New Zealand Journal of Geology and Geophysics abstracts
Pollen analysis of Pliocene-Pleistocene Kowai Formation (Kurow Group),
Mackenzie Basin, South Canterbury, New Zealand
D. C. MILDENHALL
Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
Abstract Kowai Formation in the Lake Pukaki area of the
Mackenzie Basin, is a tectonically deformed gravel sequence containing rare,
fossiliferous, fine-grained horizons with pollen assemblages that are unusual
in their composition. The sequence of vegetation types from oldest to youngest
is: (1) assemblages with high percentages of Brassospora-type beech and
Casuarina; (2) assemblages with high percentages of araucarian pollen
(position uncertain); (3) Fuscospora-type beech assemblages; and (4)
grassland/scrubland assemblages preceded by a major angular unconformity. The
Fuscospora-type beech assemblages are further divided into sequences
where, from oldest to youngest, the paleovegetation is: (a)
Fuscospora-type beech with Brassospora-type beech and
Casuarina; (b) Fuscospora-type beech with Phyllocladus
(position uncertain); (c) Fuscospora-type beech with a variety of pollen
types; (d) Fuscospora-type beech with podocarps; and (e)
Fuscospora-type beech totally dominates. The age of the beds is
Pliocene, as determined by the presence of a number of pollen species that last
appeared in the Pliocene, along with a few taxa that first appear at the same
time. The youngest grassland/scrubland assemblages, lacking extinct taxa, may
be from fluvioglacial sediments of Pleistocene age. During the early phases of
deposition, the climate was warmer and more humid than the present day, as
evidenced by the presence of abundant araucarian, Nothofagus
(Brassospora) beech and Casuarina pollen. Most of the Kowai
Formation was deposited at a time when the area was covered in a
Nothofagus (Fuscospora) beech forest, indicative of an
interglacial climate not dissimilar from that experienced in present-day beech
forests. From the top of the sequence, evidence of glacial conditions starts
appearing as the forest vegetation disappears to be replaced by
grassland/scrubland vegetation.
Keywords New Zealand; South Canterbury; Mackenzie Basin;
Kowai Formation; Pliocene; Pleistocene; palynology; vegetation history;
stratigraphy; paleoclimate
New Zealand Journal of Geology & Geophysics, 2001, Vol. 44: 97-104
0028-8306/01/4401-0097 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (1041K); (scanned from paper original: notes about this process)
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