decades has estab-lished that the Olmec were Mesoamerica’s first great civilization(Coe and Diehl, 1980; Diehl, 2004; Pool, 2007). The Olmec werelocated in the humid coastal plains of Veracruz and Tabasco between1800 and 400 cal B.C. Contact between the Olmec and their neigh-bors can be seen in the spread of religious iconography along withthe movement of a range of trade goods into and out of the Olmecheartland. The earliest Olmec center is the archaeological site of SanLorenzo, Veracruz, which was occupied continuously between 1800and 800 cal B.C. (Table 1) and developed into Mesoamerica’s firstlarge ritual andpolitical center between1400and1000 calBC (Fig.1).

Complex society at San Lorenzo was supported by a highlydiversified subsistence base tailored to its surrounding wetlandenvironment. Despite a rich resource base, San Lorenzo lacked easy

: þ1 814 863 [email protected] (A. Cyphers),[email protected] (J. De

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access to building stone and the lithic resources needed for bothcutting and grinding tools. The San Lorenzo Olmec solved part ofthis problem by importing basalt from the Tuxtla Mountainslocated 60 km away which was used for grinding implements andlarge stone monuments so important for their public displays ofreligious and political ideology. Stone for cutting implements,however, was not locally available which they resolved byimporting obsidian from distant sources. The focus of this study isthis long distance obsidian procurement network and its implica-tions for the development of early Olmec economic networks. Thegoal of this study is to provide a comprehensive view of the evo-lution of obsidian provisioning at San Lorenzo over a 1000 yearperiod between 1800 and 800 cal BC.

A total of 852 artifacts were analyzed using high precisionneutron activation and X-ray fluorescence techniques which formthe basis for reconstructing obsidian procurement networks. Theseartifacts were drawn from 50 different occupation contextscollected by the Proyecto Arqueológico San Lorenzo Tenochtitlan(PASLT) over six field seasons (Fig. 2). The large number of contextsavailable for study ensured that only artifacts from securely datedsingle component contexts were used in this analysis. These ana-lyzes document the extent and diversity of San Lorenzo’s earlyeconomic obsidian networks and provide a glimpse into thecomplexity of economic interactions involved in the developmentof Mesoamerica’s first complex society.

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Table 1San Lorenzo Chronology.

Phase Uncalibrated dates Calibrated dates

Nacaste 850e700 BC 1000e800 cal B.C.San Lorenzo B 1000e850 BC 1200e1000 cal B.C.San Lorenzo A 1150e1000 BC 1400e1200 cal B.C.Chicharras 1250e1150 BC 1500e1400 cal B.C.Bajio 1350e1250 BC 1600e1500 cal B.C.Ojochi 1600e1350 BC 1800e1600 cal B.C.

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

K. Hirth et al. / Journal of Archaeological Science 40 (2013) 2784e2798 2785

2. Previous studies of San Lorenzo obsidian procurement

Obsidian source analysis has played an important role inreconstructing past economic systems in Mesoamerica for threereasons. First, obsidian is the only material resource that permitshighly accurate reconstructions of raw material movement from itssource to its final point of consumption. Furthermore, the reductivetechnology used to transform obsidian into usable tools is bothwellknown 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 manyareas of Mesoamerica where local silicates such as chert or rhyolitewere unavailable. In these instances the control over the productionand distribution of obsidian tools, particularly prismatic blades hasbeen argued to have been a critical element in the rise of complexsociety inMesoamerica (Clark,1987) and the foundation of the earlyTeotihuacan state (Santley, 1984, 1989; Sanders and Santley, 1983;Spence, 1981, 1984). Third and finally, obsidian is one of the fewmaterials that canwithstand the highly corrosive effects of the GulfCoast environment. Obsidian tools not only preserve, but theyconstitute more than 98% of the flaked stone tool inventory recov-ered at San Lorenzo. As such, they provide a comprehensive view ofthe procurement system for one indispensable material resource.

San Lorenzo holds a special place in the history of obsidianresearch in Mesoamerica because two pioneering studies used SanLorenzo collections to test the feasibility of chemical characteriza-tion studies for the study of obsidian trade (Cobean et al., 1971,1991). These studies made two very important contributions toobsidian research in Mesoamerica. First, they provided the chem-ical characterization of 25 major obsidian sources in Mexico andGuatemala (Fig. 1) using data from Robert Cobean’s (2002) sys-tematic reconnaissance of obsidian source areas. In the processCobean et al. (1991) demonstrated that archaeological quarries andoutcrops should not be sampled as individual points but as com-ponents of large flow systems that often cover 100 sq km or more.

The second important contribution of Cobean’s initial studieswas that it demonstrated the feasibility of identifying the sourceprovenance of archaeological artifacts. A sample of 65 obsidianartifacts was compared to 208 characterizations of 25 sources(Cobean et al., 1991:69). Chemical analyzes linked the obsidianartifacts recovered at San Lorenzo to ten geological obsidian sour-ces: Guadalupe Victoria, Pico de Orizaba, Otumba, Paredon,Pachuca, Ucareo, Altotonga, and ZaragozaeOyameles, Mexico, aswell 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 orig-inally 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). Allartifacts in the 1971 report attributed to “El Paraiso, Queretaro” actually correspondto the Ucareo-Zinapecuaro source area. This identification error was caused by theinclusion in the initial Yale source analysis program of samples supposedly from ElParaiso that were not collected personally by our project (Cobean, 2002:71).

research established the value of obsidian source analysis forreconstructing prehistoric exchange networks in Mesoamerica(Pires-Ferreira, 1975, 1976).

Unfortunately, these early studies did not report the completesource determinations of the archaeological sample examined fromSan Lorenzo. The research was structured as a qualitative studyintended to identify the range of obsidian sources used at SanLorenzo rather than a quantitative study of phase-by-phasechanges in the obsidian sources used over time. The artifactsanalyzed were selected to sample “the widest possible differencesin color and in surface appearance in the hopes of obtaining sam-ples from most or all of the obsidian sources used” (Cobean et al.,1971:667). As a result, while this early study established the exis-tence of extensive exchange networks at San Lorenzo, it did notidentify changes in the frequency of obsidian sources used overtime. Only 63 of the 65 analyzed artifacts could be identified tosource (Cobean et al., 1991:84) which precluded a comprehensiveview of obsidian exchange operating at San Lorenzo throughout thelength of its occupation. Nevertheless, these analyzes identifiedthat Guadalupe Victoria supplied 73% of the obsidian during theChicharras 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 comprehensivemodel for obsidian procurement at San Lorenzo between 1800 and800 cal B.C. Obsidian samples used for source analysis rarely areconstructed on the basis of technological and social variables thataffected the quantity of material used from different sources.Instead, samples often are drawn from a small number of contextsand analyzed as if they were representative of the entire site. Toavoid this problem a large multi-dimensional sample of 852 piecesof obsidian were analyzed from 50 components that spanned thesix major occupations between 1800 and 800 cal B.C. The samplewas stratified by production technology and artifacts were selectedusing non-redundant, unique elements analogous to the identifi-cation of minimum number of individuals (MNI) used in osteo-logical studies. Table 2 summarizes the quantity of obsidiananalyzed for each of the analytical contexts used in this study.

