Recovery, Analyses and Conservation of a Prehistoric Canoe (article) by Andrew J Jalbert on AuthorsDen

A prehistoric canoe is unearthed. From UNDERWATER HERITAGE Wisconsin has more than 700 shipwrecks in its waters and dozens of industrial ports such as Bayfield, Green Bay and Milwaukee on its shores. Indeed Wisconsin’s maritime history profoundly shaped the state we live in today. However, Wisconsin also boasts a rich maritime prehistory. People have inhabited the state for approximately 10,000 years. Furthermore, Wisconsin’s 14,000 inland bodies of water, two Great Lakes and numerous rivers increase the likelihood of existing prehistoric sites and artifacts. This is evident as more and more prehistoric maritime sites are discovered. 1996 Recovery, Lake Mary, Wisconsin Recently, the oldest recorded watercraft in the state was recovered from Lake Mary in Kenosha County, dating nearly 2,000 years old. The discovery of this artifact broadens the perceived scope of Wisconsin’s maritime past. Clearly, our maritime history is not only anchored to ship sailors, lumber mills and the ore trade, but to hunter-gatherers, stone tools and mound builders as well. As is the case with many archaeological sites, the burnt white oak canoe was initially discovered by accident, and not by an archaeologist. Prop wash from a pontoon boat uncovered a section of the canoe in 1996.Thankfully, the finders contacted Dan Joyce of the Kenosha Public Museum who in turn contacted the underwater archeologist at the State Historical Society of Wisconsin. The SHSW team identified the piece as either the canoe’s bow or stern and recovered two additional fragments from the silt. All three fragments were transported to Madison for documentation, analyses and conservation. Radiocarbon age Determination Determining the age of artifacts is a crucial facet of archaeology. When dealing with historic sites such as homesteads, mines, lumber camps or shipwrecks, documents can usually be referenced to help determine the age of the site. Journals, captain’s logs and even newspaper articles will often detail specific dates such as when a particular ship sank or when a building burnt. Historic artifacts associated with these sites can also often times be easily dated through old catalogs, etc. Dating prehistoric sites however is a bit more complicated. Archaeologists cannot reference a catalog or newspaper article when working with an artifact that is a thousand years old. Consequently, the science of dating prehistoric materials has become very important to archaeologists attempting to reconstruct cultural prehistory. Several methods of dating have been developed to determine the age of prehistoric sites. These methods include numerous techniques from geological and geochemical age determination, to faunal remain association, to the aspartic acid dating of bones. The most frequently used method to determine the age of organic substances is 14C dating, also called radiocarbon dating. Through photosynthesis, atmospheric carbon enters the chemistry of plants, which in turn are consumed by animals. At the time of an organism’s death, carbon is no longer taken in but instead starts to radioactively decay. By measuring the remaining carbon in the organism (which still emits trace elements of radiation) the time elapsed since death can be determined. This difference between the original amount of carbon present and the current amount of carbon can be calculated, and by knowing the radioactive disintegration rate (known as a half-life) a material age can be assigned. Carbon has a half-life of approximately 5730 years +/- 40 years. A sample from the Canoe was sent to a lab in Florida to be radiocarbon dated. The resulting date was 1,850 years old +/- 60 years. This places the canoe temporally in the Woodland Indian stage. This stage is primarily defined by a people who produced pottery, built earthen burial mounds, and cultivated plants. The Lake Mary Canoe has been identified as the oldest documented watercraft in the state. Conservation Conservation is the scientific process used to preserve and restore archaeological materials. The basic theory behind the conservation of waterlogged wood is the removal of excess water while simultaneously replacing it with a synthetic material that stabilizes and strengthens the cell structure. One material used to perform this conservation is polyethylene glycol, or simply PEG. Fragments of the Lake Mary Canoe will ultimately be conserved by PEG treatment. For more conservation information, see FIL’s ARTICLE TITLE, in this volume. 1999 Recovery, Lake Mary, Wisconsin In October of 1999, the SHSW sent another team of divers to search for additional pieces of the Lake Mary canoe. Jeff Gray, Filippo Ronca, and the author met Dan Joyce of the Kenosha Public Museum at the site. Although the water temperature was in the low 40’s, the surface was calm and the air temperature was in the 50’s. Recovering the canoe proved to be somewhat difficult due to its inundation by the silt. A preliminary swimover and visual inspection of the lake bottom was performed in the area where the section was discovered in 1996. This simple inspection however produced no evidence of any additional pieces. Probe rods were then employed to feel beneath the silt layer for any debris within the same survey area. This too was problematic due to the large amount of debris unassociated with the canoe, including rocks, bottles, and lumber. Once encountered, these all had to be verified by touch (rocks for instance could be easily identified) or they had to be removed from the silt and visually identified. The canoe was eventually located directly adjacent to the boat dock beneath approximately five feet of silt. Divers had to pull themselves beneath the silt, either by holding on to the pier pilings or the probe rods. Pieces were then gently removed by fanning, digging or slowly rocking the fragments back and forth until they came free. Great care was taken not to fracture any of the wood. Visibility was absolute zero and divers worked exclusively by feel. Once removed from the water, the canoe fragments were given to Dan Joyce who immediately submerged them in large bins filled with fresh water so the wood would hold its cell structure until it could be properly conserved. More than 20 pieces of the canoe were recovered ranging in size from a few inches to nearly two feet. All of the pieces were transported to Madison where they will be documented, analyzed and conserved. Although these types of finds are quite rare in the state, the discovery of the Lake Mary Canoe reminds us that Wisconsin’s waterways have been utilized for thousands of years. Considering the importance of the water prehistorically as a resource base for humans, it seems very likely that more of these sites exist and hopefully, in time a more detailed prehistoric maritime record can be constructed.

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