Culture and Ecology of Chaco Canyon and the San Juan Basin

62 Chaco Project Synthesisto the Southern Plains. Southwestern and northernMexican cultures that had mixed or locally specializedeconomies were then free to move into the San JuanBasin. By 3,000 B.C., Picosa (the ElementarySouthwestern culture) covered southern California, allof Arizona, the western half of New Mexico, parts ofsoutheastern Utah, and southwestern and south-centralColorado, as well as northern Mexico (Irwin-Williams1967). This elementary Southwestern culture lasteduntil about A.D. 1, and could be divided into threeareas that often blurred at their edges. The Pinto­Amargosa complexes covered California, southernNevada, and western Arizona. The Cochise includedthe Chiricahua and San Pedro phases of southeasternArizona and southwestern New Mexico. Less wellknown materials from northwestern New Mexico,northeastern Arizona, southeastern Utah, and centraland southwestern Colorado were given the nameOshara, and were considered to be ancestral to theAnasazi (Irwin Williams 1967). In a more detaileddescription of the Oshara tradition, Irwin-Williamsplaced her data from the Arroyo Cuervo region ofNew Mexico into six temporally ordered phases andprovided illustrations of the lithic technology for eachperiod (Irwin-Williams 1973:Figures 2 through 7).Jay phase (5,500 to 4,800 B.C.). This phaserepresents a broadly mixed gathering and huntingeconomy. Sites are located on cliff tops in canyonheads, near ephemeral ponds or low mesas. Site sizeis less than 50 m2, but some represent repeated use ofthe same area. Tool kits include large, slightly shoulderedprojectile points, well-made lanceolate bifacialknives. and very well made side scrapers. No toolsfor breaking or pulverizing seeds or nuts are present.Data suggest a mixed spectrum of subsistenceactivities, and year-round exploitation of local resourceswhose maximum concentration was accessiblefrom permanent water resources.Bajada phase (A.D. 4,800t03,200B.C.). Thisphase occurred during a period of decreased moisture,and was divided into early and late parts (Irwin­Williams and Haynes 1970). It is thought to representan increasingly effective adaptation to a broadspectrumsubsistence base. Sites are located at canyonheads, with special activities taking place on adjacentsloping mesas and along canyon rims. Site sizeremains small (less than 50 ~). The tool kit duringthe early part of this phase includes points with longparallel-sided stems and basal indentation andthinning; those with shorter stems, well-definedshoulders, and decreased overall lengths are assignedto the later part of the phase. Bifacial knives are rare,and side-scrapers range from well made to poorlymade. Overall the quality of the stone tool technologydeclines. There is an increase in ground stone; e.g.large chopping tools. Small cobble-filled hearths andearth ovens appear, suggesting changes in foodprocessing. Continuity and change reflected in theartifacts probably represent an annual cycle that wasnot strongly seasonal but did have some scheduledactivities.San Jose phase (3,000 to 1,800 B.C.). Duringthis phase, there was an increase in effective moisture,dune stabilization, and soil formation that resulted inan increased reliability of springs, and an improvedquantity of reliable flora and fauna. The number ofsites increased, and the average size of a camp alsoincreased (100 to 150 m 2 ). The presence of postholessuggests the construction of temporary shelters;extensive refuse suggests repeated occupation. Thereis a decline in workmanship of chipped stone tools.Chipped and ground stone artifacts indicate shiftstoward mixed foraging as the subsistence strategy.Cooking in large subsurface or surface ovens linedwith cobbles was introduced. Irwin-Williams (1973:9) thought that this phase represents localized adaptationsthat exploited regional microenvironmentsduring a somewhat systematic annual cycle.Armijo phase (1,800 to 800 B.C.). At this timethe environment was slightly less moist; the majorchange is the addition of maize to the subsistence base.Even though maize was only a minor component, itprovided a localized and temporary seasonal surplus.A new type of site, the rockshelter, is added to thesettlements along cliff tops of canyon heads. Sitesnear ephemeral ponds are now rare. Tools in theArmijo rockshelter represent a wider range of classes,including some objects considered representative ofideological significance. Irwin-Williams (1973: 11)interpreted this period as one in which seasonalaggregation developed, possibly involving groups of30 to 50 individuals. They would have had greateropportunities for social and ceremonial activities whileliving together than during the rest of the year whenthey splintered into smaller groups.