Culture and Ecology of Chaco Canyon and the San Juan Basin

------------------- -----240 Chaco Project SynthesisDecreased population of Chaco Canyon in the mid- tolate A.D. 1100s was not as well organized as that ofthe earlier Classic period, but people did obtainvessels from many of the same areas as previously.The Mesa Verde Black-on-white ceramics representcontinuity of residency in the area by people who weremore completely tied to populations and events in thenorth or San Juan area. McKenna and Toll (1991)suggested that the San Juan area had become the focusof an economic system that replaced the ChuskaValley supply area, and that the focus of the regionshifted from Chaco Canyon to the Aztec communityalong the San Juan River. Thus, the hypothesis of aMesa Verde migration into an empty Chaco Canyonwas not upheld (McKenna and Toll 1991; Toll et al.1980).Other artifact analyses support some continuityand some change during the Mesa Verde phase. WhenCameron (1991) compared the chipped stone from thetwo occupations at 29SJ633, she demonstrated thatwhile there was continuity in lithic sources, there wasmuch less use of nonlocal materials during both phasesat this small site than there was for earlier phasematerial from Pueblo Alto. Included in the MesaVerde phase were a few pieces of obsidian from JemezRidge and Red Hill, two sources from which materialrecovered on earlier sites had been obtained. Alsopresent were 31 pieces of Narbona (Washington) Passchert (from the Chuska Mountains area), 10 pieces ofyellow-brown spotted chert (from the Zuni area), andfour Morrison Formation cherts. Technology ofmanufacture was expedient.Analysis of ornaments and minerals indicatedcontinuity in forms and materials as well; again, therewere fewer imported materials during the Mesa Verdephase than had been seen during the Late Bonitophase. Mathien (1991 b) found that the imported shellspecies were few (Glycymeris gigantea, Haliotuscracherodii, and Olivella dama) and similar to speciesfound during the Basketmaker and Pueblo I periods.As noted above for obsidian, this change suggests areturn to earlier patterns that existed during theBasketmaker III and Pueblo I periods. Does itrepresent a change in trade networks or an eliminationof more widespread or sophisticated exchangerelationships for the Classic period?In summary, Truell's excavation of 29SJ633 (inMathien 1991a) raised several questions aboutcontinuity in the use of the Chaco Canyon area, movementsof people within the region, and the meaning ofthe changes noted. Gwinn Vivian (who reviewedsections of Truell's report) subdivided the Mesa Verdephase into two components: Late McElmo and EarlyMesa Verde (A.D. 1170 to 1220), and Late MesaVerde (A.D. 1220 to 1350). These divisions werebased on survey ofChacra Mesa during the late 1950s,which revealed the presence of crescent-shaped sitesand cliff dwellings that he considered contemporaneousand attributable to the period when McElmoand early Mesa Verde black-on-white types, plus St.Johns, Houck, and Querino ceramics, were beingused. (McKenna [1991] now recognizes Houck andQuerino ceramics as part of the Wingate Polychromeseries dated ca. A.D. 1175 to 1210.) Fortified buttetopsites with later ceramics were fewer in number andfound in different locations. Gwinn Vivian (1974a)thought that these sites dated to A.D. 1250 andpossibly later. He attributed the change in locations toa shift in farming practices from those using floodwaterirrigation to those using dry farming techniques;the higher altitude and cooler temperatures, andperhaps increased precipitation, would have allowedthis change. Areas farther east of the canyon had beensettled late-only after A.D. 1075 to 1100. Thechanges in rainfall patterns at A. D. 1080 were thoughtto initiate a slow decline in the Chaco dominance ofthe San Juan Basin; the later droughts of the twelfthand thirteenth centuries were more difficult andnecessitated continuing changes that result in the MesaVerde phase (Vivian 1990:383-389).The slow eastward movement is now accepted bysome investigators. "This intense late occupation isevident east of the East community, shifting to the topof Chacra Mesa east of Pueblo Pintado Canyon(Roney 1996). Overall, classic Mesa Verde Black-onwhite,marking occupation by 1250 or later, was rare"(Windes et al. 2000:43). Windes (1987, and inCameron and Toll 2001:Table 1) now divides thePueblo III period into two phases:The McElmo Phase. This phase falls betweenapproximately A.D. 1140 and 1200. It is characterizedby the presence of McElmo Black-on-whitesherds and an indented corrugated pottery with rock,sherd, and sand temper. Dendroclimatologicalreconstruction indicates that this period included a