Stratifying the sample by technology was designed to obtain arepresentative view of the obsidian sources used at San Lorenzo.Archaeologists have long recognized that the manufacture ofpressure blades requires high quality obsidian with few impurities,while percussion flaking can utilize less pure obsidian. Sinceobsidian sources vary in the workability of the glass, it means thatthe obsidian used in percussion industries could come fromdifferent sources than those used in pressure blade production.Artifacts were selected for analysis using criteria analogous to theidentification of MNIs to avoid redundant analysis (double-count-ing) of obsidian fragments from the same artifact. Lithic artifacts atSan Lorenzowere never used as complete blades or flakes, but werebroken into anywhere from 3 to 6 segments that were hafted orused as hand-held cutting tools. To avoid double representation ofthe same artifact in the study sample, proximal sections or strikingplatforms were used since they are both easily recognizable andoccur as single elements on all flakes and blades. This insured thatindividual flakes and blades were the minimal unit of analysis.

Excavation levels were regularly sampled as complete units toinsure a representative sample of the obsidian consumed. Thewhole-level sampling of non-redundant artifacts often reduced thesample to only 1e2 artifacts per collection context. Archaeologistsoften select for diversity when choosing obsidian (e.g. Cobean et al.,1971) or do not specify the parameters used to select samples foranalysis. This is unfortunate because it adds selection bias and

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

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

K. Hirth et al. / Journal of Archaeological Science 40 (2013) 2784e27982786

Table 2Contexts analyzed at San Lorenzo (SL), Loma de Zapote (LZ), Las Camelias, El Bajioand islote site of RSLT-116a.

Contexts Single componentcontexts

No. of pieces

San LorenzoSL: A4 Ilmenitas CHE 4 14SL: A4 Ilmenitas JZN 2 20SL: A4 Ilmenitas LGL 2 10SL: A4 Platos 1 4SL: B. Jobo CW 3 20SL: B. Jobo EHG 3 24SL: B. Jobo ESLE 1 18SL: B. Jobo MVG 2 10SL: C5-6 3 24SL: C5-6, Sondeo 1 1 3SL: D4 Plan 2 26SL: D4-7 1 1SL: D4-22 1 16SL: D5-9 1 9SL: D5-9W 1 4SL: D5-31 1 13SL: Grupo C, Col A 4 29SL: Grupo C, Col B 2 5SL: Grupo C, Col C 1 1SL: Grupo D, B3-5 2 8SL: Grupo D, B3-11 2 40SL: Grupo D, B3-17 2 31SL: Grupo D, SL-30 3 25SL: Grupo D, Sondeos 1 1SL: Grupo E, SL-14 3 49SL: Grupo E, SL-73 2 16SL: P. Camilo Dgz 3 27SL: P. M. Rosas, Col A 2 3SL: P. M. Rosas, Col F 1 2SL: P. M. Rosas, Col H 2 19SL: P. Perfecto Domínguez LO 4 61SL: P. Perfecto Domínguez TV 1 50SL: P. Simon HDZ DRH 1 19SL: P. Simon HDZ PS 2 11SL: SL-53 4 89SL: SL-112 2 16SL: Trans 1W, Sondeo 2 1 2SL: Trans 1W, Sondeo 3 1 1SL: Trans 2S, Sondeo 1 1 2SL: Zanja La Mina 1 7Loma de ZapoteLZ: Malpica U 1 19LZ: P. S. Salomon 2 16LZ: PN, S. Bernal 2 7LZ: PN, S. Diego Osorio 1 4LZ: PN, S Vasconcelos 1 11LZ: Represa Azuzul 1 4LZ: S. Aguilar 3 12Other regional sitesEl Bajio 1 26Las Camelias 1 14RSLT-116a 1 9Total N ¼ 50 91 852


diminishes the representativeness and interpretability of the re-sults. Flakes and blades were selected for analysis in proportion totheir occurrence within study levels. Because of their scarcity, allflake and blade cores were analyzed since they were the objectsfrom which multiple flakes were produced. It is felt that high pre-cision analysis of samples from a large number of contexts isessential for distinguishing the multiple paths through which rawmaterial like obsidian could enter and circulate throughout a largemulti-component site like San Lorenzo.

All of the 852 obsidian artifacts discussed here were submittedto the Archaeometry Laboratory at the University of Missouri foranalysis. During the course of this multi-year project, theanalytical methods employed were changed to take advantage of

improvements in equipment and technology. The first 50 sampleswere analyzed by neutron activation analysis (NAA) using a short-irradiation procedure described by Glascock et al. (1994). Thismethod measures seven elements (Al, Ba, Cl, Dy, K, Mn, and Na)and is very powerful but has the disadvantage of being destruc-tive. The remaining 802 samples were analyzed non-destructivelyby X-ray fluorescence (XRF) which measures a different suite ofelements (the best of which are Rb, Sr, Y, Zr, and Nb). Twodifferent spectrometers operating at 40 kV and 17 microampswere used for XRF. A table-top Elva-X spectrometer with tungstenanode was used for 594 samples and a handheld portable BrukerIIIeV spectrometer with a rhodium anode and copper filter wasused on the remaining 208 samples. All of the NAA and XRF re-sults were compared to chemical data for obsidian sources fromMexico and Guatemala previously analyzed in the ArchaeometryLaboratory (Cobean et al., 1991; Glascock et al., 1988, 1998;Glascock, 2010). Two of the obsidian samples analyzed by XRF didnot agree with the source data and were further tested by thedestructive NAA procedure. One of these (SL-482) could not bematched to a known source while the other (SL-509) was iden-tified 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 Ojochipopulation occupied and initiated landscape modification acrossthe San Lorenzo landform that consisting of filling, leveling andinitial terracing. The site’s early occupation was identified acrossthe central site area and on some terraces. San Lorenzo was a largevillage community and the primary settlement in a 3-tier settle-ment hierarchy (see Symonds et al., 2002: Figure 4.1). Its in-habitants also built small earthen platforms known as islotes in thewetlands to assist in exploiting wetland resources (Cyphers andZurita-Noguera, 2012). Differentially fired ceramics, often consid-ered an Olmec hallmark, are present at this time. No public archi-tecture or monumental sculpture has been identified at the site,although one elite area (SL-53) was excavated. The presence ofobsidian at San Lorenzo, together with jade and other importedresources identified at the nearby site of El Manati (Ortiz and delCarmen Rodriguez, 2000) indicate that interregional exchangenetworks were already well established and functioning by1800 cal B.C.

Fifty obsidian artifacts were analyzed from the five Ojochi phasedeposits identified at San Lorenzo (Fig. 3b) which consisted of 49percussion flakes and one percussion flake core. Kenneth Hirth’sanalysis of the complete obsidian assemblage reveals that anexpedient flake industry predominated. Obsidian was brought intothe site as irregular fist-sized nodules which were used to producerazor 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 duringthis phase originated from Guadalupe Victoria source located312 km northwest of San Lorenzo on the western slope of theOrizaba volcano (Fig. 1, Table 3). At this source small irregularnodules are exposed in ravines and gullies in a 20 km radiusaround the modern town of Guadalupe Victoria (Cobean, 2002).These data confirm the earlier identification of this source as amajor supplier of obsidian for the early percussion industries atSan Lorenzo (Cobean et al., 1971, 1991). Two other sources alsowere identified in small amounts. These include the Pico de Ori-zaba source (6%) located in the Ixtetal Valley (Cobean, 2002) onthe northern slope of the Orizaba volcano, and the importantsource of El Chayal (2%) in the highlands of Guatemala (Table 4).

