Ch1 Like Salt or Like Gold?

1.1. Overview

Patterns in Obsidian Circulation in the South-Central Andes

Archaeologists have long recognized the central importance of interregional relationships in much of Andean prehistory, but consistent forms of evidence that can be used to gauge long-distance interaction are relatively limited. Over the past century, systematic studies on a regional scale have provided evidence of interaction based on stylistic attributes, such as the presence of non-local ceramics, design elements, and architectural styles. More recently, geochemical evidence has taken a more prominent role in documenting long-distance interaction and exchange because evidence from a variety of chemically unique materials - such as obsidian - have been accumulating in databases as chemical identification techniques are refined. This project aims to apply geochemical evidence of long-distance interaction from an obsidian source in the south-central Andes to an interpretation of regional developments.

Obsidian is among the least-perishable of a number of materials that were widely transported in the prehispanic Andes. On one level, obsidian should be understood as just another one of the widely circulated items, such as nuts, gourds, wood, shell, metal, coca, sebil, and basalt, in a list that is immeasurably long. As a regionally distributed material, however, obsidian has a number of characteristics that are distinctive from some of other goods that circulated in local and regional trade. As a lithic raw material, obsidian is a reductive technology and therefore distance decay effects are prominent in its regional distribution. Obsidian implements can have extremely sharp edges, and by far the most common formal obsidian tools produced in the south-central Andes were the projectile points. Obsidian artifacts are sometimes found in contexts - such as monuments or burials, that suggest that obsidian had ritual importance - however, throughout the region obsidian artifacts are frequently encountered in domestic contexts and middens with little compelling evidence of ritual or symbolic importance. A central concern of this research project is to avoid the simplistic, dichotomous archaeological construction of a "utilitarian" artifact group versus a "prestige" and/or "ritual" associated artifact group. As a highly visible material that was often made into projectile tips, "utilitarian" obsidian tipped implements themselves may have had a role in social influence or coercion, and were perhaps used in status competition displays. Obsidian made into a sharp weapon simultaneously represents access to non-local goods and, in the case of non-local obsidian, may reflect regional scale alliances. Thus, the circulation of obsidian may have been akin to that of utilitarian products, a such as salt, or along the lines of a precious commodity like gold or turquoise where value is related to production costs and reflects scarcity or exclusivity.


Figure 1-1. Larger study region with modern towns and roads. General obsidian distribution areas are depicted, showing largely a Formative Period extent.

Archaeologists identify these materials as non-local when they are encountered in archaeological sites far from their source areas, and in these contexts archaeologists interpret non-local materials are seen as providing evidence of the long distance movement of goods. The dramatic altitudinal zonation on the flanks of the Andes contributes to the archaeological identification of non-local materials because a number of these products are zone-specific. The major environmental and geological zones with distinctive products include the Amazonian lowlands to the east, the mineral rich western Cordillera, and the pacific littoral.

This project focuses on the source region of an obsidian type that was widely circulated in the prehispanic Andes. This chemical group, first referenced in the 1970s as the "Titicaca Basin Type" (Burger and Asaro 1977), was finally traced to its geological source in the Colca valley of Arequipa, Peru in the 1990s. In the Colca, the geochemical type was documented under two names, the Chivay Source (Burger, et al. 1998) and the Cotallalli Source (Brooks, et al. 1997). The source lies in volcanic terrain that is relatively difficult to access by the modern road network, a situation which has hampered research in this zone but has also resulted in relatively little disturbance to archaeological sites in the obsidian source area. This project sought to comprehensively research this zone in order to address a number of long-standing theoretical questions concerning the human use of obsidian in the larger region. Obsidian from the Chivay source is found in a variety of archaeological contexts in the region ranging from common residential middens to ceremonial structures and burials. Unlike other regions of the world where a variety of artifact forms are produced from obsidian, in the south-central Andes the formal implements made from obsidian are largely restricted to projectile points. Simple obsidian flakes are seen as valuable as well, as the shearing and butchering requirements of dedicated pastoralists are significant, and these sharp obsidian flakes filled a functional category akin to razor blades in modern life.

