New Zealand Journal of Marine and Freshwater Research abstracts

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²¹⁰Pb chronology from Wellington Harbour, New Zealand

JAMES R. GOFF*

Research School of Earth Sciences
Victoria University of Wellington
P. O. Box 600
Wellington, New Zealand

NEIL E. WHITEHEAD

Institute of Geological and Nuclear Sciences
P. O. Box 31 312
Lower Hutt, New Zealand

ROBERT G. DITCHBURN

Institute of Geological and Nuclear Sciences
P. O. Box 31 312
Lower Hutt, New Zealand

*Present address: Institute of Geological and Nuclear Sciences, P. O. Box 30 368, Lower Hutt, New Zealand.

Abstract  A sediment accumulation record based on the levels of "unsupported" ²¹⁰Pb was obtained from a core taken from the centre of Wellington Harbour, New Zealand. Sediment accumulation rates (SARs) varied from 3 to 5 mm yr^-1. Before 1920, SARs were sufficiently high to dilute unsupported levels of ²¹⁰Pb to background, but had fallen below the mean by 1925 maintaining constant SARs until 1953. These data provide a higher resolution chronology of early 20th century SARs than was previously available. Comparison with ¹³⁷Cs data confirms that there was a significant increase in SARs between 1953 and 1967, but that these have remained fairly constant since 1974. Data from the two radionuclides are consistent after 1974, and ²¹⁰Pb data are consistent with other chronological measurements before 1953. Therefore, it is suggested that the two radionuclides are immobile in the marine sediments of Wellington Harbour and that differences between the two SARs are real.

Keywords  Wellington Harbour; ²¹⁰Pb; ¹³⁷Cs; cores; sediment accumulation rates

M97032
Received 4 July 1997; accepted 14 November 1997



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