Dynamics of Hohokam Obsidian Circulation in the North American Southwest

Article excerpt

Introduction

With the largest canal irrigation network in North America (Doolittle 1990: 79-81), the Hohokam culture was an apex of non-state socio-political complexity in the pre-contact New World. The Hohokam were sedentary agriculturalists who lived in settlements throughout an area of the Sonoran Desert that (at times) exceeded 50,000 square miles in south-central Arizona (FIGURE 1) (Doyel 1991: 226). Hohokam society changed significantly during the transition from the Preclassic to Classic periods (c. AD 1200) and this reorganization is evident in the shift from ball courts to platform mounds and Great Houses. Ball courts were apparently communal facilities for staging ball games and other public events, whereas Classic period platform mounds and Great Houses served domestic and residential functions for dite members of Hohokam society (Lindauer & Blitz 1997). Scholars have debated the socio-political consequences of this Preclassic-Classic period reorganization for more than a century, although today most archaeologists do agree that commodity circulation changed during this process (Crown 1991a). Circulation as used here includes the entire procurement and production trajectory from initial acquisition at the source to production of obsidian artefacts, exchange of the commodities and their final deposition in the archaeological record (see White and Harris 1997).

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The placement of many large Hohokam settlements along irrigation canal networks offers archaeologists an opportunity to examine patterns of commodity circulation between different social groups. Geochemical analyses of Hohokam obsidian using X-ray fluorescence (XRF) spectrometry has already provided important perspectives on obsidian circulation within the Preclassic period (e.g. Doyel 1996) and the subsequent Classic period (e.g. Mitchell & Shackley 1995; Peterson et al. 1997). However, we still know little about long-term change in Hohokam obsidian procurement and consumption. Did obsidian circulation change with the beginning of the Classic period, when the Hohokam constructed platform mounds and Great Houses in major river valleys of the Sonoran Desert? The present research seeks to answer this question by focusing on archaeological obsidian from the Preclassic-period site of Grewe and the Classic period site of Casa Grande along the Gila River in south-central Arizona.

The sites of Grewe and Casa Grande were chosen for this study for several reasons:

1 Grewe and Casa Grande were sequentially occupied, they are in proximity to one another, and essentially they represent two temporal components of a single settlement;

2 obsidian recovered from these two sites comprises one of the largest samples of Hohokam obsidian to be geochemically characterized (N=274);

3 Grewe and Casa Grande are centrally located with respect to several major obsidian sources in the American Southwest; and

4 the large size of each of these settlements suggests that Grewe and Casa Grande were major community centres of Hohokam society, especially in the Gila River Valley.

Grewe and Casa Grande were both situated along a large-scale canal irrigation system along the middle Gila River Valley (FIGURE 1). The Preclassic period site of Grewe contains remains of pithouses, storage pits and three ball courts. One ball court at Grewe was extremely large and it was, in fact, one of the largest Hohokam ball courts. Casa Grande is a Classic period site with many adobe houses enclosed by walled compounds, three platform mounds, two ball courts and a massive multi-storey adobe structure known as a `Great House'. The Great House (FIGURE 2) was atop a platform mound; it was probably the tallest Hohokam building ever constructed.

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Archaeological sources of obsidian are widely distributed and relatively few in number in the North American Southwest, north of Chihuahua and Sonora (FIGURE 3). …