Modeling and monitoring submerged prehistoric sites during offshore sand dredging and implications for the study of Early Holocene Coastal Occupation of Southern California

Abstract

Beach sand dredging projects off the coast of Southern California provide data for improved understanding of the stratigraphic setting for early Holocene sediments and the potential for offshore buried archaeological materials. Geophysical data, core sediments, and invertebrate fossils allow models to be developed for six borrow sites within drown river valleys off San Diego County. These site-specific models were tested during dredging operations, and the dredge spoil was monitored for archaeological materials. Two of the borrow sites yielded stone bowls consistent with those found in previous offshore archaeological investigations in this region. These artifacts, however, were determined to come from nearshore and lagoonal sediments, not appropriate for direct occupation, raising questions about both the function of stone bowls and the process that resulted in their deposition. The competing hypotheses presented are that these bowls originated in settlements located adjacent to the lagoons, but were eroded and redeposited into the lagoon during transgression, or that they were part of a fishing toolkit used from boats or in shallow waters within the lagoon. This project illustrates the potential for commercial development projects to yield information on submerged archaeological resources, as well as the challenges.