Controlled-Source Electromagnetic Methods to Investigate the Submerged Cultural Landscapes of the Pacific Continental Shelf

Sea-level rise following the last glacial maximum (~20 kya) resulted in the submergence of landscapes that may have been once occupied by hunter-gatherers traveling along coastlines. Due to the high density of Paleoindian archaeological sites in southern California, it is likely that archaeological deposits may be located in the inundated regions of the continental shelf. The identification and characterization of these drowned sites and the associated paleolandforms will provide useful information on human migration into the Americas in addition to refining paleoclimate and paleoenvironmental models. As the submerged landscape is substantial, survey areas targeting cultural sites must be refined by identifying high probability paleolandforms for human occupation. Evidence from subaerial late Pleistocene and early Holocene archaeological sites indicate that paleolandscapes with features such as paleochannels, tar seeps, and paleoestuaries were highly attractive to hunter-gatherers. These features and archaeological deposits have differing electrical resistivity than the surrounding sediment due to differences in porosity or inherit material characteristics. Controlled-source electromagnetic (CSEM) methods are sensitive to these changes in electrical resistivity and can be used efficiently on small unspecialized vessels to survey large areas. We present results from a surface-towed CSEM cruise targeting the aforementioned paleolandforms on the continental shelf offshore southern California. Additionally, we present results from forward models of a proposed bottom-towed CSEM system targeting archaeological deposits directly. These results indicate that CSEM is an efficient and effective tool toward identifying and characterizing archaeological sites and paleolandforms on the continental shelf.