Emerging Technologies in the Search for the Submerged Cultural Landscapes of the Pacific Continental Shelf

Abstract

As applications for offshore renewable energy projects increase, state and federal land managers have become concerned over potential impacts to cultural heritage resources along submerged landscapes. Identification, documentation, and management of historical shipwrecks have been relatively common, but methods for identifying submerged pre-contact archaeological deposits are developing in many coastal regions of the continental United States. Permitting agencies in certain regions along the Gulf of Mexico and the Atlantic Ocean typically require management plans that include mitigation measures for submerged archaeological sites. Over the last decade, resource managers along Pacific Coast regions have become increasingly aware of the need for submerged archaeological site protection. This is especially important since the eastern Pacific continental shelf has become a focal point in the search for late Pleistocene migrations into the Americas and other evidence of pre-contact habitation in coastal regions since the Last Glacial Maximum (LGM). Integral to this search is the identification of submerged Pleistocene landforms that may favor preservation of pre-contact archaeological sites. Stemming from this, our multidisciplinary and multi-institutional effort includes marine geologists, marine biologists, and archaeologists synthesizing existing data using GIS models, and collecting new side scan sonar, CHIRP, and multibeam bathymetry data ground truthed with marine sediment cores. This methodology for the identification of submerged archaeological deposits is not new; however, the landscape approach that defines our research, and our focus on understanding paleolandscapes using modeling, sonar survey, and marine coring is the first of its kind on the eastern Pacific continental shelf. The goal of our project is to develop an archaeological sensitivity model, which the Bureau of Ocean Energy Management can consult in the offshore energy permitting process. As such, we are building our model using data from California’s Northern Channel Islands and testing the model along Oregon’s central coast. Results suggest that with the right technologies, sensitive landscape features such as paleochannels, paleoestuaries, and offshore tar seeps – all features used by Native American communities during the late Pleistocene and Holocene along the Pacific Coast – can be identified and used to model sensitive archaeological landscapes. We also are testing the efficacy of controlled-source marine electromagnetic methods in conjunction with sonar survey data for the identification of tar seeps, paleochannels, and buried archaeological shell midden deposits. This combined methodological approach is unique to North America’s Pacific Coast and represents a pioneering effort in the search for submerged archaeological deposits, which will help identify, document, and preserve underwater cultural heritage resources.