On a theoretical level, this research can contribute to anthropological models concerning the emergence of social hierarchy, the influence of regularized caravan-based trade, and the role of exchange in non-local goods that were widely-circulated in prehistory. Obsidian escapes easy classification as a "prestige item" or an "ordinary good" because the cultural meaning of the material appears to have been highly variable. Obsidian is typically abundant at archaeological sites close a geological source and scarce in areas more distant from geological sources, and obsidian flakes are plentiful at pastoralist rock shelter sites in the altiplano that appear to be relatively lacking in other material goods. Together with coca leaf and other widely circulated goods of cultural value in the Andes, obsidian appears at times in ritual contexts; for example, obsidian may be used as a knife used in a llama sacrifice, as flakes placed in a burial, or as projectile point tips represented on Tiwanaku and Nasca ceramics. However, obsidian appears to not have been a "preciosity" in the sense that large and recognizable quantities of labor were necessarily invested in the production of the material, and indeed obsidian is often found in commonplace, utilitarian contexts. As a household level enterprise, the acquisition of obsidian may constitute evidence of regional interaction which contributes to an archaeological understanding of the prehistoric emergence of regularized exchange over distance, perhaps scheduled around festivals, seasonal harvests, and other regional scale events that integrated distant communities across the Andean highlands. In sum, while it is difficult to place obsidian on a scale from ordinary to prestige good, it appears that the mere possession obsidian may have had some value as a symbol of participation in the long-distance exchange of a variety of goods of cultural value.

This project investigates the economy of Chivay obsidian in prehistory at three levels. First, fieldwork was conducted at the Chivay source in order to examine production at the obsidian source area itself. This work documented the geological exposures of the material, the archaeological sites in association with the source area, and the physical geography and trail system around the source. Second, the project area included obsidian consumption zones within a day's walk of the source in two adjacent residential areas in order to evaluate the local use of obsidian within the larger archaeological context of the Upper Colca. Third, the regional consumption patterns of Chivay obsidian in the south-central Andes were explored using existing studies from the published sources for a more complete picture of production, distribution, and consumption of the material through prehistory. This dissertation represents the integration of these three perspectives on Chivay obsidian in light of anthropological theories of exchange and Andean culture history.

Archaeological evidence for interpreting obsidian production at Chivay takes the form of differences in diagnostic materials and artifact morphology across space from a surface survey, and from measurable change in stratified deposits from test excavations. Four models of procurement and circulation are proposed here, and the material correlates for these models are evaluated based on expectations and measurable changes in artifacts that primarily consist of flakes and cores. The information potential from surface scatters is limited by the non-diagnostic nature of most artifacts at raw material quarries. Nevertheless, this research has found that a strong correlation exists between obsidian intensification and early pastoralism, and perhaps camelid caravan transport; and the research contributes to answering long-standing questions about the relationship between the Colca valley and prehispanic Titicaca Basin polities. This study explores obsidian production and circulation as a unifying theme that can be studied at a regional scale in order to examine long-term processes that led to social changes manifested in the emergence of chiefdoms and states in the Andes.

1.1.1. Prehispanic Economy

As an investigation of non-western exchange, this research relies on categories and approaches developed in economic anthropology. The analysis and interpretation applied in the Upper Colca project is rooted in the substantivist tradition, but the weaker elements of the original substantivist approach will be avoided. These weaker elements include an attempt at an explicit delimiting of culture areas (where values are assumed to be shared), and implicit evolutionary links between volume of exchange and social complexity. Concepts from economic anthropology based on the work of Polanyi (1957) that include the idea of social distance as developed by Sahlins (1972) will be used to explore diachronic change in the circulation of obsidian in the prehispanic Andes. More recent discussions of the importance of "ordinary goods" (Smith 1999), in contrast to the usual focus on prestige items, will be considered in light of the cultural importance of coca, herbs, obsidian, and other non-exclusive but widely valued items in the Andes.