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 Chicharrasphase obsidian distribution.


The presence of El Chayal obsidian in even small amounts isimportant because it demonstrates that obsidian was alreadymoving over 613 km across the Isthmus of Tehuantepec to reachSan Lorenzo (Tables 3 and 4). The SL: D4-Plan excavation area isthe only context where obsidian from all three sources wasrecovered together.

4.2. The Bajío phase (1600e1500 cal BC)

San Lorenzo grew during this phase and expanded beyondthe plateau to include settlement along the site’s periphery.Monumental construction in the form of landscape modificationwas initiated on the summit of the natural landform. These

Table 3Distance to obsidian sources used at San Lorenzo.

Obsidian source Distance from SanLorenzo (km)a

Phases present atSan Lorenzo

El Chayal, Guatemala 577 Ojochi, Bajio, Chicharras,SL-A, SL-B, Nacaste

Guadalupe Victoria, Puebla 320 Ojochi, Bajio, Chicharras,SL-A, SL-B, Nacaste

Ixtepeque, Guatemala 656 SL-A, SL-B, NacasteOtumba, Mexico 464 Chicharras, SL-A, SL-B,

NacasteParedon, Puebla 440 Chicharras, SL-A, SL-B,

NacastePico de Orizaba, Veracruz 303 Ojochi, Bajio, Chicharras,

SL-A, SL-BPachuca, Hidalgo 490 SL-B, NacasteUcareo, Michoacan 669 Chicharras, SL-A, SL-B,

NacasteZacualtipan, Hidalgo 521 SL-A, SL-BZaragozaeOyameles, Puebla 370 Chicharras, SL-A, SL-B,

NacasteZinapecuaro, Michoacan 681 Nacaste

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


architectural modifications formed the first construction phaseof what was to become the largest public earth work constructedin Mesoamerica during the Early Formative period (Cyphers,1996:70; Cyphers et al. 2008-2007). Increasing intra-site socialdifferentiation 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 patterningsuggests that San Lorenzo exerted its influence over its sur-rounding population (Cyphers, 2012). It is during the Bajío phasethat hollow figurines and decorative motifs in the Olmec styleappear in local ceramic assemblages and San Lorenzo became themajor source of Olmec influence in Mesoamerica.

Obsidian continued to be imported into the site as irregularnodules that were manufactured into usable flakes using percus-sion techniques. Seventy-eight pieces of obsidianwere analyzed forthis phase andwere drawn from eight Bajío phase contexts (Fig. 3c).

Table 4Ojochi and Bajio obsidian source determinations.

Area GuadalupeVictoria

Pico deOrizaba

El Chayal,Guat

Total

No. No. No. No.

Ojochi phase percussion, N ¼ 50SL: A4 Ilmenitas CHE 1 0 0 1SL: D4 Plan 8 2 1 11SL: Grupo C, Col A 5 0 0 5SL: Grupo C, Col B 1 0 0 1SL: SL-53 31 1 0 32Total 46 3 1 50Percent 92 6 2 100%

Area GuadalupeVictoria, Ver

Pico deOrizaba, Ver

El Chayal,Guat

Total

No. No. No. No.

Bajio phase percussion industry, N ¼ 78SL: A4 Ilmenitas CHE 1 0 0 1SL: A4 Ilmenitas LGL 2 0 0 2SL: D4 Plan 7 4 4 15SL: Grupo C, Col A 7 4 0 11SL: Grupo C, Col B 0 0 4 4SL: Grupo B, B3-5 4 0 1 5SL: P. Perfecto Dominguez LO 19 1 0 20SL-53 20 0 0 20Total 60 9 9 78Percent 71% 11.5% 11.5% 100%

This sample consists of 64 percussion flakes, five worked nodules,three flake cores, and six flake tools. Source analysis reveals that thesame sources used in the Ojochi phase continued to be exploitedthroughout the Bajío phase.

Obsidian from Guadalupe Victoria again dominated the assem-blage representing 71% of the material entering the site (Table 4).Nevertheless, several important trends are noticeable during thisphase. The first is an increase in obsidian from the Pico de Orizabaand El Chayal sources. El Chayal obsidian represents 11.5% of thecollections and now is as prevalent as material from Pico de Orizabaeven though it is 321 km further away (Table 3). Second, there isgreater variability in the distribution of these sources within SanLorenzo. For example, SL: D4-Plan is the only site area sampledwhere all three obsidian sources were recovered. This is the samepattern observed for the Ojochi phase, although the obsidian at SL:D4-Plan from Pico de Orizaba and El Chayal is now as prevalent asthat from Guadalupe Victoria. The variability in obsidian sourcesbetween the different areas of San Lorenzo suggests the operationof multiple independent sources of supply rather than a singlecentralized procurement mechanism.

4.3. The Chicharras phase (1500e1400 cal BC)

During this phase there was intensified development at SanLorenzo. Large scale terrace and earthwork construction continuedacross the plateau. We know that the entire upper plateau wasprobably occupied and the initial stages of the elite GD-1 structure(known as the Red Palace) in Group D were built. Whatever theinternal structure, the site’s political and religious institutions werecentered on the elite who claimed to be descendants of deifiedancestors (Clark, 2007:41; Cyphers, 1997b:233). Evidence for longdistance trade increased and included the importation of green-stone, iron ore mirrors, and mica into the site.

The complete obsidian analysis indicates that themajority of theobsidian cutting edge at San Lorenzo was again supplied by expe-dient flakes produced from small irregular nodules. It was duringthis phase, however, that obsidian pressure blades began to appearin low frequencies, often as single artifacts in Chicharras phasedeposits. A total of 100 pieces of obsidian was selected for analysisfrom 15 separate deposits (Fig. 3d). These included 93 percussionartifacts (78 flakes, five worked cobbles and flake cores, 10 flaketools) and seven obsidian prismatic pressure blades. Chemicalanalysis reveals widening trade relationships with obsidian fromfour new source areas arriving at the site for the first time (Table 5).

Percussion flaking continued to dominate the Chicharras phaseassemblage with obsidian from Guadalupe Victoria supplying 74%of the raw material used. The Guatemalan source of El Chayal wasthe second most commonly used source providing 20% of theobsidian used for quotidian activities. The Pico de Orizaba sourcewhich supplied 6e12% of raw material during the Ojochi and Bajíophases all but disappeared, supplying little more than 2% of theobsidian used in percussion flaking. Notably obsidian nodules fromtwo new highland sources (Ucareo and Paredon) appeared at SanLorenzo in trace amounts for the first time (Table 5).

