New Zealand Journal of Botany
abstracts
Palaeoenvironment and human
impact in modifying vegetation at Mt St John, Auckland Isthmus, New
Zealand
M. Horrocks
Microfossil Research Ltd
31 Mont Le Grand Rd
Mt Eden
Auckland, New Zealand
www.microfossilresearch.com
and
School of Geography and
Environmental Science
University of Auckland
Private Bag 92 019
Auckland, New Zealand
S. L. Nichol
D. M. D’Costa
School of Geography and
Environmental Science
University of Auckland
Private Bag 92 019
Auckland, New Zealand
P. Shane
Department of Geology
University of Auckland
Private Bag 92 019
Auckland, New Zealand
C. Prior
Rafter Radiocarbon Laboratory
Institute of Geological and Nuclear Sciences
P.O. Box 31 312
Lower Hutt, New Zealand
Abstract A
2.34 m sediment profile from the base of the crater of Mt St
John volcano (a small basaltic cone on Auckland Isthmus) provides a
partial environmental record of the Late Quaternary. The record
highlights potential age control problems with sediment cores taken
directly from archaeological sites. Two distal tephras were recorded:
9.5 ka Rotoma and 7 ka Tuhua. A date of 16 309 ±
90 14C
yr BP from the basal scoria of the profile provides a minimum date for
the eruption of Mt St John. Pollen was present only in the upper
0.33 m of the profile, in a layer of peat and soil which caps
highly weathered silts and clays eroded from the crater walls. In early
Polynesian times (most likely after c. 800 14C
yr BP), vegetation of the crater swamp was dominated by Cyperaceae
sedges and Paesia
ground fern. Dacrycarpus
trees were also present. Podocarp-hardwood forest, dominated by Metrosideros,
grew on the rim and inner slopes of the crater. Elaeocarpus,
Griselinia,
and Cyathea
were also present. A decline in Dacrycarpus
pollen and an accelerated
erosion rate mark Polynesian forest clearance within the crater. Typha
became a major component of the swamp vegetation during the Late
Polynesian-European era.
Keywords palynology;
tephra; Late Quaternary; Mt
St John; Auckland
B04032; Received 2 August 2004;
accepted 18 November 2004; Online publication date 17 March 2005
New Zealand Journal of Botany,
2005, Vol. 43: 211–221
0028–825X/05/4301–0211 © The Royal Society of New Zealand 2005
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