A principal theoretical question addressed in this dissertation concerns the circumstances of a large shift in obsidian production during the Early Formative, around 2000-1300 BCE It is argued here that the links between prestige goods circulation with models of competitive display are evident, but that influence is also accrued by individuals, such as llama caravan drivers, who generate consistent traffic between areas by circulating both information and non-local goods on a seasonal or an annual basis. The underlying assumption is not that the act of exchange inherently "creates value" (Appadurai 1986), but rather that the circulation of material goods was a pragmatic incentive for maintaining a range of important social and ideological relationships across space (Browman 1981;Nuñez and Dillehay 1995 [1979]). The caravan model described here is not adaptationalist, however, as it is not proposed that greater efficiency or social harmony led to the emergence of social complexity in the Andean highlands. Rather, the successful manipulation by aggrandizing individuals of the institutions that developed around these regional relationships was one early basis for the incipient concentration of power and the establishment of inequalities that are most apparent at early regional centers in the Andean highlands (Hayden 1998;Stanish 2003). The social and economic foundations for the emergence of these early centers clearly predate the ascendancy of these centers during the Middle and Late Formative in the Titicaca Basin, and obsidian is one class of artifact that was circulating consistently since the preceramic period that may reflect the changing socio-political role of exchange over the long term.

A study of obsidian production and circulation among Andean peoples across a time span of nearly 10,000 years demands the consideration of a wide variety of cultural contexts, economic systems, and socio-political structures. A major question about obsidian circulation through time concerns the nature of obsidian exchange and perceptions of value with increased distance from the geological source.

Obsidian was a raw material essential to the daily existence of common people. In one sense, the distribution of obsidian may have had more in common with the exchange of agricultural commodities or salt, than it did with either long distance trade in prestige goods such as lapis lazuli, turquoise, or exotic pottery, or with commodities traded long distances for ritual purposes, such as spondylus and strombus shells. Thus, one should expect the patterns of obsidian exchange to differ from exchange patterns of these other trade goods and reflect different kinds of social and economic interactions (Burger and Asaro 1977: 18).

Expanding on Burger and Asaro's (1977: 18) observation, this dissertation examines the possibility that archeologically perceptible strategies of quarrying and production at the source, considered in tandem with consumption patterns, can help to describe what these "different kinds of social and economic interactions" may have been.

How did the contexts of exchange and value change as obsidian was conveyed away from the source area geographically and with greater social distance? The expression "regimes of value" (Appadurai 1986: 5, 14-15) has been used to describe arenas where shared perceptions of value are used in the construction of worth and equivalencies for circulating goods. What was the role of frontiers, either between cultural or environmental zones, in the transmission and value ascribed to these goods? While there is no simple answer to these questions, obsidian appears to have fallen somewhere between the probable regional circulation patterns of salt on one hand, and gold or turquoise on the other. The production and circulation represented by salt and gold serve as types on a continuum in this discussion, and the given changing patterns in obsidian circulation in the south-central Andes, the pattern falls at different points along this continuum in different prehispanic time periods.

A second major theme in this research is the association between a camelid-focused economy and obsidian circulation. High altitude pastoralists had easiest access to obsidian sources as obsidian was found on geologically young volcanoes high in the puna ecological zone; and additionally, pastoralists had burden-bearing animals capable of carrying heavy loads (Burger and Asaro 1977: 41). The sharp edges of obsidian flakes have great utility for pastoralist functions including shearing, butchery, and castration, although it is important to note that these characteristics are not unique to obsidian. Alternative local materials, such as high quality cherts, are found in a number of regions in the south-central Andes where exotic obsidian was used. Obsidian appears to have been circulated largely by pastoralists following the advent of a pastoral economy; however a simple utilitarian explanation for obsidian use among pastoralists is incomplete given the regional data from consumption sites.

There is key countermanding evidence to a simple utilitarian association between obsidian consumption and the functional needs of pastoralists. First, the obsidian flakes observed at pastoralist sites, even in excavated contexts, are overwhelmingly small and apparently of insufficient size for use as shearing or butchery tools. These flakes appear to be debris from advanced stages of reduction, perhaps from projectile point production and resharpening, and utilized flakes as one would expect among pastoralists are rarely reported in the literature. Second, the trends in obsidian procurement, as will be described in this document, suggest that the focus was on acquiring large nodules; a fact that that is discordant with the predominantly small sizes of the formal obsidian points and tools found both in the vicinity of the Chivay source and in the larger region, even when accounting for distance-decay issues. If obsidian was principally utilitarian because it was used for projectile points for subsistence hunting, why did obsidian use in projectile points expand dramatically only after the food producing economy became well-established (from 3300 BCE onwards)? Finally, pastoralist sites are often found without obsidian. During the Late Intermediate Period and Late Horizon the evidence shows that camelid herds expanded markedly, yet obsidian circulation seems to have relatively declined. If obsidian was primarily for utilitarian pastoralist activities, why did it decline as the herds expanded? It appears that the distribution of Chivay obsidian was heavily influenced by the interaction of complex phenomena that included demand in a network of exchange and caravan-based links between the western margins of the altiplano and the Titicaca Basin, the enduring social network that connected communities in these different regions.

