LATE PLEISTOCENE-EARLY HOLOCENE FORESTS FROM THE GREAT LAKES REGION, USA: PRELIMINARY RADIOCARBON AND STABLE-ISOTOPE RESULTS

Special circumstances of burial or immersion have helped preserve ancient wood from forests growing around Great Lakes. These preservation conditions are variously related to alluvial, dune, bog and littoral processes and environments, glacial re-advances, and lake impoundment. In addition to litter and soil material frequently found in association with such forest deposits, the preserved wood provides tree rings for high-resolution climate-related analysis.

We have focused on obtaining wood by field collection or from archival sources from sites dating from about 12,000 to 5000 ¹⁴C yr BP, the early portion of which was marked by deglaciation exposing new terrain into which forests spread. The interval centers on the Younger Dryas period, an abrupt excursion to cooler climate evidenced in many places around the world and most notably in Europe about 10,000-11,000 BP, but whose cause might indeed originate in the Great Lakes area of central North America. Thus far, each site has a different age, with the exception of Two Creeks-age (11,800 BP) sites from 4 different locations up to 40 km apart, which will allow for some interesting regional comparisons.

Standard dendrochronological methods are being employed to develop floating ring-width chronologies from these sites as high-resolution records of environmental change. Anatomical anomalies that may relate to climate, such as flood rings, frost rings, "light" rings, and false rings, are also being identified and tabulated for comparison. Here we report some of the initial radiocarbon and stable isotope results from analysis of sequences of 5- and 10-year ring subdivisions at select sites.