Underwater Archaeology in Thunder Bay National Marine Sanctuary, Lake Huron—Preliminary Results from a Shipwreck Mapping Survey

Abstract

Off northeastern Lower Michigan, the bottom waters of Lake Huron in the Thunder Bay National Marine Sanctuary and Underwater Preserve (TBNMS/UP) contain a vast array of historic shipwrecks representing more than a century of early Great Lakes shipping. During June 2001, in collaboration with the National Oceanic and Atmospheric Administration (NOAA) and the State of Michigan, the Institute for Exploration (IFE) mapped a large portion of “Shipwreck Alley”, which extends throughout the deep-water portion of the Sanctuary and continues farther north. Seventeen shipwrecks, two of which are new discoveries, and many other interesting lakebed features were acoustically imaged and carefully surveyed using a high-frequency side-scan sonar towfish. In addition, a number of submerged sinkholes and lakebed pockmarks were discovered and mapped. These karst features in the limestone bedrock were exposed subaerially from about 10000 to 8000 years ago, when the lake level was substantially lower following the last glacial maximum. The archaeological significance of these sinkholes, the newly discovered shipwrecks, and several other promising sonar targets will be evaluated when IFE returns to TBNMS/UP in 2002. Using a remotely operated vehicle (ROV) and an advanced underwater imaging platform, we will visually survey the most important sites, collect high-definition underwater video, and ground-truth sonar targets. The work will be performed by marine geologists in collaboration with underwater archaeologists and maritime historians. This effort is part of a long-term scientific, educational, and public outreach project in the TBNMS/UP supported by NOAA's National Marine Sanctuary Program and Office of Ocean Exploration.