A geoarchaeological chronology of Holocene dune building on San Miguel Island, California

A data base of 114 C-14 dates from 40 archaeological sites in San Miguel Island sand dunes provides a general chronology for Holocene dune building. Although rising seas have probably submerged earlier evidence, postglacial dune building on San Miguel began as early as 10 000 years ago. More intensive dune building dates to the middle and late Holocene, including large parabolic dunes that traverse the island and climb some of the highest landforms. Native American peoples lived on and altered island sand dunes for nearly 10 000 years, and native burning and other landscape alterations may have contributed to periodic destabilization of island dunefields. Accumulation of cultural debris also facilitated anthropogenic soil formation in many coastal localities, however, and over the millennia midden debris protected large expanses of the island's coastal perimeter from wind erosion. With the introduction of sheep c. AD 1850, destabilization and erosion of dune soils caused by overgrazing and other human impacts reached unprecedented levels, devastating the island's natural ecology. In recent decades, with the removal of sheep and other exotic animals from the island, the dunes have begun to restabilize.