Fossil records of the cold-water scallop Zygochlamys delicatula (Mollusca : Bivalvia) off northernmost New Zealand: how cold was the Last Glacial maximum?

Three new localities for fossil Zygochlamys delicatula (Hutton) are reporte d: 20 km north of the Three Kings Islands, at 812 m depth in surface sedime nt (late Last Glacial age, 14 319 +/- 86 radiocarbon years BP); and off Nin ety Mile Beach in c. 170 m, and "a little north of Auckland" in c. 350 m, n orthwestern North Island, both in brown mixed phosphate-carbonate concretio ns (pre-Last Glacial; possibly as old as early Nukumaruan?). The most north ern 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 Ban ks Peninsula. Planktonic larvae of Z. delicatula appear to be limited to a summer maximum sea surface temperature no warmer than c. 14-15 degrees C. A drop in summer maximum sea surface temperature of at least 6 degrees C dur ing the Last Glacial maximum therefore appears to be needed to allow Z. del icatula to occur northwest of the Three Kings Islands. Enhanced upwelling n earshore off western Northland and off northernmost New Zealand during the Last Glacial maximum, perhaps caused by enhanced wind flow, apparently allo wed rare spatfalls of Z. delicatula to metamorphose and survive to adulthoo d off the Three Kings Islands. Z. delicatula might well have been quite com mon off western Northland, but if so is now largely buried beneath the seaf loor.