Kessler - Tree-Ring Dating Techniques for the Desert Basin of Southern and Central Arizona

Presented by Nicholas V. Kessler
This presentation was given live on October 16, 2023.as an AAHS monthly lecture. Due to a technology malfunction canceling the virtual portion of the presentation and the amazing generosity of the presenter, it was re-recorded on October 19, 2023 for thos

Cultural chronologies in the desert basins of the Southwestern U.S. rely on radiocarbon dates and ceramic sequences that are limited in terms of resolution. More precise dating methods, such as dendrochronology, have not been traditionally applied here due to the limited number of datable trees in arid locales. This talk will explain how recent advances in radiocarbon dating and calibration, referred to as wiggle-matching, enable high-resolution tree-ring-based chronology building. Wiggle-matching has already been applied to well-known Arizona sites such as Montezuma’s Castle and Snaketown, and the results of these case studies will be detailed. Prospects for larger scale projects—some already underway—will also be discussed, and the future of tree ring radiocarbon dating will be forecast as it pertains to what can be gained from a new focus on tree-ring dating in the desert basins of the Southwest.

Dr. Nicholas Kessler was trained in archaeological science, geoarchaeology, radiocarbon (14C) chronometry, and dendrochronology at the University of Kansas (Master’s) and the University of Arizona (Ph.D.). He is currently a Post-Doctoral Research Associate at the Laboratory of Tree-Ring Research at the University of Arizona. Since 2017, Dr. Kessler has focused on high-resolution chronology building using archaeological tree-ring samples in places where the utility of dendrochronology has traditionally been limited. This work takes a formal approach to analyzing and interpreting time, which provides new avenues for archaeologists to greatly improve their understanding of historical events. To accomplish this, Dr. Kessler has extended recent advances involving the sequential 14C dating of annual tree-rings (wiggle-matching) to produce date estimates for archaeological timbers and wooden artifacts with precision that far exceeds most other contemporary chronometric techniques. In collaboration with other archaeologists, Dr. Kessler has published revised chronologies for a variety of archaeological contexts including cliff dwellings in the Southwest, a Great Plains earth-lodge village, and monumental earthworks and objects in the Midwest. As an expert in dendrochronology and 14C dating, Dr. Kessler has also published advances in the chemical pretreatment of contaminated archival charcoal and statistical methods for interpreting common age anomalies. He teaches dendrochronology at the University of Arizona and recently served as a visiting professor at Colorado College. Current research projects involve: a complete reanalysis of the wood and charcoal collected from the Tonto Basin (funded by the National Science Foundation), a Werner-Gren funded re-dating of timbers from a Late Mississippian mound center in northern Georgia, and various collaborative projects in Arizona with the National Park Service and the Forest Service.