New Zealand Journal of Geology and Geophysics abstracts
Radiocarbon and luminescence dating of overbank deposits in outwash sediments
of the Last Glacial Maximum in North Westland, New Zealand
Anne Hormes*
Institute of Geological Sciences
Universität Bern
Baltzerstrasse 1
CH0-3012 Bern, Switzerland
email: anne.hormes@angstrom.uu.se
Frank Preusser
Institute of Geological Sciences
Universität Bern
Baltzerstrasse 1
CH-3012 Bern, Switzerland
email: preusser@geo.unibe.ch
George Denton
Department of Geological Sciences
5790 Bryand Global Sciences Center
University of Maine
Orono, Maine 04469-5790, USA
Irka Hajdas
Institute of Particle Physics
ETH Hönggerberg
HPK, CH-8093 Zürich, Switzerland
Dominik Weiss
Imperial College of Science, Technology and Medicine
Department of Earth Sciences and Engineering
Prince Consort Road
London SW7 2BP, UK
Thomas F. Stocker
Climate and Environmental Physics
Universität Bern
Sidlerstrasse 5
CH-3012 Bern, Switzerland
Christian Schlüchter
Institute of Geological Sciences
Universität Bern
Baltzerstrasse 1
CH-3012 Bern, Switzerland
*Present address: Ångströmlaboratoriet, Uppsala University, Box
534, SE-751 21 Uppsala, Sweden.
Abstract In the Grey River valley, North Westland,
New Zealand, extensive terraces of outwash sediments assigned to the Otira
glaciation form outstanding geomorphologic features. Four layers of organic
sediments subdivide stratified outwash gravels of the major terrace. The
age of the fine-grained sediments is constrained by 55 radiocarbon (14C)
ages and 8 optically stimulated luminescence (OSL) ages. The calibrated radiocarbon
ages cover the age range between 21 350 and 23 890 cal yr BP. The ages for
each different layer are consistent and are in stratigraphic order with mean
ages of 22 350 cal yr BP (layer A), 22 470 cal yr BP (layer B), 22 930 cal
yr BP (layer C), and 22 960 cal yr BP (layer D). OSL dating of the silty
overbank deposits alternating with the organic beds imply a deposition at
21 700 ± 2600 yr. The use of different organic compounds for radiocarbon
dating (separated organic residues, humic acids, terrestrial seeds) and the
consistency with the luminescence dating support the reliability of the results.
We use the informal name Raupo complex for the overbank deposits and consider
it to reflect a moderate climate oscillation between two glacial advances
during Oxygen Isotope Stage 2.
Keywords Last Glacial Maximum; radiocarbon; luminescence;
fluvial sediments; New Zealand
G01023 Received 25 July 2001; accepted 21 November 2002; published 21
March 2003
New Zealand Journal of Geology & Geophysics, 2003, Vol. 46: 95-106
0028-8306/03/4601-0095 $7.00/0 © The Royal Society of New Zealand
2003
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