Glacial to interglacial changes in non-carbonate and carbonate accumulation in the SW Pacific Ocean, New Zealand

Flutes of carbonate and non-carbonate (terrigenous + biogenic siliceous) se diment, back to a maximum of marine isotope stage (MIS) 6, were determined for 54 cores from off eastern New Zealand. Mass accumulation rates (MARs) w ere derived using dry bulk densities measured directly from fresh cores or, in the case of dry archived samples, on estimates from a density/carbonate relationship. MARs exhibit wide spatial and temporal variability in respon se to (i) the location of cores relative to the terrigenous source of New Z ealand, current pathways and local oceanographic features, and (ii) palaeoc limatic change. For MIS 1-2, non-carbonate accumulated at a high rate betwe en 27 and 18 ka (calendar years), due to an influx of waterborne and aeolia n terrigenous detritus together with localised production of biogenic silic a under a northward intrusion of subantarctic waters, and an increase in wi nd-induced upwelling. By 18-12 ka, non-carbonate MARs reduced as winds amel iorated and sea level rose to confine some of the terrigenous load to the c ontinental shelf. The Holocene transgression was accompanied by warmer sea surface temperatures, the formation of coastal and lacustrine sediment trap s, and more widespread terrestrial vegetation. These conditions further red uced the deep oceanic non-carbonate flux to levels about half those of glac ial periods. In contrast, carbonate MARs were lower in cold periods, reflec ting lower productivity, increased dissolution and, in the case of the gene rally productive waters of Chatham Rise, to redistribution by bottom curren ts. However, off central New Zealand, carbonate production was higher on th e continental margin, possibly because of enhanced upwelling under the stro ng wind regime of MIS 2. Such localised effects produced glacial carbonate MARs higher than interglacial MIS 1 values. For the rest of the region, car bonate fluxes increased to an early to middle MIS 1 maximum before generall y declining in recent times. (C) 2000 Elsevier Science B.V. All rights rese rved.