New Zealand Journal of Geology and Geophysics abstracts
Moa fossils and chronology of a Pleistocene terrace sequence, Tauweru,
Wairarapa, New Zealand
J. D. COLLEN
R. H. GRAPES
S. H. EAGAR
School of Earth Sciences
Victoria University of Wellington
P.O. Box 600
Wellington, New Zealand
Abstract The fortuitous preservation of bones of the
medium-sized moa Euryapteryx geranoides (Owen) in Pleistocene colluvial
sediments near Tauweru, Wairarapa, has allowed radiocarbon dating of a terrace
sequence along the lower Tauweru River. The bones were in a shelly,
conglomeratic sandstone on an erosion surface cut into mid-Pliocene (Waipipian)
siltstone, and were overlain by loess and situated immediately adjacent to
onlapping fluvial gravels. Most of the bones are from a single skeleton buried
articulated and apparently nearly complete, and there is also a single left
tibiotarsus from a slightly larger bird.
Bone from the right femur gave a radiocarbon age of 14 262 +/- 87 yr BP
by accelerator mass spectrometry. The material was slightly chalky and had a
low collagen yield with a relatively large amount of humic material;
contamination which would lower the measured age is thus possible. However, an
amino acid profile characteristic of collagen makes it unlikely that high
contaminant levels are present. The radiocarbon age for the bone is likely to
be 14-18 ka (16-22 000 cal. yr) or possibly older, with the lower limit
being set by the radiocarbon age and the upper limit inferred from the amount
of humic contamination. This is thus the oldest moa skeleton reported from
Wairarapa.
Loess overlying the bones contains disseminated shards of clear rhyolitic
glass with a composition identical to that of the 22.6 ka (24 500 cal. yr)
Kawakawa Tephra, and gave an age by optical dating of 26 +/- 2 ka. A thicker
tephra deposit within loess on a higher, deeply dissected surface may also be
partly reworked; optical dating of a sample of loess from 2 m beneath it gave
an age of 22 +/- 2 ka. Thermoluminescence dating of two samples of the
conglomeratic deposits surrounding the bones gave ages of 52 +/- 13.2 and 102
+/- 18 ka, respectively, indicating redeposition of these sediments without
resetting of the thermoluminescence signal. One of these samples was also dated
by optical luminescence at 39 +/- 2 ka, and this age may similarly include a
component of inherited age.
Optical ages and the presence of reworked tephra confirm that all loess
overlying the skeleton is Ohakean (deposited between 25 and 9.5 ka BP) and
probably Oh2. The radiocarbon age implies that the surface beneath the skeleton
is probably equivalent to the Ohakean Oh1 terrace defined from the Rangitikei
area, with an estimated age of 18 000 yr BP. The most extensive fluvial
gravel surface in the area is probably equivalent to the Ratan surface.
Keywords Euryapteryx geranoides; Kawakawa Tephra;
loess; moa; optical dating; Ohakean; Pleistocene terraces; radiocarbon dating;
Ratan; thermoluminescence dating; Wairarapa
New Zealand Journal of Geology & Geophysics, 2000, Vol. 43:
483-491
0028-8306/00/4304-0483 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (2752K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
