Iron-rich sediments similar to those forming on other active mid-oceanic ridges have been found in the Median Valley of the Mid-Atlantic Ridge near 45 °N. The sediments are enriched in arsenic and mercury, and are thought to have formed largely as a result of submarine hydrothermal activity associated with the generation of new ocean floor at the ridge crest.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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.

Supplement to: Cronan, David S (1972): The Mid-Atlantic Ridge near 45 °N, XVII: Al, As, Hg, and Mn in Ferruginous Sediments from the Median Valley. http://store.pangaea.de/Projects/NOAA-MMS/e72-025.pdf, Canadian Journal of Earth Sciences, 9(3), 319-323