Absolute Tree-Ring Chronology for the Last 5000 Years for the Eastern Mediterranean

Cornell University, Ithaca NY

Investigators

Abstract

With National Science Foundation support, Dr. Peter Kuniholm and collaborators will continue to construct a master tree-ring curve for the Eastern Mediterranean and to provide precise dates for sites of archaeological interest. Dendrochronology (tree-ring dating) is the most accurate known dating technique with a theoretically possible resolution of one year, sometimes under ideal circumstances to a specific season within the year. Because the thickness of annual growth increments is affected by temperature and rainfall, internannual variations allow the researcher to start with living trees, plot a thickness or density curve back from today's starting date, and then extend the series further backward in time with the addition of samples from archaeological and geological contexts. These absolutely-dated tree-ring sequences are also being used as a proxy for palaeoclimatic reconstruction in the period before instrumental measurements exist. Dr. Kuniholm and his colleagues have worked for many years (10 million microscope measurements so far) to construct master chronologies for Greece, Turkey, Italy, the former Yugoslavia, Lebanon, and other countries in the Eastern Mediterranean, now covering some 6,500 of the last 9,200 years. Already their work has demonstrated a need for a re-interpretation of some radiocarbon dates with offsets of 20-30 years during periods of global cooling. The focus of their work for 2003-2006 will be the centuries on either side of the AD/BC transition, currently a "gap" in their chronology because of the large number of Roman buildings built in stone and which therefore did not collapse and preserve the wooden architectural members in the same way that Bronze Age mudbrick buildings do. Over the next three years the team will focus on fleshing out this "gap" by radiocarbon wiggle-matching the 82 discontinuous chronologies or ring-sequences already developed for that period. They will also visit and analyze wood from 40-50 sites a year in the eastern Mediterranean and Near East. The end-product by the end of June 2006 should be a complete, continuous, and therefore absolute chronology for the last 5000 years, the entire period of literate civilization as we know it. The project is extremely important because the resulting sequence will permit the absolute dating of large numbers of archaeological occurrences to the year. Because the laboratory involves many undergraduate students (over 20 a year) it will continue to play an important role is science education. More than 40 graduates of the lab have gone on to Ph.D. degrees, more than 29 to M.D. degrees, and over 100 to a Masters degree of one kind or another.