Some marine iron pisolite beds from the Toarcian of western Sicily are described for the first time. These beds, which generally overlie the Liassic platform carbonates, are usually chocolate-brown in colour; they attain a maximum thickness of about 40 cm at one locality but are often tracable as centimetre-thick remanie horizons elsewhere. Their fauna comprises Tethyan ammonites, belemnites, gastropods, rare brachiopods, fish teeth, foraminifera and crinoid ossicles.The pisoliths themselves contain calcite, limonite (goethite), haematite and, in rare cases, chamosite; electron-probe microanalysis shows that they are enriched in certain trace elements, particularly manganese, relative to many iron ooliths. The high content of trace elements suggests deposition in a pelagic environment, as do the faunal associations of this deposit; and, since fragments of sanidine trachyte are invariably associated with this lithology - sometimes even forming the cores of the pisoliths themselves - submarine volcanism and exhalations seem a likely source for the ferruginous and manganiferous material.The stratigraphical position of the iron pisolite, often between two stromatolitic sediments, and the traces of boring algae in the pisoliths, suggest deposition within the photic zone, probably some tens of metres deep.
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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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: Jenkyns, Hugh C (1970): Submarine volcanism and the toarcian iron pisolites of western Sicily. Eclogae Geologicae Helvetiae, 63(2), 549-572