Prismatic pressure blades are little more than 2% of the totalobsidian assemblage. The seven blades (Table 5) are an opportu-nistic sample analyzed to obtain a preliminary identification of thesources exploited. Although the number analyzed is small, a notablediversity was observed in the sources used tomanufacture obsidianblades. The sources represented include the three Mexican sourcesof Paredon (N¼ 3), Otumba (N¼ 1) and ZaragozaeOyameles (N¼ 1),alongwith El Chayal, Guatamala (N¼ 2). There is no evidence for on-sitemanufacture of obsidian blades (sensu De León et al., 2009) so itis likely that thesematerials reached San Lorenzo as a result of tradein finished blades (Jackson and Love, 1991).

Table 5Chicharras phase obsidian source determinations.

Area Guad.Victoria

Pico deOrizaba

El Chayal,Guat

Ucareo,Mich

Paredon,Mex

Otumba,Mex

Zaragoza,Pue

Total

Chicharras phase percussion (N [ 93)SL: A4 Ilmenitas CHE 1 0 0 0 0 0 0 1SL: B. Jobo CW 0 0 3 1 0 0 0 4SL: B. Jobo EHG 1 0 0 0 0 0 0 1SL: B. Jobo MVG 2 0 4 0 0 0 0 6SL: C5-6 2 0 2 0 0 0 0 4SL: Grupo C, Col A 5 0 1 0 0 0 0 6SL: Grupo C, Col C 0 0 0 0 1 0 0 1SL: Grupo D, B3-5 1 0 0 0 0 0 0 1SL: Grupo D, SL-30 13 0 3 0 1 0 0 17SL: Grupo D, Sondeos 0 0 0 0 0 0 0 0SL: Grupo E, SL-73 0 0 1 0 0 0 0 1SL: P. Perfecto Domínguez LO 10 1 2 0 0 0 0 13SL: Simon Hdz DRH 15 0 3 0 0 0 0 18SL: P. Simon Hdz PS 1 0 0 0 0 0 0 1SL: SL-53 18 1 0 0 0 0 0 19Total Percussion 69 2 19 1 2 0 0 93Percentage of Percussion 74.2% 2.15% 20.4% 1.1% 2.15% 0% 0% 100%Pressure BladesSL: B. Jobo MVG 0 0 1 0 0 0 0 1SL: Grupo D, B3-5 0 0 0 0 2 0 0 2SL: Grupo D, Sondeos 0 0 0 0 1 0 0 1SL: P. Simon Hdz DRH 0 0 1 0 0 0 0 1SL: SL-53 0 0 0 0 0 1 1 2Total Pressure Blades 0 0 2 0 3 1 1 7Total Obsidian 69 2 21 1 5 1 1 100


4.4. The San Lorenzo A phase (1400e1200 cal BC)

San Lorenzo emerged as the largest site in Mesoamerica duringthis phase growing to more than 690 ha (Cyphers, 1996:70;Lunagómez Reyes, 1995; Cyphers et al. 2008-2007). It is now andduring the following San Lorenzo B phase that the site reached theheight of its cultural development. Massive filling operationscreated a monumental construction in the shape of a terracedearthen plateau. Large public buildings were constructed and therewere sculpture workshops in the central plateau that producedcolossal heads and medium sized stone monuments used in ritualdisplays and to reinforce the dynastic authority of San Lorenzorulers (Cyphers, 1997b, 2012). San Lorenzo was the most influentialcenter in the southern Gulf Coast and its location on the ancientCoatzalcoalcos river system provided a locational advantage forparticipation in regional and interregional trade. Both Loma deZapote and Laguna de los Cerros developed into secondary centers(Cyphers, 2012; Symonds et al., 2002) and household inventoriesreveal differences in wealth indicative of status differences both atSan Lorenzo and throughout sites in the surrounding region(Cyphers, 1996, 1997a).

The complete lithic analysis shows that percussion flaking ofblocky nodules continued to supply most of the cutting edge usedat San Lorenzo. Nevertheless, there was a clear increase in thenumber of prismatic pressure blades used in both domestic andnon-domestic contexts across the site. A total of 193 pieces ofobsidian were sourced that consisted of 156 percussion flakes andflake tools and 37 prismatic pressure blades (Table 6). This samplewas drawn from 19 well preserved San Lorenzo phase A deposits(Fig. 4). Chemical analysis reveals that exchange intensified alongthe trade routes established during the Chicharras phase and twonew areas were exploited which raised the number of sources usedat San Lorenzo to nine (Table 6).

The bulk of obsidian exchange remained focused on the pro-curement of small irregular and blocky nodules for the productionof usable flakes. Eight sources supplied these nodules with Gua-dalupe 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 patternestablished in the previous Chicharras phase. The remaining sour-ces exploited (Pico de Orizaba, Ucareo, ZaragozaeOyameles,Zacualtipan, and Ixtepeque) occur in trace amounts of only 0.6e1.9%. 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). Theappearance of these new sources is significant because they reflectthe continued broadening of trade connections with San Lorenzo.

Prismatic pressure blades were manufactured from six differentsources and comprise 6% of the obsidian recovered during thisphase. Nearly 90% of these blades come from the four highlandMexican sources of Paredon (27.1%), Otumba (21.6%), Ucareo (21.6%)and ZaragozaeOyameles (18.9%). The other two sources used wereEl Chayal, Guatemala (8.1%) and Guadalupe Victoria (2.7%). ThatGuadalupe Victoria obsidian also was used tomanufacture pressureblades is surprising given its high level of inclusions which impedeblade removal. Particularly striking is the variable consumption ofobsidian blades across the site. Blades comprise 80% of the obsidiansample from the non-elite residential area of P. Camilo Domínguez(N ¼ 11) and 37% of the samples from the GD-1 or Red Palacestructure (areas SL:B3-11 and SL:B3-17) in Group D. Conversely,blade consumption is low at both monuments SL: SL-53 (6%) and inSL: Grupo E, SL-14 (8%). All indications are that pressure bladesreached 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 thisphase. Regional population grew to its maximum size and there isthe possibility that large sites like Laguna de los Cerros becamemore independent, eventually competing with San Lorenzo(Borstein, 2001, 2008; Cyphers, 2012). Many of the public monu-ments found at San Lorenzo date to this phase and it is likely thatthere were changes in the site’s ruling dynasty. Evidence formonument recycling suggests that either rulers were losing the

Table 6San Lorenzo A phase obsidian source determinations.

