ANCIENT WOOD IN THE GREAT LAKES REGION: A SIGNIFICANT PALEOENVIRONMENT AND PALEOECOLOGY RESOURCE

Favorable geologic conditions related to ice, water, wind and sediments have contributed to preservation of ancient wood samples around Wisconsin and the Great Lakes over many millennia. Early geologists were among the first to record the presence of wood and its relevance to the local geologic sequence of events, as in the case of the classic Two Creeks site, but botanists and ecologists often follow up with analyses of extant species and site conditions. Furthermore, with the development of radiocarbon dating, wood became a key means to obtaining an absolute age of the deposit.

Although the simple presence of wood (implying forest or woodland biome) and identification of wood species (usually associated with specific habitats and environmental ranges) are important, such information might also be readily inferred from palynology. However, one particularly unique feature of preserved wood is the presence of growth rings that offer potential insight into high-resolution (annual to subannual) environmental variability and site history. Besides standard ring-width analysis, other tools such as stable isotope analysis and micro-anatomical features can provide additional information with which to construct a more comprehensive picture of site conditions.

This paper presents examples of (1) old and new sites where wood has been found, (2) various types of analysis recently conducted on bulk wood samples and tree rings, and (3) environmental inferences from the wood analysis. The extraction of high-resolution environmental information from Holocene and late Quaternary wood samples is still in its early stages, but the prospects for a continuous supply of these valuable paleoenvironmental resources are probably quite good because drilling, excavations, and land disturbances are continuously releasing these formerly hidden macrofossil riches from their long-term entombment.