New Zealand Journal of Geology and Geophysics abstracts
Fossil records of the cold-water scallop Zygochlamys delicatula
(Mollusca: Bivalvia) off northernmost New Zealand: how cold was the Last
Glacial maximum?
A. G. BEU
Institute of Geological & Nuclear Sciences Ltd
P.O. Box 30 368
Lower Hutt, New Zealand
email: a.beu@gns.cri.nz
Abstract Three new localities for fossil Zygochlamys
delicatula (Hutton) are reported: 20 km north of the Three Kings
Islands, at 812 m depth in surface sediment (late Last Glacial age,
14 319 +/- 86 radiocarbon years BP); and off Ninety Mile Beach in
c. 170 m, and "a little north of Auckland" in c. 350 m,
northwestern North Island, both in brown mixed phosphate-carbonate concretions
(pre-Last Glacial; possibly as old as early Nukumaruan?). The most northern
locality is >600 km north of the previously northernmost fossil record,
in early Nukumaruan rocks of central Hawke's Bay, and c. 1000 km
north of the northernmost abundant living specimens, in Pegasus Canyon, north
of Banks Peninsula. Planktonic larvae of Z. delicatula appear to be
limited to a summer maximum sea surface temperature no warmer than
c. 14-15deg.C. A drop in summer maximum sea surface temperature of at
least 6deg.C during the Last Glacial maximum therefore appears to be needed to
allow Z. delicatula to occur northwest of the Three Kings Islands.
Enhanced upwelling nearshore off western Northland and off northernmost New
Zealand during the Last Glacial maximum, perhaps caused by enhanced wind flow,
apparently allowed rare spatfalls of Z. delicatula to metamorphose and
survive to adulthood off the Three Kings Islands. Z. delicatula might
well have been quite common off western Northland, but if so is now largely
buried beneath the seafloor.
Keywords fossils; bivalves; Pectinidae; climate change;
glaciation
New Zealand Journal of Geology & Geophysics, 1999, Vol. 42:
543-550
0028-8306/99/4204-0543 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (1589K); (scanned from paper original: notes about this process)
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