Surface sediment samples have been obtained from the near-shore portion of the shelf off the west coast of the North Island, New Zealand, from depths between 5 and 50 fathoms. The percentage of magnetic ironsand in the sediments has been determined by magnetic separation. The highest percentages (30 per cent by weight) are found close to the shore; at the 50-fathom line-the maximum depth of the samples considered here-ironsand percentage is very low. The concentration of ironsand is ascribed to processes operating in the present and late Pleistocene wave zones.
The principal facies of the surface sediments of the Southwestern Pacific and Samoan Basins have been characterised by differences in colour, grain size, lithology, mineralogy, and chemical composition, based on 77 dredge and grab samples collected during 2 cruises of the NZOI research vessel RV Tangaroa.Light-coloured foram/nannofossil oozes mixed with coarse volcaniclastics (pumice, ash) occupy the relatively shallow seafloor areas near volcanoes of New Zealand, the Tonga-Kermadec island are, Samoan chain, and Cook Islands. Up to several hundred kilometres east of the North Island of New Zealand and the Tonga-Kermadec volcanoes, volcaniclastics are the dominant sediment component, being mixed with increasing amounts of clay minerals eastward. In the western part of the Samoan Basin, and the area immediately to the south, a siliceous microfossil (mostly radiolarian) hash ooze is found, probably containing volcanic ash. The siliceous ooze and ash-rich sediments are mostly grey coloured. The sediment changes gradationally in character eastward as microfossil and/or ash content decreases. It becomes darker in colour, finer grained, and contains higher concentrations of Mn, Ni, Cu, and Co. The dominant sediment of the eastern sector of the study area is a Received 14 January 1982, accepted 16 September 1982 brown to dark brown detrital silt-bearing, RSObearing to RSO-rich clay. Manganese nodules are principally associated with this sediment facies. The eastward changes in sediment character are interpreted as the result of a decreasing sedimentation rate.
A series of sediment samples from a selected area of the New Zealand western continental slope show an increase in the percentage of carbonate with depth, and in finer grade sediment with depth and distance from shore. Median diameters of calcareous and detrital components are variable and decrease sharply with depth to 700 m. Below this depth, sediments are dominantly formed of calcareous fragments and coccoliths in the silt and clay grades, with planktonic foraminifera comprising nearly the whole of the remainder of the sediment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.