A New Tree-Ring Width, delta-13C and 14C Investigation of the Two Creeks Site

Abstract

We have made isotopic and dendrochronologic measurements on material collected from the Two Creeks site. Radiocarbon dating of outside wood of four logs yielded an average age of 11,760 +/100 BP, in good agreement with results of Broecker and Farrand (1963) over 25 years ago. The range of 11,640 +/160 to 11,900 +/160 BP suggests a period of forest growth of 200-300 years, consistent with a ring-width chronology established by Kaiser (1987). Ring counting of five specimens gave a range of individual tree ages from 110 to 182 years, and width measurements indicate very low year-to-year variation in ring size. However, preliminary cross-dating of five samples produced a 202-year floating chronology. Stable-carbon isotope chronologies on cellulose from five-year ring groups show delta-13C scatter among trees typical of that found within modern sites, with some matches of isotopic maxima and minima. Some downward delta-13C trends may result from physiological response to rising lake levels (and/or cooling temperatures) at the site, which also produced very narrow rings in the outer ca. 50 +/20 years.