Area Guad.Victoria

Pico deOrizaba

El Chayal,Guat

Ucareo,Mich

Paredon,Mex

Otumba,Mex

Zaragoza,Pue

Zacualtipan, Hid Ixtepeque,Guat

Total

PercussionSL: A4 Ilmenitas CHE 10 1 0 0 0 0 0 0 0 11SL: A4 Ilmenitas JZN 0 0 1 0 0 0 0 0 0 1SL: A4 Ilmenitas LGL 7 1 0 0 0 0 0 0 0 8SL: B. Jobo CW 8 0 2 0 1 0 0 0 0 11SL: B. Jobo EHG 12 1 0 0 1 0 0 0 0 14SL: C5-6 2 0 1 0 0 0 0 0 0 3SL: Grupo C, Col A 5 0 2 0 0 0 0 0 0 7SL: Grupo D, B3-11 7 0 3 0 1 0 1 0 0 12SL: Grupo D, B3-17 6 0 1 0 1 0 0 0 0 8SL: Grupo D, SL-30 1 0 0 0 0 0 0 0 0 1SL: Grupo E, SL-14 19 0 4 0 0 0 0 0 1 24SL: Grupo E, SL-73 3 0 1 1 0 0 0 1 2 8LZ: PN, S. Bernal 0 0 2 0 0 0 0 0 0 2LZ: S. Aguilar 0 0 0 0 0 0 0 0 0 0SL: P. Camilo Domínguez 2 0 0 0 0 0 0 0 0 2SL: P. Miguel Rosas 0 0 1 0 0 0 0 0 0 1SL: P. Perfecto Domínguez LO 8 0 7 0 0 0 0 0 0 15SL: SL-112 6 0 4 0 3 0 0 0 0 13SL: SL-53 15 0 0 0 0 0 0 0 0 15Total Percussion 111 3 29 1 7 0 1 1 3 156Percentage of Percussion 71.2 1.9 18.6 0.6 4.5 0.0 0.6 0.6 1.9 99.9

Area Guad. Victoria El Chayal, Guat Ucareo, Mich Paredon, Mex Otumba, Mex Zaragoza, Pue Total

Pressure bladesSL: B. Jobo CW 0 0 0 1 0 0 1SL: Grupo D, B3-11 0 2 2 0 1 0 5SL: Grupo D, B3-17 0 0 2 3 2 0 7SL: Grupo E, SL-14 1 0 0 1 0 0 2SL: Grupo E, SL-73 0 1 0 1 0 5 7LZ: PN, S. Bernal 0 0 0 1 1 0 2LZ: S. Aguilar 0 0 1 0 0 0 1SL: P. Camilo Domínguez 0 0 3 2 2 2 9SL: SL-112 0 0 0 1 1 0 2SL: SL-53 0 0 0 0 1 0 1Total Pressure Blades 1 3 8 10 8 7 37Percentage of Pressure Blades 2.7 8.1 21.6 27.1 21.6 18.9 100


ability to command the labor necessary to import large basaltblocks from the Tuxtla mountains and/or older monuments weredefaced and recycled to remove the images of earlier rulers frompublic spaces. The quantity and diversity of imported goods indi-cate that San Lorenzo was at the center of an extensive tradenetwork that included green stone, ilmenite, mica and polishedmagnetite mirrors. The massive deposits of drilled ilmenite blocksdate to this phase and indicate both high levels of interregionaltrade and the on-site manufacture of exotic craft goods (Cyphers,1996; Di Castro Stringher, 1997).

A significant change also occurred in the organization of SanLorenzo lithic assemblages. While percussion flakes still accountedfor most of the lithic artifacts recovered (68.6%), obsidian pressureblades rose sharply in popularity accounting for 31.4% of all theobsidian artifacts recovered at San Lorenzo. This was a transitionalperiod for blade use at San Lorenzo with blade frequencies soaringfrom 6% during the preceding phase. Of course, 31.4% is the averagelevel of blade consumption for the entire phase. Since bladesrepresent only 6% at the start of this phase, usage rates would havehad to be very high by the end of San Lorenzo phase B to produce anaverage usage rate of 31% for the entire phase.

A total of 331 obsidian artifacts were chemically analyzed whichwere drawn from 34 well preserved deposits at San Lorenzo andthe nearby sites of Loma de Zapote and El Bajío (Figs. 2 and 5). Thissample was composed of 177 percussion flakes, cores and flaketools, and 154 pressure blades (Table 7). Obsidian continued tomove 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 duringthis phase.

Procurement networks were remarkably stable from the pre-ceding phase with the same eight sources supplying raw materialfor the percussion industry. The nearby source of Guadalupe Vic-toria supplied the bulk of this material (58.7%) although in loweramounts than during the preceding phase. El Chayal (19.2%), Par-edon (10.2%) and Ucareo (7.9%) also provided significant amounts ofnodular material. The remaining four sources (Pico de Orizaba,Otumba, ZaragozaeOyameles, Ixtepeque) contributed only traceamounts of obsidian in the range of 0.6e1.1% for percussion flaking.The increase in nodular material from Ucareo and Paredon fromprevious phases was very likely a side product of the large numberof 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 impor-tant of these was Ucareo (37.6%) followed by Paredon (27.3%) andOtumba (16.2%). The sources of ZaragozaeOyameles (6.5%) and ElChayal (5.2%) also supplied a small but important quantity ofblades. Blades also appeared for the first time from three newsources in trace amounts: Ixtepeque (3.2%), Zacualtipan (1.3%) andSierra de Pachuca (0.7%).

4.6. The Nacaste phase (1000e800 cal BC)

The Nacaste phase witnessed the waning of San Lorenzo as amajor center in the Gulf Coast. Its political influence declinedsharply along with its on-site population. A dispersed population

Fig. 4. San Lorenzo A phase obsidian distribution.


continued to live on the plateau but there is no evidence for majorarchitectural construction across the plateau either in the form orterracing or the construction of monumental public buildings.Nevertheless, San Lorenzo shared ceramic and figurine styles withother sites in the Gulf Coast (Coe and Diehl, 1980:188; Lowe,1989:53e57) even though it was eclipsed by La Venta and othersites in the Gulf Coast after 1000 cal BC.

Despite changes in the internal organization of San Lorenzo, thetotal obsidian analysis indicates that blades continued to increasein 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, flakeswere smaller than they were during all previous phases. It is likelythat prismatic blades provided the majority of the cutting edgeused at San Lorenzo at this time.

A sample of 100 pieces of obsidian was chemically analyzed forthis phase that consisted of 38 percussion flakes and 62 pressureblades (Table 8). This samplewas collected fromnine Nacaste phasecontexts at San Lorenzo (Fig. 6). The major source for obsidianblades was the highland source of Otumba, Mexico (40.3%). Otherimportant 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 obsidianfrom Pico de Orizaba and Zacualtipan reflects a slight shrinkage inprocurement patterns. Zinapecuaro obsidian appeared in traceamounts for the first time and probably entered the site throughthe same channels as material from its neighboring source ofUcareo.

Changes can be observed in the procurement networks thatsupplied small nodules for percussion flaking. There was a sharp

decrease in the quantity of material from Guadalupe Victoria fromnearly 59% during the preceding phase to only 36.9% duringNacaste. The decrease in Guadalupe Victoria obsidian was offset byincreases in raw material from both El Chayal (34.2%) and Paredon(15.8%). Obsidian fromUcareo (7.9%), Otumba (2.6%) and ZaragozaeOyameles (2.6%) supplied the remainder of nodular raw materialused at the site.

5. Discussion

The results of this study expand on the pioneering in-vestigations conducted of obsidian procurement at San Lorenzo(Cobean et al., 1971, 1991). This investigation confirms that theobsidian used at San Lorenzo came from a large number of sources.Furthermore, it adds new information by analyzing a large sampleof obsidian artifacts from each of the six phases of site developmentfrom 1800 to 800 cal B.C. The results allow us to identify thestructure of obsidian procurement networks by recognizing whichsources supplied raw material and finished goods in differentquantities over the life of the site. Eleven obsidian sources wereidentified that are distributed across the greater breadth of Meso-america (Fig. 1, Table 8). San Lorenzo had access to, and drew ma-terial from, most of the major obsidian source areas in the Mexicanand Guatemalan highlands before 1000 cal BC. This has importantimplications for understanding the structure of early trade andprocurement networks that need to be explored in greater depth infuture studies.

