An extensive field of iron-rich, nickel- and copper-poor manganese nodules covers the deep sea-floor of the northeastern quadrant of the Southwestern Pacific Basin, and the eastern side of the Samoan Basin. The nodule field has a relatively well-defined western boundary, the location of which is determined by differences in sedimentation regimes. Immediately east of the Tonga-Kermadec volcanic arc and New Zealand, as well as around Rarotonga (Cook Islands) and the Samoan chain, rapid accumulation of volcanic ash and microfossils has buried potential nodule nuclei before significant ferromanganese oxide encrustation could occur. Further east, where sedimentation rates are lower, the nodule field has developed. The nodules occur almost exclusively on medium to dark brown silty clays which contain a significant proportion (5-15%) of red-brown semi-opaque oxides (RSO's). The brown silty clays consist principally of phyllosilicates (illite, montmorillonite, chlorite and kaolinite) plus subsidiary quartz and feldspar. Microfossils are generally rare, but all of the brown silty clays contain trace quantities of calcareous nannofossils.

From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.