Paleoenvironmental reconstruction at Canyon del Muerto,Arizona, based on principal-component analysis

A multivariate statistical technique, principal-component analysis, is used to interpret pollen assemblages from archaeological context in terms of paleoenvironmental information. The pollen samples originate from an archaeological site in northeastern Arizona (Canyon del Muerto) covering the period between AD 700 and AD 1300. Through the use of principal-component analysis the percentage constraint in the pollen counts is removed and the data set effectively reduced to groups of co-varying taxa. Once these groups are ecologically defined as to the environment they represent, their changes of dominance through time can be analysed. This study has shown a correlation between a population expansion in Canyon del Muerto (AD 1050–1150) and the dominance of upland forest types suggesting slightly cooler and/or wetter conditions. The pollen data compare well with the tree-ring indices for this region. Local disturbance is reflected in the record during the period of greatest population. A shift to a shrubland vegetation during the peak construction phase indicates the clearing of cottonwood, fir, spruce and pine (all found within the site) by local inhabitants. Thus, the palynological evidence suggests both cultural and climatic factors are involved in the explanation of pollen deposition.