Obsidian supplied the primary cutting edge at San Lorenzo andhad to be transported long distances to reach the site. The in-habitants of San Lorenzo had established contact with two majorsource regions by 1800 cal BC. These were: 1) the slopes of the

Fig. 5. San Lorenzo B phase obsidian distribution.


Orizaba volcano where the Guadalupe Victoria and Pico de Orizabasources were located, and 2) the Valley of Guatemala with itsimportant obsidian source at El Chayal (Fig. 1). Guadalupe Victoriaand Pico de Orizaba are the closest sources to San Lorenzo. Located300 km northwest of San Lorenzo, these sources supplied themajority of the hand-sized obsidian nodules used to produce flakesat the site. The earliest use of Orizaba obsidian is an obsidian pro-jectile point recovered from El Riego phase deposits in the Tehua-can Valley (Cobean et al., 1971:668) which predates its appearanceat San Lorenzo by nearly 4000 years. This underscores the earlyimportance of obsidian and its movement over long distances tosupply quotidian cutting tasks.

What is more surprising is that obsidian from El Chayal,Guatemala, occurs at San Lorenzo during the Ojochi and Bajíophases. El Chayal is more than 600 km from San Lorenzo, fully twicethe distance of the two sources near the Orizaba volcano. While ElChayal obsidian is a higher quality of glass than obsidian fromGuadalupe Victoria, it provides no real technological advantages forexpedient percussion flaking. All three sources provide razor sharpflakes suitable for hand-held cutting tasks. The greater distance tothe El Chayal source should have precluded its use at San Lorenzobecause of its higher transportation costs (Drennan, 1984; Hassig,1985). Clearly resource provisioning was not structured purely inenergetic terms. Instead, resource procurement more likely oper-ated through multiple, nested interregional social networks thatmoved material over space irrespective of the distances involved.

Interregional procurement networks operating during the Ojo-chi and Bajío phases expanded dramatically during the Chicharrasphase around 1500 cal BC. Two important developments occurredat this time. First, the quantity of obsidian moving through the

Guatemalan source network increased substantially, indicating anexpansion and intensification of long distance relationshipsthrough the Isthmus of Tehuantepec and into the Guatemalanhighlands (sensu Zeitlin, 1982). Second, there is the expansion ofsource networks north and west into the Mexican highlandsreaching as far west as the Cuitzeo Basin in eastern Michoacan. Thishighland Mexican route represents a third procurement networkthat provided obsidian from four new sources. These new sourcesincluded: ZaragozaeOyameles in the eastern Puebla highlands,Otumba and El Paredon in the northeastern Basin of Mexico, andUcareo in the Cuitzeo Basin of Michoacan. The direct line distancesto these sources range from 360 km to ZaragozaeOyameles to over660 km to Ucareo (Table 3).

The obsidian that moved through this new highland networkwas small in quantity and relatively insignificant in terms of pro-visioning San Lorenzo residents with usable cutting edge. Theimportance of the obsidian data is that it documents the creation ofnetwork relationships that linked San Lorenzo to highland Mexico.These contacts provided the linkages for the reciprocal movementof people, ideology, technology and material goods. It was alongthis corridor and at least a century later that Gulf Coast ceramicsmoved into the Basin of Mexico (Blomster et al., 2005; Neff et al.,2006) and West Mexico. Likewise it was through this networkthat highland goods including obsidian blade technology reachedthe Gulf Coast. Obsidian pressure blades manufactured fromOtumba, Paredon, and ZaragozaeOyameles obsidian reached SanLorenzo during the Chicharras phase. Although Ucareo obsidianmoved across the highland route as small nodules, blades and othergoods appear to have followed this network as trade expandedafter 1400 cal BC.

Table 7San Lorenzo B phase obsidian source determinations.

Area Guad.Victoria

Pico deOrizaba

El Chayal,Guat

Ucareo,Mich

Paredon,Mex

Otumba,Mex

Zaragoza,Pue

Ixtepeque,Guat

Unknown Total

PercussionSL: A4 Ilmenitas JZN 1 0 10 0 1 0 0 0 0 12SL: A4 Platos 0 0 0 0 1 0 0 0 0 1SL: B. Jobo CW 3 0 0 0 1 0 0 0 0 4SL: B. Jobo EHG 6 0 2 0 0 0 0 0 0 8SL: B. Jobo MVG 1 0 0 0 0 0 0 0 0 1SL: C5-6 6 0 1 0 2 0 0 0 0 9SL: D4-22 1 1 2 0 1 0 0 0 0 5SL: D5-9 3 0 0 0 0 0 0 0 0 3SL: D5-9W 1 0 0 0 0 0 0 0 0 1SL: D5-31 5 0 1 0 5 0 0 0 0 11SL: Grupo D, B3-11 6 0 5 1 0 0 0 0 0 12SL: Grupo D, B3-17 2 0 1 0 3 0 1 0 0 7SL: Grupo D, SL-30 1 0 4 0 0 0 0 0 0 5SL: Grupo E, SL-14 7 0 0 0 0 0 0 1 0 8Las Camelias 0 0 0 2 1 0 1 0 0 4LZ: Malpica U 0 0 0 7 0 0 0 0 0 7LZ: P. S. Salomon 2 0 0 0 0 1 0 0 0 3LZ: PN, S. Diego Osorio 0 0 1 0 0 0 0 0 0 1LZ: S. Aguilar 1 0 0 0 0 0 0 0 0 1SL: P. Camilo Domínguez 3 0 0 0 0 0 0 0 0 3SL: P. M. Rosas, Col A 1 0 1 0 0 0 0 0 0 2SL: P. M. Rosas, Col F 1 0 0 0 0 0 0 0 0 1SL: P. Perfecto Domínguez LO 2 1 1 0 0 0 0 0 0 4SL: Perfecto Domínguez TV 27 0 4 0 3 0 0 0 0 34RSLT-116a 9 0 0 0 0 0 0 0 0 9SL: Trans 1W, Sondeo 2 2 0 0 0 0 0 0 0 0 2SL: Trans 2S, Sondeo 1 1 0 0 0 0 0 0 0 0 1SL: Zanja La Mina 2 0 0 0 0 0 0 0 0 2El Bajio 10 0 1 4 0 0 0 0 1 16Total Percussion 104 2 34 14 18 1 2 1 1 177Percentage of Percussion 58.7 1.1 19.2 7.9 10.2 0.6 1.1 0.6 0.6 100%

