Tree-Ring Dating

Dendrochronology, the study of tree-time, is a multidisciplinary science providing chronometric, environmental, behavioral, and other data to scholars of all kinds, as well as to curious members of the general public. For archaeologists, the most important result of dendrochronological analysis is the assignment of solar calendar dates to the growth rings of trees. The fundamental principle of dendrochronology is crossdating, or the systematic analytical process that matches ring-width variations within and between trees, usually of the same species, and which are growing in close proximity. Crossdating begins with the analysis of cores or cross-sections from living trees for which the calendar-year date of the outside ring is known and from which calendar year dates for interior rings may then be inferred. Crossdating ends with the construction of a master tree-ring chronology in which all anomalous (i.e., missing, double, or otherwise problematic) rings have been identified and accounted for, and Common Era calendar dates have been accurately assigned to all growth rings present in the chronology. Once a master chronology has been built, ring sequences from archaeological specimens may then be compared to that of the master chronology to then (hopefully) obtain a date. Unfortunately, not all tree-ring specimens yield dates. Some species cannot be crossdated; some samples don’t have enough growth rings present to provide secure dating, for example. Tree-ring dating developed in the early 20th century in the American Southwest, where astronomer Andrew Ellicott Douglass of the University of Arizona sought a terrestrial record of sunspot cycles. After nearly three decades’ work, he successfully dated archaeological specimens for the first time in 1929. Since then, dendrochronologists have dated tens of thousands of individual samples from thousands of archaeological sites in the American Southwest, the American Southeast, all over northern Europe, and, in a small number of cases, in Latin America and Asia. Today, dendrochronology enjoys an astonishing array of worldwide applications relevant to archaeology and anthropology, including climatology, forest ecology, architectural analysis, volcanology, geomorphology, art history, history, and many others. This bibliography covers published resources relating the method, theory, techniques, and history of dendrochronology, and offers a sampling of important archaeological, art-historical, historical, and other case studies from around the world.