For 7 pelagic sediment cores, the decrease in unsupported 130Th activity with depth in the core was used to establish the mean accumulation rate over the last 300 000 years. Because CaCO3 is a Mn-free diluent, the Mn concentration results and the sediment accumulation rate results are given on a carbonate-free basis. CaCO3 content ofcores raised from below the carbonate compensation level is taken as zero. The in situ density of water-free deep-sea cores was assumed to be 0.7 g/cm³ , this could lead in some cases to an error.
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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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 propriatory 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.This dataset represents the digitized Table 1 - Part 2, pp. 144 of the related publication.