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Spatial variation in pollen and charcoal records in relation to the 665 yr B.P. Kaharoa tephra at Harataonga Bay, Great Barrier Island, northern New Zealand: preliminary results
Horrocks M, Nichol SL, Jones MD, Shane PA, Sutton DG. 2002. In: Jones M, Sheppard P. (eds) Australasian connections and new directions. Proceedings of the 7th Australasian Archaeometry Conference. Auckland, Research in Anthropology and Linguistics, Department of Anthropology, University of Auckland. Pp. 155-170.
Abstract
We present preliminary results of a pollen study examining spatial variability using the 665 14C yr B.P. Kaharoa tephra as the key stratigraphic marker. Our aim is to highlight potential differences in pollen and charcoal profiles from adjacent sites, and to point out the implications of these differences for the interpretation of pollen records. Three sediment cores were taken from swampy ground behind foredunes at Harataonga Bay, a small catchment on Great Barrier Island. Core 1 provides a c. 5000 14C yr record of the swamp and is typical of northern New Zealand pollen profiles in that the deforestation signal appears immediately after Kaharoa tephra. Cores 2 and 3, however, show this signal at least 1 m below the tephra layer. Also, artefact pollen of gourd (Lagenaria), an introduced Polynesian cultigen, was found 80 cm below the tephra layer in Core 2.This apparent difference in the timing of the human signal may be explained by the occurrence of small-scale, highly localised fires that are not recorded at adjacent sites. This has implications for inferring date of human presence in extensive areas, such as regions or large catchments, from a small number of pollen cores taken from within those areas. An alternative explanation is that sediments in Cores 2 and 3 have been reworked to a much greater extent than those in Core 1. This has implications for the use of tephra as critical data for events, particularly when using recent tephra such as Kaharoa for dating human presence when the necessary resolution is to decades or centuries rather than millenia.
