Dendrochronology at the Mission San Xavier del Bac convento (Tucson, Arizona, USA)

The Spanish Colonial Mission San Xavier del Bac near Tucson, Arizona has been studied extensively for its contribution to the origin and development of Tucson as an urban center. While the general timeline of construction is understood from historical documentation, suggestions of timber reuse from earlier structures (Fontana, 2015) have not been scientifically evaluated. Three vigas (horizontal roof support timbers) and an internal wall beam were sampled for tree-ring analysis and compared to tree-ring chronologies from the nearby Santa Rita, Catalina, and Rincon mountain ranges. Dates for the timbers suggest that timber reuse from earlier structures is not supported in the case of one room, the convento. Additionally, chronologies from the Santa Rita, Catalina, and Rincon ranges do cross-date with these and other historic materials from downtown Tucson, demonstrating potential for dating of local structures from the same period.