This research at the Chivay source supports earlier observations by Burger et al. (2000: 348) where the strongest correlation with widely distributed obsidian types appears to have been the availability of large nodules of homogeneous obsidian. Given the diminutive size of the formal obsidian tools found in the archaeological record, and despite the issue of resharpening, there is an important display aspect to large obsidian nodules that is lost in utilitarian explanations linking obsidian with pastoralism. The link between camelid pastoralism and increased obsidian consumption in the south-central Andes is not causal, as pastoralists also make wide use of other materials, yet the appearance of pastoralism followed by the traffic of regularized long distance caravans appears to have been largely responsible for disseminating the material.

In light of the patterns of obsidian production and circulation, the anthropological relevance of obsidian appears to go beyond the fact that the material was used to produce sharp-edged tools of use to pastoralists. The analysis in this dissertation, therefore, focuses on the large-scale social and economic changes that occurred in the south-central Andes and on the possible role of obsidian as a material used by early leaders to represent contact with sustained regional networks and to signal social differentiation.

1.1.2. Chemical characterization work in the Andes

This study benefits from the work of the many archaeologists who have documented obsidian in archaeological contexts throughout the south-central Andes and who have conducted chemical characterization studies of Andean obsidian. The basis for research at the Chivay obsidian source returns largely to obsidian sourcing efforts by Richard Burger and by Karen Mohr-Chavez in the 1970s because it was these early studies that established the regional significance of this obsidian type. These studies further served to demonstrate the utility of obsidian for examining regional relationships in the Andes and for catalyzing greater interest in the context and form of obsidian artifacts among archaeologists working in the region. The first chemical analysis of obsidian from the region was Mohr-Chavez and Gordus in 1971 at the University of Michigan (Burger, et al. 2000:271;Chávez 1977). In the 1974-1975 study at Lawrence Berkeley Labs the analysis conducted by Burger and Asaro (1977) analyzed 800 artifacts from 141 archaeological sites in Peru and Bolivia (Burger, et al. 2000:273). They isolated eight major chemical groups from this study, however twelve artifacts did not belong to any of these twelve groups and they were designated "rare" types.

A number of important chemical characterization studies have taken place in the region, though none as sweeping as Burger and Asaro's early work. The most significant work with respect to this study was the sampling conducted by Sarah O. Brooks in the Colca valley during the mid-1990s. Additional samples were collected by Steven Wernke during his 1999 Colca survey work. In the course of the present research, samples were collected throughout the study region. New developments in sourcing technology, in particular the portable XRF machine, promise to expand greatly on the insights provided by the chemical characterization studies of the twentieth century.

1.2. Structure of the Dissertation

1.2.1. Organization of presentation

Following this introduction, chapter 2 provides an overview of theoretical approaches to exchange and to raw material procurement areas from anthropological studies worldwide. Chapter 3 shifts the focus to the Andes with a review of the existing research that informs this investigation. In chapter 3 a discussion of economy, exchange, and long-distance interaction in the region is presented, as well as a summary of the evidence of Chivay obsidian consumption through time. Chapter 4 is a geographically oriented chapter with a discussion of the region in terms of climate, economy, geology, obsidian deposits, and finally the original chemical sourcing work that accompanied this research project. Chapter 5 describes the methods used in this dissertation with a focus on the novel methods employed by this project. Chapter 6 presents the results and analysis of a 33 km2 archaeological surface survey in six blocks throughout the Upper Colca study area. Chapter 7 describes the results of the testing program that included eight 1x1m test units, five of which are analyzed in detail here. Finally, chapter 8 is the summary of significant findings from this research and chapter 8 strives to reconcile the results of this research with the theoretical objects of the study.

1.2.2. Digital data availability

While a major methodological goal of this project was to exploit new technologies for spatial data and the organization of information, the presentation in this Ph.D. dissertation is largely confined by the traditional format of the library monograph. Large segments of data from this project are available online at

where additional maps, photos of features and artifacts, and searchable GIS datasets are available permanently. Links to online materials are provided, as well, in the Appendices at the end of this document.

