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Test of AMS 14 C dating of pollen concentrates using tephrochronology
Author(s) -
Newnham Rewi M.,
Vandergoes Marcus J.,
Garnett Mark H.,
Lowe David J.,
Prior Christine,
Almond Peter C.
Publication year - 2007
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/jqs.1016
Subject(s) - tephra , radiocarbon dating , tephrochronology , pollen , geology , macrofossil , sediment , peat , contamination , sedimentary depositional environment , physical geography , geochemistry , paleontology , archaeology , holocene , ecology , geography , volcano , structural basin , biology
Previous attempts to radiocarbon date sediments >10 kyr from the high rainfall region of Westland, New Zealand, a critical location for investigation of interhemispheric patterns of climate change, have been problematic. This study, building on recent work by Vandergoes and Prior (2003), shows that AMS 14 C dating of pollen concentrates has potential to provide more reliable ages than other sediment constituents, including plant macrofossils. The method was applied to sediments from three sites containing the 22.6k 14 C yr Kawakawa Tephra, which provided an independent test of the 14 C ages. Although some minor laboratory contamination was detected in tests on background standards, the modelled relationship between sample mass and measured 14 C content permitted an appropriate correction to be determined. Improved pollen concentrations derived by density separation between 1.4 and 1.2 specific gravity and sieving in the range 10–50 μm provided either older ages than other fractions of the same sample or, where in situ contamination was not evident, equivalent ages. Differences in degree of in situ contamination between depositional environments indicated that, in Westland, lake sites may be less susceptible to contamination by younger carbon than peat sites, where this process may be facilitated by root penetration into underlying sediments. Copyright © 2006 John Wiley & Sons, Ltd.