Area Guad.Victoria

El Chayal,Guat

Ucareo,Mich

Paredon,Mex

Otumba,Mex

Zaragoza,Pue

Zacualtipan,Hid

Ixtepeque,Guat

Pachuca,Hid

Unknown Total

Pressure bladesSL: A4 Ilmenitas JZN 0 1 1 5 0 0 0 0 0 0 7SL: A4 Platos 0 1 0 0 1 0 0 1 0 0 3SL: B. Jobo EHG 0 0 0 1 0 0 0 0 0 0 1SL: B. Jobo MVG 0 0 0 1 1 0 0 0 0 0 2SL: C5-6 0 0 0 4 4 0 0 0 0 0 8SL: C5-6, Sondeo 1 0 0 0 3 0 0 0 0 0 0 3SL: D4-22 0 0 4 2 3 1 1 0 0 0 11SL: D4-7 0 1 0 0 0 0 0 0 0 0 1SL: D5-9 0 0 4 0 2 0 0 0 0 0 6SL: D5-9W 0 0 0 1 2 0 0 0 0 0 3SL: D5-31 0 0 0 1 1 0 0 0 0 0 2SL: Grupo D, B3-11 1 2 3 3 0 1 1 0 0 0 11SL: Grupo D, B3-17 0 0 5 2 1 1 0 0 0 0 9SL: Grupo D, SL-30 0 0 1 0 1 0 0 0 0 0 2Las Camelias 0 1 5 1 1 1 0 1 0 0 10LZ: Malpica U 0 1 10 0 0 0 0 0 1 0 12LZ: P. S. Salomon 0 0 2 2 1 0 0 0 0 0 5LZ: PN, Diego Osorio 0 0 1 0 1 1 0 0 0 0 3LZ: Represa Azuzul 0 0 1 1 2 0 0 0 0 0 4LZ S. Aguilar 0 0 0 2 0 0 0 0 0 0 2P Camilo DGZ 0 0 1 1 0 0 0 0 0 0 2SL: P. M. Rosas, Col F 0 0 1 0 0 0 0 0 0 0 1SL: P. M. Rosas, Col H 0 0 1 1 0 0 0 1 0 0 3SL: P. Perfecto Domínguez LO 0 0 4 2 0 3 0 0 0 0 9SL: P. Perfecto Domínguez TV 0 0 7 6 1 1 0 0 0 1 16SL: SL-112 0 0 1 0 0 0 0 0 0 0 1SL: Trans 1W, Sondeo 3 0 0 0 1 0 0 0 0 0 0 1SL: Trans 2S, Sondeo 1 0 0 0 1 0 0 0 0 0 0 1SL: Zanja La Mina 0 0 2 1 1 1 0 0 0 0 5El Bajio 1 1 4 0 2 0 0 2 0 0 10Total Pressure Blades 2 8 58 42 25 10 2 5 1 1 154Percentage of Pressure Blades 1.3 5.2 37.6 27.3 16.2 6.5 1.3 3.2 0.7 0.7 100%


Fig. 6. Nacaste phase obsidian distribution.

Table 8Nacaste phase obsidian source determinations.

Area Guad. Victoria El Chayal, Guat Ucareo, Mich Paredon, Mex Otumba, Mex Zaragoza, Pue Total

PercussionSL: B. Jobo ESLE 3 1 1 2 0 0 7SL: Grupo E, SL-14 5 2 1 1 0 0 9LZ: P. S. Salomon 0 0 0 1 0 0 1LZ: PN, S. Bernal 0 0 0 1 0 0 1LZ: PN, S. Vasconcelos 1 7 0 0 0 0 8LZ: S. Aguilar 2 1 0 1 0 0 4SL: P. Camilo Domínguez 1 1 0 0 0 0 2SL: P. M. Rosas 0 0 1 0 0 1 2SL: P. Simon Hdz PS 2 1 0 0 1 0 4Total percussion obsidian 14 13 3 6 1 1 38Percentage percussion obsidian 36.9 34.2 7.9 15.8 2.6 2.6 100%

Area El Chayal,Guat

Ucareo,Mich

Paredon,Mex

Otumba,Mex

Zaragoza,Pue

Ixtepeque,Guat

Pachuca,Hid

Zinapecuaro,Mich

Total

Pressure bladesSL: B. Jobo ESLE 2 4 3 0 1 1 0 0 11SL: Grupo E, SL-14 0 2 0 1 2 0 0 1 6LZ: P. S. Salomon 0 5 1 1 0 0 0 0 7LZ: PN, S. Bernal 0 0 0 2 0 0 0 0 2LZ: PN, S. Vasconcelos 0 0 0 2 0 0 1 0 3LZ: S. Aguilar 0 0 2 1 1 0 0 0 4SL: P. Camilo Domínguez 3 4 1 0 1 0 0 0 9SL: P. M. Rosas 0 2 0 12 0 0 0 0 14SL: P. Simon Hdz PS 0 0 0 6 0 0 0 0 6Total Pressure Blades 5 17 7 25 5 1 1 1 62Percentage of Pressure Blades 8.1 27.4 11.3 40.3 8.1 1.6 1.6 1.6 100%



San Lorenzo reached its cultural apogee during San Lorenzophases A and B. Between 1400 and 1000 cal BC it was the primaryOlmec center and a source of cultural influences throughout theGulf coast and possibly beyond (Footnote6). The obsidian infor-mation indicates an increased volume of raw material and finishedblades moving along trade circuits across Guatemala and theMexican highlands. The same also was true for ceramic and othergoods (Blomster et al., 2005; Herrera et al., 1999; Neff et al., 2006;Pires-Ferreira, 1975). Most notably the increased consumption ofobsidian blades at the beginning of the San Lorenzo A phasecontinued well into its decline during the Nacaste phase. Bladesconstituted 6% of the obsidian assemblage during the San Lorenzo Aphase, 31% during the San Lorenzo B phase, and nearly one-half ofthe assemblage (47.5%) during the Nacaste phase. During thesethree phases fully 90% of all blades consumed at San Lorenzo wereproduced from obsidian from highland sources (Footnote7). Fournew highland sources (Zacualtipan, Ixtepeque, Pachuca, Zinape-cuaro) were added during these three phases, all of which occur asprismatic blades by the San Lorenzo B or Nacaste phase.

It is important that the frequency of obsidian blades continuedto increase unabated into the Nacaste phase. Blade use in domesticcontexts continued to rise to 47.5% throughout the Nacaste phasedespite San Lorenzo’s political decline and the decreased impor-tance of the site elite. This high level of blade use differs from thatreported near La Venta where pressure blades constitute only 28%of the obsidian assemblage at the Middle Formative site of SanAndres (Doering, 2002:72; see also Raab et al., 2000). Clearly eco-nomic systems operated independently of the political events thatengulfed San Lorenzo during its decline. The economic needs of SanLorenzo domestic units were too important to have political dis-ruptions interfere with them. Obsidian blades reached Nacastephase households well after the elite had departed or declined inregional importance at San Lorenzo.

Clark (1987) has suggested that blade technology spreadthroughout Mesoamerica as a direct result of elite action. Thisproposed involvement took two forms: 1) the procurement ofobsidian cores from distant sources, and 2) sponsorship of the ar-tisans with specialized skills to produce obsidian blades (Clark,1987:278). Elite involvement is assumed to be motivated by thecontrol over unique or preferred goods that they could selectivelydistribute to individuals for elite political advantage (sensuBrumfiel and Earle, 1987; Clark, 1987:280).

