Coastal Restoration Trust of New Zealand

Coastal Dune Ecosystem Reference Database

Role of mean circulation, tides, and waves in the transport of bottom sediment on the New Zealand continental shelf Journal Paper

Carter, L.; Heath, R.A.
Journal / Source
New Zealand Journal of Marine and Freshwater Research
offshore, economic geology, west New Zealand coast, ironsand, sedimentation, continental shelf, mineral resources, mineral deposits
The ironsand component (ilmenite, titanomagnetite, and/or magnetite) of surficial sediments on New Zealand's western continental shelf is highest on the inner-middle shelf between Auckland and Taranaki where the mean concentration is x = 3.85% by weight. Sediments off Westland and Nelson contain only x = 0.17% ironsand. The subsurface distribution of ironsand, as revealed in piston cores, resembles that at the surface except that subsurface concentrations are markedly lower (e.g., x = 0.77% for AucklandTaranaki). Textural and compositional data from the Auckland-Taranaki shelf suggest irons and was originally concentrated under littoral conditions during the Holocene transgression and was dispersed north and southeast of the main primary source, the Egmont volcanics. The irons and and host sediment are now approaching equilibrium with the modem hydraulic regime of waves and storminduced currents and, therefore, are regarded as palimpsest. Any irons and concentrated on the WestlandNelson shelf during a lower stand of sealevel is now covered by ironsand-poor modem sediment; the Auckland-Taranaki shelf has a far lower modem sediment supply and, thus, the ironsand has remained exposed.