PRELIMINARY TREE-RING ANALYSES OF LAST GLACIAL MAXIMUM SPRUCE (PICEA) FORESTS, SOUTHWESTERN OHIO

The overrun subfossil spruce forests of southwestern Ohio and Indiana provide important radiocarbon dates on the Last Glacial Maximum of North America. Tree-ring analysis has potential as a correlation tool to test for age equivalence between forest beds and to refine the radiocarbon-dated chronology for the region.

We report on a 239-year ring-width, tree-ring chronology assembled with 15 series from 7 logs from sites near Sharonville, Ohio. The average number of rings per tree is 136 with the longest individual series of 207 years. Decreasing ring widths with age for most series follow a negative exponential curve suggesting a relatively undisturbed open canopy forest. Average series intercorrelation for the chronology is 0.51 showing a fairly strong common signal among the trees.

A radiocarbon age of 19,960 BP on one of the logs incorporated in the chronology is consistent with numerous other ages showing ice advance at this time. The crossdated, ring-width series shows the trees died over a 30-year period prior to being overrun by the advancing Miami sublobe. Individual logs from other nearby sites of similar age have 220 rings and now can be compared with the Sharonville chronology. In addition to the value of tree-ring analyses as a correlation tool, the annual-dated time series can help define the yearly to centennial-scale variability of the climate system during full glacial conditions.