Archaeology and holocene sand dune stratigraphy on Chatham Island

Abstract

Four depositional episodes based on sand deposits and the soils on them are proposed for Holocene coastal sand dunes on Chatham Island: Te Onean Depositional Episode (c. 5,000 to 2,200 years BP), Okawan Depositional Episode (c. 2,200 to 450 years BP), Kekerionean Depositional Episode (c. 450 to 150 years BP) and Waitangian Depositional Episode (c. 150 years BP to present day). Each depositional episode has two phases: an unstable phase with a high rate of deposition and no soil formation, followed by a stable phase with a low rate of deposition and soil formation. The Okawan, Kekerionean, and Waitangian episodes closely match late Holocene depositional episodes on the New Zealand mainland. The earliest human occupation remains (Moriori) are in Kekerionean sands and the inferred date for Moriori settlement of Chatham Island is between 400 and 450 years BP. Bones of Hooker's sea lion are found in Te Onean and Okawan deposits. The most recent bones are in Kekerionean middens and it is inferred that Hooker's sea lion was driven from the Chatham Islands by human predation. The depositional episodes appear to be unrelated to sea level changes, tectonic activity, or cultural influence. It is suggested that they may be related to coastal erosion initiated by storms.