Culture and Ecology of Chaco Canyon and the San Juan Basin

174 Chaco Project SynthesisEvaluation of seven trenches in this field (Loose andLyons 1976a) suggested intentional flattening of thesurface, earthen levees, and probably intermittentfloods across the area. Two possible laminated strata,the lowest associated with Pueblo I sherds, wereattributed to overbank flooding of the wash. Two gatesystems suggest continued use. A single archaeometricdate of A.D. 1250 from the upper layer byNichols (1975:4-8) does not correlate well with thelatest Bonito phase sherds recovered in the testtrenches (Loose and Lyons 1976a).Lagasse et al. (1984) do not believe that the largerainfall events flowing through the major watershedscould have been controlled by facilities such as thosein Rincon 4 near Penasco Blanco (Gwinn Vivian 1972:Figure 5.4). Vivian (1992) suggested that the captureof all water, especially that from ,small precipitationevents, would have provided some moisture that mayhave been sufficient to soak some gridded garden plotswithin the system.SummaryWith the new data from survey and excavation,Chaco Project archaeologists were able to better definethe chronological sequence for the Classic period.Pueblo II sites were divided into early and latesegments, as were Pueblo III sites. The Classicflorescence was described in three phases: The EarlyBonito phase (Red Mesa ceramic assemblage); theClassic Bonito phase (Gallup ceramic assemblage);and the Late Bonito phase (Late Mix ceramicassemblage), which included Early Pueblo III sites.Although the calendrical dates assigned to theseperiods shifted slightly (Appendix B, Figure B.l), thearchitectural styles and artifacts assigned to themprovided a basis for more detailed discussions ofchange through time, including the movement ofmajor settlements in the canyon. The distinct differencesamong large and small sites in the adoption ofwall masonry, wall foundations, ventilator shaft construction,and location of trash disposition, as well asformalization of features in great kivas and enclosureof plazas, will be presented in the following chapter.By approximately A.D. 850, communitiesaround three great houses were established. Not onlywere additions to these three great houses built duringthe A.D. 900s, but several other great houses withtype I masonry were constructed during the tenth century;e.g., Chaco East. Una Vida and Kin Nahasbaswere contemporaneous and close together. In thelatter case, participation in a communications systemand not location next to a major drainage seems amore likely explanation for placement on the slope ofthe north mesa. The burst of construction at greathouses during the mid- to late-lOOOs and early l100s,the diversity that appears in small site rooms in theearly A.D. looos, and the changes in room sizes andfunction at Pueblo Alto suggested two major shifts insocial organization around A.D. 1050 and 1100 thatwere marked by the beginning and end of thedominance of Gallup Black-on-white in the ceramicassemblage (H. Toll and McKenna 1997). Thesefiner-grained chronological distinctions, which dividedthree phases of the Bonito period, would be correlatedwith climatic fluctuations and changes in materialculture. Some results of those analytical studies onlybecame available recently.With new data come new questions. Once thegreat houses were found to have different types ofrooms, not all of which were living quarters, thenumber of families using these structures year-roundbecame an issue. The differences in big-room suitesbetween those with firepits vs. heating pits and thepresence of road-related rooms suggested multiplefunctions for the great houses during the ClassicBonito phase between A.D. 1050 and 1100. Thefunction of trash mounds and roads, both associatedwith the great houses during this period, are alsounclear. Are they ritual structures?At great houses such as Pueblo Alto, Windes(1987[11]:605) described the trash mound as havingdistinct layers separated by a thick layer of aeolianfill, which led to the interpretation of deposition asbeing cyclical and different from that at small siteswhere no such definite divisions are apparent. Truell(1992:209-210) acknowledged that there are differencesin exotics and bone frequencies at small housesite trash middens, but she did see internal layering.She suggested that the mounds had different functions.The mounds at small sites represent a slow accretionof regularly accumulated debris; those at the largesites contained large quantities of construction debrisand very little trash. Wills's (2001) recent reevaluationof the trash mound came to a similarconclusion about the function of trash mounds; their