1.2.3. Dates

Throughout this dissertation chronology will be discussed in calibrated years Before the Common Era (BCE). Where possible, 14C dates will be completely reported using the form that follows. The actual radiocarbon years before present will be presented with a lowercase "bp", the laboratory identification will follow, and then the range of 2? (95.4%) calibrated Before Common Era dates are shown as reported by OxCal v3.9 (Ramsey 1995;Ramsey 2003) using data presented in Stuiver, et al. (1998). Calibrated Before Common Era dates are shown with the uppercase letters "BCE".

1.2.4. Spatial data

Most spatial data from the Andes is in coordinate systems referenced to the Provisional South American Datum of 1956 (La Canoa) based on the International 1924 ellipsoid. In order to be compatible with topographic data, imagery, and the datum native to the GPS system the coordinates have all been converted to the modern WGS1984 datum using the ArcGIS three parameter transformation function "1208: PSAD_1956_To_WGS_1984_8". The 1991 three parameter transformation to WGS1984 for metric UTM data for Peru is as follows ?X = -279 m ± 6 m, ?Y = +175 m ± 8 m, ?Z = -379 m ± 12 m, and was based on 6 collocated points (Mugnier 2006).

A GIS database of chemically-sourced obsidian samples has been compiled from the central and south-central Andes based almost entirely on published materials. In the text that follows travel times are been reported between the source and the consumption locale as calculated using Tobler's (1993) Hiking Function. This function models travel velocity as a function of slope.

Walking velocity (km/hr) = 6 exp (-3.5 * abs (S + 0.05))
Where S = slope in degrees (?Z/?X)

Figure 1-2. Tobler's (1993) Hiking Function models foot travel velocity as a function of slope.

Tobler's function follows Imhof (1950) in deriving travel speeds of 5 km/hr on flat terrain and an optimum travel speed of just over 6 km/hr on a -3.5° downslope. Further elaboration of this hiking speed function, such as on or off path travel and llama caravan versus hiking speed was not attempted as there are too many unknowns to reliably model such differences. While the absolute travel velocity may be unreliable, the relative speeds for comparing one consumption site to the next are informative and correctly factor in the effects of travel over steep terrain versus travel across the gentle slopes of the altiplano. The function has been used elsewhere in archaeological contexts (Gorenflo and Gale 1990;Jennings and Craig 2001; href="/biblio/ref_4270">Kantner 1996;Van Leusen 2002).

Topographic data used in this project derive from GPS and from Digital Elevation Models (DEM) generated from two space-borne remote sensing platforms. Three dimensional GPS data was gathered throughout the project using Trimble GPS units and post-processed using the Arequipa IGS base station. Local topographic relief was acquired from the ASTERDEM dataset (30m), and regional scale topographic data was acquired from the SRTM (90m) dataset. As will be described in more detail in Chapter 5, ASTER imagery and DEM data proved to be extremely useful in designing and executing this work in the mountainous terrain of the Chivay source area.

Quickbird satellite imagery for portions of the study region were made available in 2006 as a part of GoogleEarth v4. These data are distributed by DigitalGlobe and they are 2.4m per pixel multi-spectral imagery pan-sharpened with 0.68m per pixel panchromatic imagery for natural color imagery, and GoogleEarth topographic relief is blended into the imagery from the SRTM 90m layer.

1.2.5. Photographs and scale

Linear units used in this project are exclusively metric. A tape measure was extended to exactly 1m in landscape photographs to provide scale. Despite the tape not being legible, the total length of the exposed tape is always 1m unless otherwise noted. In some instances the tape is not perpendicular to the photographer position, a situation that could lead to foreshortening and in such cases the 1m scale would become invalid. Laboratory photos were taken on a matte grey background with a 1cm grid in the background. Additional notes regarding the methodology are provided in Chapter 5.

1.3. Conclusion

This dissertation combines a theoretical discussion of economy in anthropology and a review of existing knowledge regarding Chivay obsidian in the south-central Andes with new data from the Upper Colca research project. The significance and implications of the data presented here will be need to be reassessed in the future when investigators are provided with additional chemical sourcing studies, new archaeological research in the south-central Andes, and further studies of the Colca area itself.