The San Lorenzo data expands our understanding of obsidianprocurement in two ways. First, obsidian was the dominant mate-rial used for cutting tools during the Ojochi phase indicating that itmoved readily through interregional exchange networks by1800 cal BC. This obsidian moved into San Lorenzo in nodular formand probably reached the site through the same type of reciprocal,

6 For the broader debate on the role of the Olmec in Mesoamerica prehistory thereader can consult: Blomster et al. (2005) Clark (1997), Cyphers (2012), Flanneryand Marcus (2000), Grove (1993), Neff et al. (2006), Pool (2007), and Wilk (2004).

7 Blades recovered at San Lorenzo were predominantly manufactured fromobsidian sources in the Mexican highlands. Exact percentages of the bladeassemblage manufactured from Mexican obsidian sources were 89.2% during theSan Lorenzo A phase, 90.3% during San Lorenzo B, and 90.3% during the Nacastephase. This contrasts with analysis of obsidian from the Tuxtla region whereZaragozaeOyameles was identified as the only highland Mexican source enteringthe region during the Early Formative period (Santley et al., 2001). ZaragozaeOyameles was also the only highland obsidian identified at Tres Zapotes duringthe Early Formative period (Pool et al., 2010:99e100) although this conclusion restsprimarily on visual identification. These differences demonstrate the type of vari-ation found in site-oriented procurement networks during the Early Formative.Unfortunately the Tuxtla study lacks the chronological precision and assemblageseparation into percussion and pressure industries necessary for an exact com-parison with obsidian procurement at San Lorenzo.

down-the-line exchange networks through which obsidian nod-ules 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 thedistribution of prismatic pressure blades was a political process asClark (1987) suggests, then the frequency of blades should havedecreased during the Nacaste phase with the decrease in elites andtheir influence over a reduced population. This is not whathappened. Rather blade consumption at San Lorenzo continued torise into the Nacaste phase. What these data imply is that neitherthe procurement of obsidian, nor the production of blades,depended completely upon the presence of elite. Instead the firstobsidian blades probably arrived as trade goods moving throughthe same networks as obsidian nodules (De León, 2008).

This study has examined the obsidian imported and consumedat San Lorenzo from 1800 to 800 cal BC. It was not designed toreconstruct the network of economic relationships through whichit moved. Nevertheless the data are suggestive. They imply thatduring the Early Formative period obsidian moved through anetwork of decentralized domestic exchanges. Domestic tradenetworks often operated through trade partner relationships(Heider,1969) with resources moving fromhousehold to householdas gifts or reciprocal exchanges (Wiessner, 1982; Yan, 2005).Because these networks are household centered, they produce amatrix of independent and overlapping connections through whichresources move. The result is a greater diversity in the type anddistribution of the resources moving through household networkscompared to centralized systems. Winter and Pires-Ferreira (1976)have demonstrated that domestic exchange networks were theprincipal conduits for obsidian provisioning in the Valley of Oaxacaduring the Tierras Largas phase 1150e1400 BC.

Diversity in the distribution of obsidian from different sources isfound across San Lorenzo during all phases of site occupation.During the Ojochi and Bajío phases the SL: D4-Plan area displaysgreater variation in the sources of nodular obsidian used than doareas SL-53 or Perfecto Dominguez LO (Table 4). These differencesbecame exaggerated once obsidian blades increased in popularity.During San Lorenzo B, variation in blade occurrence was pro-nounced. Blades ranged from 10 to 11% of lithic materials recoveredfrom ritual and domestic areas at C5-6 and D5-31, to 48% of thedomestic assemblage in the residence of D4-22 (De León, 2008:Tables 6.14e6.43). This variation continued into the Nacaste phasewhere Otumba obsidian dominated blade assemblages at SL: P.Miguel Rosas and SL: P. Simon Hdz in contrast to SL: B. Jobo ESLEand LZ: P. S. Salomonwhere Ucareo, Paredon and El Chayal obsidianpredominated (Table 8).

6. Conclusions

This study has developed a comprehensive model for obsidianprocurement and exchange at San Lorenzo between 1800 and800 cal B.C. Chemical analysis of 852 obsidian artifacts reveals thatobsidian moved over distances of 300e600 km as early as 1800 calBC. Furthermore, the results document that San Lorenzo was pro-visioned from 11 different obsidian sources over the length of itsoccupation. This investigation examined the procurement re-quirements of two different production technologies: the produc-tion of obsidian percussion flakes from obsidian nodules and theobsidian manufactured into prismatic blades. The high percentageof blades manufactured from highland Mexico obsidian is verylikely a function of the early development of craft specialization inthis area and the early trade in finished blades by the specialistswho produced them (Boksenbaum, 1978; Boksenbaum et al., 1987;De León et al., 2009). Nevertheless, it appears that obsidian nodulesand finished blades from most Mexican and Guatemalan sources


probably moved together through interregional procurementnetworks.

Most of the discussion of Early Formative Gulf Coast culturefocuses on the San Lorenzo period from 1400 to 1000 cal BC. Thiswas the period of rulers, palaces and impressive stone monuments.It was also when San Lorenzo reached its maximum size andimportance and an array of exotic goods reached the site throughextensive interregional trade. This is the Olmec story as we havecome to know it. Obsidian, however, supplies a differentperspective.

Obsidian analysis illustrates that by 1800 cal BC San Lorenzowasinvolved in two long distance procurement networks, oneextending north into central Veracruz and the Orizaba region, andthe other extending south across the Isthmus of Tehuantepec andinto Guatemala. A significant moment in Olmec development ap-pears to have been the Chicharras phase (1500e1400 cal B.C.). Notonly were strong leaders and the foundations of Olmec societyemerging at San Lorenzo, but also the site extended its procure-ment networks deep into the Mexican highlands as far as theUcareo obsidian source in West Mexico. It is likely that most if notall of the obsidian moved along these routes through down-line-exchange. What is important for Olmec development is thattrading networks stretching from Guatemala to West Mexico werealready established and operating by 1400 cal BC, at the beginningof San Lorenzo’s rapid growth and development. This frameworkserved as the foundation for expanded interregional exchange byboth Olmec and non-Olmec groups and it was through these net-works that both resources and ideologies moved across the greaterbreadth of Mesoamerica (Blomster et al., 2005; Coe, 1989).

Obsidian does not provide all the answers to questions aboutresource procurement, trade and exchange during prehispanictimes. What it does supply, however, is a solid empirical foundationfor reconstructing the structure of exchange networks betweensource areas and points of consumption like San Lorenzo. What areneeded now are data from other sites on the landscape so that afuller reconstruction of trade relationships is possible for the areasthat were directly or indirectly liked to San Lorenzo and theobsidian sources that they used.

Acknowledgments

We are grateful to the Dirección General de Asuntos del PersonalAcadémico-Universidad Nacional Autónoma de México forproviding the financing for this project. Our special thanks toMichael Coe who worked with Cobean and Glascock in the originalYale and Missouri obsidian projects. We acknowledge the NationalScience Foundation for grants BCS-0802757 and BCS-1110793supporting the Archaeometry Laboratory at MURR. We also thankGreg Luna for drafting the accompanying maps.

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